Bermudez Yira, Ahmadi Shirrin, Lowell Nancy E, Kruk Patricia A
Department of Pathology and Cell Biology, University of South Florida, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA.
Cancer Detect Prev. 2007;31(2):119-28. doi: 10.1016/j.cdp.2006.12.002. Epub 2007 Feb 28.
Dietary factors influence tumor formation and progression. Vitamin E is a dietary anti-oxidant capable of eliminating free radical damage, inducing apoptosis and decreasing oncogene expression. Therefore, Vitamin E may be a strong candidate for cancer prevention and/or chemotherapeutic intervention. Since telomerase, a ribonucleoprotein uniquely expressed in over 95% of cancers, plays an important role in cellular immortalization, cell growth and tumor progression, the present study investigated the effects of Vitamin E on telomerase activity in human ovarian cancer.
Normal and malignant ovarian surface epithelial (OSE) cells were cultured with and without D-alpha tocopheryl acetate (Vitamin E). MTS and Western immunoblot assays were used to examine the effect of Vitamin E on cell growth, survival and cytotoxicity. PCR-ELISA, RT-PCR and luciferase reporter assays were performed to determine the effect of Vitamin E on telomerase activity.
Vitamin E suppressed endogenous telomerase activity in ovarian cancer cells, but had no similar effects in telomerase-negative normal OSE cells. Vitamin E also reduced hTERT-mRNA transcript levels and reduced hTERT promoter activity maximally targeting the -976 to -578bp promoter regions. In addition, Vitamin E improved cisplatin-mediated cytotoxicity as evidenced by reduced cancer cell growth and increased cleaved caspase 3 activity. In contrast, Vitamin E protected telomerase-negative OSE cells from cisplatin-mediated cytotoxicity as evidenced by decreased cleaved caspase 3 activity.
Our data suggest that, by suppressing telomerase activity, Vitamin E may be an important protective agent against ovarian cancer cell growth as well as a potentially effective therapeutic adjuvant.
饮食因素影响肿瘤的形成和进展。维生素E是一种饮食抗氧化剂，能够消除自由基损伤、诱导细胞凋亡并降低癌基因表达。因此，维生素E可能是癌症预防和/或化疗干预的有力候选者。由于端粒酶是一种在超过95%的癌症中独特表达的核糖核蛋白，在细胞永生化、细胞生长和肿瘤进展中起重要作用，本研究调查了维生素E对人卵巢癌中端粒酶活性的影响。
正常和恶性卵巢表面上皮（OSE）细胞在添加和不添加D-α生育酚醋酸酯（维生素E）的情况下进行培养。采用MTS和Western免疫印迹分析来检测维生素E对细胞生长、存活和细胞毒性的影响。进行PCR-ELISA、RT-PCR和荧光素酶报告基因分析以确定维生素E对端粒酶活性的影响。
维生素E抑制卵巢癌细胞中的内源性端粒酶活性，但对端粒酶阴性的正常OSE细胞没有类似影响。维生素E还降低了hTERT-mRNA转录水平，并最大程度地降低了靶向-976至-578bp启动子区域的hTERT启动子活性。此外，维生素E改善了顺铂介导的细胞毒性，表现为癌细胞生长减少和裂解的半胱天冬酶3活性增加。相反，维生素E保护端粒酶阴性的OSE细胞免受顺铂介导的细胞毒性，表现为裂解的半胱天冬酶3活性降低。
我们的数据表明，通过抑制端粒酶活性，维生素E可能是预防卵巢癌细胞生长的重要保护剂以及潜在有效的治疗佐剂。
