Materials provided by Stanford University Medical Center. Original written by Krista Conger. Note: Content may be edited for style and length.
Finding a “cure” for cancer is the Holy Grail of medical research. However, a single catch-all solution is unlikely; cancer comes in many shapes and forms.
Some researchers have referred to cancer as a “constellation” of diseases.
One drug—Sorafenib—showed “marginal” benefits in a multicenter Phase 3 trial for one type of lung cancer. However, side effects were significant, causing some patients to drop out of the trial early.
However, the adverse effects of taking high doses of aspirin would need to be managed; for instance, the chance of excessive bleeding is increased. For individuals with no other treatment options, however, the negative impacts of aspirin would be outweighed by the benefits.
Withaferin A (WA, Fig. 13) is a withanolide isolated from the Indian medicinal plant of Withania somnifera (commonly known as “Ashwagandha” or “Indian Winter Cherry” in Ayurvedic medicine) and possesses diverse biological activities, such as anti-inflammatory (Kaileh et al., 2007), antistress, antioxidant, immunomodulatory (Mishra, Singh, & Dagenais, 2000), antiangiogenesis (Mohan et al., 2004), and anticancer activities (Yang, Shi, & Dou, 2007). Since its discovery in the late 1960s, withaferin A has been extensively studied for its anticancer activity, and numerous mechanisms and molecular targets proposed (Falsey et al., 2006; Kaileh et al., 2007; Shohat, Gitter, Abraham, & Lavie, 1967; Srinivasan, Ranga, Burikhanov, Han, & Chendil, 2007; Yang et al., 2007; Yokota, Bargagna-Mohan, Ravindranath, Kim, & Mohan, 2006). It has been reported that withaferin A inhibits nuclear factor-κB (NF-κB) activation of IκB kinase via a thioalkylation-sensitive redox mechanism (Kaileh et al., 2007) induces apoptosis in prostate cancer cells through Par-4 induction (Srinivasan et al., 2007), targets β5 subunit of tumor proteasome (Yang et al., 2007), and covalently binds to Annexin II to alter cytoskeletal architecture (Falsey et al., 2006). In 2010, Yu and coworkers demonstrated that withaferin A exhibits antiproliferative activity and inhibits Hsp90 in pancreatic cells where it was reported to deplete cellular levels of Hsp90-dependent client proteins (Akt, Cdk4, and GR) (Yu et al., 2010). In addition, it was observed that withaferin A induces Hsp70 expression, without affecting Hsp90 levels. Moreover, these researchers found that withaferin A binds Hsp90 and halts the Hsp90 chaperone cycle through a novel ATP-independent mechanism. To identify the domain to which withaferin A binds in Hsp90, a pull-down assay using WA-biotin was used, which suggested interaction with the chaperone’s C-terminal domain (Yu et al., 2010). Coimmunoprecipitation studies showed that withaferin A disrupts formation of the Hsp90/Cdc37 complex in pancreatic cancer cells (Yu et al., 2010). Structure–activity relationship studies have identified a pharmacophore of WA that involves the 4-hydroxy-5,6-epoxy-22-en-1-one moiety and its unsaturated lactone as critical for cytotoxic activity (Mohan et al., 2004; Yousuf et al., 2011). Recent studies with the withanolides indicate that the 5,6-epoxide may react with reactive cysteine residues in Hsp90 and induce aggregation, leading to disruption of Hsp90 function (Gu et al., 2014).
Posted on April 22, 2018 by ymccooper2013 Tagged EMT; breast cancer; vimentin; withaferin A	CommentsNo Comments on Mol Carcinog. 2015 Jun;54(6):417-29. doi: 10.1002/mc.22110. Epub 2013 Nov 30. Withaferin A inhibits experimental epithelial-mesenchymal transition in MCF-10A cells and suppresses vimentin protein level in vivo in breast tumors.
Mol Carcinog. 2015 Jun;54(6):417-29. doi: 10.1002/mc.22110. Epub 2013 Nov 30. Withaferin A inhibits experimental epithelial-mesenchymal transition in MCF-10A cells and suppresses vimentin protein level in vivo in breast tumors.
Lee J1, Hahm ER, Marcus AI, Singh SV.
Department of Pharmacology & Chemical Biology, and University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
We have shown previously that withaferin A (WA), a bioactive component of the medicinal plant Withania somnifera, inhibits growth of cultured and xenografted human breast cancer cells and prevents breast cancer development and pulmonary metastasis incidence in a transgenic mouse model. The present study was undertaken to determine if the anticancer effect of WA involved inhibition of epithelial-mesenchymal transition (EMT). Experimental EMT induced by exposure of MCF-10A cells to tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β) was partially reversed by treatment with WA but not by its structural analogs withanone or withanolide A. Combined TNF-α and TGF-β treatments conferred partial protection against MCF-10A cell migration inhibition by WA. Inhibition of TNF-α and TGF-β-induced MCF-10A cell migration by WA exposure was modestly attenuated by knockdown of E-cadherin protein. MCF-7 and MDA-MB-231 cells exposed to WA exhibited sustained (MCF-7) or transient (MDA-MB-231) induction of E-cadherin protein. On the other hand, the level of vimentin protein was increased markedly after 24 h treatment of MDA-MB-231 cells with WA. WA-induced apoptosis was not affected by vimentin protein knockdown in MDA-MB-231 cells. Protein level of vimentin was significantly lower in the MDA-MB-231 xenografts as well as in MMTV-neu tumors from WA-treated mice compared with controls. The major conclusions of the present study are that (a) WA treatment inhibits experimental EMT in MCF-10A cells, and (b) mammary cancer growth inhibition by WA administration is associated with suppression of vimentin protein expression in vivo.
