Mesenchymal stem cells: a potential targeted-delivery vehicle for anti-cancer drug loaded nanoparticles

POTENTIAL CLINICAL RELEVANCE Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174 – 184

Review Article

nanomedjournal.com

Mesenchymal stem cells: a potential targeted-delivery vehicle for anti-cancer drug loaded nanoparticles Zibin Gao, PhD a,⁎, Linan Zhang, PhD a , Jie Hu, PhD b , Yongjun Sun, PhD a a

Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang, P. R. China b Department of Immunology, Hebei Medical University, Shijiazhuang, P. R. China Received 5 January 2012; accepted 4 June 2012

Abstract The targeted delivery of anticancer agents is a promising field in anticancer therapy. Mesenchymal stem cells (MSCs) have inherent tumortropic and migratory properties, which allow them to serve as vehicles for targeted drug delivery systems for isolated tumors and metastatic diseases. MSCs have been successfully studied and discussed as a vehicle for cancer gene therapy. However, MSCs have not yet been discussed adequately as a potential vehicle for traditional anticancer drugs. In this review, we will examine the potential of MSCs as a targeted-delivery vehicle for anticancer drug-loaded nanoparticles (NPs), summarize various challenges, and discuss possible solutions for these challenges. From the Clinical Editor: In this review, the feasibility of mesenchymal stem cell-based targeted delivery of anticancer agents is discussed. © 2013 Elsevier Inc. All rights reserved. Key words: Mesenchymal stem cells; Vehicle; Targeted delivery; Cancer; Nanoparticle

Cancer remains one of the leading causes of mortality and morbidity throughout the world and accounted for an estimated one-fourth of human deaths among all age groups in the United States in 2010. 1 The targeted delivery of anticancer agents is a promising field in anticancer therapy. The use of drug delivery systems as nanocarriers can improve the pharmacologic properties of traditional chemotherapeutics by altering drug pharmacokinetics and biodistribution. 2-4 However, the rapid recognition and clearance of nanocarriers from the blood stream by the reticuloendothelial system (RES) limits their usefulness as drug carriers. Meanwhile, coating the surface of nanocarriers with polyethylene glycol (PEG) has been shown to dramatically improve their circulation times in vivo by substantially reducing protein adsorption and opsonization. 5-7 Coupling these effects with the special tumor microvasculature and microenvironment, which is characterized by vascular hyperpermeability and the lack of functional lymphatic vessels, 8,9 a phenomenon commonly referred to as the enhanced permeability and retention (EPR) effect 10,11 occurs, thereby allowing for increased The authors have no conflicts of interest. This study was supported by the Natural Science Foundation of China (NSFC, 30801444), the Natural Science Foundation of Hebei Province (H2012208020) and the Hebei University of Science and Technology Discipline Construction Office. ⁎Corresponding author: Department of Pharmacy, Hebei University of Science and Technology, Shijiazhuang 050018, P. R. China. E-mail address: [email protected] (Z. Gao).

accumulation of the encapsulated drug within tumor tissues. Modification of nanocarriers with the PEG moiety is helpful in controlling the pharmacokinetics of the drug; however, the uptake by the tumor cell can also be dramatically reduced because of the steric barrier between the nanocarrier and the tumor cells caused by the surface coating. 12,13 Therefore, up to now, drugs encapsulated in nanocarriers are mainly delivered via a “passive” form, which is based on the leakage into the tumor microenvironment. To overcome this problem, more “active” forms of drug delivery are currently being studied by researchers around the world, involving the addition of surface ligands to nanocarriers. 9 Mesenchymal stem cells (MSCs) have inherent tumor-tropic and migratory properties, 14 which allow them to serve as vehicles for the targeted delivery of agents for the treatment of isolated tumors and metastatic disease. 15-19 MSCs have many unique and therapeutically advantageous features, which make them ideally suited for as vehicles for drug delivery, such as easy acquisition, hypoimmunogenic properties, fast ex vivo expansion, and feasibility of autologous transplantation. 20 Over the past few years, MSCs have been successfully studied and discussed as a cancer gene therapy vehicle. 14,20,21 A novel delivery system for traditional anticancer drugs is expected from the combination of the hypoimmunogenic and active targeting properties of the MSCs with the controlled release ability of the nanoparticles (NPs); however, further discussion is needed. In this review article, we will examine the promising application of using MSCs as a targeted-delivery vehicle for

1549-9634/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.nano.2012.06.003 Please cite this article as: Gao Z., Zhang L., Hu J., Sun Y., Mesenchymal stem cells: a potential targeted-delivery vehicle for anti-cancer drug loaded nanoparticles. Nanomedicine: NBM 2013;9:174-184, http://dx.doi.org/10.1016/j.nano.2012.06.003

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184

anticancer drug-loaded NPs and summarize various challenges. Moreover, possible solutions for these challenges will be discussed, such as the ways to improve particle uptake, how to keep the vitality of the MSCs after internalization of the cytotoxic anticancer drug-loaded NPs, and how to study the pharmacokinetics of this type of drug delivery system (DDS) and control the fate of the MSCs in vivo. Internalization process of nanoparticles The cellular uptake for NPs involve several possible mechanisms such as passive transport 22 and active endocytosis. 23-25 Endocytosis includes non-specific endocytosis and receptor-mediated endocytosis, such as clathrin-mediated endocytosis and caveolae-mediated endocytosis, through which the pathway of cellular uptake of the NPs mainly depends on their size. 24,26 Considering the limiting number of targeting MSCs in the microenvironment of the tumor, 27 it is important to have enough drug-loaded nanoparticles incorporated into the MSCs and to achieve a therapeutic drug concentration in the tumor tissues. The internalization of NPs can be improved by modification of the NPs, size control, proper incubation time, and NP concentration (Table 1). Methods of enhancing NP uptake Various cationic polymers have been widely used to promote cellular uptake through the electrostatic interaction between their positive charge and the negative charge on the cell membrane. 29,38,47,49,50 Although poly(l-lysine) (pLL) has been widely used, it has exhibited a low uptake efficacy and evidence of cytotoxicity. 51,52 In the case of poly(ethylenimine) (PEI), its uptake and cytotoxicity levels are closely related to the molecular weight of the polymer. 53 Although PEI with a molecular weight above 25 kDa has high uptake efficiency, it is accompanied by cytotoxicity. Lower molecular weight PEI, such as PEI2k, is more biocompatible. 54,55 A recent report introduced a simple and wellcontrolled method to form biocompatible low-molecular weight N-alkyl-PEI2k/SPIO nanocomposites with an efficient MSClabeling capability. 37 The zeta potential measurements showed that all of the nanocomplexes displayed positive charges of approximately +40 mV, which confirmed the presence of the amino groups of the alkylated PEI2k on the surface of the nanocomplexes. The size, zeta potential and interactions with cells of the novel superparamagnetic iron oxide (SPIO) nanocomposites can be easily controlled by adjusting the ratio of alkylated PEI2k and SPIO nanoparticles. The labeled MSCs are unaffected in their viability, proliferation, or differentiation capacity. Chitosan (CS) is a natural cationic polysaccharide consisting of two subunits, d-glucosamine and N-acetyl-d-glucosamine, linked together by β(1,4) glycosidic bonds. CS has excellent characteristics including biocompatibility, low immunogenicity and minimal cytotoxicity. 56,57 This polymer has also been shown to destabilize the lipid bilayer, which thus facilitates its cellular uptake. 58-60 CSDNA NPs were synthesized from the complexation of the cationic polymer with a DNA plasmid by Corsi et al, 34 Pimpha et al, 35 and Wang et al 33 Water-soluble CS (N,N,N-trimethyl chitosan chloride [TMC]) was used by Wang et al 33 and has favorable characteristics

