Kala Rishabh, Shah Harsh N, Martin Samantha L, Tollefsbol Trygve O
Department of Biology, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, AL, 35294, USA.
Comprehensive Center for Healthy Aging, University of Alabama at Birmingham, 1530 3rd Avenue South, Birmingham, AL, 35294, USA.
BMC Cancer. 2015 Oct 12;15:672. doi: 10.1186/s12885-015-1693-z.
Nutrition is believed to be a primary contributor in regulating gene expression by affecting epigenetic pathways such as DNA methylation and histone modification. Resveratrol and pterostilbene are phytoalexins produced by plants as part of their defense system. These two bioactive compounds when used alone have been shown to alter genetic and epigenetic profiles of tumor cells, but the concentrations employed in various studies often far exceed physiologically achievable doses. Triple-negative breast cancer (TNBC) is an often fatal condition that may be prevented or treated through novel dietary-based approaches.
HCC1806 and MDA-MB-157 breast cancer cells were used as TNBC cell lines in this study. MCF10A cells were used as control breast epithelial cells to determine the safety of this dietary regimen. CompuSyn software was used to determine the combination index (CI) for drug combinations.
Combinatorial resveratrol and pterostilbene administered at close to physiologically relevant doses resulted in synergistic (CI <1) growth inhibition of TNBCs. SIRT1, a type III histone deacetylase (HDAC), was down-regulated in response to this combinatorial treatment. We further explored the effects of this novel combinatorial approach on DNA damage response by monitoring γ-H2AX and telomerase expression. With combination of these two compounds there was a significant decrease in these two proteins which might further resulted in significant growth inhibition, apoptosis and cell cycle arrest in HCC1806 and MDA-MB-157 breast cancer cells, while there was no significant effect on cellular viability, colony forming potential, morphology or apoptosis in control MCF10A breast epithelial cells. SIRT1 knockdown reproduced the effects of combinatorial resveratrol and pterostilbene-induced SIRT1 down-regulation through inhibition of both telomerase activity and γ-H2AX expression in HCC1806 breast cancer cells. As a part of the repair mechanisms and role of SIRT1 in recruiting DNMTs, the effects of this combination treatment was also explored on DNA methyltransferases (DNMTs) expression. Interestingly, the compounds resulted in a significant down-regulation of DNMT enzymes with no significant effects on DNMT enzyme expression in MCF10A control cells.
Collectively, these results provide new insights into the epigenetic mechanisms of a novel combinatorial nutrient control strategy that exhibits synergy and may contribute to future recalcitrant TNBC prevention and/or therapy.
营养被认为是通过影响表观遗传途径（如DNA甲基化和组蛋白修饰）来调节基因表达的主要因素。白藜芦醇和紫檀芪是植物产生的植保素，是其防御系统的一部分。单独使用这两种生物活性化合物已被证明可改变肿瘤细胞的遗传和表观遗传特征，但在各种研究中使用的浓度往往远远超过生理可达到的剂量。三阴性乳腺癌（TNBC）是一种通常致命的疾病，可通过新型的基于饮食的方法进行预防或治疗。
本研究使用HCC1806和MDA-MB-157乳腺癌细胞系作为TNBC细胞系。MCF10A细胞用作对照乳腺上皮细胞，以确定这种饮食方案的安全性。使用CompuSyn软件确定药物组合的组合指数（CI）。
以接近生理相关剂量联合使用白藜芦醇和紫檀芪可导致TNBC的协同（CI<1）生长抑制。III型组蛋白去乙酰化酶（HDAC）SIRT1在这种联合治疗后表达下调。我们通过监测γ-H2AX和端粒酶表达，进一步探索了这种新型联合方法对DNA损伤反应的影响。这两种化合物联合使用后，这两种蛋白质显著减少，这可能进一步导致HCC1806和MDA-MB-157乳腺癌细胞的显著生长抑制、凋亡和细胞周期停滞，而对对照MCF10A乳腺上皮细胞的细胞活力、集落形成潜力、形态或凋亡没有显著影响。在HCC1806乳腺癌细胞中，敲低SIRT1可重现联合使用白藜芦醇和紫檀芪诱导的SIRT1下调的效果，即抑制端粒酶活性和γ-H2AX表达。作为修复机制的一部分以及SIRT1在招募DNA甲基转移酶中的作用，还探讨了这种联合治疗对DNA甲基转移酶（DNMTs）表达的影响。有趣的是，这些化合物导致DNMT酶显著下调，而对MCF10A对照细胞中的DNMT酶表达没有显著影响。
总的来说，这些结果为一种新型联合营养控制策略的表观遗传机制提供了新的见解，该策略具有协同作用，可能有助于未来难治性TNBC的预防和/或治疗。
