组蛋白去甲基化酶JMJD2B调控胃癌侵袭转移的机制研究

Invasion and metastasis is the primary factor leading to the death of patients with gastric cancer. Epithelial-mesenchymal transition (EMT) is the key mechanism to initiate invasion and metastasis of tumors of epithelial origin. The epigenetic regulation is an important scientific issue in the EMT and metastasis research field. Our preliminary study showed that the expression of EMT related markers were regulated by JMJD2B in gastric cancer cells. Moreover, JMJD2B depletion significantly inhibited the migration capacity of gastric cancer cells and induced the morphologic change. The above observation indicated the potential role of JMJD2B in the regualtion of EMT and metastasis of gastric cancer. Based on the previous findings, we will make further investigation on the following aspects: (1) analyze the role of JMJD2B in the invasion and metastasis of gastric cancer and gastric cancer cell stemness as well as the mechanism of JMJD2B on regulating EMT on cellular and molecular level; (2) investigate the biological role of JMJD2B in the invasion and metastasis of gastric cancer in nude mice model; (3) determine the correlation between the expression of JMJD2B and EMT associated molecules as well as the invasion and metastatic status of gastric cancer patients on human tissues. Through the investigation, we aim to clarify the mechanism of JMJD2B on regulating EMT and invasion and metastasis of gastric cancer and provide theoretical basis for the intervention of EMT and the progression of gastric cancer.

侵袭转移是导致胃癌患者死亡的首要因素，其中上皮-间质转化（EMT）是上皮来源肿瘤侵袭转移的重要机制。表观遗传学调控是EMT和侵袭转移研究领域的重要科学问题。本课题组研究发现表观遗传分子组蛋白去甲基化酶JMJD2B在胃癌细胞中影响EMT关键分子的表达，干扰JMJD2B的表达显著抑制胃癌细胞的迁移能力并诱导细胞形态的转变,提示JMJD2B在EMT和胃癌侵袭转移中的潜在作用。在此基础上，课题组将进一步研究：（1）细胞和分子水平上JMJD2B对胃癌侵袭转移和胃癌干细胞活性的作用及其对EMT的调控机制；（2）体内水平上裸鼠转移模型中JMJD2B对EMT和胃癌侵袭转移的作用；（3）人体组织标本上JMJD2B和EMT关键分子表达的相关性及其与胃癌侵袭转移的相关性。从而阐明JMJD2B作为表观遗传分子在EMT和胃癌侵袭转移中的作用机制，为干预EMT控制胃癌侵袭转移提供理论依据。

胃癌是世界范围内最常见的恶性肿瘤之一，位居全球癌症相关死亡率第二位。胃癌早期诊断率低，多数患者就诊时已进入中晚期，五年生存率很低。因此，揭示胃癌发生发展的致病机理，阐明胃癌发生侵袭转移的机制成为当务之急。.EMT是上皮细胞来源的恶性肿瘤细胞获得迁移和侵袭能力的重要生物学过程。我们在高侵袭能力的HGC27和MGC803胃癌细胞中转染JMJD2B特异性小干扰RNA抑制JMJD2B的表达，发现细胞由疏松的长梭形间质样表型向紧密的鹅卵石样的上皮表型转变。继而WB和QRT-PCR检测发现胃癌细胞抑制JMJD2B表达后间质化标记分子vimentin和Snail1的表达下降而上皮化标记E-cadherin的表达上调，而过表达JMJD2B后vimentin和Snail1的表达上调，E-cadherin表达下降。双荧光素酶实验检测发现抑制JMJD2B表达，vimentin启动子荧光素酶活性下降，而过表达JMJD2B后vimentin启动子荧光素酶活性升高。转染β-catenin/TCF结合位点失活的vimentin启动子突变质粒后， 抑制JMJD2B表达突变质粒荧光素酶活性不再降低，而过表达JMJD2B后其活性也未升高，这表明JMJD2B对vimentin的转录调控依赖于β-catenin。接着免疫共沉淀实验证实JMJD2B与β-catenin存在物理性相互作用。染色质免疫共沉淀实验（ChIP）显示JMJD2B结合于vimentin启动子区，干扰JMJD2B后vimentin启动子区β-catenin结合减少，vimentin启动子区的H3K9me3累积而 H3K9me2减少。此外，我们通过细胞免疫荧光实验发现胃癌细胞中抑制JMJD2B，TGF-β1介导的β-catenin的核转位和vimentin的表达也减少。细胞划痕实验、Transwell基质胶侵袭实验和裸鼠尾静脉注射肺转移实验从体内外水平表明干扰JMJD2B后胃癌细胞迁移和侵袭能力明显下降。最后临床组织样本免疫组化检测显示JMJD2B的表达与胃癌的侵袭转移呈正相关。.该研究阐明了JMJD2B在胃癌侵袭转移中的作用，为其作为干预胃癌进展的药物靶点的开发提供了理论依据。