Elevated Peripheral Monocyte Counts After SBRT: Clinical and. Preclinical Evidence. L. Deng,1,2 S. Wang,3 S. Chernikova,2 L. Zhou,1 Y. Hai,4 R. Liu,4 Y. Cai,4.
Poster Viewing Session E513
Volume 93 Number 3S Supplement 2015 minimum of 32.2 pg/ml; TNF-alpha from 29.9 pg/ml to 26.9 pg/ml and IL10 from 42.5 pg/ml to 35.2 pg/ml. Conclusion: Patients with malignancies in abdomen-basin and head and neck have significantly higher base line pro-inflammatory as well as antiinflammatory cytokines compared to healthy volunteers. This underlines a hyper-reactive immune system under conditions of cancer. Furthermore, patients with cancer entities in the abdomen-basin region that obtain radiation and chemotherapy showed significantly more fluctuation in cytokines than patients with head and neck cancer. Author Disclosure: E. Boelke: None. S. Doerges: None. C. Matuschek: None. M. van Griensven: None. W. Budach: None.
3284 Effect of Differential DNA Repair Process Inhibition on Radiosensitization A.H. Kesarwala,1 N. Miura,1 W.G. DeGraff,1 and J.B. Mitchell2; 1National Cancer Institute, National Institutes of Health, Bethesda, MD, 2National Institute of Health/National Cancer Institute, Bethesda, MD Purpose/Objective(s): DNA repair is a critical determinant of radiation sensitivity. We questioned whether inhibition of processes involved in DNA double strand break repair, namely the activity of ataxia telangiectasia mutated (ATM) and homologous recombination repair, would result in differential radiosensitization of normal and tumor cells. Materials/Methods: HT29 colorectal and A549 lung human cancer cells and 1522 normal human fibroblast cells were exposed to 5 mM KU-60019, an ATM kinase inhibitor, 60-250 mM RI-1, a Rad51 inhibitor, and/or 10 mM LY294002, a phosphoinositide 3-kinase inhibitor. Survival was assessed by clonogenic assay and cell cycle distributions were determined by flow cytometry. Dose modifying factors (DMF) were calculated at 10% survival from radiation survival curves. Results: KU-60019, RI-1, and LY294002 exhibited little to no cytotoxicity to tumor cells, while RI-1 was cytotoxic to 1522 cells above 60 mM. KU-60019 treatment of HT29, A549, and 1522 cells immediately after exposure to radiation resulted in DMFs of 2.2, 3.4, and 2.5, respectively. Co-treatment of HT29 cells with KU-60019 and RI-1 resulted in a DMF of 2.6. RI-1 post-treatment did not radiosensitize A549 cells but resulted in DMFs of 1.1 for HT29 cells and 1.4 for 1522 cells. LY294002 post-treatment did not radiosensitize A549 cells but co-treatment with LY249002 and RI-1 immediately after exposure to radiation decreased survival by 30%. Conclusion: These preliminary data with inhibition of processes involved in DNA repair suggest that normal human fibroblasts, wild-type Ras/ mutant p53 HT29 colorectal cancer cells, and mutant Ras/wild-type p53 A549 lung cancer cells have differential dependences on homologous recombination repair at baseline. Further data will be presented addressing the potential mechanism of differential DNA repair process inhibition in these and additional human tumor cell lines. Author Disclosure: A.H. Kesarwala: Research Grant; ASTRO. N. Miura: None. W.G. DeGraff: Stock; Pfizer. J.B. Mitchell: None.
