- Email: [email protected]
Molecular-targeted Radiosensitization by Small Fusion Peptides for Prostate Cancer
I. J. Radiation Oncology d Biology d Physics
S144
Volume 81, Number 2, Supplement, 2011
probe was applied to the fixed cells (4% paraformaldehyde) to allow target-probe binding, followed by multiple PBS washes to remove any unbound probe. Flow cytometry and MR imaging were performed in vitro to evaluate cell targeting and reduction in sample T1 relaxation times, respectively. Using flow cytometry, the shift in fluorescent intensity (SFI) was used to determine the relative EGFR expression level and the cell targeting ability of the probe. T1 relaxation times as a function of Gd concentrations were determined by an inversion recovery fast spin echo imaging sequence on a 3T MR system at 25oC with the following settings: TE = 12 ms, TR = 6000 ms, inversion time, TI = 40-2800 ms. Binding specificity of the probe in vivo was tested in the nude mice that were implanted with 15B xenografts and imaged under MR to observe region-of-interest specific uptake following injection of the probe via the tail vein. Results: Flow cytometry data revealed high targeted binding affinity of the probe to 15B (SFI = 1800) and low affinity to HEK293 (SFI = 300), demonstrating the functionality and specificity of the probe at the molecular level in vitro. Sample T1 relaxation times in vitro were 1600 ms, 1100 ms, and 450 ms for the cells without any probe, HEK293 with probe, and 15B with probe, respectively. Contrast levels were substantially enhanced in the region of 15B tumor implant in mice and compared to normal tissues. Conclusions: We have developed a novel EGFR targeting and imaging probe by combining the therapeutic antibody and Gd for MRI contrast enhancement. The probe is able to selectively target the EGFR receptor and allows drug uptake to be imaged. Author Disclosure: C. Hung: None. Y. Kuo: None. E. Choi: None. S.R. Raghavan: None. N.N. Mistry: None. R. Gullapalli: None. R.G. Lapidus: None. M. Suntharalingam: None. W.D. D’Souza: None.
289
Development of Nanoparticle-loaded Drug Eluting Biodegradable Spacers for Prostate Brachytherapy
A. Z. Wang1,2, S. Karve1,2, M. E. Werner1,2, R. Sukumar1,2, J. E. Tepper1,2, R. C. Chen1, J. M. DeSimone3,2 1 University of North Carolina School of Medicine, Chapel Hill, NC, 2Carolina Center for Cancer Nanotechnology Excellence, Chapel Hill, NC, 3Department of Chemistry, University of North Carolina, Chapel Hill, NC
Purpose/Objective(s): Prostate brachytherapy is an important curative treatment for patients with localized prostate cancer. The main side effects of this treatment are acute urinary retention and subacute urinary frequency and urgency. These side effects can cause significant morbidity and has limited the use of this treatment. The majority of the urinary side effects are due to prostatic swelling from the brachytherapy procedure. The incorporation of controlled, locally released anti-inflammatory drugs such as dexamethasone into spacers could potentially reduce the side effects of prostate brachytherapy. As proof of principle, we aimed to develop a biodegradable drug eluting spacer that can release dexamethasone with a high release rate over the first week, and with lesser release over the first month. Materials/Methods: Particle Replication In Non-wetting Templates (PRINT) technology was utilized to formulate dexamethasone loaded polylactic-co-glycolic acid (PLGA, molar ratio 85:15) particles. The particles were suspended in silyl ether based biocompatible material, which were then photocured to form a matrix. The matrix was precisely cut to form spacers with dimensions of 1 mm in diameter and 0.5 cm in length to be accommodated inside the implant needles. Drug release from these spacers was evaluated in phosphate buffer and in canine prostate ex vivo at 37 C. Results: In order to control the release of dexamethasone, we utilized advances in nanotechnology and chemical engineering to develop dexamethasone-loaded particles, which were then incorporated into biodegradable spacers. Dexamethasone-loaded PLGA particles of different shapes and dimensions were evaluated for stability, loading efficiencies and content retention. The particles showed no aggregation after storage for 7 days at -20 C. The particles show stable retention of dexamethasone and controlled release over a period of 25 days. In particular, the particles show controlled release of 30-40% dexamethasone within the first few days and long slow release thereafter. We then incorporated these particles into silyl-ether based biodegradable spacers. Release of dexamethasone from particle-loaded spacers in canine prostate showed initial high release over a period of 2 days and prolonged release for an additional four weeks. Conclusions: We have successfully developed a nanoparticle-loaded drug eluting biodegradable spacer platform for prostate brachytherapy. We have demonstrated that these spacers can release dexamethasone in a controlled and prolonged fashion in vitro and ex vivo. We believe our innovation has high potential for decreasing acute toxicity from prostate brachytherapy treatment. Author Disclosure: A.Z. Wang: None. S. Karve: None. M.E. Werner: None. R. Sukumar: None. J.E. Tepper: None. R.C. Chen: None. J.M. DeSimone: None.