Posted on April 22, 2018 by ymccooper2013 Tagged apoptosisVimentinwithaferin A (WFA)	CommentsNo Comments on Chem Biol. 2007 Jun;14(6):623-34. The tumor inhibitor and antiangiogenic agent withaferin A targets the intermediate filament protein vimentin.
Chem Biol. 2007 Jun;14(6):623-34. The tumor inhibitor and antiangiogenic agent withaferin A targets the intermediate filament protein vimentin.
Bargagna-Mohan P1, Hamza A, Kim YE, Khuan Abby Ho Y, Mor-Vaknin N, Wendschlag N, Liu J, Evans RM, Markovitz DM, Zhan CG, Kim KB, Mohan R.
Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, KY 40536, USA.
The natural product withaferin A (WFA) exhibits antitumor and antiangiogenesis activity in vivo, which results from this drug’s potent growth inhibitory activities. Here, we show that WFA binds to the intermediate filament (IF) protein, vimentin, by covalently modifying its cysteine residue, which is present in the highly conserved alpha-helical coiled coil 2B domain. WFA induces vimentin filaments to aggregate in vitro, an activity manifested in vivo as punctate cytoplasmic aggregates that colocalize vimentin and F-actin. WFA’s potent dominant-negative effect on F-actin requires vimentin expression and induces apoptosis. Finally, we show that WFA-induced inhibition of capillary growth in a mouse model of corneal neovascularization is compromised in vimentin-deficient mice. These findings identify WFA as a chemical genetic probe of IF functions, and illuminate a potential molecular target for withanolide-based therapeutics for treating angioproliferative and malignant diseases.
FiVe1 also , that is blocks the growth of tumors called sarcomas, which originate from mesenchymal tissues including bone, fat, cartilage, muscle and blood vessels. The compound blocks mitosis by binding to a structural protein, vimentinroduced abundantly in mesenchymal-type cells. Drugs that work via this mechanism should spare many of the healthy, fast-dividing cells, such as hair follicle cells, that are harmed by standard chemotherapy drugs.
Researchers have become aware in just the last decade that breast, colon and other epithelial-derived tumor cells sometimes exploit the EMT to detach from a primary tumor and acquire stem-like properties. Whether they originate from EMT-transformed epithelial cells or from mesenchymal tissues, mesenchymal cancer cells are prone to form deadly metastases and are generally difficult to treat with drugs—surgical removal is often the only good option.
The TSRI researchers, including lead author Michael J. Bollong, PhD, currently a Scripps Fellow in the Department of Chemistry, discovered FiVe1 by screening a library of about 50,000 small-molecule compounds for activity against EMT-transformed breast cancer cells. The engineered cell line was developed by collaborating researcher Sendurai A. Mani, PhD, of MD Anderson Cancer Center at the University of Texas. The cells express FOXC2, a transcription factor gene that promotes the EMT and makes cancer cells more stem-like, more prone to metastasis and more resistant to treatment.
One compound performed particularly well at curbing the growth of the FOXC2-expressing cells without affecting non-FOXC2-expressing cells, and had other properties that make it potentially suitable as a small-molecule drug. Follow-up molecular biology studies revealed that the compound blocks mitosis in the FOXC2-expressing cancer cells by binding to a structural protein called vimentin, produced principally in mesenchymal cell types. The compound, in addition to blocking mitosis, caused EMT-transformed breast cancer cells to quickly revert to a lower-grade, epithelial appearance. Lairson and colleagues named the compound FOXC2-inhibiting Vimentin effector 1 (FiVe1).
FiVe1’s selectivity for vimentin-containing mesenchymal cancer cells means that it wouldn’t have the same side-effects as traditional chemotherapy drugs. Vimentin is not expressed at significant levels in the hair follicle cells and mouth- and gut-lining epithelial cells damaged by standard chemotherapy drugs. “A drug that blocks mitosis by targeting vimentin should be less toxic than traditional chemotherapeutic drugs that targets cell-division,” Lairson said. He and his colleagues envision future drugs based on this strategy being used against carcinomas as add-on therapies to suppress EMT-transformed tumor cells that are prone to metastasize. Against sarcomas—tumors that are entirely mesenchymal—anti-vimentin drugs could be primary therapies.
The researchers currently are working to optimize FiVe1 and a few other promising compounds with chemical modifications. With help from a new National Institutes of Health grant they also are screening larger compound libraries to find other potential drug compounds that selectively attack mesenchymal and EMT-transformed cancers. The team plans to begin tests in animal models of cancer once they have an optimized compound.