Breast cancer is the second leading cause of mortality among women in the US. A contributing factor to such dire statistics is that conventional therapies are all too often compromised due to tumor relapse. Clearly there is an urgent need for agents that can circumvent resistance when combined with conventional therapies. RRR-α-tocopherol ether-linked acetic acid analog (α-TEA), a small bioactive lipid, exhibits in vitro and in vivo anticancer actions in a variety of cancers, including breast, prostate, and ovarian with little or no effect on normal cells and tissues, which potentially makes it an ideal chemotherapeutic agent. My studies investigated the anticancer actions of α-TEA alone and in combination with therapeutic agents using human breast cancer cell lines. Data show that: (i) Endoplasmic reticulum (ER) stress plays an important role in α-TEA induced apoptosis by enhancing DR5/caspase-8 pro-apoptotic signaling and suppressing anti-apoptotic factors c-FLIP and Bcl-2 via ER stress mediated JNK/CHOP/DR5/caspase-8 signaling, (ii) α-TEA plus tamoxifen act cooperatively to circumvent acquired and de novo tamoxifen resistance, resulting in cancer cell death by apoptosis. Mechanistically, the circumvention of tamoxifen resistance involved induction of DR5/caspase-8 pro-apoptotic mediators and suppression of anti-apoptotic factors c-FLIP and Bcl-2 via ER stress mediated JNK/CHOP/DR5/caspase-8 signaling. (iii) α-TEA alone or with tamoxifen circumvents tamoxifen resistance via disruption of membrane cholesterol rich lipid raft microdomains. Cholesterol blocked the ability of α-TEA + tamoxifen to circumvent tamoxifen resistance. (iv) α-TEA in combination with PI3K, MEK or mTOR inhibitors acted cooperatively to induce apoptosis, by down-regulation of IRS-1/PI3K mediators via JNK. (v) α-TEA plus doxorubicin or cisplatin enhanced apoptosis in p53 mutant human breast cancer cells via targeting p53-inducible genes in a p73-dependent manner; namely, via up-regulation of death receptor-5 (DR5), CD95/APO-1 (Fas), Bax and Noxa, as well as down-regulation of anti-apoptotic mediator Bcl-2. Data showed that p73 responses were downstream of c-Abl, JNK and Yap. (vi) FASN inhibitor alone or with Tamoxifen or α-TEA circumvents tamoxifen resistance, thereby, providing novel strategies for restoring tamoxifen sensitivity to tamoxifen resistant cancers. In summary data show, α-TEA alone and in combination with multiple clinically-relevant anticancer agents is a promising anticancer agent. / text

alpha-TEA (alpha-tocopherol ether linked acetic acid) has been shown to induce apoptosis in human prostate, ovarian and breast cancer cells in culture and in xenograft models by promoting pro-apoptotic pathways and inhibiting anti-apoptotic pathways. Studies investigated the ability of alpha-TEA to induce apoptosis in human hematological malignant cell lines Jurkat, Raji and U266, representing T cell leukemia, B cell lymphoma and multiple myeloma, respectively. The three cell lines were cultured in the presence of different concentrations of alpha-TEA for different time periods, and examined for apoptosis by annexin V – FITC analyses, DAPI staining, and western blotting for poly (ADP-ribose) polymerase cleavage. alpha-TEA induced apoptosis in all three cell lines in a dose and time dependent manner. Levels of pro-apoptotic molecules DR5, c-Jun N-terminal protein kinase (JNK), C/EBP homologous protein (CHOP), caspase 9, and caspase 3 were upregulated in alpha-TEA treated cells in comparison to vehicle controls. Caspase 8 was activated in Jurkat and U266 cells but not in Raji cells. Apoptosis and pro-death signaling mediators were blocked by ceramide inhibitor, desipramine. The anti-apoptotic nuclear factor kappa B (NF-[kappa]B) signaling pathway was down-regulated in alpha-TEA treated Raji and U266 cells. Combinations of omega-3 fatty acid docosahexaenoic (DHA) and alpha-TEA significantly enhanced apoptosis in Jurkat cells in comparison to single treatments and vehicle control. In summary, alpha-TEA induced apoptosis in the malignant hematological cell lines is via shared and distinct pathways. ASMase/ceramide-mediated JNK activation and endoplasmic reticulum (ER) stress mitochondrial dependent apoptosis are involved in alpha-TEA induced apoptosis in the three cell lines; however, the cell lines exhibit cell type-specific responses to alpha-TEA: activation of death receptor/caspase 8 pathway is involved in Jurkat cells, suppression of NF-[kappa]B signaling is involved in Raji cells, and the U266 cells share both of these pathways for the induction of apoptosis. / text