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.
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.
‘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)