290
Molecular-targeted Radiosensitization by Small Fusion Peptides for Prostate Cancer
C. Lin1, H. Zhao1, Y. Cui2 1 Jilin University First Hospital, Changchun, China, 2Harbin Medical University Cancer Hospital, Harbin, China Purpose/Objective(s): Radiation therapy is one of the critical treatments for prostate cancer. Tumor specific radiosensitization would increase the treatment outcome and reduce radiation damage to normal tissues. DNA damage signal transducers such as the ATM and ATR kinases play critical roles to initiate the DNA damage response and determine the radiosensitivity by phosphorylating specific serine or threonine residues (SQ or TQ). Of the target proteins, the two effector kinases Chk1 and Chk2 are particularly important because they phosphorylate additional substrates to amplify the signals. To explore novel approaches to molecularly targeted radiosensitization, we characterized small fusion peptides containing the ATM and ATR phosphorylation sequences of Chk1 and Chk2. Materials/Methods: We synthesized nine small fusion peptides which contain two functional domains: one for internalization (the HIV-TAT sequence) and the other for blocking Chk1 or Chk2 phosphorylation. The fusion peptides include TAT-only, Chk1 peptides TAT-wild-type Serine 317, TAT-wild-type Serine 345, Chk2 peptides TAT-wild-type Threonine-68, TATwild-type Threoine-383, TAT-wild-type Threonine 387, and their respective mutants TAT-Chk1 Ser317Ala, TAT-Chk1 Ser345Ala, TAT-Chk2 Thr68Ala, TAT-Chk2 Thr383Ala, TAT-Chk2 Thr387Ala. To characterize the radiosensitization effect of the peptides, we utilized two prostate cancer cell lines (PC-3 and DU-145). Cells were exposed to irradiation (IR) after incubation with either of the peptides. We assessed IR-induced Chk1 and Chk2 activation and phosphorylation using
Proceedings of the 53rd Annual ASTRO Meeting immunoblotting using phospho-specific antibodies. We also investigated effects of the peptides on IR-induced cell cycle checkpoints. Finally we assessed radiosensitivity using the clonogenic survival assay. Results: We found that wild-type peptides of Chk1 and Chk2 can clock ATM and ATR mediated Chk1 and Chk2 phosphorylation/ activation. The mutant peptides did not process any inhibitory effects on the kinases. Treatment with Chk1 or Chk2 peptides resulted in loss of the IR-induced G2/M checkpoint. Cells exposed to the wild-type Chk1 or Chk2 fusion peptides have increased radiosensitivity, with TAT-wild-type Chk2 Threonine-68 the highest Sensitization Enhancement Ratio (2.17). Conclusions: Small inhibitory peptides on Chk1 and Chk2 activation and phosphorylation can be explored to be novel agents for radiosensitization in prostate cancer as well other cancer types. Author Disclosure: C. Lin: None. H. Zhao: None. Y. Cui: None.
