Expression of the human BCL‐2 transgene increases the radiation resistance of a hematopoietic progenitor cell line

Abstract

AbstractWe investigated the effect of overexpression of a BCL‐2 transgene on the irradiation survival of the interleukin (IL)‐3‐dependent 32D cl 3 cell line in vitro. The 32D‐BCL‐2 clonal subline was selected by transfection of 32D cl 3 cells with a BCL‐2 and neor‐containing plasmid vector selecting for G418 resistance. Cell line 32D‐BCL‐2 was IL‐3‐dependent and showed detectable BCL‐2 protein expression by Western analysis of cell lysates. The cells expressing BCL‐2 showed the characteristic block of apoptosis by DNA ladder analysis of cells following deprivation of IL‐3, where a decrease in DNA fragmentation of 32D‐BCL‐2 compared to 32D cl 3 DNA was observed after 200 to 1,000 cGy irradiation. The 32D‐BCL‐2 cell line demonstrated increased radioresistance at a dose rate of 110 cGy/min with an ñ and D0 of 8.70 and 130 cGy, respectively, compared to 5.03 and 101 cGy for parent 32D cl 3 cells (P = 0.015 and 0.018, respectively). At the clinical low dose rate of 7.5 cGy/min, the ñ and D0 for 32D‐BCL‐2 were 2.51 and 178 cGy compared to 1.96 and 148 cGy for 32D cl 3 (P = 0.074 and 0.071, respectively). Thus, expression of a BCL‐2 transgene increased the gamma‐irradiation resistance of 32D cl 3 cells in vitro. These data are consistent with recently published evidence for a role of BCL‐2 in reducing intracellular free oxygen radicals. These results may explain the unexpected survival of BCL‐2‐containing tumor cells in bone marrow transplant recipients after low‐dose‐rate total body irradiation. © Wiley‐Liss, Inc.