- Email: [email protected]
Supramolecular Assemblies for Macrophage Activation in Cancer Therapy
TRECAN 305 No. of Pages 2
Spotlight
Supramolecular Assemblies for Macrophage Activation in Cancer Therapy Franklin Mejia,1 Tanyel Kiziltepe,1,2 and Basar Bilgicer1,2,3,4,* Recently, immunotherapy has emerged as a potential, possibly safer, alternative to more traditional chemotherapeutic treatments. Nevertheless, combating the tumor microenvironment (TME) and reactivating the immune system is not without complications. A recent report suggests a rationally designed supramolecular assembly to offer a solution to this problem. Recent advances in immuno-oncology have fueled the development of immunotherapies as a powerful tool in the battle against cancer. Under healthy physiological conditions, immune cells, such as macrophages, natural killer (NK), and CD8+ T cells, are programmed to clear pathogens and diseased self cells, including cancer cells. Nevertheless, the ability of the tumor to alter these mechanisms through immunomodulatory cytokines and receptors is now recognized as a hallmark of cancer [1,2]. One scenario that has garnered interest is that of tumor-associated macrophages (TAMs). While macrophages typically serve as early responders in the presence of pathogens, their accumulation in the TME has been associated with poor prognosis. This seemingly contradictory outcome is a consequence of macrophage polarization by cytokines released into the TME. Specifically, cancer cells secrete macrophage colony-stimulating factors (MCSF) that, upon interaction with receptors such as CSF-1R, promote the transition from an
M1 to an M2 macrophage phenotype. While M1 macrophages are proinflammatory and generally tumor suppressing, M2 macrophages promote immunosuppression, angiogenesis, and wound repair, resulting in a favorable environment for tumor progression [3]. Several strategies have been developed to combat the effects of TAMs on tumor progression. For instance, Zeisberger et al. [4] used clodronate-loaded liposomes to chemically deplete various macrophage subsets; however, depletion of macrophages in the spleen could limit applications of this strategy due to potential adverse effects. In another study, Georgoudaki et al. [5] inhibited tumor growth and reduced metastasis by using an antibody to target the MARCO receptor on suppressive TAMs, which enhanced immune checkpoint therapy. An immunization strategy was developed by Luo et al. [6] in the form of a legumainbased DNA vaccine that resulted in TAMs being cleared by a specific subset of CD8+ T cells. More recently, Weissleder et al. [7] promoted polarization towards the M1 phenotype by delivering resiquimod, an agonist for Toll-Like Receptors 7 and 8, using cyclodextrin nanoparticles. In a study by Kulkarni et al. published in Nature Biomedical Engineering [8], TAM polarization was tackled by developing a self-assembled supramolecule (termed anti-SIRPa–AK750) capable of redirecting macrophages from an M2 to an M1 subtype (Figure 1). To a limited extent, this had been previously achieved by CSF-1R inhibitors, such as BLZ945, which is currently in clinical trials [9]. The authors enhanced therapeutic efficacy of CSF1R inhibitor by incorporating it into the amphiphilic pharmacophore of a supramolecule they designed computationally. When mixed with co-lipids (SOPC and PEG-DSPE), the pharmacophore selfassembled into spherical nanoparticles
with a hydrodynamic diameter (Dh) of 175 nm. The authors reported that at 20% pharmacophore loading, the supramolecule achieved a sustained release that accelerated in a cell lysate, suggesting a reduction in off-target effects. The supramolecule was tested in vitro for its ability to inhibit CSF-1R signaling in naïve macrophages and polarized M2 macrophages. AK750 outperformed other clinically tested inhibitors, showing near-complete inhibition of CSF-1R phosphorylation, as well as other key proteins in macrophage function, such as the AKT-mTOR-P70S6K pathway. Importantly, markers of M1 populations, such as SOCS3/SOCS1 and iNOS/Arg-1 ratios, were highest in cells treated with AK750, suggesting that macrophages had been polarized towards the M1 subtype. Of note, the efficacy of AK750 was maintained for 72 h, further validating the importance of a sustained release. The supramolecule was further modified by conjugating an anti-SIRPa antibody on its surface for targeting macrophages. Additionally, this served the purpose of inhibiting SIRPa-CD47 interactions, which trigger a ‘do not eat me’ signal [8]. The drug:antibody ratio (DAR) was varied to maximize the phagocytosis of tumor cells, with maximum efficacy obtained at DAR 17 000. The efficacy of the design was confirmed in vivo by challenging AK750 in syngeneic melanoma and breast cancer models. Remarkably, the supramolecule resulted in an eightfold increase in drug accumulation in the tumor compared with the free drug, and significantly inhibited tumor growth compared with BLZ945 and an anti-CSF1 antibody after a single administration. In accordance with in vitro validation, analysis of the tumors revealed complete inhibition of pCSF-1R, a reduced M2 population, and an increase in the M1 macrophage population.
