Researchers have shown that 3-azidoWA abrogated neovascularisation "in vivo" in a dose-dependent manner. Withaferin A has been shown to inhibit cell proliferation in HUVECs at significantly lower doses through the inhibition of Cyclin D1 expression. Inhibition of cell proliferation is due to the cytostatic nature of withaferin, resulting in cell arrest in the G0G1 phase of the cell cycle. Researchers have shown that withaferin A has an anti-angiogenic activity "in vivo" at doses much lower than required for its anti-tumor activity. NF-κB is a transcription factor that regulates many genes involved in cell survival, growth, immune response and angiogenesis. Withaferin A inhibits NF-κB at a very low concentration by targeting the ubiquitin-mediated proteasome pathway (UPP) in endothelial cells. Scientists believe that the site at which withaferin acts on UPP must be different from the site of action of 20s proteasome inhibitor. "In vitro" experiments demonstrated that withaferin A interferes with TNF-induced NF-κB activation at the level or upstream of IKKβ. It also inhibits other transcription factors including Ap1 and Sp1 which are important mediators of many signalling pathways that are down-regulated by various chemotherapeutic agents. It can induce oxidative stress, alter gene expression, depolarize mitochondria. Withaferin A also down regulates VEGF gene expression and can affect calcium signaling. Mohan et al. showed that withaferin A could inhibit endothelial cell proliferation at low concentrations and thus non-toxic to cells. Researchers have demonstrated the regulation of Hsp90 co-chaperone CDC37 through direct irreversible binding of withaferin A to C-terminus of Hsp90. Withaferin induces aggregation of Hsp90, dissociation of Hsp90- CDC37 complex and down regulation of Hsp90 target proteins mediated through proteasomal degradation. Induction of heat shock response by withaferin provides cytoprotective property whereas inhibition of heat shock protein activity will lead to apoptosis. This dual property of withaferin on heat shock protein might be due to the concentration of withaferin and cellular content. Withania extracts suppresses the production of various pro-inflammatory molecules in many in vitro models. Anti-inflammatory property of withaferin A has been attributed to its ability to suppress alpha-2 macroglobulin, NF-κB and AP1.