Isoquinoline Alkaloid Berberine Exerts its Antineoplastic Activity by Inducing Molecular DNA Damage in HeLa Cells: A Comet Assay Study

Molecular damage of DNA plays an important role in the cell killing and several anti-neoplastic agents exert their cytotoxic effects by inducing DNA damage in the cancer cells. DNA damaging effect of various concentrations of berberine chloride (BCL), an isoquinoline alkaloid was studied in HeLa cells by alkaline comet assay. The DNA damage has been expressed as olive tail moment (OTM). Incubation of HeLa cells with BCL for 4 h showed greater amount of DNA damage (OTM) than 2 h treatment. BCL treatment caused a concentration dependent rise in the DNA damage in HeLa cells and exposure of HeLa cells with 1 μg/ml BCL caused a10 fold rise in baseline DNA damage, whereasa maximum rise in DNA damage was observed in HeLa cells exposed to 8 μg/ml BCL. The study of DNA repair kinetics at different BCL post-treatment times revealed a constant rise in the DNA damage in BCL treated cells up to 24 h except for 1 -4 μg/ml BCL, where the highest DNA damage was observed at 12 h post-BCL treatment. The clonogenic assay showed that BCL treatment resulted in a concentration dependent rise in its cell killing effect. The cell survival and molecular DNA damage in HeLa cells treated with BCL has an inverse correlation indicating that with increased DNA damage cell survival declined. Our study demonstrates that anti-neoplastic effect of BCL is mainly due to its ability to cause damage to the cellular genome.