175

for the uptake of MSCs without being cytotoxic. Acid-soluble CS was used in both of these studies. Although using CS alone could not improve the transfection of the MSCs, 34 CS combined with PEI enhanced the level of gene transfection and prolonged the period of expression for the MSCs. 35 Our unpublished results showed that modifying paclitaxel-loaded PLGA-NPs with acid-soluble CS could increase the zeta potential of the NPs from 3.5 mV to 10.5 mV, and the internalization of NPs by MSCs was improved effectively (Figure 1). These diverse results may also be a result of the acidic environment of the secondary lysosome, which is a topic that will be discussed later. Although most studies have shown that a positive surface charge can improve the internalization of NPs by MSCs, Chung et al 61 reported that for hMSCs, the cellular uptake of mesoporous silica nanoparticles (MSNs) is so highly efficient that an improvement of labeling efficiency induced by the surface charge was only evident for the highly positively charged MSNs. Lorenz et al 24 demonstrated that there is no clear correlation between the amount of surface charge and the uptake of the particles by MSCs. They speculated that the high amount of pseudopodia in the MSCs and other factors regarding the preparation of the particles, such as particle size and amount of coagulation of the particles in the medium, influenced the amount of uptake or adherence. Furthermore, NPs with negative zeta potentials could also be incorporated into MSCs effectively. 28,31,44 Therefore, we can conclude that surface charge may play an important role in the internalization of NPs by MSCs; however, this is not the unique factor. Cell-penetrating peptides (CPPs) have the ability to insert into and cross biologic membranes, and this ability is the result of short sequences of less than 20 amino acids, which are highly rich in basic residues. After covalently linking CPPs to cargos, including macromolecular proteins and nanoparticulates, 43 these CPPs have been shown to be capable of translocating the attached cargos into all cell types in vitro and in vivo. Suh et al 39 reported on the membrane translocation capabilities of several non-toxic, arginine-rich peptides that are called low-molecular weight protamines (LMWPs), which were prepared by enzymatic digestion of natural protamine. 62 LMWPs can enhance the transduction of various types of compounds into cells, regardless of their physical and chemical attributes such as size and hydrophilicity. 63 Moreover, LMWPs were conjugated to iron oxide particles, which induced an efficient internalization of the SPIO NPs into MSCs. A L-CPP containing nine arginines was synthesized by Liu et al 42 Gadolinium modified by L-CPP was efficiently internalized into MSCs in a time- or concentrationdependent manner. We propose that short amphipathic peptide carriers, such as MPG and PEP, could be an alternative to covalent strategies for the delivery of anticancer drug-loaded NPs into MSCs. MPG and PEP have been successfully used for the delivery of various biologically active cargoes both ex vivo and in vivo in several animal models. 64,65 These types of small amphipathic peptides are able to form stable NPs with the cargo and enter the cell independently of the endosomal pathway, thus allowing the controlled release of the cargo into the cytoplasm. Furthermore, the formation of stable NPs with the cargos does not require any cross-linking or chemical modification, which is helpful for maintaining the activity of drugs.

176

Table 1 Methods to improve NP uptake Modifying material

Preparation of NPs

Size of NPs

Zeta potential

Important findings

Poly(DL-lactic acid-co-α, β-malic acid)(PLMA)

Fluorescein isothiocyanate (FITC)

Traditional solvent evaporation procedure

10-20 nm

−34.5 mV

Poly lactide-co-glycolic acid (PLGA)

Poly (ethyleneimine) (PEI)

82 nm

Negative surface charge was changed to positive with PEI coating

PLGA

Poly-L-lysine (PLL)

Water-in-oil-in-water solvent evaporation technique for PLGA-NPs; physical adsorption for PEI-PLGA-NPs/DNA complexes Single emulsion encapsulation technique

1. Time and concentration-dependent uptake 2. The adsorption process can ascribe to the combined effects of the surface negative charge and hydrophobicity 28 Time and concentration-dependent uptake 29

Lipophilic Labrafac®CC; Lipoïd® S75-3 Lipophilic Labrafac®CC; Lipoïd® S75-3 Poly-lactic acid

Solutol®HS15

Phase inversion temperature method

88 ± 2 nm; PDI: 0.060

−3.7 ± 0.9 mV

Solutol®HS15

Phase inversion temperature method

76 ± 2 nm; PDI: 0.1

Slightly negative

Polyvinyl alcohol

Single emulsion solvent evaporation technique

136 ± 1 nm, PDI: 0.040

−2.11 ± 0.2 mV

Electrostatic adsorption

DLS:120 nm; SEM: 60 nm

Complex coacervation technique PEI/CS NPs: emulsion polymerization; pDNA and CS/PEI complex: electrostatic adsorption Physical adsorption

Less than 100 nm

N,N,N-trimethyl chitosan chloride (TMC) Chitosan (acid soluble) Chitosan (acid soluble)

PEI

PEG blocked PLL (PLL-b-PEG) SPIO nanoparticles

N-alkyl-PEI2k

Electrostatic adsorption

1–2 μm

DSL: 129-162 nm; SEM: 182-224 nm; PDI: 1.17-1.25

+22.0 to 30.5 mV

240.2 ± 4.6 nm

+22.5 ± 2.2 mV

DLS: 54.7 ± 9.5 nm; AFM: 65 ± 17.2 nm

Approximately +40 mV

The internalization was increased by modifying the surface with a positive charge or with an antibody directed toward an MSC surface antigen 30 Time and concentration-dependent cell uptake 31 Cellular vehicles and NPs can be combined to treat brain tumors 32 Time and concentration-dependent cell uptake 31 Satisfied transfection efficiency 33 Unsatisfied transfection efficiency 34 Satisfied transfection efficiency 35

Satisfied transfection efficiency at an optimal PEG seeding density 36 1. The vitality of labeled MSCs is unaffected 2. Time and dose-dependent cell uptake 37

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184

Material

Silica nanoparticles SPIO

112 ± 8 nm 26.77 ± 0.42 nm

Coated the MNPs with a silica shell

Approximately 50 nm

Emulsifying wax

Brij 78

138.09 ± 6.90 nm

Gadolinium

Cell penetrating peptides (L-CPP) Tat peptide (CRRRQRRKKRG)

Oil-in-water microemulsion technique. CPPs was conjugated to gadolinium by DTPA Tat peptide was conjugated to nanosensor by sulfo-SMCC

miniemulsion polymerization

210 nm; PDI: 0.09

−18.5 mV

Electrostatic adsorption

115–180 nm

+10 to 20 mV

Polyacrylamide nanosensors

Phosphonate functionalized polystyrene NPs PAMAM dendrimer (generation 5)

Hydrophobic alkyl chains

PAMAM dendrimer (generation 4)

Lycium barbarum polysaccharides (cLBP)

Cationized pullulan derivatives

+3.8 ± 1.1 mV

DLS: 45 nm

QDs: −19.3 mV; PAMAM dendrimer-QDs +2.76 mV

Electrostatic adsorption

Ethylenediamine (Ed)

SPIO:−51.54 ± 2.68; LMWP-SPIO: +16.97 ± 0.05

Electrostatic adsorption

190 nm

Conventional co-precipitation

The size and zeta potential were changed by altering the mixing molar ratio of pullulan OH groups to ferric ions and the mixing percentage of pullulan derivatives, respectively.