Trends in Cancer, Month Year, Vol. xx, No. yy
1
TRECAN 305 No. of Pages 2
An-SIRPα-AK750 Tumor
Phagocytosis M2
M1 repolarizaon
variability when manufactured on a large scale remain a challenge for nanomedicine. Nevertheless, we expect the simplicity of the design, its remarkable stability, and possibilities for ease of modifications to be beneficial for the translation of this therapy to the clinic. Thus, Kulkarni et al. have laid the foundation for a promising immunotherapy with the potential to be successful in treating a variety of cancers by effectively reprogramming the immune cells at the tumor site. These results highlight the potential of creative and rational nanomedicine design, which promises a positive impact on the treatment of cancers as well as of other diseases. 1 University of Notre Dame, Department of Chemical and Biomolecular Engineering, Notre Dame, IN, USA
M2 macrophage
Cancer cell
SIRPα
MCSF
CD47
M1 macrophage
An-SIRPα
2 Mike and Josie Harper Cancer Research Institute, Notre Dame, IN, USA 3 University of Notre Dame, Department of Chemistry and Biochemistry, Notre Dame, IN, USA 4 Advanced Diagnostics and Therapeutics Initiative, Notre Dame, IN, USA
*Correspondence: [email protected] (B. Bilgicer).
Figure 1. Schematic Illustrating the Repolarization of Tumor-Associated Macrophages (TAMs) by Anti-SIRPa–AK750 Treatment. In the tumor microenvironment (TME), macrophages are polarized to a proangiogenic M2 phenotype. Delivery of CSF-1R inhibitors and blockage of the CD47–SIRPa interaction resulted in the repolarization of TAMs to a proinflammatory M1 phenotype and inhibited tumor growth in syngeneic mouse tumor models.
valuable because previous reports comparing skin and lung cancer models suggested that the location of the tumor affects the origin and development of TAMs [10] and could require different lines of treatments for each scenario. Although no tests were performed with clinical samples, current understanding of the targeted receptors (SIRPa and CSF1R), as well as ongoing clinical trials on Success of this bifunctional therapy can similar therapies, suggests that the be attributed to the re-establishment of a described strategy can have a significant tumor-suppressing environment. The impact on cancer treatments. process is initiated by repolarization of TAMs and reactivation of their phagocy- Ultimately, the likelihood of clinical and totic capacities followed by increased commercial success of this immunotherrecruitment of CD4+ and CD8+ popula- apy will also depend on the ease of scaltions, which has been related to favorable ability of the manufacturing of these prognosis in the clinic [3]. Evaluation in supramolecular assemblies because partidifferent tumor models was particularly cle homogeneity and batch-to-batch However, whether immunotherapy by itself will be enough when translated to human cancers remains to be seen. Nevertheless, these results show that immunotherapy could improve treatment tolerance by minimizing the need for chemotherapeutic agents and could also reduce the number of required visits to treatment centers.
