Preliminary Study Of Radiobiological Effects In Human Hepatocarcinoma Cells BEL-7402 Irradiated By Different Irradiation Model

Objective To investigate the changes of radiobiological effects of BEL-7402 cells irradiated by two irradiation protocols(3-Dimensional conformal radiation therapy and acute irradiation), and its changes of surviving fraction and radiobiological parameters; To observe the differences of radiosensitivity between human hepatocarcinoma cells BEL-7402 and hepatic cells QSG-7701, approach the possible theoretical evidence .Methods BEL-7402 cells irradiated to total doses of 0Gy, 1Gy, 2Gy, 3Gy, 5Gy, 7Gy, 9Gy, 10Gy at a dose rate of 3Gy/min in two different delivery patterns. In modeling acute irradiation, the fraction-delivery-time was 0-4 min; while in modeling 3-Dimensional conformal radiation therapy (3DCRT), the fraction-delivery-time was lasted 13-15 min. The surviving fractions were determined by classical colony forming assay. The radiobiological parameters were calculated, and cell survival curves were plotted according to"the single-hit multi-target model". The survivability, apoptosis and cell cycles of BEL-7402 and QSG-7701 cells, which cultured in vitro and irradiated by 6MV X-ray with a single dose of 5 Gy, were assessed by methyl thiazole tetrazolium (MTT) assay and flow cytometry ( FCM ) at different time after irradiation.Results The value of D0, Dq, SF2 of BEL-7402 cell line in acute irradiation pattern and 3DCRT irradiation pattern were 1.69 and 1.78 , 1.45 and 1.54, 0.625 and 0.654. The number of apoptotic BEL-7402 cells reached a peak (32 %) and a lowest survival (65%) at the 12h after irradiation, while irradiated apoptotic QSG-7701 cells showed highest (18%) at the 24h. Radiation induced significant differences in apoptosis and survival between the two cell lines at 12h(P<0.01). Cell cycle accumulation at G2/M phase of QSG-7701 cell after 24h exposure to this dose, and of BEL-7402 cell after 12h (23.03±4.00%,43.23±6.44%).Conclusion 1.The radiobiological effectiveness can be influenced by prolonged fraction-delivery-time for 3DCRT. 2. The two cell lines were distinct from each other in radiosensitivity after irradiation. 3. To shorten fractionation schedules may have a beneficial effect of radiotherapy of hepatoma.