18β-glycyrrhetinic Acid Induces Cell Cycle Arrest and Apoptosis in HPV18+ HeLa Cervical Cancer Cells

Aims: In recent years, natural products have received great attention to cancer prevention owing to their various health benefits, lack of toxicity, and side effects. Accumulating evidence shows that 18β-glycyrrhetinic acid (GRA) has antiproliferative and apoptotic activities on many cancer cell lines, while its role in cervical cancer remains unknown. Thus, the current research was conducted to illustrate GRA's cytotoxic effect against the HeLa cell line of HPV18 + human cervical cancer.

Methodology: The effect of GRA on HeLa cell line was tested by MTT and Trypan blue dye exclusion assay. Cell cycle analysis was carried out by flow cytometry after PI staining. Apoptosis was assessed after annexin V / PI double staining by flow cytometry. The Caspase activation assay kit analysed caspase activation. Reactive oxygen species (ROS) generation was measured by fluorimeter after DCFDA dye staining.

Results: Results of the current study have shown that GRA exposure significantly inhibited the cell viability of HeLa cells in a dose- and time-dependent manner. GRA induced growth arrest of HeLa cells at G0/G1 phase of the cell cycle. Moreover, GRA's antiproliferative action was mediated through apoptosis, as evident from caspase-3 and -9 activation. Caspase inhibitors blocked the GRA-induced caspase activation and ameliorated the GRA-induced cytotoxicity. This suggested the role of the intrinsic pathway of apoptosis stimulated by GRA. The intracellular ROS generation assay showed a dose-related increment in ROS production induced by GRA. Co-culturing of HeLa cells with N-acetyl cysteine (NAC), a ROS inhibitor, completely abrogated GRA-induced cell cycle arrest and apoptosis. Thus, the effect of NAC suggested the involvement of intracellular ROS in the GRA-induced cytotoxicity.

Conclusion: In summary, GRA exhibited strong antiproliferative and apoptotic properties and, thus, could act as an adjunct in the prevention and management of cervical cancer.