+11 mV

Enhanced cell uptake 38 Enhanced internalization of the SPIO NPs 39 MNPs@SiO2 (RITC) can efficiently label MSCs within 3 h, and MNPs@SiO2(RITC) do not enter the nucleus 40 Satisfied cellular uptake efficiency 41 Concentration and time dependent cell uptake 42 There will be an overload limit, which when breached, will cause severe physical perturbation to the cells 43 A promising basis for the development of NPs with high intracellular uptake rates for drug delivery or cell labeling 44 The advantage of the cationic nature of the dendrimer was joined with the capacity of lipids to interact with biologic membranes 45 1. Enhanced cellular uptake and endosomal escape of QDs 2. Concentration- and time-dependent cell uptake 46 Ed-LBP NPs exhibited an improved transfection efficiency compared with spermine-LBP and PEI-LBP NPs 47 Small size and positive charge iron oxide-pullulan NPs were more susceptible to cell internalization 48

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184

Electrostatic adsorption LMWP was conjugated to SPIO

Magnetic nanoparticles

PEI Low-molecular weight protamine (LMWP) Silica

177

178

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184

Figure 1. Internalization of anticancer drug-loaded CS-PLGA-NPs.

The importance of size is obvious for effective cellular uptake, and smaller NPs were more susceptible to internalization by MSCs if the surface charge is similar. 48 It has been reported that a size of less than 100 nm is required for polycation-DNA gene delivery systems, which mostly enter the cell by endocytosis or pinocytosis. 66,67 It is worth noting that although nano-sized particles will be readily internalized by MSCs as mentioned above, small particles (less than 1 μm) were rapidly exocytosed in other cell types unless they were conjugated to the cell membrane. 68-70 Because the exocytosis of NPs will result in failure of this cell vehicle-based targeted drug delivery, further research in this field is needed. Studies have shown that the process of NP uptake in MSCs displays a time- and dose-dependent behavior. 30,31,37 Modifying the surface of the NP with an antibody directed toward an MSC surface antigen (eg, CD90) could also increase the kinetics of internalization. 30 Horák et al believed that NP uptake is related to cell expansion and proliferation. 71 The highest uptake efficiency was obtained between the second and fourth passages when the cells were growing and expanding rapidly. At the fifth passage, cell growth and expansion were not as robust nor was the NP uptake. Endosomal escape Because NPs are usually transported to the endo-lysosomal system after internalization and destroyed, endosomal escape is vital in keeping the integrity and sustained release ability of the NPs. The polyamidoamine (PAMAM) dendrimer has a sufficient cationic charge, which can promote cellular uptake though electrostatic interactions. 46 In addition, it is more important that the PAMAM dendrimer has a strong pH-buffering capacity that can enhance proton absorption in acidic organelles and buildup of osmotic pressure across the organelle membrane. These processes can promote endosomal escape and release into the cytoplasm. 72,73 Similarly, the surface charge of PLGA or PLA-

NPs would change from anionic to cationic in the acidic environment of the secondary lysosome and initiate a local interaction between NPs and the endosomal membrane that results in the escape of the NPs into the cytoplasm. 68,74 In this case, NPs composed mainly of CS are destroyed in the secondary lysosome because of the dissolution of CS and lose their ability to sustain the release of the drug. Meanwhile, modifying the surface of the NPs (such as in the case of PLGA-NPs) with CS is still a reasonable method to improve uptake, as mentioned above. The lysosomotropic property of the hydroxystearate-PEG of the Solutol, which constitutes the most external phase of the LNCs, may play an important role in the endosomal escape of LNCs. 75 Maintaining the vitality of MSCs after NP uptake Another challenge is how to maintain the vitality of the MSCs, especially their tumor migratory properties after the internalization of anticancer drug-loaded NPs. Studies have shown that MSCs are sensitive to various types of anticancer drugs, especially a panel of cytotoxic agents, such as paclitaxel, vincristine, etoposide, cytarabine topotecan, cisplatin, and daunorubicin. 76-79 With the uptake of NPs, the total drug amount and its local concentration in the plasma of the MSCs increase dramatically, which could cause the death of or induce apoptosis in the MSCs. This principle has already been applied to reverse the multidrug resistance (MDR) of cancer cells. It should be possible to choose chemotherapeutic agents that human MSCs are resistant to, such as busulphan and methotrexate. 76 Meanwhile, novel effectual strategies should be used for cytotoxic agents, which are widely used and have good clinical activities in the treatment of cancer. Isolating a new subpopulation of MSCs Several subpopulations of BMSCs with distinct features have been reported. These subpopulations include multipotent adult

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184

179

Figure 2. Anticancer drug-loaded NP-MDR-MSC delivery system.

progenitor cells (MAPCs), 80,81 marrow-isolated adult multilineage inducible (MIAMI) cells 82 and very small embryoniclike (VSEL) stem cells. 83 MIAMI cells were isolated by differential adhesion of iliac crest aspirate from human donors and amplified using particular culture conditions such as low oxygen tension (3%), which mimics the MSCs niche. 82,84 MIAMI cells were originally used in adult cell therapy of the nervous system. 85-87 Recently, Roger and his colleagues 32 used MIAMI cells as a vehicle for loading with LNCs containing an organometallic and cytotoxic complex (ferrociphenol or Fc-diOH) to treat brain tumors. They demonstrated that MIAMI cells internalized Fc-diOH-LNCs, which did not affect the viability of MIAMI cells. Meanwhile, Fc-diOH-LNC-loaded MIAMI cells had cytotoxic effects on U87MG glioma cells not only in vitro but also in vivo by intratumoral injection of the Fc-diOH-LNC-loaded MIAMI cells into a heterotopic U87MG glioma model in nude mice. Roger and his colleagues 32 concluded that MIAMI cells could be promising drug-loaded LNC carriers for the treatment of brain tumors. To develop MIAMI as a delivery platform for anticancer-loaded NPs, more model drugs should be evaluated, and the mechanism of resistance of the MIAMI cells to the cytotoxic agents should be studied in depth. Modifying MSCs and controlling the release profile of drug-loaded NPs Multidrug resistance 1 (MDR1) gene therapy has been applied increasingly often to protect normal cells from the toxic effects of anticancer drugs in high-dose chemotherapy (HDCT). 88-93 Recently, MSCs were also transduced with the MDR1 gene, which encodes plasma membrane P-glycoprotein (P-gp) and enhances the resistance of MSCs to chemotherapeutic agents. 94-96 In our laboratory, various anticancer drug-loaded NPs were internalized into MDR1-modified MSCs (Figure 2). 97