291
Folate-targeted Nanoparticle Formulation of Docetaxel as an Effective Biologically Targeted Radiosensitizer for Head and Neck Cancer
M. E. Werner1,2, S. Karve1,2, J. A. Copp1,2, N. D. Cummings1,2, R. Sukumar1,2, R. C. Chen1, A. D. Cox1, M. E. Napier3,2, A. Z. Wang1,2 1 University of North Carolina School of Medicine, Chapel Hill, NC, 2Carolina Center for Cancer Nanotechnology Excellence, Chapel Hill, NC, 3Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, Chapel Hill, NC
Purpose/Objective(s): Nanoparticle (NP) therapeutic is an emerging class of cancer chemotherapies. NPs are also particularly well suited as radiosensitizers. Unlike small molecule chemotherapeutics which are broadly distributed in malignant and normal tissue, NPs passively accumulate in tumors through the enhanced permeability and retention (EPR) effect. Such differential distribution can result in higher efficacy as well as lower toxicity when combined with radiotherapy. Furthermore, recent developments of biologically targeted nanoparticles have been shown to further enhance the drug concentration and efficacy in tumor cells. Therefore, we hypothesized that a biologically targeted NP formulation of docetaxel (Dtxl) is a more effective radiosensitizer than Dtxl. In this study, we evaluated the effectiveness of a folate targeted NP Dtxl as a novel radiosensitizer in vitro and in vivo using a head and neck cancer model. Since NP Dtxl has very different pharmacokinetic properties compared to that of Dtxl, we also characterized the optimal timing of radiotherapy for NP Dtxl. Materials/Methods: Folate targeted polymer-lipid NP platform was synthesized by nanoprecipitation method. The resulting NPs have a hydrophobic polymeric core (PLGA) covered by a self-assembled monolayer of lipid, lipid-PEG and lipid-PEG-folate. Folate receptor (FR) expressing KB head and neck cancer cell line was used as the model tumor and HTB-43, a low FR expressing head and neck cancer cell line, as a control. Using both clonogenic assays and tumor bearing mice, we studied the optimal timing for radiotherapy to achieve maximal radiosensitization as well as the comparative effectiveness of folate-targeted NPs encapsulating Dtxl (FT-NP Dtxl) vs. non-targeted NPs (NP Dtxl) and free Dtxl. Results: High FR expressing KB cells, but not HTB-43 cells, demonstrated greater uptake of FT-NP Dtxl compared to NP Dtxl. The folate mediated uptake led to FT-NP Dtxl as a more effective radiosensitizer than NP Dtxl in KB cells, but not HTB-43 cells. An in vivo efficacy study using mice bearing KB xenografts showed FT-NP Dtxl is a significantly more effective radiosensitizer than NP Dtxl or free Dtxl. We also demonstrated in KB xenografts that the greatest radiosensitization with FT-NP Dtxl occurs when the tumor is irradiated 12 hrs post NP treatment. Conclusions: We have demonstrated that a biologically targeted NP, FT-NP Dtxl, is an effective radiosensitizer of head and neck cancer cells in vitro and in vivo. We have also identified the optimal timing for radiotherapy given with NP Dtxl is different than that of free Dtxl. The optimal timing is 12 hours post-FT-NP Dtxl treatment. These findings have broad implications, especially in the clinical translation of NP therapeutics as radiosensitizers. Author Disclosure: M.E. Werner: None. S. Karve: None. J.A. Copp: None. N.D. Cummings: None. R. Sukumar: None. R.C. Chen: None. A.D. Cox: None. M.E. Napier: None. A.Z. Wang: None.
