The regulatory mechanism involved in paclitaxel-induced apoptosis: The role of ATF-3 on apoptosis in cervical cancer cell line (HeLa cell)

Abstract

16052 Background: Paclitaxel, which is a potent anti-cancer drug and microtubule-binding agent, has been found to be effective against several tumors, including cervical cancer. However, the exact mechanism underlying the apoptotic effects of paclitaxel is poorly understood. Methods: We show that paclitaxel induces apoptosis, as demonstrated by DNA fragmentation, TUNEL assay, and flow cytometry analysis in cervical cancer HeLa cells, correlating with enhanced caspase-3 activation and p73 as well as p21, which are inhibited strongly by p73 siRNA. Results: The paclitaxel treatment followed by the overexpression of wild type ATF3 potentiated apoptosis is by enhancing p73 expression, but these events were attenuated in C-terminal deleted ATF3 or ATF3 siRNA-transfected cells. Interestingly, paclitaxel-induced ATF3 colocalizes with transfected GFP-p73 in nucleus, but not in p73 siRNA-transfected cells. Conversely, p73 may not affect ATF3 expression, as increase of ATF3 expression did not detect in p73-overexpressing cells. Furthermore, we observed that ATF3 binds to DNA binding domain of p73, confirmed by GST-pull down assay for ATF3. Additionally, ATF3 potentiates p21 gene, a downstream target of p73, promoter activity and p73-p21 binding activity induced by paclitaxel and also we have obtained similar data in the tissue of cervical cancer patient treated with paclitaxel. Conclusions: Collectively, these results demonstrate that overexpression of ATF3 potentiates paclitaxel-induced apoptosis in HeLa cells, at least in part, through stimulating the p73 expression and its transcriptional activity. ATF3 may function as a tumor-inhibiting factor by regulating directly p73 and may suggest a functional link between ATF3 and p73. No significant financial relationships to disclose.