Arsenic trioxide allosterically inhibits human telomerase, validated by in-silico and in-vitro cancer and non cancer cell lines.

Till now liver cancer is not successfully treated by chemotherapy, radiation treatment, or other adjuvant medications. According to reports, arsenic trioxide (ATO) causes the production of ROS in cells, which raises the possibility that it might cause telomerase suppression and telomere dysfunction in hepatocellular carcinoma cell. Telomere length aberration increases the risk of carcinogenesis by promoting genomic instability, which in turn causes chromosomal abnormalities and hence telomere length may serve as a biomarker for cancer risk. At various time intervals, the anticancer efficacy of ATO was tested, on human control liver cell line (Wrl-68 treated cells) and cancer liver cell line (HepG2). The viability and cytotoxicity were evaluated in vitro, wound healing, DCFDA & Annexin V/PI test was used to assess ROS mediated apoptosis, and immunoblotting, qRT-PCR, Trap assay, EMSA along with insilico studies, were used to assess the expression, activity and binding interaction of telomerase. ATO may act as a potential inhibitor for the enzyme telomerase as shown by molecular docking and MD simulation study. In the presence of ATO, the binding energy between DNA (telomeres) and telomerase enzymes reduces dramatically, yet the contact between them remains with the least stability, meeting the requirements of allosteric inhibition. This was further supported by in vitro study which demonstrated that ATO stimulates the production of ROS and inhibits telomerase regulation in HepG2 cells. This was confirmed by docking studies that ATO inhibit telomerase allosterically and causes HepG2 cells to undergo normal cellular senescence and triggers telomerase-mediated cell death. These findings offer new insight into the anticancer properties of ATO which may help in the treatment of hepatocellular carcinoma.