292
‘Breaking through the Tumor BBB’: Enhancing the Efficacy of Nanobiopolymer Therapeutics against Intracranial Tumors with Targeted Radiation Therapy
B. C. Baumann1, J. F. Dorsey1, X. Xu1, T. Harada2, C. Chapman1, J. Benci1, S. Jaiswal1, A. Mahmud2, D. E. Discher2, G. D. Kao1 1 Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, PA, 2Department of Chemical and Biomolecular Engineering, University of Pennsylvania School of Engineering, Philadelphia, PA
Purpose/Objective(s): The grim prognosis of many brain cancers is attributed, in part, to the inability to achieve therapeutic levels of anti-cancer drugs due to the impermeability of the tumor-associated blood-brain barrier (T-BBB). Novel drug delivery systems using nanocarrier polymers loaded with chemotherapy may increase serum half-life but are still limited by the T-BBB. Based on preliminary evidence that radiation therapy (RT) increases the permeability of the T-BBB, we developed a novel bioluminescent orthotopic mouse model of glioblastoma multiforme (GBM) to facilitate investigations of RT modulation of the TBBB, and using this model, we tested the efficacy of combined RT and nanopolymerized paclitaxel (NP) for treating GBM. Materials/Methods: U251 human-derived GBM cells expressing luciferase were established so that bioluminescent imaging (BLI) could serially assess tumor growth and response to treatment non-invasively. These cells were injected into nude mice, either stereotactically into the brain or into the flank. The resultant mice with tumors were stratified into groups based on BLI signals to assess the efficacy of NP and RT. Overall survival was calculated based on death or sustained loss of .20% of pre-treatment weight. BBB integrity was assessed via staining for extravasation out of the systemic circulation of IgG or fluorescent Evans Blue (EB) dye. Results: We confirmed that RT disrupatients the integrity of the BBB. Brains treated with 20 Gy RT showed substantial extravasation of IgG and EB (p \ 0.05) while un-irradiated brains showed no extravasation. Intracranial tumors treated to 3 Gy x 4 showed increased T-BBB disruption compared to untreated tumors, with extravasation peaking at 20 days post-RT and gradually decreasing by days 35 and 55 (p \ 0.05). Flank tumors treated with NP had significant delays in tumor progression (p \ 0.05)
S145
S144
Volume 81, Number 2, Supplement, 2011
probe was applied to the fixed cells (4% paraformaldehyde) to allow target-probe binding, followed by multiple PBS washes to remove any unbound probe. Flow cytometry and MR imaging were performed in vitro to evaluate cell targeting and reduction in sample T1 relaxation times, respectively. Using flow cytometry, the shift in fluorescent intensity (SFI) was used to determine the relative EGFR expression level and the cell targeting ability of the probe. T1 relaxation times as a function of Gd concentrations were determined by an inversion recovery fast spin echo imaging sequence on a 3T MR system at 25oC with the following settings: TE = 12 ms, TR = 6000 ms, inversion time, TI = 40-2800 ms. Binding specificity of the probe in vivo was tested in the nude mice that were implanted with 15B xenografts and imaged under MR to observe region-of-interest specific uptake following injection of the probe via the tail vein. Results: Flow cytometry data revealed high targeted binding affinity of the probe to 15B (SFI = 1800) and low affinity to HEK293 (SFI = 300), demonstrating the functionality and specificity of the probe at the molecular level in vitro. Sample T1 relaxation times in vitro were 1600 ms, 1100 ms, and 450 ms for the cells without any probe, HEK293 with probe, and 15B with probe, respectively. Contrast levels were substantially enhanced in the region of 15B tumor implant in mice and compared to normal tissues. Conclusions: We have developed a novel EGFR targeting and imaging probe by combining the therapeutic antibody and Gd for MRI contrast enhancement. The probe is able to selectively target the EGFR receptor and allows drug uptake to be imaged. Author Disclosure: C. Hung: None. Y. Kuo: None. E. Choi: None. S.R. Raghavan: None. N.N. Mistry: None. R. Gullapalli: None. R.G. Lapidus: None. M. Suntharalingam: None. W.D. D’Souza: None.