2
Trends in Cancer, Month Year, Vol. xx, No. yy
https://doi.org/10.1016/j.trecan.2018.09.008 References 1. Sengupta, S. (2017) Cancer nanomedicine: lessons for immuno-oncology. Trends Cancer 3, 551–559 2. Finn, O.J. (2012) Immuno-oncology: understanding the function and dysfunction of the immune system in cancer. Ann. Oncol. 23, viii6–viii9 3. Solinas, G. et al. (2009) Tumor-associated macrophages (TAM) as major players of the cancer-related inflammation. J. Leukoc. Biol. 86, 1065–1073 4. Zeisberger, S.M. et al. (2006) Clodronate-liposome-mediated depletion of tumour-associated macrophages: a new and highly effective antiangiogenic therapy approach. Br. J. Cancer 95, 272–281 5. Georgoudaki, A. et al. (2016) Reprogramming tumor-associated macrophages by antibody targeting inhibits cancer progression and metastasis. Cell Rep. 15, 2000–2011 6. Luo, Y. et al. (2006) Targeting tumor-associated macrophages as a novel strategy against breast cancer. J. Clin. Invest. 116, 2132–2141 7. Rodell, C.B. et al. (2018) TLR7/8-agonist-loaded nanoparticles promote the polarization of tumour-associated macrophages to enhance cancer immunotherapy. Nat. Biomed. Eng. 2, 578–588 8. Kulkarni, A. et al. (2018) A designer self-assembled supramolecule amplifies macrophage immune responses against aggressive cancer. Nat. Biomed. Eng. 2, 589–599 9. Cannarile, M.A. et al. (2017) Colony-stimulating factor 1 receptor (CSF1R) inhibitors in cancer therapy. J. Immunother. Cancer 5, 53 10. Lehmann, B. et al. (2017) Tumor location determines tissue-specific recruitment of tumor-associated macrophages and antibody-dependent immunotherapy response. Sci. Immunol. 2, eaah6413
Spotlight
Supramolecular Assemblies for Macrophage Activation in Cancer Therapy Franklin Mejia,1 Tanyel Kiziltepe,1,2 and Basar Bilgicer1,2,3,4,* Recently, immunotherapy has emerged as a potential, possibly safer, alternative to more traditional chemotherapeutic treatments. Nevertheless, combating the tumor microenvironment (TME) and reactivating the immune system is not without complications. A recent report suggests a rationally designed supramolecular assembly to offer a solution to this problem. Recent advances in immuno-oncology have fueled the development of immunotherapies as a powerful tool in the battle against cancer. Under healthy physiological conditions, immune cells, such as macrophages, natural killer (NK), and CD8+ T cells, are programmed to clear pathogens and diseased self cells, including cancer cells. Nevertheless, the ability of the tumor to alter these mechanisms through immunomodulatory cytokines and receptors is now recognized as a hallmark of cancer [1,2]. One scenario that has garnered interest is that of tumor-associated macrophages (TAMs). While macrophages typically serve as early responders in the presence of pathogens, their accumulation in the TME has been associated with poor prognosis. This seemingly contradictory outcome is a consequence of macrophage polarization by cytokines released into the TME. Specifically, cancer cells secrete macrophage colony-stimulating factors (MCSF) that, upon interaction with receptors such as CSF-1R, promote the transition from an
M1 to an M2 macrophage phenotype. While M1 macrophages are proinflammatory and generally tumor suppressing, M2 macrophages promote immunosuppression, angiogenesis, and wound repair, resulting in a favorable environment for tumor progression [3]. Several strategies have been developed to combat the effects of TAMs on tumor progression. For instance, Zeisberger et al. [4] used clodronate-loaded liposomes to chemically deplete various macrophage subsets; however, depletion of macrophages in the spleen could limit applications of this strategy due to potential adverse effects. In another study, Georgoudaki et al. [5] inhibited tumor growth and reduced metastasis by using an antibody to target the MARCO receptor on suppressive TAMs, which enhanced immune checkpoint therapy. An immunization strategy was developed by Luo