Deletion or mutation of the androgen receptor (AR) renders prostate tumors refractory to apoptosis by androgen ablation,

Curcumin (Diferuloylmethane) is a major chemical component of turmeric (curcuma longa) and is used as a spice to give a specific flavor and yellow color in Asian food. Curcumin exhibits growth inhibitory effects in a broad range of tumors as well as in TPA-induced skin tumors in mice. This study was undertaken to investigate the radiosensitizing effects of curcumin in p53 mutant prostate cancer cell line PC-3. Compared to cells that were irradiated alone (SF 2 ¼ 0.635; D 0 ¼ 231 cGy), curcumin at 2 and 4 lM concentrations in combination with radiation showed significant enhancement to radiation-induced clonogenic inhibition (SF 2 ¼ 0.224: D 0 ¼ 97 cGy and SF 2 ¼ 0.080: D 0 ¼ 38 cGy) and apoptosis. It has been reported that curcumin inhibits TNF-a-induced NFjB activity that is essential for Bcl-2 protein induction. In PC-3 cells, radiation upregulated TNF-a protein leading to an increase in NFjB activity resulting in the induction of Bcl-2 protein. However, curcumin in combination with radiation treated showed inhibition of TNF-a-mediated NFjB activity resulting in bcl-2 protein downregulation. Bax protein levels remained constant in these cells after radiation or curcumin plus radiation treatments. However, the downregulation of Bcl-2 and no changes in Bax protein levels in curcumin plus radiation-treated PC-3 cells, together, altered the Bcl2 : Bax ratio and this caused the enhanced radiosensitization effect. In addition, significant activation of cytochrome c and caspase-9 and -3 were observed in curcumin plus radiation treatments. Together, these mechanisms strongly suggest that the natural compound curcumin is a potent radiosesitizer, and it acts by overcoming the effects of radiation-induced prosurvival gene expression in prostate cancer.

Notch signaling plays a crucial role in the development of colon cancer; targeting the Notch pathway may sensitize colon cancers to various adjuvant agents. The focus of our current study is to identify natural compounds that target Notch signaling and that might be beneficial for the prevention and treatment of colon cancer. Withaferin-A (WA) is a bioactive compound derived from Withania somnifera, which inhibits Notch-1 signaling and downregulates prosurvival pathways, such as Akt/NF-κB/Bcl-2, in three colon cancer cell lines (HCT-116, SW-480, and SW-620). In addition, WA downregulated the expression of mammalian target of rapamycin signaling components, pS6K and p4E-BP1, and activated c-Jun-NH2-kinase–mediated apoptosis in colon cancer cells. We also established the molecular link between Notch/Akt/mammalian target of rapamycin signaling by complementary approaches (i.e., overexpression of Notch-1 or inhibition of Notch-1 by small interfering RNA). Our results suggest that WA inhibits Notch-mediated prosurvival signaling, which facilitates c-Jun-NH2-kinase–mediated apoptosis in colon cancer cell lines. These results underscore the anticancer activity of WA, which exhibits potential for further development for targeted chemotherapy and/or chemoprevention strategies in the context of colon cancer. Mol Cancer Ther; 9(1); 202–210

In recent years, Akt signaling has gained recognition for its functional role in more aggressive, therapy‐resistant malignancies. As it is frequently constitutively active in cancer cells, several drugs are being investigated for their ability to inhibit Akt signaling. The purpose of this study is to determine effect of diosgenin (fenugreek), a dietary compound on Akt signaling and its downstream targets on estrogen receptor positive (ER+) and estrogen receptor negative (ER−) breast cancer (BCa) cells. Diosgenin inhibits pAkt expression and Akt kinase activity without affecting PI3 kinase levels, resulting in the inhibition of its downstream targets, NF‐κB, Bcl‐2, survivin and XIAP. The Raf/MEK/ERK pathway, another functional downstream target of Akt, was inhibited by diosgenin in ER+ but not in ER− BCa cells. Additionally, we found that diosgenin caused G1 cell cycle arrest by downregulating cyclin D1, cdk‐2 and cdk‐4 expression in both ER+ and ER− BCa cells resulting in the inhibition of cell proliferation and induction of apoptosis. Interestingly, no significant toxicity was seen in the normal breast epithelial cells (MCF‐10A) following treatment with diosgenin. Additionally, in vivo tumor studies indicate diosgenin significantly inhibits tumor growth in both MCF‐7 and MDA‐231 xenografts in nude mice. Thus, these results suggest that diosgenin might prove to be a potential chemotherapeutic agent for the treatment of BCa. © 2009 UICC

Cadmium (Cd) is a toxic, heavy industrial metal that poses serious environmental health hazards to both humans and wildlife. Lately, Cd and Cd containing compounds have been classified as known human carcinogens and epidemiological data show causal associations with prostate, breast and lung cancer. The molecular mechanisms involved in Cd-induced carcinogenesis are poorly understood and are only now beginning to be elucidated. The effects of chronic exposure to Cd have recently become of great interest due to the development of malignancies in Cd-induced tumorigenesis in animal. Briefly, various in vitro studies demonstrate that Cd can act as a mitogen, stimulate cell proliferation, inhibit apoptosis and DNA repair, and induce carcinogenesis in several mammalian tissues and organs. Thus, the various mechanisms involved in chronic Cd exposure and malignant transformations warrant further investigation. In this review, we will focus on recent evidence of various leading general and tissue specific molecular mechanisms that follow chronic exposure to Cd in prostate, breast and lung transformed malignancies. In addition, this review considers less defined mechanisms such as epigenetic modification and autophagy, which are thought to play a role in the development of Cd-induced malignant transformation.