289
Development of Nanoparticle-loaded Drug Eluting Biodegradable Spacers for Prostate Brachytherapy
A. Z. Wang1,2, S. Karve1,2, M. E. Werner1,2, R. Sukumar1,2, J. E. Tepper1,2, R. C. Chen1, J. M. DeSimone3,2 1 University of North Carolina School of Medicine, Chapel Hill, NC, 2Carolina Center for Cancer Nanotechnology Excellence, Chapel Hill, NC, 3Department of Chemistry, University of North Carolina, Chapel Hill, NC
Purpose/Objective(s): Prostate brachytherapy is an important curative treatment for patients with localized prostate cancer. The main side effects of this treatment are acute urinary retention and subacute urinary frequency and urgency. These side effects can cause significant morbidity and has limited the use of this treatment. The majority of the urinary side effects are due to prostatic swelling from the brachytherapy procedure. The incorporation of controlled, locally released anti-inflammatory drugs such as dexamethasone into spacers could potentially reduce the side effects of prostate brachytherapy. As proof of principle, we aimed to develop a biodegradable drug eluting spacer that can release dexamethasone with a high release rate over the first week, and with lesser release over the first month. Materials/Methods: Particle Replication In Non-wetting Templates (PRINT) technology was utilized to formulate dexamethasone loaded polylactic-co-glycolic acid (PLGA, molar ratio 85:15) particles. The particles were suspended in silyl ether based biocompatible material, which were then photocured to form a matrix. The matrix was precisely cut to form spacers with dimensions of 1 mm in diameter and 0.5 cm in length to be accommodated inside the implant needles. Drug release from these spacers was evaluated in phosphate buffer and in canine prostate ex vivo at 37 C. Results: In order to control the release of dexamethasone, we utilized advances in nanotechnology and chemical engineering to develop dexamethasone-loaded particles, which were then incorporated into biodegradable spacers. Dexamethasone-loaded PLGA particles of different shapes and dimensions were evaluated for stability, loading efficiencies and content retention. The particles showed no aggregation after storage for 7 days at -20 C. The particles show stable retention of dexamethasone and controlled release over a period of 25 days. In particular, the particles show controlled release of 30-40% dexamethasone within the first few days and long slow release thereafter. We then incorporated these particles into silyl-ether based biodegradable spacers. Release of dexamethasone from particle-loaded spacers in canine prostate showed initial high release over a period of 2 days and prolonged release for an additional four weeks. Conclusions: We have successfully developed a nanoparticle-loaded drug eluting biodegradable spacer platform for prostate brachytherapy. We have demonstrated that these spacers can release dexamethasone in a controlled and prolonged fashion in vitro and ex vivo. We believe our innovation has high potential for decreasing acute toxicity from prostate brachytherapy treatment. Author Disclosure: A.Z. Wang: None. S. Karve: None. M.E. Werner: None. R. Sukumar: None. J.E. Tepper: None. R.C. Chen: None. J.M. DeSimone: None.
