组蛋白去甲基化酶Jarid1b对下咽鳞癌增殖与分化的表观遗传学调控

Hypopharyngeal squamous cell carcinomas (HPSCC) have the worst survival of all head and neck cancers. It has been reported that there is no significant survival differences between the organ preservation and surgery arms, suggesting the importance of non-surgical treatment in this type of cancers. Here we show that JARID1B is elevated in moderate and high differentiated human hypopharyngeal squamous cell carcinoma (HPSCC) compared to low differentiated HPSCC. Overexpression of JARID1B in Fadu cells increased epithelial differentiation marker K10 expression and inhibited cell proliferation. JARID1B and K10 mRNA expression is high correlated in HPSCC patients. Mechanistically, we found JARID1B directly bound to PI3K/AKT signaling inhibitor SHIP1 gene promoter and decreased SHIP1 gene expression. Taken together, our findings provide first evidence that elevated expression of JARID1B plays a critical role in promoting HPSCC differentiation and inhibiting proliferation, suggesting JARID1B may function as a tumor suppressor in HPSCC. In this study we will use Western Blot, qRT-PCR, IF and ChIP methods to investigate the Jarid1b overexpression effect on HPSCC biological phenotypes at clinical, cell and animal levels and examine the role of Jarid1b in control of PI3K/AKT pathway. In addition, we plan to explore the important target genes of Jarid1b by ChIP-seq and protein interactome and construct the Jarid1b regulation network. Our findings will reveal a novel function of Jarid1b in control of the tumor differentiation and may provide perspective to develop novel therapeutic interventions for HPSCC and other squamous cell carcinomas.

下咽鳞癌是头颈部肿瘤中恶性度最高的肿瘤之一。研究表明保留器官功能的非手术治疗和手术切除对患者生存率影响无明显差别，因此探索下咽鳞癌发生发展的调控机制具有重要意义。我们前期研究发现Jarid1b仅在中高分化下咽鳞癌中过表达，Jarid1b和上皮分化标志角蛋白10(K10)表达高度正相关。FaDu细胞中过表达Jarid1b上调K10表达并抑制细胞增殖。同时发现Jarid1b通过直接抑制Ship1激活PI3K/AKT通路影响K10表达。我们首次提出假说：Jarid1b过表达促进下咽鳞癌分化，发挥抑癌基因作用。本研究拟从临床、分子及动物水平研究Jarid1b过表达对下咽鳞癌增殖分化等生物学功能的影响，阐明Jarid1b通过对PI3K/AKT通路调控影响下咽鳞癌生物学功能的分子机制，筛选Jarid1b靶分子，构建Jarid1b调控网络。Jarid1b这个新视点将为下咽鳞癌诊疗开拓新思路，提供新靶点。

下咽鳞癌是一种生存率较低的头颈部肿瘤，发病部位隐蔽，症状不典型，往往就诊时已是中晚期。有研究表明非手术治疗与手术切除对患者生存率影响无统计学差异，而保留器官功能的保守治疗极大提高了生存质量。因此，深入挖掘其发生发展的生物学机制对下咽鳞癌的诊疗有极大的意义。肿瘤的分化程度是决定肿瘤恶性度的重要因素。遗憾的是在获取肿瘤标本时已经无法取得其发展初期的组织样本了，这无疑影响了对肿瘤的“精准分析”。表皮未分化层和分化层物理结构分离，各层生物学蛋白标志明确，易于体外培养，增高钙离子可模拟体内诱导分化。表皮的这些优势无疑成为了研究分化的理想模型。.我们结果发现，高分化下咽鳞癌中H3K4me3表达显著低于低分化鳞癌，而JARID1B则相反；JARID1B表达和分化标志角蛋白K10正相关。对表皮的研究也表明，在表皮组织分化和体外高钙诱导表皮HaCaT细胞分化中H3K4me3表达下降；其相关的甲基化转移酶和去甲基化酶表达均增高，其中去甲基化酶JARID1B变化最为显著，表明去甲基化酶可能在H3K4me3下调中发挥重要作用。在HaCaT和下咽鳞癌FaDu细胞中过表达Jarid1b促进分化抑制增殖迁移，基因沉默Jarid1b则引起相反结果。裸鼠重组皮肤模型显示基因沉默JARID1B严重损害表皮分化。机制上，我们结果表明在HaCaT和FaDu细胞中JARID1B直接结合PI3K-AKT通路抑制分子SHIP1基因的启动子区抑制SHIP1的转录，从而激活AKT及其下游通路。在FaDu细胞中AKT激活下游的β-catenin转位细胞核中激活AP1转录因子促进K10的转录；在HaCaT细胞中AKT可以上调MET基因进而增高K10表达。.我们结果表明下咽鳞癌的分化可能与正常鳞状上皮的分化享有某些共同的机制。表皮分化的研究对筛选下咽鳞癌增殖分化的重要分子和阐明机制可能会有很大的借鉴意义。