Nimbolide epigenetically regulates autophagy and apoptosis in breast cancer

Abstract

Autophagy is a critical regulator of cellular homeostasis and its dysregulation often results in various disease manifestations, including cancer. Nimbolide, an active chemical constituent of neem (Azadirachta indica) exhibits potent anticancer effects. Although, nimbolide mediated apoptosis activation in breast cancer cells is well known. Nevertheless, its role in autophagy induction mechanism and epigenetic alteration is not explored previously. Our current study intended to bridge the gaps in the existing research by exploring the potential of nimbolide in inducing autophagy, which could counter regulate the transformations in breast cancer. In our studies, nimbolide significantly inhibited the cell proliferation of MDA-MB-231 and MCF-7 cells with IC₅₀ values of 1.97 ± 0.24 and 5.04 ± 0.25 μM, respectively. Nimbolide markedly arrested the cell cycle progression and cell survival with loss of mitochondrial membrane potential by reducing Bcl-2 concomitantly inducing Bax and caspases protein expression with modulation of HDAC-2 and H3K27Ac expression. Consequently, characteristic autophagolysosome accumulation was observed by acridine orange, monodansylcadaverine (MDC) and Lysotracker Red staining. Moreover, nimbolide induced autophagy signaling by increasing Beclin 1 and LC3B along with decreased p62 and mTOR protein expression. Thus, our findings imply that nimbolide induces autophagy mediated apoptotic cell death in breast cancer with epigenetic modifications.

Keywords: Apoptosis; Autophagy; H3K27Ac; HDAC-2; Nimbolide.