et al. [6] in the form of a legumainbased DNA vaccine that resulted in TAMs being cleared by a specific subset of CD8+ T cells. More recently, Weissleder et al. [7] promoted polarization towards the M1 phenotype by delivering resiquimod, an agonist for Toll-Like Receptors 7 and 8, using cyclodextrin nanoparticles. In a study by Kulkarni et al. published in Nature Biomedical Engineering [8], TAM polarization was tackled by developing a self-assembled supramolecule (termed anti-SIRPa–AK750) capable of redirecting macrophages from an M2 to an M1 subtype (Figure 1). To a limited extent, this had been previously achieved by CSF-1R inhibitors, such as BLZ945, which is currently in clinical trials [9]. The authors enhanced therapeutic efficacy of CSF1R inhibitor by incorporating it into the amphiphilic pharmacophore of a supramolecule they designed computationally. When mixed with co-lipids (SOPC and PEG-DSPE), the pharmacophore selfassembled into spherical nanoparticles
with a hydrodynamic diameter (Dh) of 175 nm. The authors reported that at 20% pharmacophore loading, the supramolecule achieved a sustained release that accelerated in a cell lysate, suggesting a reduction in off-target effects. The supramolecule was tested in vitro for its ability to inhibit CSF-1R signaling in naïve macrophages and polarized M2 macrophages. AK750 outperformed other clinically tested inhibitors, showing near-complete inhibition of CSF-1R phosphorylation, as well as other key proteins in macrophage function, such as the AKT-mTOR-P70S6K pathway. Importantly, markers of M1 populations, such as SOCS3/SOCS1 and iNOS/Arg-1 ratios, were highest in cells treated with AK750, suggesting that macrophages had been polarized towards the M1 subtype. Of note, the efficacy of AK750 was maintained for 72 h, further validating the importance of a sustained release. The supramolecule was further modified by conjugating an anti-SIRPa antibody on its surface for targeting macrophages. Additionally, this served the purpose of inhibiting SIRPa-CD47 interactions, which trigger a ‘do not eat me’ signal [8]. The drug:antibody ratio (DAR) was varied to maximize the phagocytosis of tumor cells, with maximum efficacy obtained at DAR 17 000. The efficacy of the design was confirmed in vivo by challenging AK750 in syngeneic melanoma and breast cancer models. Remarkably, the supramolecule resulted in an eightfold increase in drug accumulation in the tumor compared with the free drug, and significantly inhibited tumor growth compared with BLZ945 and an anti-CSF1 antibody after a single administration. In accordance with in vitro validation, analysis of the tumors revealed complete inhibition of pCSF-1R, a reduced M2 population, and an increase in the M1 macrophage population.
Trends in Cancer, Month Year, Vol. xx, No. yy
1
TRECAN 305 No. of Pages 2
An-SIRPα-AK750 Tumor
Phagocytosis M2
M1 repolarizaon
variability when manufactured on a large scale remain a challenge for nanomedicine. Nevertheless, we expect the simplicity of the design, its remarkable stability, and possibilities for ease of modifications to be beneficial for the translation of this therapy to the clinic. Thus, Kulkarni et al. have laid the foundation for a promising immunotherapy with the potential to be successful in treating a variety of cancers by effectively reprogramming the immune cells at the tumor site. These results highlight the potential of creative and rational nanomedicine design, which promises a positive impact on the treatment of cancers as well as of other diseases. 1 University of Notre Dame, Department of Chemical and Biomolecular Engineering, Notre Dame, IN, USA
M2 macrophage
Cancer cell
SIRPα
MCSF
CD47
M1 macrophage
An-SIRPα
2 Mike and Josie Harper Cancer Research Institute, Notre Dame, IN, USA 3 University of Notre Dame, Department of Chemistry and Biochemistry, Notre Dame, IN, USA 4 Advanced Diagnostics and Therapeutics Initiative, Notre Dame, IN, USA
*Correspondence: [email protected] (B. Bilgicer).
