Hernández-Rosas Fabiola, Hernández-Oliveras Andrés, Flores-Peredo Lucía, Rodríguez Gabriela, Zarain-Herzberg Ángel, Caba Mario, Santiago-García Juan
Programa de Doctorado en Ciencias Biomédicas, Universidad Veracruzana, Xalapa, Veracruz 91190, México.
Instituto de Investigaciones Biológicas, Universidad Veracruzana, Xalapa, Veracruz 91190, México.
Oncol Lett. 2018 Aug;16(2):1981-1990. doi: 10.3892/ol.2018.8851. Epub 2018 May 31.
Period circadian regulator (Per)1 and Per2 genes are involved in the molecular mechanism of the circadian clock, and exhibit tumor suppressor properties. Several studies have reported a decreased expression of Per1, Per2 and Per3 genes in different types of cancer and cancer cell lines. Promoter methylation downregulates Per1, Per2 or Per3 expression in myeloid leukemia, breast, lung, and other cancer cells; whereas histone deacetylase inhibitors (HDACi) upregulate Per1 or Per3 expression in certain cancer cell lines. However, the transcriptional regulation of Per1 and Per2 in cancer cells by chromatin modifications is not fully understood. The present study aimed to determine whether HDACi regulate Per1 and Per2 expression in gastric cancer cell lines, and to investigate changes in chromatin modifications in response to HDACi. Treatment of KATO III and NCI-N87 human gastric cancer cells with sodium butyrate (NaB) or Trichostatin A (TSA) induced Per1 and Per2 mRNA expression in a dose-dependent manner. Chromatin immunoprecipitaion assays revealed that NaB and TSA decreased lysine 9 trimethylation on histone H3 (H3K9me3) at the Per1 promoter. TSA, but not NaB increased H3K9 acetylation at the Per2 promoter. It was also observed that binding of Sp1 and Sp3 to the Per1 promoter decreased following NaB treatment, whereas Sp1 binding increased at the Per2 promoter of NaB- and TSA-treated cells. In addition, Per1 promoter is not methylated in KATO III cells, while Per2 promoter was methylated, although NaB, TSA, and 5-Azacytidine do not change the methylated CpGs analyzed. In conclusion, HDACi induce Per1 and Per2 expression, in part, through mechanisms involving chromatin remodeling at the proximal promoter of these genes; however, other indirect mechanisms triggered by these HDACi cannot be ruled out. These findings reveal a previously unappreciated regulatory pathway between silencing of Per1 gene by H3K9me3 and upregulation of Per2 by HDACi in cancer cells.
周期昼夜节律调节因子（Per）1和Per2基因参与生物钟的分子机制，并具有肿瘤抑制特性。多项研究报道，在不同类型的癌症及癌细胞系中，Per1、Per2和Per3基因的表达降低。启动子甲基化可下调髓系白血病、乳腺癌、肺癌及其他癌细胞中Per1、Per2或Per3的表达；而组蛋白去乙酰化酶抑制剂（HDACi）可上调某些癌细胞系中Per1或Per3的表达。然而，染色质修饰对癌细胞中Per1和Per2的转录调控尚未完全明确。本研究旨在确定HDACi是否调控胃癌细胞系中Per1和Per2的表达，并探究HDACi作用下染色质修饰的变化。用丁酸钠（NaB）或曲古抑菌素A（TSA）处理KATO III和NCI-N87人胃癌细胞，可呈剂量依赖性诱导Per1和Per2 mRNA表达。染色质免疫沉淀试验显示，NaB和TSA可降低Per1启动子上组蛋白H3赖氨酸9三甲基化（H3K9me3）水平。TSA可增加Per2启动子上的H3K9乙酰化水平，而NaB无此作用。此外还观察到，NaB处理后，Sp1和Sp3与Per1启动子的结合减少，而在NaB和TSA处理的细胞中，Sp1与Per2启动子的结合增加。另外，KATO III细胞中Per1启动子未发生甲基化，而Per2启动子发生甲基化，尽管NaB、TSA和5-氮杂胞苷并未改变所分析的甲基化CpG。总之，HDACi部分通过涉及这些基因近端启动子染色质重塑的机制诱导Per1和Per2表达；然而，不能排除这些HDACi引发的其他间接机制。这些发现揭示了癌细胞中H3K9me3沉默Per1基因与HDACi上调Per2基因之间此前未被认识的调控途径。