3285 Elevated Peripheral Monocyte Counts After SBRT: Clinical and Preclinical Evidence L. Deng,1,2 S. Wang,3 S. Chernikova,2 L. Zhou,1 Y. Hai,4 R. Liu,4 Y. Cai,4 J. Xue,5 M. Brown,2 and Y. Lu6; 1Department of Thoracic Oncology, Cancer Center, West China Hospital, Sichuan University, Chengdu, China, 2 Department of Radiation Oncology, Stanford University, Palo Alto, CA, 3 Radiation Physics Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, China, 4Huaxi Student Society of Oncology Research, West China School of Medicine, Sichuan University, Chengdu, China, 5Department of Thoracic Oncology, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China, 6Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China Purpose/Objective(s): Previous preclinical studies demonstrated that monocytes/macrophages from bone marrow facilitate post-irradiation
tumor recurrence by influx into the irradiated tumors. It is unknown whether this migration can be detected in the peripheral blood. Materials/Methods: Human U251 glioma and A549 lung cell lines were implanted into the hind legs of nude mice. Tumors were irradiated with 12Gy/1f. Peripheral blood was collected for monocyte counts. PLX3397, a CSF1-R inhibitor that targets monocytes/macrophages was given p.o. to mice after 12 Gy. Medical records of patients who received stereotactic body radiation therapy were retrospectively reviewed for patient characteristics, treatment information and peripheral monocyte counts. Patients who received bone marrow stimulating agents and chemotherapy within 30 days before blood collection were excluded. Pre-SBRT period was defined as within 30 days prior to first fraction, and the most recent count was used when more than one count was available. Results: Gradual peripheral monocyte count increased up to day 14 after 12Gy/1f to the U251 tumor compared to pre-irradiation levels. Administration of PLX3397, which has been shown to reduce monocyte/macrophage infiltration into irradiated tumor and enhance radiation efficacy, abrogated this rise. Peripheral monocyte count increase was also observed 4 weeks after 12Gy/1f in the A549 tumor model. 40 patients with 78 peripheral monocyte counts were analyzed. Significant increase of peripheral monocyte counts was observed on day 22-28 (0.6010^9/L, nZ6) after first fraction of SBRT compared to pre-treatment period (0.3510^9/L, nZ26, pZ0.02). Conclusion: Mobilization of monocyte/macrophage by irradiation into tumors, which facilitate recurrence, can be detected in the peripheral blood monocyte count in animals and patients. Further prospective and larger studies are needed to confirm this and explore its prognostic role. Author Disclosure: L. Deng: None. S. Wang: None. S. Chernikova: None. L. Zhou: None. Y. Hai: None. R. Liu: None. Y. Cai: None. J. Xue: None. M. Brown: None. Y. Lu: None.
3286 Triapine Enhances Radiosensitivity of HPV Negative Head and Neck Squamous Cell Carcinoma Cells K. Yao, R. Patel, G. Ferris, and N.L. Oleinick; Department of Radiation Oncology, Case Western Reserve University, Cleveland, OH Purpose/Objective(s): Human papilloma virus (HPV) negative head and neck squamous cell carcinoma (HNSCC) has a very poor prognosis with 3 year overall survival only 46%. Further research is needed to improve the treatment outcomes. Triapine or 3-AP (3-aminopyridine-2-carboxaldehyde thiosemicarbazone) is a potent inhibitor of ribonucleotide reductase and has been shown to be a radiosensitizer in a variety of cancers. In this project, we test if triapine can be used as a radiosensitizer in HPV negative HNSCC. Materials/Methods: FaDu cell, a human epithelial cell line from a HNSCC of the hypopharynx was used. The cells were exposed to increasing doses of radiation (0-6 Gy) in the absence and presence of triapine and clonogenic assay was used to determine if triapine can enhance radiation killing of the cells. The optimal timing of exposing triapine to the cells was also tested. Western blot was used to measure phosphorylation of histone gH2AX after exposure of the cells to radiation with and without triapine. Results: Using clonogenic assay, we determined whether FaDu cells were sensitized to radiation by a 6-hour exposure to 5 mM triapine. It was found that triapine is highly effective, with a dose enhancement factor of 1.9. We then tested various time sequences of the addition of triapine and 4 Gy radiation, and showed that the addition of triapine 1 or 3 hours before radiation is more effective than adding triapine 1 hour after radiation. Using Western blot, it showed that control cells had a very low level of gH2AX. As expected, radiation increased the level of gH2AX. In the absence of triapine, a decrease in gH2AX over the next 5-24 hours was noted due to subsequent DNA repair. When triapine was added 1 hour before radiation, the drug itself produced an increase in gH2AX that was further increased by radiation, and the level of gH2AX remained high over 5-24 hours, indicating inhibition of DNA repair in the presence of triapine. Conclusion: Triapine can radiosensitize HPV negative HNSCC cells, most likely due to inhibition of DNA repair. Further research will be needed to
