Institute of Drug Metabolism and Pharmaceutical Analysis, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China (Y.Z., C.Y., L.C., J.Le., S.G., S.Z., L.Y.); Departments of Pharmacy (Y.L.) and Radiation Oncology (J.Li.), The First Affiliated Hospital and Intensive Care Unit, The Children's Hospital (S.Y.), School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
Institute of Drug Metabolism and Pharmaceutical Analysis, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China (Y.Z., C.Y., L.C., J.Le., S.G., S.Z., L.Y.); Departments of Pharmacy (Y.L.) and Radiation Oncology (J.Li.), The First Affiliated Hospital and Intensive Care Unit, The Children's Hospital (S.Y.), School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
Mol Pharmacol. 2020 Apr;97(4):259-266. doi: 10.1124/mol.119.118216. Epub 2020 Jan 31.
Colorectal cancer (CRC) is known to be the third most common cancer disease and the fourth-leading cause of cancer-related deaths worldwide. Bile acid, especially deoxycholic acid and lithocholic acid, were revealed to play an important role during carcinogenesis of CRC. In this study, we found organic solute transporter (OST), an important subunit of a bile acid export transporter OST-OST, was noticeably downregulated in CRC. The decline of OST expression in CRC was determined by Western blot and real-time polymerase chain reaction (RT-PCR), whereas chromatin immunoprecipitation (ChIP) was used to evaluate the histone acetylation state at the OST promoter region in vivo and in vitro. CRC cell lines HT29 and HCT15 were treated with trichostation A (TSA) for the subsequent determination, including RT-PCR, small interfering RNA (siRNA) knockdown, ChIP, and dual-luciferase reporter gene assay, to find out which histone acetyltransferases and deacetylases exactly participated in regulation. We demonstrated that after TSA treatment, OST expression increased noticeably because of upregulated H3K27Ac state at promoter region. We found that stimulating the expression of p300 with CTB (Cholera Toxin B subunit, an activator of p300) and inhibiting p300 expression with C646 (an inhibitor of p300) or siRNA designed for could control OST expression through modulating H3K27Ac state at promoter region. Therefore, downregulated expression of p300 in CRC may cause low expression of OST in CRC via epigenetic regulation. Generally, we revealed a novel epigenetic mechanism underlying OST repression in CRC, hoping this mechanism would help us to understand and inhibit carcinogenesis of CRC. SIGNIFICANCE STATEMENT: Organic solute transporter () expression is lower in colon cancer tissues compared with adjacent normal tissues. We revealed the epigenetic mechanisms of it and proved that p300 controls OST expression through modulating H3K27Ac state at promoter region and hence causes low expression of OST in colorectal cancer.
结直肠癌（CRC）是全球第三大常见癌症疾病，也是癌症相关死亡的第四大主要原因。胆酸，特别是脱氧胆酸和石胆酸，被发现在 CRC 的癌变过程中起着重要作用。在这项研究中，我们发现有机溶质转运蛋白（OST），一种重要的胆汁酸外排转运体 OST-OST 的亚基，在 CRC 中明显下调。CRC 中 OST 表达的下降通过 Western blot 和实时聚合酶链反应（RT-PCR）确定，而染色质免疫沉淀（ChIP）用于评估体内和体外 OST 启动子区域的组蛋白乙酰化状态。用 Trichostation A（TSA）处理 CRC 细胞系 HT29 和 HCT15，进行随后的测定，包括 RT-PCR、小干扰 RNA（siRNA）敲低、ChIP 和双荧光素酶报告基因测定，以确定哪些组蛋白乙酰转移酶和去乙酰化酶确实参与了调控。我们证明，TSA 处理后，由于启动子区域 H3K27Ac 状态上调，OST 表达明显增加。我们发现，用 CTB（霍乱毒素 B 亚基，p300 的激活剂）刺激 p300 的表达，用 C646（p300 的抑制剂）或针对 设计的 siRNA 抑制 p300 的表达，可以通过调节启动子区域的 H3K27Ac 状态来控制 OST 的表达。因此，CRC 中 p300 的下调表达可能通过表观遗传调控导致 CRC 中 OST 的低表达。总的来说，我们揭示了 OST 在 CRC 中下调的一种新的表观遗传机制，希望这一机制有助于我们理解和抑制 CRC 的癌变。
与相邻正常组织相比，结肠癌组织中有机溶质转运蛋白（）的表达较低。我们揭示了其表观遗传机制，并证明 p300 通过调节启动子区域的 H3K27Ac 状态来控制 OST 的表达，从而导致结直肠癌中 OST 的低表达。
