Histone modifications play a key role in the epigenetic regulation of gene transcription in cancer cells. Histone acetylations are regulated by two classes of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). HDACs are increased in ovarian carcinomas and they are involved in carcinogenesis and resistance to chemotherapeutic agents. In our study we investigated anticancer effect of HDAC inhibitor sodium butyrate (NaBu) on cisplatin-sensitive and cisplatin-resistant ovarian cell lines A2780 and A2780cis. A2780 and A2780cis were treated with NaBu alone or in combination with cisplatin (CP). NaBu inhibited the growth of both cell lines and enhanced cytotoxic effect of CP. Exposure to NaBu for 24 h induced cell cycle arrest. The expressions of EMT-related genes and proteins were further investigated by qPCR and western blot analysis. Loss of E-cadherin has been shown to be crucial in ovarian cancer development. We found that NaBu dramatically induce expression of E-cadherin gene (CDH1) and protein levels in A2780 and A2780cis. We investigated correlation between transcription and methylation of CDH1gene. Methylation level analysis in 32 CpG sites in CDH1 gene (promoter/exon1 regions) was performed using bisulfite NGS (Next Generation Sequencing). We found that cisplatin-resistant cell line A2780cis cells differ from their cisplatin-sensitive counterparts in the CDH1 methylation. Methylation in A2780cis cells is elevated compared to A2780. However, NaBu-induced expression of CDH1 was not accompanied by CDH1 demethylation. NaBu treatment induced changes in expression of EMT-related genes and proteins. Interestingly E-cadherin zinc finger transcriptional repressor SNAIL1 was upregulated in both cell lines. Mesenchymal marker vimentin was downregulated. Matrix metalloproteases (MMPs) are necessary for pericellular proteolysis and facilitate migration and invasion of tumour cells. NaBu induced mRNA expression of MMPs, mild changes in activities of gelatinases MMP2 and MMP9 were detected. Our data demonstrate that NaBu sensitizes cisplatin-resistant ovarian cancer cells, re-established E-cadherin expression, but it was not able to reverse the EMT phenotype completely.

组蛋白修饰在癌细胞基因转录的表观遗传调控中起关键作用。组蛋白的乙酰化受两类酶的调节：组蛋白乙酰转移酶（HATs）和组蛋白脱乙酰基酶（HDACs）。HDACs在卵巢癌中增加，并且参与致癌作用和对化学治疗剂的耐药性。在我们的研究中，我们研究了HDAC抑制剂丁酸钠（NaBu）对顺铂敏感和顺铂耐药的卵巢细胞系A2780和A2780cis的抗癌作用。A2780和A2780cis分别用NaBu或与顺铂（CP）组合治疗。NaBu抑制两种细胞系的生长并增强CP的细胞毒性作用。暴露于NaBu 24 h诱导细胞周期停滞。通过qPCR和western blot分析进一步研究EMT相关基因和蛋白的表达。E-钙黏着蛋白的丢失已被证明在卵巢癌的发展中至关重要。我们发现NaBu可以显着诱导E-cadherin基因的表达（A2780和A2780cis中的CDH1）和蛋白质水平。我们调查了CDH1基因的转录和甲基化之间的相关性。使用亚硫酸氢盐NGS（下一代测序）对CDH1基因（启动子/外显子1区域）中32个CpG位点的甲基化水平进行了分析。我们发现顺铂耐药细胞系A2780cis细胞在CDH1甲基化中不同于顺铂敏感细胞。与A2780相比，A2780cis细胞中的甲基化水平升高。但是，NaBu诱导的CDH1表达并不伴随CDH1去甲基化。NaBu处理可诱导EMT相关基因和蛋白质表达的变化。有趣的是E-钙粘着蛋白锌指转录阻遏物SNAIL1在两种细胞系中均被上调。间质标记波形蛋白被下调。基质金属蛋白酶（MMPs）对于细胞周蛋白水解是必需的，并促进肿瘤细胞的迁移和侵袭。NaBu诱导MMPs mRNA表达，检测明胶酶MMP2和MMP9活性的轻度变化。我们的数据表明NaBu可以增强顺铂耐药性卵巢癌细胞的敏感性，重新建立E-cadherin的表达，但是它不能完全逆转EMT的表型。