STRATEGIC DOWN-REGULATION OF DNA-POLYMERASE-BETA BY ANTISENSE RNA SENSITIZES MAMMALIAN-CELLS TO SPECIFIC DNA-DAMAGING AGENTS

Previously, mouse NIH 3T3 cells were stably transfected with human DNA polymerase beta (beta-pol) cDNA in the antisense orientation and unde r the control of a metallothionein promoter [Zmudzka,B.Z. and Wilson,S .H. (1990) Som. Cell Mol. Gen., 16, 311-320]. To assess the feasibilit y of enhancing the efficacy of chemotherapy by an antisense approach a nd to confirm a role for beta-pol in cellular DNA repair, we looked fo r increased sensitivity to DNA damaging agents under conditions where beta-pol is down-regulated in the antisense cell line. Such a sensitiz ation is anticipated only where beta-pol is rate-limiting in a DNA rep air pathway. A number of agents were tested: cis-diamminedichloroplati num II (cisplatin); 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU); ioniz ing radiation and the radio-mimetic drug bleomycin; the bifunctional a lkylating agents nitrogen mustard and L-phenylalanine mustard (melphal an); the monofunctional alkylating agent methyl methane sulfonate (MMS ) and ultraviolet (UV) radiation. In the cases of cisplatin and UV rad iation, a significant enhancement of cytotoxicity was observed. Damage as a result of both of these agents is thought to be repaired by the nucleotide excision repair (NER) pathway. The results suggest that, in this cell line, beta-pol is involved in and is rate-limiting in NER. We propose that down-regulation of beta-pol by antisense approaches mi ght be used to enhance the cytotoxic effects of cisplatin and other DN A damaging chemotherapeutic agents.