Molecular Insights into Withaferin-A-Induced Senescence: Bioinformatics and Experimental Evidence to the Role of NFκB and CARF

Abstract

Withaferin-A (Wi-A) has been shown to possess anticancer activity. Molecular mechanism(s) of its action has not been fully resolved. We recruited low dose of Wi-A that caused slow growth arrest in cancer cells and was relatively safe for normal cells. Consistently, we detected nuclear translocation of nuclear factor kappa B (NF?B) and activation of p38MAPK selectively in cancer cells. Bioinformatics analyses revealed that Wi-A did not disrupt IKKa/IKKb-Nemo complex that regulates NF?B activity. However, it caused moderate change in the conformation of IKKb-Nemo interacting domain. Experimental data revealed increased level of phosphorylated I?Ba in Wi-A-treated cells, suggesting an activation of IKK complex that was supported by nuclear translocation of NF?B. Molecular docking analysis showed that Wi-A did not disrupt; however, decreased the stability of the NF?B-DNA complex. It was supported by downregulation of DNA-binding and transcriptional activities of NF?B. Further analysis revealed that Wi-A caused upregulation of CARF (collaborator of ARF) demonstrating an activation of DNA damage oxidative stress response in both cancer and normal cells. In line with this, upregulation of p21WAF1, p16INK4A, and hypophosphorylated pRB and induction of senescence were observed demonstrating that Wi-A-induced senescence is mediated by multiple pathways in which CARF-mediated DNA damage and oxidative stress play a major role.