Abstract
ObjectiveCisplatin, the most common chemotherapeutic drug for the treatment of advanced stage cervical cancers has limitations in terms of drugs resistance observed in patients partly due to functional DNA damage repair (DDR) processes in the cell. Mediator of DNA damage checkpoint 1 (MDC1) is an important protein in the Ataxia telangiectasia mutated (ATM) mediated double stranded DNA break (DSB) repair pathway. In this regard, we investigated the effect of MDC1 change in expression on the cisplatin sensitivity in cervical cancer cells.ResultsThrough modulation of MDC1 expression in the cervical cancer cell lines; Hela, SiHa and Caski, we found that all the three cell lines silenced for MDC1 exhibited higher sensitivity to cisplatin treatment with inefficiency in accumulation of p γH2AX, Ser 139 foci and increased accumulation of pChk2 Thr 68 at the damaged chromatin followed by enhanced apoptosis. Further, we observed the increased p53 Ser 15 phosphorylation in the MDC1 depleted cells. Our studies suggest that MDC1 expression could be a key determinant in cervical cancer prognosis and its depletion in combination with cisplatin has the potential to be explored for the sensitisation of chemo-resistant cervical cancer cells.
Highlights
Cervical cancer is amongst the commonly diagnosed cancers in women, with a significant proportion of patients treated with cisplatin based chemo-radiotherapy (CRT) [1]
Smaller number of surviving colonies were observed in Mediator of DNA damage checkpoint 1 (MDC1) knocked down cell lines whereas MDC1 high expression rendered the cell lines insensitive to the drug treatment, evident as maximum number of colonies observed in these cell lines (Fig. 1b and c)
human papillomavirus (HPV) proteins are known to be responsible for activating the ATMChk2 pathway for aiding viral genome amplification [4]
Summary
Stable cell line generation and effect of cisplatin on MDC1 expression modulated cervical cancer cells Stable cervical cancer cell lines were generated (Additional file 3: Figure S3). The difference between control cells and MDC-ov cells was found to be statistically insignificant in all the three cervical cancer cell lines studied (Additional file 4: Figure S4). We performed immunofluorescence studies with our cell lines exposed to 2 h of cisplatin treatment and observed significant decline in the γ-H2AX foci formation in MDC1 knocked down cell lines with a concomitant increased accumulation of the same in MDC1 overexpressed cells. Our results showed high cisplatin sensitivity in combination with MDC1 depletion in all the three cervical cancer cell lines (Fig. 3a and b). The exact mechanism for the decrease in p53 phosphorylation in combination with MDC1 overexpression still remains elusive but on the basis of our results, it could be interpreted that down regulating MDC1 expression in cervical cancer cells favoured p53 mediated apoptosis in response to cisplatin treatment
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