Role of P53 protein in activation of atm- and parp-mediated dna damage repair (DDR) pathways induced by topoisomerase type II inhibitors

Aim. To study the mechanisms of doxorubicin genotoxic effects in terms of poly-(ADP)-ribose-polymerase (PARP) and the ATM-kinase (Ataxia Telangiectasia Mutated) inhibition in cell lines with different p53 status.

Methods. The study was conducted on BJ and BJp53DD human fibroblasts cell lines, cultured in DMEM medium supplemented with fetal bovine serum, L-glutamine and antibiotics. Inhibition of PARP and ATM-kinase activity was attained by adding synthetic inhibitors Nu1025 and Ku55933 respectively. Chemotherapy drug doxorubicin was used to induce deoxyribonucleic acid (DNA) damages. Cell viability analysis was performed using MTS-test. Repair system proteins and apoptotic markers expression was assessed by western blotting. Cells distribution by cell cycle phases was performed by flow cytometry.

Results. Adding PARP and ATM-kinase inhibitors to the BJ p53DD cell line culture resulted in a significant reduction in the viable cells number amid DNA damage induction caused by doxorubicin. Cell death in these samples occurs according to the apoptosis mechanism, what was confirmed by the increase in hypodiploid cells number and increased expression of cleaved forms of PARP-1 and caspase-3. The above-described effects of the type II topoisomerase inhibitor doxorubicin were significantly higher in BJ fibroblasts line with non-functional p53 protein (p53DD) compared with conventional BJ human fibroblasts line.

Conclusion. In the context of the failure of p53-dependent mechanisms of cell cycle regulation in BJ p53DD human fibroblasts, PARP and ATM-kinase activity inhibition leads to increased cell death by apoptosis mechanism induced by the doxorubicin action.