290
Molecular-targeted Radiosensitization by Small Fusion Peptides for Prostate Cancer
C. Lin1, H. Zhao1, Y. Cui2 1 Jilin University First Hospital, Changchun, China, 2Harbin Medical University Cancer Hospital, Harbin, China Purpose/Objective(s): Radiation therapy is one of the critical treatments for prostate cancer. Tumor specific radiosensitization would increase the treatment outcome and reduce radiation damage to normal tissues. DNA damage signal transducers such as the ATM and ATR kinases play critical roles to initiate the DNA damage response and determine the radiosensitivity by phosphorylating specific serine or threonine residues (SQ or TQ). Of the target proteins, the two effector kinases Chk1 and Chk2 are particularly important because they phosphorylate additional substrates to amplify the signals. To explore novel approaches to molecularly targeted radiosensitization, we characterized small fusion peptides containing the ATM and ATR phosphorylation sequences of Chk1 and Chk2. Materials/Methods: We synthesized nine small fusion peptides which contain two functional domains: one for internalization (the HIV-TAT sequence) and the other for blocking Chk1 or Chk2 phosphorylation. The fusion peptides include TAT-only, Chk1 peptides TAT-wild-type Serine 317, TAT-wild-type Serine 345, Chk2 peptides TAT-wild-type Threonine-68, TATwild-type Threoine-383, TAT-wild-type Threonine 387, and their respective mutants TAT-Chk1 Ser317Ala, TAT-Chk1 Ser345Ala, TAT-Chk2 Thr68Ala, TAT-Chk2 Thr383Ala, TAT-Chk2 Thr387Ala. To characterize the radiosensitization effect of the peptides, we utilized two prostate cancer cell lines (PC-3 and DU-145). Cells were exposed to irradiation (IR) after incubation with either of the peptides. We assessed IR-induced Chk1 and Chk2 activation and phosphorylation using
Proceedings of the 53rd Annual ASTRO Meeting immunoblotting using phospho-specific antibodies. We also investigated effects of the peptides on IR-induced cell cycle checkpoints. Finally we assessed radiosensitivity using the clonogenic survival assay. Results: We found that wild-type peptides of Chk1 and Chk2 can clock ATM and ATR mediated Chk1 and Chk2 phosphorylation/ activation. The mutant peptides did not process any inhibitory effects on the kinases. Treatment with Chk1 or Chk2 peptides resulted in loss of the IR-induced G2/M checkpoint. Cells exposed to the wild-type Chk1 or Chk2 fusion peptides have increased radiosensitivity, with TAT-wild-type Chk2 Threonine-68 the highest Sensitization Enhancement Ratio (2.17). Conclusions: Small inhibitory peptides on Chk1 and Chk2 activation and phosphorylation can be explored to be novel agents for radiosensitization in prostate cancer as well other cancer types. Author Disclosure: C. Lin: None. H. Zhao: None. Y. Cui: None.
291
Folate-targeted Nanoparticle Formulation of Docetaxel as an Effective Biologically Targeted Radiosensitizer for Head and Neck Cancer
M. E. Werner1,2, S. Karve1,2, J. A. Copp1,2, N. D. Cummings1,2, R. Sukumar1,2, R. C. Chen1, A. D. Cox1, M. E. Napier3,2, A. Z. Wang1,2 1 University of North Carolina School of Medicine, Chapel Hill, NC, 2Carolina Center for Cancer Nanotechnology Excellence, Chapel Hill, NC, 3Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, Chapel Hill, NC
Purpose/Objective(s): Nanoparticle (NP) therapeutic is an emerging class of cancer chemotherapies. NPs are also particularly well suited as radiosensitizers. Unlike small molecule chemotherapeutics which are broadly distributed in malignant and normal tissue, NPs passively accumulate in tumors through the enhanced permeability and retention (EPR) effect. Such differential distribution can result in higher efficacy as well as lower toxicity when combined with radiotherapy. Furthermore, recent developments of biologically targeted nanoparticles have been shown to further enhance the drug concentration and efficacy in tumor cells. Therefore, we hypothesized that a biologically targeted NP formulation of docetaxel (Dtxl) is a more effective radiosensitizer than Dtxl. In this study, we evaluated the effectiveness of a folate targeted NP Dtxl as a novel radiosensitizer in vitro and in vivo using a head and neck cancer model. Since NP Dtxl has very different pharmacokinetic properties compared to that of Dtxl, we