Ability to undergo apoptosis does not correlate with the intrinsic radiosensitivity (SF2) of human cervix tumor cell lines

Purpose: To investigate the relationship between radiation-induced apoptosi s and clonogenic cell kill in 9 cervical cancer cell lines. Methods and Materials: Cells were irradiated with 0, 2, 8, and 30 Gy. The l evel of apoptosis was evaluated using flow cytometry (Annexin-V binding), l ight microscropy (morphology), gel electrophoresis (DNA ladder formation), and TUNEL assay. Cell survival was measured using a clonogenic assay. Results: Of the 9 cervical carcinoma cell lines analyzed, 3 underwent radia tion-induced apoptosis: CaSki, HT3, and 778. The levels of apoptosis, obtai ned 72 h after a dose of 30 Gy, were 49%, 28%, and 26%, respectively. All c ell lines exhibited some level of background apoptosis measured by Annexin- V binding (mean = 2.6% a 0.8; range, 0.2-6.9%) that correlated with the lev el of radiation-induced apoptosis (r = 0.92, p = 0.001). In 6 of the 9 Line s, necrosis was the dominant form of cell death. A significant inverse rela tionship was found between the level of radiation-induced apoptosis and nec rosis after 30 Gy (r = -0.87, p = 0.002). No relationship was found between radiation-induced apoptosis and intrinsic radiosensitivity measured, using a clonogenic assay, as surviving fraction at 2 Gy (SF2). Conclusion: Cervical carcinoma cells do not readily undergo radiation-induc ed apoptosis in vitro. There is no relationship between ability to undergo apoptosis and intrinsic radiosensitivity measured using a clonogenic assay. (C) 2001 Elsevier Science Inc.