Figure 1. Schematic Illustrating the Repolarization of Tumor-Associated Macrophages (TAMs) by Anti-SIRPa–AK750 Treatment. In the tumor microenvironment (TME), macrophages are polarized to a proangiogenic M2 phenotype. Delivery of CSF-1R inhibitors and blockage of the CD47–SIRPa interaction resulted in the repolarization of TAMs to a proinflammatory M1 phenotype and inhibited tumor growth in syngeneic mouse tumor models.
valuable because previous reports comparing skin and lung cancer models suggested that the location of the tumor affects the origin and development of TAMs [10] and could require different lines of treatments for each scenario. Although no tests were performed with clinical samples, current understanding of the targeted receptors (SIRPa and CSF1R), as well as ongoing clinical trials on Success of this bifunctional therapy can similar therapies, suggests that the be attributed to the re-establishment of a described strategy can have a significant tumor-suppressing environment. The impact on cancer treatments. process is initiated by repolarization of TAMs and reactivation of their phagocy- Ultimately, the likelihood of clinical and totic capacities followed by increased commercial success of this immunotherrecruitment of CD4+ and CD8+ popula- apy will also depend on the ease of scaltions, which has been related to favorable ability of the manufacturing of these prognosis in the clinic [3]. Evaluation in supramolecular assemblies because partidifferent tumor models was particularly cle homogeneity and batch-to-batch However, whether immunotherapy by itself will be enough when translated to human cancers remains to be seen. Nevertheless, these results show that immunotherapy could improve treatment tolerance by minimizing the need for chemotherapeutic agents and could also reduce the number of required visits to treatment centers.
2
Trends in Cancer, Month Year, Vol. xx, No. yy
https://doi.org/10.1016/j.trecan.2018.09.008 References 1. Sengupta, S. (2017) Cancer nanomedicine: lessons for immuno-oncology. Trends Cancer 3, 551–559 2. Finn, O.J. (2012) Immuno-oncology: understanding the function and dysfunction of the immune system in cancer. Ann. Oncol. 23, viii6–viii9 3. Solinas, G. et al. (2009) Tumor-associated macrophages (TAM) as major players of the cancer-related inflammation. J. Leukoc. Biol. 86, 1065–1073 4. Zeisberger, S.M. et al. (2006) Clodronate-liposome-mediated depletion of tumour-associated macrophages: a new and highly effective antiangiogenic therapy approach. Br. J. Cancer 95, 272–281 5. Georgoudaki, A. et al. (2016) Reprogramming tumor-associated macrophages by antibody targeting inhibits cancer progression and metastasis. Cell Rep. 15, 2000–2011 6. Luo, Y. et al. (2006) Targeting tumor-associated macrophages as a novel strategy against breast cancer. J. Clin. Invest. 116, 2132–2141 7. Rodell, C.B. et al. (2018) TLR7/8-agonist-loaded nanoparticles promote the polarization of tumour-associated macrophages to enhance cancer immunotherapy. Nat. Biomed. Eng. 2, 578–588 8. Kulkarni, A. et al. (2018) A designer self-assembled supramolecule amplifies macrophage immune responses against aggressive cancer. Nat. Biomed. Eng. 2, 589–599 9. Cannarile, M.A. et al. (2017) Colony-stimulating factor 1 receptor (CSF1R) inhibitors in cancer therapy. J. Immunother. Cancer 5, 53 10. Lehmann, B. et al. (2017) Tumor location determines tissue-specific recruitment of tumor-associated macrophages and antibody-dependent immunotherapy response. Sci. Immunol. 2, eaah6413