Modulation of excision repair cross complementation group 1 (ercc-1) mrna expression by pharmacological agents in human ovarian carcinoma cells

Abstract

Excision repair cross complementation group 1 ( ERCC-1) is a DNA repair gene that is essential for life, and it appears to be a marker gene for nucleotide excision repair activity. Overexpression of ERCC-1 during cisplatin-based chemotherapy is associated with clinical and cellular drug resistance. We therefore began to assess the influence of various pharmacological agents on the induction of ERCC-1 mRNA in A2780/CP70 human ovarian carcinoma cells. Cisplatin exposure in culture resulted in a 4- to 6-fold induction for the steady-state level of ERCC-1 mRNA in A2780/CP70 cells. ERCC-1 mRNA induction was concentration and time dependent. Cyclosporin A and herbimycin A, which suppress c- fos and c- jun gene expressions, respectively, blocked the cisplatin-induced increase in ERCC-1 mRNA. This effect of cyclosporin A or herbimycin A on the down-regulation of ERCC-1 correlates with enhanced cytotoxicity of cisplatin in this system. The products of c- fos and c- jun are components of the transcription factor AP-1 (activator protein 1). 12- O-Tetradecanoylphorbol 13-acetate (TPA), a known AP-1 agonist, induced ERCC-1 mRNA to the same extent as cisplatin, but did not synergize with cisplatin in this regard. The TPA effect was biphasic, with an initial increase during the first 1–6 hr, followed by decreasing mRNA levels at 24–72 hr. These data suggest that the effects of these pharmacological agents on ERCC-1 gene expression may be mediated through the modulation of AP-1 activities.