P-gp consists of two transmembrane domains and two ATPbinding domains and can release various drugs such as anthracyclines, vinca alkaloids, and taxanes from cells in an ATP-dependent manner. 98 This process was considered to be responsible for the multidrug resistance of MDR, whereby cancer cells became resistant to the cytotoxic effects of various structurally and mechanistically unrelated chemotherapeutic agents. 99 Thus, MDR is a major problem in the clinical treatment of cancer. To circumvent this problem, NPs have been used in the past decade to increase the local drug concentrations in cancer cell plasma and to reverse MDR as mentioned above. However, contradictory results were obtained from different studies. For example, Sahoo and Labhasetwar's research 100 demonstrated that P-gp−mediated MDR could be overcome by encapsulating anticancer drugs such as paclitaxel in transferrinconjugated PLGA-NPs. Meanwhile, another study suggested that PLGA-NPs do not enhance the therapeutic efficacy of paclitaxel in MDR tumor cells. 101 When comparing these two studies, we found that the authors used the same technique to prepare the NPs (emulsion-solvent evaporation) and same conditions to study the in vitro release of NPs. The difference between the two studies was that the latter study used a higher molecular weight polymer (∼40,000 Da) compared with the former study (23,000 Da). This difference resulted in the observed slower release of paclitaxel during the early time points, which was no more than 10% in the first 10 days for the latter study and with 30% cumulative drug release occurring in the first week. 102 Because of the initial lag period in the paclitaxel release, the PLGA nanoparticles did not enhance the therapeutic efficacy of paclitaxel in the MDR cancer cells because the drug delivered into the cytoplasm was actively effluxed by P-gp. Although we are discussing the interaction between the NPs and the MDR cancer cells, the condition is similar to that for the NPs and the MDR-MSCs. Therefore, we can infer that the balance between the amount of drugs released

180

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184

by the NPs and effluxed by P-gp of the MSCs was vital in maintaining the vitality of MSCs. In other words, we can achieve this goal through varying the expression of P-gp using different transfection efficiencies of MDR1 and adjusting the release profile of NPs using various types and molecular weight NP materials and by different preparation methods. Although we have previously adopted MDR1 gene-transfected MSCs to carry anticancer drug-loaded NPs and constructed a preliminary tumor targeting drug delivery system, intensive studies should be performed in the future to optimize this technique and to find safer transfecting vectors. Targeting tumors in vivo Although the inherent tumor tropism migratory properties have been extensively studied and reviewed, the dynamics of MSCs in vivo still remain ambiguous. However, the knowledge of the dynamics of MSCs in vivo, especially in patients with cancer, is crucial in developing an effective and feasible targeted drug delivery system. Relationship between the administration route and MSC targeting According to the current reports, the dynamics of the MSCs are closely related to the administration routes. Intravenous (iv) administration is the most convenient route for cell delivery. Studeny et al 19 demonstrated that MSCs were randomly distributed in the lung parenchyma and tumor nodules of mice with established A375SM melanomas in the lungs 1 day after iv administration (through the tail vein). However, after 8 days, MSCs were found mainly in the tumors and had been cleared from normal lungs. Similarly, MSCs were detected in tumors but not in the lung parenchyma 60 days after injection. The percentage of MSCs in tumors was stable during the experiment (day 1, 3% ± 2%; day 8, 11% ± 2%; and day 60, 5% ± 1%). The percentage of MSC-derived cells in the lung tumors in this study was determined as the number of AS02-positive cells to all nuclei counterstained with Gill's hematoxylin per field (×100). Kidd et al 103 demonstrated that human MSCs (hMSCs) systemically delivered to non-tumor−bearing animals initially reside in the lungs and then egress to the liver and spleen and then gradually decrease. In syngeneic and xenogeneic breast carcinoma-bearing mice, the systemically delivered MSCs revealed persistent, specific colocalization with sites of tumor development. This pattern of tropism was also observed in an ovarian tumor model in which the MSCs were intraperitoneally (ip) injected. Albarenque et al 27 reported that after iv administration, between 2% and ~ 5% of the cells (the number in the tumor tissue to the total number of MSCs injected) were found in the tumor masses. The number of MSCs in tumor tissue sections contributing to the cellular density of the tumor was almost the same as in the bone marrow and lymph nodes. Furthermore, it should be noted that during the initial period of iv administration, the majority of MSCs were reported to be filtered by the lung, and only rare hMSCs were integrated into the tumor (at least when examined 6-7 days after injection), 15,103 which might result in a low targeting efficiency for the NP-MSC system and toxicity toward non-targeted tissues. Although, the intratu-

moral (it) injection of the MSCs was recently adopted by several studies 31,32,104 and satisfying results were obtained, the extensive use of this administration route may be limited by the special microenvironment of solid tumors, which is characterized by interstitial hypertension. 8 Intravascular delivery has the advantage of obviating invasive surgical interventions and because repeated injections over an extended period are clinically feasible. Because hMSC-based intravascular delivery is disseminated within tumors, rather than being focused at a single site as with local injection, the smaller dose delivered by hMSCs was sufficient to produce a therapeutic effect comparable with it injection. Several studies have validated this administration route. 15,104,105 Yong et al 105 found that hMSCs can be located within tumor vessels within 1 hour after intravascular injection. The hMSCs were found in clusters until the second day, after which they were dispersed throughout the tumor. These results suggested that hMSCs were localized to the gliomas via the vasculature and then migrated into the tumor parenchyma. Other targeting strategies Magnetic targeting for tumors, which is a traditional strategy used in chemotherapy, was recently introduced to localize magnetic NP-loaded cell delivery to target lesions in vivo. 106-109 However, its applications are limited by magnetic attenuation in the deep magnetic capture of cells for spatial targeting therapeutics. Recently, Huang et al 110 designed a magnetic pole in which the magnetic field density can be focused at a certain distance from the pole. The magnetic NP-loaded MSCs were highly enriched at the site distant from the magnetic pole. This technique may be particularly important for the iv administration of MSCs, the most convenient route of cell delivery, and the combination of this technique with anticancer drug-loaded NP-MSCs could be a promising and valuable method of targeted delivery. It has been reported that local irradiation may enhance the migration and engraftment specificity of MSCs. 111 These findings could be explained by the general stem cell tropism for injured tissues, and they may enhance the potential synergism between radiotherapy and tumor specific NP-MSC targeting. Extensive studies have shown that the migration of MSCs is dependent on the different types of cytokine/receptor pairs, such as SDF-1/CXCR4, SCF-c-Kit, HGF/c-Met, VEGF/VEGFR, PDGF/PDGFr, MCP-1/CCR2, and HMGB1/RAGE. 112 The adjustment of certain types of cytokines or receptors, such as the overexpression of CXCR1, 113 could be a useful tool for achieving a sufficient quantity of therapeutic MSCs in tumor tissues. This technique may be another potential candidate to enhance the targeting of NP-MSCs. Future perspectives At the present, few studies has been reported about the pharmacokinetics of anticancer drug-loaded NP-MSCs, especially the local pharmacokinetics of this system in tumor tissues, which is extremely important in developing this drug delivery system and determining the dosing interval. According to our knowledge, the main impediment might be that it is difficult to

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184

181

Figure 3. Study of the local PK of anticancer drug-loaded NP-MSCs in tumors using the microdialysis technique.

