UVC-induced expression of a tumor-associated antigen in human cell hybrids (HeLa X skin fibroblasts): repair of potentially lethal and potentially transforming damage.

The UVC-induced expression of a cell surface protein which correlates with the induction of tumorigenicity has been observed in human cell hybrids (HeLa X skin fibroblasts). A dose - response curve for the induction of this marker of neoplastic transformation has been obtained. Studies of the repair of potentially lethal and potentially transforming damage indicate a slow repair process which results in enhanced survival and decreased neoplastic transformation over the period 6-24 h post-treatment. The kinetics of this repair process are consistent with previously published work on the kinetics of removal of thymine dimers from UVC-irradiated human skin fibroblasts. During the first few hours post-irradiation (0-6 h) there are fluctuations in transformation frequency while survival remains essentially constant. It is during this period that 6-4 photoproducts are removed from UV-irradiated DNA. It is possible that repair of these lesions may lead to an increase in transformation frequency and have no impact in terms of survival.