| Silibinin, a flavonolignan, has shown promising cancer chemopreventive and anti-cancer potential against various epithelial cancers including lung cancer. Though relevant studies have identified the signaling cascades that are targeted and regulated by silibinin, its precise role in the modulation of key epigenetic related events remains unclear. Related to this aspect, the aims of my proposed studies are: (1) to assess the anti-cancer efficacy of silibinin in human NSCLC cells and to identify its primary molecular targets involved in its efficacy; (2) to determine the combinatorial effects of silibinin and HDACi on proliferation and apoptosis of NSCLC; (3) to determine the combinatorial effects of silibinin and HDACi or DNMTi on the re-expression of E-cadherin (an epithelial marker) in NSCLC cells; and (4) to determine the biological efficacy of these combination treatments on the invasion and migration of NSCLC cells.;Our studies revealed that silibinin treatments causes G1 arrest of NSCLC cells, and concomitantly up regulates the expression of CDK inhibitors such as p21. In this context, we delineated the possible involvement of HDACs in relation to the silibinin-mediated induction of p21 levels. Silibinin treatments notably reduced HDAC (1, 2 and 3) protein levels and caused accumulation of acetylated histones (H3 and H4) in total cellular chromatin. Furthermore, co-treatments of silibinin and HDACi significantly augmented the acetylation states of histone (H3 and H4) at the p21 promoter, which resulted in increased transcription of the gene. Mechanistically, these epigenetic modifications led to cell cycle associated alterations specifically at the p21-cyclin B1 nexus, which directly translated into enhanced anti-proliferative and pro-apoptotic effects of combined treatments against NSCLC.;Studies in the literature have strongly implicated the involvement of epigenetic events to be associated with loss of E-cadherin in NSCLC cells, contributing to the aggressive phenotype. In this regard, our results also revealed that silibinin treatment alone as well as in combination with epigenetic therapies, led to a sustained increase/restoration of E-cadherin protein expression with concomitant reduction of Zeb1 levels. Consequently, silibinin treatment alone as well as in combination with HDACi or DNMTi effectively reduced the invasion/migratory potential of NSCLC cells, which was elaborately explored. |