distinguish drugs outside of the MSCs (released from MSCs) from those inside MSCs. With the traditional sample technique, the tumor drug concentration is investigated via the analysis of the tumor homogenate, which can be vulnerable to artifacts because of inadvertent measurements of intravascular drugs and drugs in the MSCs. However, the free drug concentration in the extracellular fluid (ECF) of the tumor is responsible for the outcome of patients or animals with the tumor. The reasonable solution to this problem may be the microdialysis technique (Figure 3), which is clinically feasible, increasingly cost efficient and reliable for assessing tumor pharmacokinetic (PK) data in preclinical and clinical settings. 114 Studies in this field are currently being conducted in our laboratory. Another difficult problem is that MSCs are a “double-edged sword” in their interaction with tumors. 27,115-119 Extensive studies should be carried out to evaluate the fate of MSCs in various types of cancer, and the safety of MSCs should be established. In addition, we can control their fate by selectively eradicating MSCs when malignant transformation is suspected by incorporating cellular suicide genes into MSCs or by constructing NPs with a retarded release profile. 111 The retarded release of NPs will result in NPs initially releasing little or no drugs so that the vitality of the MSCs will not be affected before they have targeted to tumor tissues. Meanwhile, NPs will later release the drugs relatively fast and kill the MSCs as well as tumor cells after the MSCs have accomplished their mission as a targeting cell vehicle. In this case, appropriate materials and techniques should be developed, and the environment of the MSCs plasma and ECF of the tumor should be further studied. As a result, it may take a long time to develop ideal anticancer drug-loaded NP-MSCs.

References 1. Jemal A, Siegel R, Xu J, Ward E. Cancer statistics, 2010. CA Cancer J Clin 2010;60:277-300. 2. Allen TM, Cullis PR. Drug delivery systems: entering the mainstream. Science 2004;303:1818-22. 3. Torchilin VP. Micellar nanocarriers: pharmaceutical perspectives. Pharm Res 2007;24:1-16. 4. Cukierman E, Khan DR. The benefits and challenges associated with the use of drug delivery systems in cancer therapy. Biochem Pharmacol 2010;80:762-70. 5. Gabizon AA. Stealth liposomes and tumor targeting: one step further in the quest for the magic bullet. Clin Cancer Res 2001;7:223-5. 6. Bedu-Addo FK, Tang P, Xu Y, Huang L. Effects of polyethyleneglycol chain length and phospholipid acyl chain composition on the interaction of polyethyleneglycol-phospholipid conjugates with phospholipid: implications in liposomal drug delivery. Pharm Res 1996;13:710-7. 7. Photos PJ, Bacakova L, Discher B, Bates F, Discher DE. Polymer vesicles in vivo: correlations with PEG molecular weight. J Control Release 2003;90:323-34. 8. Fukumura D, Jain RK. Tumor microvasculature and microenvironment: targets for anti-angiogenesis and normalization. Microvasc Res 2007;74:72-84. 9. Danhier F, Feron O, Preat V. To exploit the tumor microenvironment: Passive and active tumor targeting of nanocarriers for anti-cancer drug delivery. J Control Release 2010;148:135-46. 10. Roby A, Erdogan S, Torchilin VP. Enhanced in vivo antitumor efficacy of poorly soluble PDT agent, meso-tetraphenylporphine, in PEG-PEbased tumor-targeted immunomicelles. Cancer Biol Ther 2007;6:1136-42. 11. Matsumura Y, Gotoh M, Muro K, Yamada Y, Shirao K, Shimada Y, et al. Phase I and pharmacokinetic study of MCC-465, a doxorubicin (DXR) encapsulated in PEG immunoliposome, in patients with metastatic stomach cancer. Ann Oncol 2004;15:517-25.

182

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184

12. Hatakeyama H, Akita H, Kogure K, Oishi M, Nagasaki Y, Kihira Y, et al. Development of a novel systemic gene delivery system for cancer therapy with a tumor-specific cleavable PEG-lipid. Gene Ther 2007;14:68-77. 13. Gabizon AA. Pegylated liposomal doxorubicin: metamorphosis of an old drug into a new form of chemotherapy. Cancer Invest 2001;19: 424-36. 14. Shah K. Mesenchymal stem cells engineered for cancer therapy. Adv Drug Deliv Rev 2012;64:739-48. 15. Nakamizo A, Marini F, Amano T, Khan A, Studeny M, Gumin J, et al. Human bone marrow-derived mesenchymal stem cells in the treatment of gliomas. Cancer Res 2005;65:3307-18. 16. Studeny M, Marini FC, Dembinski JL, Zompetta C, Cabreira-Hansen M, Bekele BN, et al. Mesenchymal stem cells: potential precursors for tumor stroma and targeted-delivery vehicles for anticancer agents. J Natl Cancer Inst 2004;96:1593-603. 17. Loebinger MR, Eddaoudi A, Davies D, Janes SM. Mesenchymal stem cell delivery of TRAIL can eliminate metastatic cancer. Cancer Res 2009;69:4134-42. 18. Sasportas LS, Kasmieh R, Wakimoto H, Hingtgen S, van de Water JA, Mohapatra G, et al. Assessment of therapeutic efficacy and fate of engineered human mesenchymal stem cells for cancer therapy. Proc Natl Acad Sci U S A 2009;106:4822-7. 19. Studeny M, Marini FC, Champlin RE, Zompetta C, Fidler IJ, Andreeff M. Bone marrow-derived mesenchymal stem cells as vehicles for interferon-beta delivery into tumors. Cancer Res 2002;62:3603-8. 20. Porada CD, Almeida-Porada G. Mesenchymal stem cells as therapeutics and vehicles for gene and drug delivery. Adv Drug Deliv Rev 2010;62:1156-66. 21. Hu YL, Fu YH, Tabata Y, Gao JQ. Mesenchymal stem cells: a promising targeted-delivery vehicle in cancer gene therapy. J Control Release 2010;147:154-62. 22. Banerji SK, Hayes MA. Examination of nonendocytotic bulk transport of nanoparticles across phospholipid membranes. Langmuir 2007;23:3305-13. 23. Schulze E, Ferrucci JT, Poss K, Lapointe L, Bogdanova A, Weissleder R. Cellular uptake and trafficking of a prototypical magnetic iron oxide label in vitro. Invest Radiol 1995;30:604-10. 24. Lorenz MR, Holzapfel V, Musyanovych A, Nothelfer K, Walther P, Frank H, et al. Uptake of functionalized, fluorescent-labeled polymeric particles in different cell lines and stem cells. Biomaterials 2006;27:2820-8. 25. Rejman J, Oberle V, Zuhorn I, Hoekstra D. Size-dependent internalization of particles via the pathways of clathrin- and caveolae-mediated endocytosis. Biochem J 2004;377:159-69. 26. Conner SD, Schmid SL. Regulated portals of entry into the cell. Nature 2003;422:37-44. 27. Albarenque SM, Zwacka RM, Mohr A. Both human and mouse mesenchymal stem cells promote breast cancer metastasis. Stem Cell Res 2011;7:163-71. 28. Wang L, Neoh KG, Kang ET, Shuter B, Wang SC. Biodegradable magnetic-fluorescent magnetite/poly(dl-lactic acid-co-alpha, betamalic acid) composite nanoparticles for stem cell labeling. Biomaterials 2010;31:3502-11. 29. Kim JH, Park JS, Yang HN, Woo DG, Jeon SY, Do HJ, et al. The use of biodegradable PLGA nanoparticles to mediate SOX9 gene delivery in human mesenchymal stem cells (hMSCs) and induce chondrogenesis. Biomaterials 2011;32:268-78. 30. Sarkar D, Ankrum JA, Teo G, Carman CV, Karp JM. Cellular and extracellular programming of cell fate through engineered intracrine-, paracrine-, and endocrine-like mechanisms. Biomaterials 2011;32: 3053-61. 31. Roger M, Clavreul A, Venier-Julienne MC, Passirani C, Sindji L, Schiller P, et al. Mesenchymal stem cells as cellular vehicles for delivery of nanoparticles to brain tumors. Biomaterials 2010;31: 8393-401.

