Cytotoxic and Anti-proliferative Effects of Moringa oleifera Lam. on HeLa Cells

Background: The aim of the study was to determine the mechanism of Moringa oleifera-induced apoptosis in HeLa cells. HeLa cells over-express cyclin E and cyclin B1, abrogate G0-G1 and G2-M cell cycle arrest, promoting tumorigenesis. Cyclin E, cyclin B1, E2F1 and telomerase expression, and caspase-3 and -7 activation were assessed after 24-treatment with M. oleifera leaf fractions. Methods: Apoptosis through caspase-3 and caspase-7 activation was determined quantitatively by the FAM FLICA™ Caspase-3/7 assay. Cyclin E, cyclin B1 and E2F1 were quantified by flow cytometry. Telomerase was evaluated by Telomeric Repeat Amplification Protocol (TRAP reaction). The effects on colony formation were assessed by seeding treated cells in six-well plates for 7 days under culture conditions. The MTT assay was used to determine cell survival. Results: HeLa cells treated for 24 hours with M. oleifera leaf fractions showed dose-dependent cytotoxicity, activation of caspases-3 and -7, down regulation of cyclin E, cyclin B1, E2F1, and inhibition of telomerase expression. Cell cycle analysis of the dead cell population showed G2-M cellcycle arrest. Conclusion: M. oleifera leaf fractions triggered apoptosis through the mitochondrial pathway and cell cycle arrest at G2-M phase in HeLa cells after 24-hour treatment, through down regulation of cyclin E and cyclin B1 expression, and caspase-3 and -7 activation. In addition, M. oleifera leaf extract induces senescence in HeLa cells through the down-regulation of telomerase. Colony formation and cell proliferation were inhibited in a dose-dependent manner, corresponding with telomerase inhibition.