also characterized the optimal timing of radiotherapy for NP Dtxl. Materials/Methods: Folate targeted polymer-lipid NP platform was synthesized by nanoprecipitation method. The resulting NPs have a hydrophobic polymeric core (PLGA) covered by a self-assembled monolayer of lipid, lipid-PEG and lipid-PEG-folate. Folate receptor (FR) expressing KB head and neck cancer cell line was used as the model tumor and HTB-43, a low FR expressing head and neck cancer cell line, as a control. Using both clonogenic assays and tumor bearing mice, we studied the optimal timing for radiotherapy to achieve maximal radiosensitization as well as the comparative effectiveness of folate-targeted NPs encapsulating Dtxl (FT-NP Dtxl) vs. non-targeted NPs (NP Dtxl) and free Dtxl. Results: High FR expressing KB cells, but not HTB-43 cells, demonstrated greater uptake of FT-NP Dtxl compared to NP Dtxl. The folate mediated uptake led to FT-NP Dtxl as a more effective radiosensitizer than NP Dtxl in KB cells, but not HTB-43 cells. An in vivo efficacy study using mice bearing KB xenografts showed FT-NP Dtxl is a significantly more effective radiosensitizer than NP Dtxl or free Dtxl. We also demonstrated in KB xenografts that the greatest radiosensitization with FT-NP Dtxl occurs when the tumor is irradiated 12 hrs post NP treatment. Conclusions: We have demonstrated that a biologically targeted NP, FT-NP Dtxl, is an effective radiosensitizer of head and neck cancer cells in vitro and in vivo. We have also identified the optimal timing for radiotherapy given with NP Dtxl is different than that of free Dtxl. The optimal timing is 12 hours post-FT-NP Dtxl treatment. These findings have broad implications, especially in the clinical translation of NP therapeutics as radiosensitizers. Author Disclosure: M.E. Werner: None. S. Karve: None. J.A. Copp: None. N.D. Cummings: None. R. Sukumar: None. R.C. Chen: None. A.D. Cox: None. M.E. Napier: None. A.Z. Wang: None.
292
‘Breaking through the Tumor BBB’: Enhancing the Efficacy of Nanobiopolymer Therapeutics against Intracranial Tumors with Targeted Radiation Therapy
B. C. Baumann1, J. F. Dorsey1, X. Xu1, T. Harada2, C. Chapman1, J. Benci1, S. Jaiswal1, A. Mahmud2, D. E. Discher2, G. D. Kao1 1 Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, PA, 2Department of Chemical and Biomolecular Engineering, University of Pennsylvania School of Engineering, Philadelphia, PA
Purpose/Objective(s): The grim prognosis of many brain cancers is attributed, in part, to the inability to achieve therapeutic levels of anti-cancer drugs due to the impermeability of the tumor-associated blood-brain barrier (T-BBB). Novel drug delivery systems using nanocarrier polymers loaded with chemotherapy may increase serum half-life but are still limited by the T-BBB. Based on preliminary evidence that radiation therapy (RT) increases the permeability of the T-BBB, we developed a novel bioluminescent orthotopic mouse model of glioblastoma multiforme (GBM) to facilitate investigations of RT modulation of the TBBB, and using this model, we tested the efficacy of combined RT and nanopolymerized paclitaxel (NP) for treating GBM. Materials/Methods: U251 human-derived GBM cells expressing luciferase were established so that bioluminescent imaging (BLI) could serially assess tumor growth and response to treatment non-invasively. These cells were injected into nude mice, either stereotactically into the brain or into the flank. The resultant mice with tumors were stratified into groups based on BLI signals to assess the efficacy of NP and RT. Overall survival was calculated based on death or sustained loss of .20% of pre-treatment weight. BBB integrity was assessed via staining for extravasation out of the systemic circulation of IgG or fluorescent Evans Blue (EB) dye. Results: We confirmed that RT disrupatients the integrity of the BBB. Brains treated with 20 Gy RT showed substantial extravasation of IgG and EB (p \ 0.05) while un-irradiated brains showed no extravasation. Intracranial tumors treated to 3 Gy x 4 showed increased T-BBB disruption compared to untreated tumors, with extravasation peaking at 20 days post-RT and gradually decreasing by days 35 and 55 (p \ 0.05). Flank tumors treated with NP had significant delays in tumor progression (p \ 0.05)
S145