32. Roger M, Clavreul A, Huynh NT, Passirani C, Schiller P, Vessieres A, et al. Ferrociphenol lipid nanocapsule delivery by mesenchymal stromal cells in brain tumor therapy. Int J Pharm 2012;423:63-8. 33. Wang W, Li B, Li Y, Jiang Y, Ouyang H, Gao C. In vivo restoration of full-thickness cartilage defects by poly(lactide-co-glycolide) sponges filled with fibrin gel, bone marrow mesenchymal stem cells and DNA complexes. Biomaterials 2010;31:5953-65. 34. Corsi K, Chellat F, Yahia L, Fernandes JC. Mesenchymal stem cells, MG63 and HEK293 transfection using chitosan-DNA nanoparticles. Biomaterials 2003;24:1255-64. 35. Pimpha N, Sunintaboon P, Inphonlek S, Tabata Y. Gene delivery efficacy of polyethyleneimine-introduced chitosan shell/poly(methyl methacrylate) core nanoparticles for rat mesenchymal stem cells. J Biomater Sci Polym Ed 2010;21:205-23. 36. Park JW, Mok H, Park TG. Physical adsorption of PEG grafted and blocked poly-L-lysine copolymers on adenovirus surface for enhanced gene transduction. J Control Release 2010;142:238-44. 37. Liu G, Wang Z, Lu J, Xia C, Gao F, Gong Q, et al. Low molecular weight alkyl-polycation wrapped magnetite nanoparticle clusters as MRI probes for stem cell labeling and in vivo imaging. Biomaterials 2011;32:528-37. 38. Park JS, Na K, Woo DG, Yang HN, Kim JM, Kim JH, et al. Non-viral gene delivery of DNA polyplexed with nanoparticles transfected into human mesenchymal stem cells. Biomaterials 2010;31:124-32. 39. Suh JS, Lee JY, Choi YS, Yu F, Yang V, Lee SJ, et al. Efficient labeling of mesenchymal stem cells using cell permeable magnetic nanoparticles. Biochem Biophys Res Commun 2009;379:669-75. 40. Park KS, Tae J, Choi B, Kim YS, Moon C, Kim SH, et al. Characterization, in vitro cytotoxicity assessment, and in vivo visualization of multimodal, RITC-labeled, silica-coated magnetic nanoparticles for labeling human cord blood-derived mesenchymal stem cells. Nanomedicine 2010;6:263-76. 41. Tseng CL, Shih IL, Stobinski L, Lin FH. Gadolinium hexanedione nanoparticles for stem cell labeling and tracking via magnetic resonance imaging. Biomaterials 2010;31:5427-35. 42. Liu M, Guo YM, Wu QF, Yang JL, Wang P, Wang SC, et al. Paramagnetic particles carried by cell-penetrating peptide tracking of bone marrow mesenchymal stem cells, a research in vitro. Biochem Biophys Res Commun 2006;347:133-40. 43. Coupland PG, Fisher KA, Jones DR, Aylott JW. Internalisation of polymeric nanosensors in mesenchymal stem cells: analysis by flow cytometry and confocal microscopy. J Control Release 2008;130: 115-20. 44. Tautzenberger A, Lorenz S, Kreja L, Zeller A, Musyanovych A, Schrezenmeier H, et al. Effect of functionalised fluorescence-labelled nanoparticles on mesenchymal stem cell differentiation. Biomaterials 2010;31:2064-71. 45. Santos JL, Oliveira H, Pandita D, Rodrigues J, Pego AP, Granja PL, et al. Functionalization of poly(amidoamine) dendrimers with hydrophobic chains for improved gene delivery in mesenchymal stem cells. J Control Release 2010;144:55-64. 46. Higuchi Y, Wu C, Chang KL, Irie K, Kawakami S, Yamashita F, et al. Polyamidoamine dendrimer-conjugated quantum dots for efficient labeling of primary cultured mesenchymal stem cells. Biomaterials 2011;32:6676-82. 47. Wang M, Deng WW, Fu M, Cao X, Yang Y, Su WY, et al. Efficient gene transfer into rat mesenchymal stem cells with cationized Lycium barbarum polysaccharides nanoparticles. Carbohydrate Polymers 2011;86:1509-18. 48. Jo J, Aoki I, Tabata Y. Design of iron oxide nanoparticles with different sizes and surface charges for simple and efficient labeling of mesenchymal stem cells. J Control Release 2010;142:465-73. 49. Yang HN, Park JS, Woo DG, Jeon SY, Do HJ, Lim HY, et al. C/EBPalpha and C/EBP-beta-mediated adipogenesis of human mesenchymal stem cells (hMSCs) using PLGA nanoparticles complexed with poly(ethyleneimmine). Biomaterials 2011;32:5924-33.

