Vitamin E analog alpha-TEA, methylseleninic acid, and trans-resveratrol in combination synergistically inhibit human breast cancer cell growth.
ABSTRACT Alpha-tocopherol ether-linked acetic acid analog [2,5,7,8-tetramethyl-2R-(4R, 8R-12-trimethyltridecyl) chroman-6-yloxyacetic acid (alpha-TEA)] is a novel form of vitamin E effective at killing cancer cells but not normal cells. alpha -TEA alone and together with methylseleninic acid (MSA) and trans-resveratrol (t-RES) were investigated for ability to induce apoptosis, DNA synthesis arrest, and cellular differentiation and inhibit colony formation in human MDA-MB-435-F-L breast cancer cells in culture. The 3 agents alone were effective in inhibiting cell growth by each of the 4 different assays, and 3-way combination treatments synergistically inhibited cell proliferation in each assay in comparison to individual treatments. Furthermore, combinations of alpha -TEA, t-RES, and MSA significantly enhanced levels of apoptosis in human breast (MDA-MB-231, MCF7, and T47D) and prostate (LnCaP, PC-3, and DU-145) cancer cell lines as well as in immortalized but nontumorigenic MCF10A cells but not primary cultures of human mammary epithelial cells. Western immunoblotting confirmed the induction of apoptosis in that the 3 agents induced poly(adenosine diphosphate-ribose) polymerase cleavage, with earlier detection and more complete cleavage seen in the combination treatment. Mechanistic studies showed combination treatments to inhibit cell proliferation via downregulation of cyclin D1 and induce apoptosis via activation of caspases 8 and 9 and downregulation of prosurvival proteins FLIP and survivin. In summary, the combination of alpha-TEA, MSA, and t-RES is more effective than single treatments for inhibiting cell proliferation, inducing cellular differentiation, and inducing cell death by apoptosis in human cancer cells in culture.
Article: α-TEA-induced death receptor dependent apoptosis involves activation of acid sphingomyelinase and elevated ceramide-enriched cell surface membranes.[show abstract] [hide abstract]
ABSTRACT: Alpha-tocopherol ether-linked acetic acid (α-TEA), an analog of vitamin E (RRR-alpha-tocopherol), is a potent and selective apoptosis-inducing agent for human cancer cells in vivo and in vitro. α-TEA induces apoptosis via activation of extrinsic death receptors Fas (CD95) and DR5, JNK/p73/Noxa pathways, and suppression of anti-apoptotic mediators Akt, ERK, c-FLIP and survivin in breast, ovarian and prostate cancer cells. In this study, we demonstrate that α-TEA induces the accumulation of cell surface membrane ceramide, leading to co-localization with Fas, DR5, and FADD, followed by activation of caspases-8 and -9 and apoptosis in human MDA-MB-231 breast cancer cells. α-TEA treatment leads to increased acid sphingomyelinase (ASMase) activity by 30 min, peaking at 4 hrs, which is correlated with ASMase translocation from cytosol to the cell surface membrane. Functional knockdown of ASMase with either the chemical inhibitor, desipramine, or siRNA markedly reduces α-TEA-induced cell surface membrane accumulation of ceramide and its co-localization with Fas, DR5, and FADD, cleavage of caspases-8 and -9 and apoptosis, suggesting an early and critical role for ASMase in α-TEA-induced apoptosis. Consistent with cell culture data, immunohistochemical analyses of tumor tissues taken from α-TEA treated nude mice bearing MDA-MB-231 xenografts show increased levels of cell surface membrane ceramide in comparison to tumor tissues from control animals. Taken together, these studies demonstrate that ASMase activation and membrane ceramide accumulation are early events contributing to α-TEA-induced apoptosis in vitro and perhaps in vivo.Cancer Cell International 10/2010; 10:40. · 1.97 Impact Factor