Withaferin A induces apoptosis by activating p38 mitogen-activated protein kinase signaling cascade in leukemic cells of lymphoid and myeloid origin through mitochondrial death cascade

Abstract

Withaferin A (WA) is present abundantly in Withania somnifera, a well-known Indian medicinal plant. Here we demonstrate how WA exhibits a strong growth-inhibitory effect on several human leukemic cell lines and on primary cells from patients with lymphoblastic and myeloid leukemia in a dose-dependent manner, showing no toxicity on normal human lymphocytes and primitive hematopoietic progenitor cells. WA-mediated decrease in cell viability was observed through apoptosis as demonstrated by externalization of phosphatidylserine, a time-dependent increase in Bax/Bcl-2 ratio; loss of mitochondrial transmembrane potential, cytochrome c release, caspases 9 and 3 activation; and accumulation of cells in sub-G0 region based on DNA fragmentation. A search for the downstream pathway further reveals that WA-induced apoptosis was mediated by an increase in phosphorylated p38MAPK expression, which further activated downstream signaling by phosphorylating ATF-2 and HSP27 in leukemic cells. The RNA interference of p38MAPK protected these cells from WA-induced apoptosis. The RNAi knockdown of p38MAPK inhibited active phosphorylation of p38MAPK, Bax expression, activation of caspase 3 and increase in Annexin V positivity. Altogether, these findings suggest that p38MAPK in leukemic cells promotes WA-induced apoptosis. WA caused increased levels of Bax in response to MAPK signaling, which resulted in the initiation of mitochondrial death cascade, and therefore it holds promise as a new, alternative, inexpensive chemotherapeutic agent for the treatment of patients with leukemia of both lymphoid and myeloid origin.

Anti-cancer activity of withaferin A in B-cell lymphoma

“…al., we conclude that WA inhibits the growth and survival of DLBCL by interacting and inhibiting the activity of the chaperone Hsp90, resulting in reduced expression of its client proteins. 15 Studies also indicate that WA has no noticeable toxicity on normal lymphocytes 28 , and our results illustrate that WA does not appear to affect proliferating colon epithelial cells in vivo. Further analyses on in vivo stability of WA and its effects on normal tissues need to be completed in order evaluate the clinical potential of WA as a therapeutic for DLBCL but current findings are promising.…”

“…Previously a few studies have examined the effect of WA, a naturally occurring steroid lactone on lymphoblastic and myeloid leukemia, 28,29 but none had studied its ability to modulate the growth of DLBCL which are aggressive tumors. Here we showed that WA has a significant anti-cancer role in the growth and survival of this aggressive tumor using both in vitro as well as an in vivo lymphoma model.…”

Withanolides and Related Steroids

“…Withaferin A (1) has been investigated extensively in this respect, with several recent studies also addressing its mechanism of action (191,(237)(238)(239).…”

Nf-κb-Dependent Inhibition of HIV-1 Transcription by Withaferin A

“…Studies have shown that therapeutic doses of WA exert anti-cancer, anti-inflammatory, and anti-angiogenesis effects [9,16,[39][40][41]. Our results suggest that WA, a bioactive compound derived from Indian Ashwagandha, disrupts viral gene expression through the inhibition of NF-κB activation.…”

“…W. somnifera is the source of the largest and structurally most diversified set of withanolides, of which withaferin A (WA) is among the first of the group to be isolated and to show significant pharmacological properties, such as anti-tumor, anti-inflammatory, and immunomodulatory activity [9]. WA exhibits strong inhibitory effects on the growth of several human leukemic cell lines [16], and causes mitotic arrest in human breast cancer cells [12]. Recent studies have shown that W. somnifera extract, including its main component WA, inhibits NF-κB activation by blocking the activation of IκB-α, which is in turn induced by tumor necrosis factor-α in several cell types, such as L929 fibrosarcomic cells, and were stored at -20°C until needed.…”