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184 50. Park JS, Yang HN, Woo DG, Jeon SY, Do HJ, Lim HY, et al. Chondrogenesis of human mesenchymal stem cells mediated by the combination of SOX trio SOX5, 6, and 9 genes complexed with PEImodified PLGA nanoparticles. Biomaterials 2011;32:3679-88. 51. Wu GY, Wu CH. Receptor-mediated in vitro gene transformation by a soluble DNA carrier system. J Biol Chem 1987;262:4429-32. 52. Han S, Mahato RI, Sung YK, Kim SW. Development of biomaterials for gene therapy. Mol Ther 2000;2:302-17. 53. Godbey WT, Wu KK, Mikos AG. Size matters: molecular weight affects the efficiency of poly(ethylenimine) as a gene delivery vehicle. J Biomed Mater Res 1999;45:268-75. 54. Pack DW, Hoffman AS, Pun S, Stayton PS. Design and development of polymers for gene delivery. Nat Rev Drug Discov 2005;4:581-93. 55. Mintzer MA, Simanek EE. Nonviral vectors for gene delivery. Chem Rev 2009;109:259-302. 56. Rao SB, Sharma CP. Use of chitosan as a biomaterial: studies on its safety and hemostatic potential. J Biomed Mater Res 1997;34:21-8. 57. Richardson SC, Kolbe HV, Duncan R. Potential of low molecular mass chitosan as a DNA delivery system: biocompatibility, body distribution and ability to complex and protect DNA. Int J Pharm 1999;178:231-43. 58. Fang N, Chan V, Mao HQ, Leong KW. Interactions of phospholipid bilayer with chitosan: effect of molecular weight and pH. Biomacromolecules 2001;2:1161-8. 59. Teijeiro-Osorio D, Remunan-Lopez C, Alonso MJ. Chitosan/cyclodextrin nanoparticles can efficiently transfect the airway epithelium in vitro. Eur J Pharm Biopharm 2009;71:257-63. 60. Klausner EA, Zhang Z, Chapman RL, Multack RF, Volin MV. Ultrapure chitosan oligomers as carriers for corneal gene transfer. Biomaterials 2010;31:1814-20. 61. Chung TH, Wu SH, Yao M, Lu CW, Lin YS, Hung Y, et al. The effect of surface charge on the uptake and biological function of mesoporous silica nanoparticles in 3T3-L1 cells and human mesenchymal stem cells. Biomaterials 2007;28:2959-66. 62. Chang LC, Lee HF, Yang Z, Yang VC. Low molecular weight protamine (LMWP) as nontoxic heparin/low molecular weight heparin antidote (I): preparation and characterization. AAPS PharmSci 2001;3: E17. 63. Park YJ, Chang LC, Liang JF, Moon C, Chung CP, Yang VC. Nontoxic membrane translocation peptide from protamine, low molecular weight protamine (LMWP), for enhanced intracellular protein delivery: in vitro and in vivo study. Faseb J 2005;19:1555-7. 64. Munoz-Morris MA, Heitz F, Divita G, Morris MC. The peptide carrier Pep-1 forms biologically efficient nanoparticle complexes. Biochem Biophys Res Commun 2007;355:877-82. 65. Morris MC, Robert-Hebmann V, Chaloin L, Mery J, Heitz F, Devaux C, et al. A new potent HIV-1 reverse transcriptase inhibitor. A synthetic peptide derived from the interface subunit domains. J Biol Chem 1999;274:24941-6. 66. De Smedt SC, Remaut K, Lucas B, Braeckmans K, Sanders NN, Demeester J. Studying biophysical barriers to DNA delivery by advanced light microscopy. Adv Drug Deliv Rev 2005;57:191-210. 67. Gao H, Shi W, Freund LB. Mechanics of receptor-mediated endocytosis. Proc Natl Acad Sci U S A 2005;102:9469-74. 68. Panyam J, Labhasetwar V. Dynamics of endocytosis and exocytosis of poly(D, L-lactide-co-glycolide) nanoparticles in vascular smooth muscle cells. Pharm Res 2003;20:212-20. 69. Jin H, Heller DA, Sharma R, Strano MS. Size-dependent cellular uptake and expulsion of single-walled carbon nanotubes: single particle tracking and a generic uptake model for nanoparticles. ACS Nano 2009;3:149-58. 70. Chithrani BD, Chan WC. Elucidating the mechanism of cellular uptake and removal of protein-coated gold nanoparticles of different sizes and shapes. Nano Lett 2007;7:1542-50. 71. Horák D, Babič M, Jendelová P, Herynek V, Trchová M, Likavčanová K, et al. Effect of different magnetic nanoparticle

72.

73.

74.

75.

76.

77.

78.

79.

80.

81.

82.

83.

84.

85.

86.

87.

88.

89.

183

coatings on the efficiency of stem cell labeling. J Magn Magn Mater 2009;321:1539-47. Akinc A, Thomas M, Klibanov AM, Langer R. Exploring polyethylenimine-mediated DNA transfection and the proton sponge hypothesis. J Gene Med 2005;7:657-63. Sonawane ND, Szoka FC, Verkman AS. Chloride accumulation and swelling in endosomes enhances DNA transfer by polyamine-DNA polyplexes. J Biol Chem 2003;278:44826-31. Panyam J, Zhou WZ, Prabha S, Sahoo SK, Labhasetwar V. Rapid endolysosomal escape of poly(DL-lactide-co-glycolide) nanoparticles: implications for drug and gene delivery. Faseb J 2002;16:1217-26. Paillard A, Hindre F, Vignes-Colombeix C, Benoit JP, Garcion E. The importance of endo-lysosomal escape with lipid nanocapsules for drug subcellular bioavailability. Biomaterials 2010;31:7542-54. Li J, Law HK, Lau YL, Chan GC. Differential damage and recovery of human mesenchymal stem cells after exposure to chemotherapeutic agents. Br J Haematol 2004;127:326-34. Cao J, Tan MH, Yang P, Li WL, Xia J, Du H, et al. Effects of adjuvant chemotherapy on bone marrow mesenchymal stem cells of colorectal cancer patients. Cancer Lett 2008;263:197-203. Kemp K, Morse R, Wexler S, Cox C, Mallam E, Hows J, et al. Chemotherapy-induced mesenchymal stem cell damage in patients with hematological malignancy. Ann Hematol 2010;89:701-13. Li J, Law HK, Liu YL, Chan GC. Effect of cisplatin, topotecan, daunorubicin and hydroxyurea on human mesenchymal stem cells. Zhongguo Shi Yan Xue Ye Xue Za Zhi 2010;18:991-6. Reyes M, Lund T, Lenvik T, Aguiar D, Koodie L, Verfaillie CM. Purification and ex vivo expansion of postnatal human marrow mesodermal progenitor cells. Blood 2001;98:2615-25. Jiang Y, Jahagirdar BN, Reinhardt RL, Schwartz RE, Keene CD, OrtizGonzalez XR, et al. Pluripotency of mesenchymal stem cells derived from adult marrow. Nature 2002;418:41-9. D'Ippolito G, Diabira S, Howard GA, Menei P, Roos BA, Schiller PC. Marrow-isolated adult multilineage inducible (MIAMI) cells, a unique population of postnatal young and old human cells with extensive expansion and differentiation potential. J Cell Sci 2004; 117:2971-81. Kucia M, Reca R, Campbell FR, Zuba-Surma E, Majka M, Ratajczak J, et al. A population of very small embryonic-like (VSEL) CXCR4(+) SSEA-1(+)Oct-4+ stem cells identified in adult bone marrow. Leukemia 2006;20:857-69. D'Ippolito G, Diabira S, Howard GA, Roos BA, Schiller PC. Low oxygen tension inhibits osteogenic differentiation and enhances stemness of human MIAMI cells. Bone 2006;39:513-22. Curtis KM, Gomez LA, Schiller PC. Rac1b regulates NT3-stimulated Mek-Erk signaling, directing marrow-isolated adult multilineage inducible (MIAMI) cells toward an early neuronal phenotype. Mol Cell Neurosci 2012;49:138-48. Delcroix GJ, Curtis KM, Schiller PC, Montero-Menei CN. EGF and bFGF pre-treatment enhances neural specification and the response to neuronal commitment of MIAMI cells. Differentiation 2010;80: 213-27. Delcroix GJ, Garbayo E, Sindji L, Thomas O, Vanpouille-Box C, Schiller PC, et al. The therapeutic potential of human multipotent mesenchymal stromal cells combined with pharmacologically active microcarriers transplanted in hemi-parkinsonian rats. Biomaterials 2011;32:1560-73. Cowan KH, Moscow JA, Huang H, Zujewski JA, O'Shaughnessy J, Sorrentino B, et al. Paclitaxel chemotherapy after autologous stem-cell transplantation and engraftment of hematopoietic cells transduced with a retrovirus containing the multidrug resistance complementary DNA (MDR1) in metastatic breast cancer patients. Clin Cancer Res 1999;5:1619-28. Hesdorffer C, Ayello J, Ward M, Kaubisch A, Vahdat L, Balmaceda C, et al. Phase I trial of retroviral-mediated transfer of the human MDR1 gene as marrow chemoprotection in patients undergoing high-dose

184

90.

91.

92.

93.

94.

95.

96.

97.

98. 99.

100.

101.

102.

103.

104.

