Sphaerocoryne affinis fruit extract causes DNA damage leading to inhibited cell proliferation and activated apoptosis in cervical cancer cells

Abstract

Abstract Background The roots, bark, leaves, branches, and flowers of Sphaerocoryne affinis (family Annonaceae) reportedly exert anti-cancer activity. Herein, we examined the anti-cancer potential of S. affinis fruit extracts using cervical cancer HeLa cells. Methods The solvent fractions of the S. affinis fruit extract were prepared and subjected to in vitro testing in cervical cancer (HeLa) and human embryonic kidney 293 (Hek-293) cells. The CCK 8 assay was used to determine the time- and dose-dependent cytotoxicity. DAPI staining was performed to determine the number of nuclei and assess cell morphology. The expression of γH2AX, cleaved-caspase-3, and cyclin E was determined using western blotting. Quantitative PCR determined the relative transcription levels of pro-apoptotic BAX, anti-apoptotic BCL2, and proliferating cell nuclear antigen (PCNA). Results The hexane fraction of S. affinis fruit extract exhibited cytotoxicity against HeLa and Hek293 cells, as determined by IC50 values (95% confidence interval [CI] 4.05–4.34 µg/mL and 10.61–37.52 µg/mL, respectively). Accordingly, S. affinis fruit extract exerted selective toxicity against cancer cells relative to normal cells, with a selectivity index between 2.45–9.26. In addition, the cells displayed abnormal morphology and nucleus shrinkage. The time-dependent cytotoxicity assay revealed that cell viability was unaltered during the initial 24 h of treatment. Cells treated with the hexane fraction of S. affinis fruit extract showed increased levels of the histone H2A variant, γH2AX, a marker for DNA damage. Furthermore, caspase-3 was activated in the extract-treated cell group. Expression of cyclin E, crucial for the G1 to S phase transition, was reduced in cells treated with the S. affinis fruit extract. Simultaneously, treatment with S. affinis fruit extract decreased the expression of PCNA mRNA, which is essential for replication. Conclusion Collectively, these findings indicate that S. affinis fruit extracts exert an anti-cancer effect by arresting the cell cycle of HeLa cells and inducing apoptosis owing to irreversible DNA damage.