Silk sericin induced pro-oxidative stress leads to apoptosis in human cancer cells.

Pro-oxidative stress induced by dietary polyphenols elevates reactive oxygen species (ROS) production in cancer cells, which subsequently leads to oxidative stress-mediated apoptosis. Sericin, a principal component of silk is associated with a mixture of polyphenols and flavonoids, possesses various biomedical attributes including anticancer activity. In the present study, we have evaluated the pro-oxidative effect of Bombyx mori sericin (BMS), Antheraea assamensis sericin (AAS), and Philosamia ricini sericin (PRS) against different cancer cells. Cytotoxicity of silk sericin (SS) evaluated using A431, SAS, and MCF-7 cells showed ≥50% reduction in their viability at 4 mg/mL. Intracellular ROS levels, cell cycle arrest, and apoptosis assessed using flow cytometry corroborated that SS treatment elevated the intracellular ROS levels, caused cell cycle arrest at the sub-G1 phase and resulted in apoptotic cell death. SS treated A431 and SAS cells showed upregulation of p53 and dysregulation of Bax and Bcl-2 gene expression. Whereas, AAS treated MCF-7 cells showed upregulation of Bax and downregulation of Bcl-2 gene expression. AAS treated MCF-7 and SAS cells showed downregulation of Bcl-2 protein expression in comparison to their control cells. Thus, the present study demonstrates that the pro-oxidative effect induced by SS suppresses the cancer growth indicating its potential anticancer activity.