Z. Gao et al / Nanomedicine: Nanotechnology, Biology, and Medicine 9 (2013) 174–184 chemotherapy and autologous stem-cell transplantation. J Clin Oncol 1998;16:165-72. Abonour R, Williams DA, Einhorn L, Hall KM, Chen J, Coffman J, et al. Efficient retrovirus-mediated transfer of the multidrug resistance 1 gene into autologous human long-term repopulating hematopoietic stem cells. Nat Med 2000;6:652-8. Mitsuhashi J, Hosoyama H, Tsukahara S, Katayama K, Noguchi K, Ito Y, et al. In vivo expansion of MDR1-transduced cells accompanied by a post-transplantation chemotherapy regimen with mitomycin C and methotrexate. J Gene Med 2010;12:596-603. Mitsuhashi J, Tsukahara S, Suzuki R, Oh-hara Y, Nishi S, Hosoyama H, et al. Retroviral integration site analysis and the fate of transduced clones in an MDR1 gene therapy protocol targeting metastatic breast cancer. Hum Gene Ther 2007;18:895-906. Takahashi S, Aiba K, Ito Y, Hatake K, Nakane M, Kobayashi T, et al. Pilot study of MDR1 gene transfer into hematopoietic stem cells and chemoprotection in metastatic breast cancer patients. Cancer Sci 2007;98:1609-16. Chen HL, Bai H. Transfection of gene mdr1 into human bone marrow mesenchymal stem cells by lentiviral vector. Zhongguo Shi Yan Xue Ye Xue Za Zhi 2009;17:690-4. Wang WB, Liu ZH, Zheng WP, Sun LY. Method to transfect the mesenchymal stem cells from placenta by retrovirus taking MDR1 gene. Chin J Lab Diagn 2008;12:857-9. Ye MZ, Han LY, Yue X, Li HL. The transfection of multidrug resistance gene into mesenchymal stem cells derived from human bone marrow reinforcing the resistance to chemotherapy. Chin J Lab Diagn 2007;11:10-2. Gao ZB, Xei YH, Su SW, Geng JN, Cao XY, Wang Q. A novel drug delivery system for anti-cancer drug loaded nanoparticles. CHN Patent No. 201110165034.2. Ambudkar SV, Kimchi-Sarfaty C, Sauna ZE, Gottesman MM. Pglycoprotein: from genomics to mechanism. Oncogene 2003;22:7468-85. Ho EA, Soo PL, Allen C, Piquette-Miller M. Impact of intraperitoneal, sustained delivery of paclitaxel on the expression of P-glycoprotein in ovarian tumors. J Control Release 2007;117:20-7. Sahoo SK, Labhasetwar V. Enhanced antiproliferative activity of transferrin-conjugated paclitaxel-loaded nanoparticles is mediated via sustained intracellular drug retention. Mol Pharm 2005;2:373-83. Chavanpatil MD, Patil Y, Panyam J. Susceptibility of nanoparticleencapsulated paclitaxel to P-glycoprotein-mediated drug efflux. Int J Pharm 2006;320:150-6. Sahoo SK, Ma W, Labhasetwar V. Efficacy of transferrin-conjugated paclitaxel-loaded nanoparticles in a murine model of prostate cancer. Int J Cancer 2004;112:335-40. Kidd S, Spaeth E, Dembinski JL, Dietrich M, Watson K, Klopp A, et al. Direct evidence of mesenchymal stem cell tropism for tumor and wounding microenvironments using in vivo bioluminescent imaging. Stem Cells 2009;27:2614-23. Seo SH, Kim KS, Park SH, Suh YS, Kim SJ, Jeun SS, et al. The effects of mesenchymal stem cells injected via different routes on modified IL12-mediated antitumor activity. Gene Ther 2011;18:488-95.

105. Yong RL, Shinojima N, Fueyo J, Gumin J, Vecil GG, Marini FC, et al. Human bone marrow-derived mesenchymal stem cells for intravascular delivery of oncolytic adenovirus Delta24-RGD to human gliomas. Cancer Res 2009;69:8932-40. 106. Polyak B, Fishbein I, Chorny M, Alferiev I, Williams D, Yellen B, et al. High field gradient targeting of magnetic nanoparticle-loaded endothelial cells to the surfaces of steel stents. Proc Natl Acad Sci U S A 2008;105:698-703. 107. Kim JA, Lee HJ, Kang HJ, Park TH. The targeting of endothelial progenitor cells to a specific location within a microfluidic channel using magnetic nanoparticles. Biomed Microdevices 2009;11:287-96. 108. Wilhelm C, Bal L, Smirnov P, Galy-Fauroux I, Clement O, Gazeau F, et al. Magnetic control of vascular network formation with magnetically labeled endothelial progenitor cells. Biomaterials 2007; 28:3797-806. 109. Kobayashi T, Ochi M, Yanada S, Ishikawa M, Adachi N, Deie M, et al. A novel cell delivery system using magnetically labeled mesenchymal stem cells and an external magnetic device for clinical cartilage repair. Arthroscopy 2008;24:69-76. 110. Huang Z, Pei N, Wang Y, Xie X, Sun A, Shen L, et al. Deep magnetic capture of magnetically loaded cells for spatially targeted therapeutics. Biomaterials 2010;31:2130-40. 111. Francois S, Bensidhoum M, Mouiseddine M, Mazurier C, Allenet B, Semont A, et al. Local irradiation not only induces homing of human mesenchymal stem cells at exposed sites but promotes their widespread engraftment to multiple organs: a study of their quantitative distribution after irradiation damage. Stem Cells 2006;24:1020-9. 112. Momin EN, Vela G, Zaidi HA. Quinones-Hinojosa a. the oncogenic potential of mesenchymal stem cells in the treatment of cancer: directions for future research. Curr Immunol Rev 2010;6:137-48. 113. Kim SM, Kim DS, Jeong CH, Kim DH, Kim JH, Jeon HB, et al. CXC chemokine receptor 1 enhances the ability of human umbilical cord blood-derived mesenchymal stem cells to migrate toward gliomas. Biochem Biophys Res Commun 2011;407:741-6. 114. Blakeley J, Portnow J. Microdialysis for assessing intratumoral drug disposition in brain cancers: a tool for rational drug development. Expert Opin Drug Metab Toxicol 2010;6:1477-91. 115. Dai LJ, Moniri MR, Zeng ZR, Zhou JX, Rayat J, Warnock GL. Potential implications of mesenchymal stem cells in cancer therapy. Cancer Lett 2011;305:8-20. 116. Lu YR, Yuan Y, Wang XJ, Wei LL, Chen YN, Cong C, et al. The growth inhibitory effect of mesenchymal stem cells on tumor cells in vitro and in vivo. Cancer Biol Ther 2008;7:245-51. 117. Nakamura K, Ito Y, Kawano Y, Kurozumi K, Kobune M, Tsuda H, et al. Antitumor effect of genetically engineered mesenchymal stem cells in a rat glioma model. Gene Ther 2004;11:1155-64. 118. Karnoub AE, Dash AB, Vo AP, Sullivan A, Brooks MW, Bell GW, et al. Mesenchymal stem cells within tumour stroma promote breast cancer metastasis. Nature 2007;449:557-63. 119. Xu WT, Bian ZY, Fan QM, Li G, Tang TT. Human mesenchymal stem cells (hMSCs) target osteosarcoma and promote its growth and pulmonary metastasis. Cancer Lett 2009;281:32-41.