Correlation Between the Parameters of Radiosensitivity in Human Cancer Cell Lines

Park, Woo Yoon; Kim, Won Dong; Min, Kyung Soo

Abstract

PURPOSE: We conducted clonogenic assay using human cancer cell lines (MKN-45, PC-14, Y-79, HeLa) to investigate a correlation between the parameters of radiosensitivity.
MATERIALS AND METHODS
Human cancer cell lines were irradiated with single doses of 1, 2, 3, 5, 7 and 10Gy for the study of radiosensitivity and sublethal damage repair capacity was assessed with two fractions of 5Gy separated with a time interval of 0, 1, 2, 3, 4, 6 and 24 hours. Surviving fraction was assessed with clonogenic assay using Sperman-K rber method and mathematical analysis of survival curves was done with linear-quadratic (LQ), multitarget-single hit (MS) model and mean inactivation dose (D).
RESULTS
Surviving fractions at 2Gy (SF2) were variable among the cell lines, ranged from 0.174 to 0.85. The SF2 of Y-79 was lowest and that of PC-14 was highest (p<0.05, t-test). LQ model analysis showed that the values of alpha for Y-79, MKN-45, HeLa and PC-14 were 0.603, 0.356, 0.275 and 0.102 respectively, and those of beta were 0.005, 0.016, 0.025 and 0.027 respectively. Fitting to MS model showed that the values of Do for Y-79, MKN-45, HeLa and PC-14 were 1.59, 1.84, 1.88 and 2.52 respectively, and those of n were 0.97, 1.46, 1.52 and 1.69 respectively. The s calculated by Gauss-Laguerre method were 1.62, 2.37, 2.61 and 3.95 respectively. So the SF2 was significantly correlated with alpha, Do and D. Their Pearson correlation coefficiencics were -0.953 and 0.993, 0.999 respectively (p<0.05). Sublethal damage repair was saturated around 4 hours and recovery ratios (RR) at plateau phase ranged from 2 to 3.79. But RR was not correlated with SF2, alpha, beta, Do, D.
CONCLUSION
The intrinsic radiosensitivity was very different among the tested human cell lines. Y-79 was the most sensitive and PC-14 was the least sensitive. SF2 was well correlated with alpha, Do, and D. RR was high for MKN-45 and HeLa but had nothing to do with radiosensitivity parameters. These basic parameters can be used as baseline data for various in vitro radiobiological experiments.