P13.09.B INVESTIGATING THE EFFECTS OF RADIATION FRACTION DOSES ON THE MOLECULAR BARRIER PERMEABILITY OF AN IN VITRO BLOOD-BRAIN BARRIER MODEL
Bildiriler > Özet Bildiri
Yazarlar: M Ozturk, F Caglar, Murat KÖYLÜ, Emine Serra KAMER
Neuro-Oncology, , , Uluslararası, Özet Bildiri, Wos, cilt 26, ss v73-v73
DOI: 10.1093/neuonc/noae144.242
Özet
Abstract BACKGROUND Brain tumors and metastases are major causes of death. The blood-brain barrier (BBB) makes it difficult to treat these conditions as it prevents drugs from reaching the tumor. We aim to evaluate the BBB’s permeability changes caused by varying radiotherapy doses. This will help develop treatment strategies that can benefit from this impaired function. MATERIAL AND METHODS We used an in vitro model of BBB by seeding cells in a 24-well plate with a porous membrane-separated insert. Human umbilical vein endothelial cells (HUVEC) and human astrocyte cells (NHA) were used for seeding. Transendothelial electrical resistance (TEER) measurements verified the accuracy of the model. A device developed by the Department of Physics was used for TEER measurement. Radiation was delivered in single fractions of 2, 4, 6, 8, 16, and 25 Gy. After ionizing radiation, the cells were incubated with the TEER device for 72 hours, with measurements taken every two hours. In addition, glioblastoma (GBM) cell lines were seeded at the bottom of the 24-well plate where the insert was placed to assess drug dose efficiency, which can vary according to membrane permeability. Two different drugs were applied to the irradiated BBB model. Membrane permeability was determined by ELISA, MTT proliferation assay, and cell wound healing assay. RESULTS There was a significant decrease in TEER values in all dose groups after irradiation compared to the control group (p<0.001). No significant difference was found when fraction doses were evaluated (p=0.639). The most significant dose-independent decrease occurred between hours 2 and 6. It was noted that the change in the rate of resistance decline increased in direct proportion to the dose. Temozolomide (TMZ), used to evaluate the proliferation of GBM cell lines seeded on the bottom after irradiation, was effective on GBM cell proliferation, and the lowest dose for effective permeability was 4 Gy. In the cell wound healing experiment performed as an indicator of repopulation and repair capacity, it was observed that while bridging started in the early hours after irradiation in the TMZ-treated groups at low fraction doses, there was no wound closure at the end of 72 hours at high fraction doses. When the results of ELISA measurements made after the application of trastuzumab (TRAS), which is 750 times larger than TMZ, were evaluated, TRAS levels below 500 ng/ml were found at doses of 2, 4, and 6 Gy. TRAS levels of 1500 ng/ml were measured at doses of 8, 16, and 25 Gy. CONCLUSION Our study demonstrates that different doses of ionizing radiation combined with chemotherapy may increase tumor access to therapeutic agents and evaluates the time course of this relationship. We conclude that permeability through the BBB is related to molecular weight, which increases proportionally with increasing dose fraction.