肿瘤抑制基因ARHI的研究进展

ARHI是Ras超家族中第一个被报道的肿瘤抑制基因,定位于人染色体lp31,属小GTP结合蛋白,与Ras拥有相似的GTP／GDP结构域,却具有抑癌作用。ARHI是母源性印迹、父源性表达,可参与细胞周期调控和信号通路转导,从而负向调节细胞生长。在正常人类多种组织中都存在ARHI基因的表达,但在肿瘤组织中其表达却下调。ARHI的表达异常可能与印迹基因的杂合性丢失,DNA甲基化和染色体乙酰化修饰等转录水平的调节失常有关。     

ARHI和P130 在子宫内膜癌中的表达和意义

目的：探讨ARHI和P130 蛋白在子宫内膜癌中的表达状况,同时分析两因子在子宫内膜癌中的关联性。方法：收集80 例子 宫内膜癌,子宫内膜非典型增生型80 例及同时期因子宫肌瘤切除的40 例正常的子宫内膜的详细病例及高质量切片,设计分组 并使用免疫组化S-P法检测ARHI 蛋白和pRb2/P130的表达状况,并探究此两因子与子宫内膜癌的关联性。结果：ARHI蛋白阳 性表达率在正常子宫内膜组（97.50%）,子宫内膜非典型增生型组（53.75%）和子宫内膜癌组中（38.75%）三组中依次递减,组间差 异有统计学意义,P<0.05。ARHI蛋白阳性表达降低或缺失与子宫内膜癌的的恶性程度,手术病理分期有关(P<0.05),与子宫内膜 癌的类型无关（P>0.05）。Rb2/p130 蛋白的阳性表达率在三组中逐渐降低,在正常子宫内膜组（100%）,子宫内膜非典型增生型组 （56.25 %）及子宫内膜癌组（36.25 %）,组间差异有统计学意义,P<0.05。Rb2/P130 的阳性表达率降低或缺失与子宫内膜癌的组织 恶性程度,手术病理级别和组织学类型有关(P<0.05),同时Spearman 等级相关性分析表明：ARHI蛋白和Rb2/p130 蛋白表达在子 宫内膜癌中为正相关,r=0.435。结论：ARHI蛋白和Rb2/p130 的阳性表达率降低或缺失可能在某种程度上导致子宫内膜癌的产生 和恶化。     

Aplasia Ras homologue member I overexpression induces apoptosis through inhibition of survival pathways in human hepatocellular carcinoma cells in culture and in xenograft

The aim of the present study was to determine the effects of ARHI (aplasia Ras homologue member I; also known as DIRAS3), a member of the Ras superfamily, on HCC (hepatocellular carcinoma) cells and to define the molecular pathways involved. Stable transfection of ARHI into the HCC cell line Hep3B that lacks expression of this gene reduced cell proliferation significantly as compared with the transfection of empty vector (P<0.01). Moreover, the re-expression of ARHI induced significant apoptosis, whereas a few vector transfectants or non-transfected cells displayed apoptosis. Mechanistically, ARHI restoration impeded the activation of both Akt (also called protein kinase B) and NF-κB (nuclear factor κB). In vivo, restoring ARHI also exerted suppressive effects on xenograft tumour growth, which was coupled with increased apoptosis. Together, these results indicate that ARHI has pro-apoptotic effects on HCC cells, which is associated with the inactivation of both Akt and NF-κB survival pathways.     

Autophagy and tumorigenesis

Autophagy, or cellular self-digestion, is activated in cancer cells in response to multiple stresses and has been demonstrated to promote tumor cell survival and drug resistance. Nonetheless, genetic evidence supports that autophagy functions as a tumor suppressor mechanism. Hence, the precise role of autophagy during cancer progression and treatment is both tissue and context dependent. Here, we discuss our current understanding of the biological functions of autophagy during cancer development, overview how autophagy is regulated by cancer-associated signaling pathways, and review how autophagy inhibition is being exploited to improve clinical outcomes.     

The tumor suppressor gene ARHI (DIRAS3) inhibits ovarian cancer cell migration through multiple mechanisms

ARHI is an imprinted tumor suppressor gene that is downregulated in > 60% of ovarian cancers, associated with decreased progression-free survival. ARHI encodes a 26 kDa GTPase with homology to Ras. Re-expression of ARHI inhibits ovarian cancer growth, initiates autophagy and induces tumor dormancy. Recent studies have demonstrated that ARHI also plays a particularly important role in ovarian cancer cell migration. Re-expression of ARHI decreases motility of IL-6- and EGF-stimulated SKOv3 and Hey ovarian cancer cells, inhibiting both chemotaxis and haptotaxis. ARHI inhibits cell migration by binding and sequestering STAT3 in the cytoplasm, and preventing STAT3 translocation to the nucleus and localization in focal adhesion complexes. Re-expression of ARHI inhibits FAK^Y397 phosphorylation, disrupts focal adhesions and blocks FAK-mediated RhoA signaling, resulting in decreased levels of GTP-RhoA. Re-expression of ARHI disrupts formation of actin stress fibers in a FAK- and RhoA-dependent manner. Recent studies indicate that re-expression of ARHI inhibits expression of β-1 integrin which may also contribute to inhibition of migration, adhesion and invasion.