Al-Yousef Nujoud, Shinwari Zakia, Al-Shahrani Bushra, Al-Showimi Maram, Al-Moghrabi Nisreen
Cancer Epigenetics Section, Department of Molecular Oncology, King Faisal Specialist Hospital and Research Centre, Riyadh 11211, Kingdom of Saudi Arabia.
Oncol Rep. 2020 Mar;43(3):827-838. doi: 10.3892/or.2020.7473. Epub 2020 Jan 20.
Restoration of normal DNA promoter methylation and expression states of cancer‑related genes may be an option for the prevention as well as the treatment of several types of cancer. Constitutional promoter methylation of BRCA1 DNA repair associated (BRCA1) gene is linked with a high risk of developing breast and ovarian cancer. Furthermore, hypomethylation of the proto‑oncogene γ synuclein (SNCG) is associated with the metastasis of breast and ovarian cancer and reduced disease‑free survival (DFS). In the present study, we evaluated the potential of curcumin to re‑express hypermethylated BRCA1 and to suppress hypomethylated SNCG in triple‑negative breast cancer (TNBC) cell line HCC‑38, the estrogen receptor‑negative/progesterone receptor‑negative (ER‑/PR‑) cell line UACC‑3199, and the ER+/PR+ cell line T47D. The cells were treated with 5 and 10 µM curcumin for 6 days and with 5‑aza‑2'‑deoxycytidine (5'‑aza‑CdR) for 48 h. Methylation‑specific PCR and bisulfite pyrosequencing assays were used to assess DNA promoter methylation while gene expression levels were analyzed using quantitative real‑time PCR and immunoblotting. We found that curcumin treatment restored BRCA1 gene expression by reducing the DNA promoter methylation level in HCC‑38 and UACC‑3199 cells and that it suppressed the expression of SNCG by inducing DNA promoter methylation in T47D cells. Notably, 5'‑aza‑CdR restored BRCA1 gene expression only in UACC‑3199, and not in HCC‑38 cells. Curcumin‑induced hypomethylation of the BRCA1 promoter appears to be realized through the upregulation of the ten‑eleven translocation 1 (TET1) gene, whereas curcumin‑induced hypermethylation of SNCG may be realized through the upregulation of the DNA methyltransferase 3 (DNMT3) and the downregulation of TET1. Notably, miR‑29b was found to be reversely expressed compared to TET1 in curcumin‑ and 5'‑aza‑CdR‑treated cells, suggesting its involvement in the regulation of TET1. Overall, our results indicate that curcumin has an intrinsic dual function on DNA promoter methylation. We believe that curcumin may be considered a promising therapeutic option for treating TNBC patients in addition to preventing breast and ovarian cancer, particularly in cancer‑free females harboring methylated BRCA1.
恢复癌症相关基因的正常DNA启动子甲基化和表达状态可能是预防和治疗多种癌症的一种选择。乳腺癌1号基因（BRCA1）DNA修复相关基因的组成型启动子甲基化与患乳腺癌和卵巢癌的高风险相关。此外，原癌基因γ突触核蛋白（SNCG）的低甲基化与乳腺癌和卵巢癌的转移及无病生存期（DFS）缩短有关。在本研究中，我们评估了姜黄素在三阴性乳腺癌（TNBC）细胞系HCC-38、雌激素受体阴性/孕激素受体阴性（ER-/PR-）细胞系UACC-3199和ER+/PR+细胞系T47D中重新表达高甲基化BRCA1以及抑制低甲基化SNCG的潜力。细胞用5和10 μM姜黄素处理6天，并用5-氮杂-2'-脱氧胞苷（5'-aza-CdR）处理48小时。甲基化特异性PCR和亚硫酸氢盐焦磷酸测序分析用于评估DNA启动子甲基化，同时使用定量实时PCR和免疫印迹分析基因表达水平。我们发现姜黄素处理通过降低HCC-38和UACC-3199细胞中的DNA启动子甲基化水平来恢复BRCA1基因表达，并且它通过诱导T47D细胞中的DNA启动子甲基化来抑制SNCG的表达。值得注意的是，5'-aza-CdR仅在UACC-3199中恢复了BRCA1基因表达，而在HCC-38细胞中未恢复。姜黄素诱导的BRCA1启动子低甲基化似乎是通过上调10-11易位蛋白1（TET1）基因实现的，而姜黄素诱导的SNCG高甲基化可能是通过上调DNA甲基转移酶3（DNMT3）和下调TET1实现的。值得注意的是，在姜黄素和5'-aza-CdR处理的细胞中发现miR-29b与TET1呈反向表达，表明其参与TET1的调节。总体而言，我们的结果表明姜黄素在DNA启动子甲基化方面具有内在的双重功能。我们认为，除了预防乳腺癌和卵巢癌外，姜黄素可能被认为是治疗TNBC患者的一种有前景的治疗选择，特别是对于携带甲基化BRCA1的无癌女性。
