Mammary Cancer Chemoprevention by Withaferin A Is Accompanied byIn VivoSuppression of Self-Renewal of Cancer Stem Cells

Abstract

Current dogma favors elimination of therapy-resistant cancer stem cells (bCSC) for chemoprevention of breast cancer. We showed recently that mammary cancer development in a transgenic mouse model (mouse mammary tumor virus-neu; MMTV-neu) was inhibited significantly upon treatment with withaferin A (WA), a steroidal lactone derived from a medicinal plant. Herein, we demonstrate that the mammary cancer prevention by WA is accompanied by in vivo suppression of bCSC. In vitro mammosphere formation was dose-dependently inhibited by WA treatment in MCF-7 and SUM159 human breast cancer cells. Other markers of bCSC including aldehyde dehydrogenase 1 (ALDH1) activity and CD44high/CD24low/epithelial specific antigen-positive (ESA+) fraction were also decreased significantly in the presence of plasma achievable doses of WA. On the other hand, WA exposure resulted in cell line-specific changes in Oct4, SOX-2, and Nanog mRNA expression. WA administration to MMTV-neu mice (0.1 mg/mouse, three times/week for 28 weeks) resulted in inhibition of mammosphere number and ALDH1 activity in vivo. Mechanistic studies revealed that while urokinase-type plasminogen activator receptor overexpression conferred partial protection against bCSC inhibition by WA, Notch4 was largely dispensable for this response. WA treatment also resulted in sustained (MCF-7) or transient (SUM159) downregulation of Bmi-1 (B cell-specific Moloney murine leukemia virus insertion region-1) protein. Ectopic expression of Bmi-1 conferred partial but significant protection against ALDH1 activity inhibition by WA. Interestingly, WA treatment caused induction of Kruppel-like factor 4 (KLF4) and its knockdown augmented bCSC inhibition by WA. In conclusion, the present study shows in vivo effectiveness of WA against bCSC.

Treatment of adult and pediatric high-grade gliomas with Withaferin A: antitumor mechanisms and future perspectives

“…These genes normally function to prevent differentiation of quiescent cells, aiding cancer progression. Whether in monotherapy or in combination effect with cisplatin, WA treatment also resulted in an increase in ROS production and DNA damage, therefore causing cell death and apoptosis in GSLCs [37]. These results reveal the ability of WA to overcome and sensitize the protective barriers exhibited by GSLCs.…”

“…Studies with mice bearing human ovarian tumors have shown that WA alone can preferentially target putative cancer stem-like cells (CSLCs), causing dose-related cell death [36,37]. Furthermore, combining WA with cisplatin resulted in a synergistic effect, reducing tumor size by 70-80 % and preventing metastasis [36].…”

“…The latter is displayed in WA's ability to inhibit epithelial-mesenchymal transition by suppressing vimentin, a key protein in mesenchymal mobility [38]. Indicators of CT resistant GSLCs, such as aldehyde dehydrogenase 1 (ALDH1) activity, and stem cell marker gene expression (CD44, CD24 and CD 117) were significantly decreased when exposed to WA [37]. Notch1 signaling, which plays an important role in cancer stem cell self-renewal, was also inhibited upon WA treatment, resulting in inhibition of Notch1 downstream signaling genes Hes1 and Hey1.…”

“…WA inhibited TNF-induced NF-jB activation in murine fibrosarcoma and human embryonic kidney cell lines [37,67]. Another study showed that WA increased ubiquitinated-proteins in TNF-a-treated human umbilical vein endothelial cells at global levels, which suggests that WA tends to target the ubiquitin-proteasome pathway (UPP) [50,68].…”

Potential Anticancer Properties and Mechanisms of Action of Withanolides

“…WFA has shown to have potent cytotoxic effects on various cancer cell types. Anticancer activity of WFA has been reported against uveal melanoma [9], glioblastoma cells [10], neuroblastoma and multiple myeloma [11], leukemia [12,13], breast [14][15][16][17], colon [18], ovarian [19], pancreatic [20], prostate [21,22], thyroid [23], and head and neck cancer cells [24].…”