肿瘤抑制基因ARHI的生物学功能及研究进展

肿瘤是一种基因病，抑癌基因在抵御肿瘤发生、发展中起着重要作用。ARHI(aplysia ras homolog I)／NOEY2是一个新发现的抑癌基因．是ras/rap超家族成员之一．与ras家族有50％～60％的同源性．位于人染色体1p31，属小GTP结合蛋白，是该家族第1个被报道的肿瘤抑制基因。ARHI基因编码的蛋白在人类多种组织表达，其中正常卵巢的ARHI表达最高。ARHI是一个印迹基因．印迹机制可能与其CpG岛的差异甲基化有关。ARHI参与细胞周期调控可能作用于cyclin D1，使其不能与CDK结合形成活性激酶，从而使细胞停止于G1期。ARHI可能通过依赖caspase和calpain两条途径参与信号通路传导诱发细胞凋亡。该基因的异常表达跟多种肿瘤的发生、发展有关。ARHI基因参与了乳腺癌的发生和发展，该基因的表达缺失可能与乳腺癌的转移机制有关。卵巢癌、乳腺癌存在广泛的1p31缺失，其中ARHI基因是最常见的一个缺失区域。ARHI基因和蛋白在胰腺癌组织中有较高比例的缺失，提示该基因和蛋白在胰腺癌的发生中起一定作用。ARHI基因在膀胱癌、肝癌、前列腺癌等其他肿瘤中也有不同程度的表达异常。     

肿瘤抑制基因ARHI的生物学功能及研究进展

肿瘤是一种基因病,抑癌基因在抵御肿瘤发生、发展中起着重要作用。ARHI(aplysia ras hom olog I)/NOEY2 是一个新发现的抑癌基因,是 ras/rap超家族成员之一,与 ras家族有50%~60%的同源性,位于人染色体1p31,属小GTP结合蛋白,是该家族第1个被报道的肿瘤抑制基因。ARHI基因编码的蛋白在人类多种组织表达,其中正常卵巢的ARHI表达最高。ARHI是一个印迹基因,印迹机制可能与其CpG岛的差异甲基化有关。ARHI 参与细胞周期调控可能作用于cyclin D1 ,使其不能与 CDK结合形成活性激酶,从而使细胞停止于 G1 期。AR HI可能通过依赖caspase和 calpain两条途径参与信号通路传导诱发细胞凋亡。该基因的异常表达跟多种肿瘤的发生、发展有关。ARHI基因参与了乳腺癌的发生和发展,该基因的表达缺失可能与乳腺癌的转移机制有关。卵巢癌、乳腺癌存在广泛的1p31缺失,其中 ARHI 基因是最常见的一个缺失区域。ARHI基因和蛋白在胰腺癌组织中有较高比例的缺失,提示该基因和蛋白在胰腺癌的发生中起一定作用。ARHI基因在膀胱癌、肝癌、前列腺癌等其他肿瘤中也有不同程度的表达异常。     

ras超家族中的肿瘤抑制基因

 引言ras超家族是一类重要的功能蛋白。它们介导生长因子、细胞因子和多种细胞外信号的信息通路,对细胞生长、分化、存活、增殖等多种功能的调节发挥重要作用。尽管ras超家族各成员之间存在差异,但它们也具有一些共同特征:(1)都是单体小G蛋白,拥有高度保守的GTP结合域(G1 G5 ) ,能与GTP和GDP结合;(2 )都有内源性GTP酶活性,能水解GTP生成GDP ;(3)多数ras超家族成员通过翻译后的脂酰化修饰与膜结合[1] 。ras超家族在细胞信号转导中可作为信号转换器或分子开关,它们通过与GTP结合(激活态)和GDP结合(失活态)的转换导致信号的转导或终止[2 ] 。该家族许多成员是癌基因,当其被异常激活后会导致细胞无限制地增殖,引起肿瘤。近年来,研究发现ras超家族中包括一些独特的成员,作为生长负向调节者,具有肿瘤抑制作用,本文现予以概述。1　ARHI(AplysiarasHomologI)ARHI是ras超家族中第一个被报道的肿瘤抑制基因,它是美国德克萨斯大学Anderson癌症中心于1999年利用差异展示PCR (differentialdisplayPCR)发现,又名NOEY2或ras同源基因家...     

ARHI在肿瘤发生和发展中的作用与机制研究进展

ARHI是1999年发现的母源性印迹基因,属于小G蛋白Ras超家族,是该家族第1个被报道的抑癌基因。ARHI的功能包括抑制小鼠生长和生殖发育,抑制细胞增殖、迁移,参与周期调控和凋亡,近年来研究发现ARHI还具有调控肿瘤细胞自噬、抑制肿瘤转移的作用。ARHI蛋白在人体卵巢、乳腺等多种组织中表达,在卵巢癌、乳腺癌、甲状腺癌、胰腺癌、肝癌组织中表达下调,ARHI基因高表达可提示卵巢癌、胰腺癌的预后良好。ARHI表达调控机制包括杂合性丢失、DNA甲基化、组蛋白去乙酰化、转录因子调节、miRNA和突变,应用表观遗传学技术调节ARHI表达可能在一些肿瘤中具有抗肿瘤临床应用价值。ARHI基因参与调节肿瘤细胞休眠过程,有望成为诱导肿瘤细胞休眠、抗肿瘤转移复发的关键点。     

抗增殖家族成员TOB1基因与肿瘤

人类ErbB2转录因子1（TOB1）基因编码抗增殖蛋白Tob1,属于BTG／TOB蛋白家族,通过Ras／MAPK信号通路,以及与CCR4 Caf1结合形成复合体等多种途径参与调控细胞周期进程,抑制细胞增殖。TOB1作为抑癌基因与肿瘤发生、发展及转移密切相关,在大多数肿瘤中表达下调,其功能性失活与磷酸化积累及亚细胞分布相关,而且TOB1表达变化还与癌细胞电离辐射的敏感性相关。     

TP53家族基因TP73与肿瘤发生的研究进展

p73蛋白是p53蛋白家族的主要成员之一,其编码基因TP73与TP53基因高度同源.与p53蛋白类似,p73蛋白功能涉及细胞生命活动的各个方面;但又与p53不同,p73蛋白在机体正常的细胞活动和肿瘤的发生发展中不仅扮演着抑癌因子的角色,其功能的复杂性和重要性丝毫不亚于p53蛋白.肿瘤发生涉及多种细胞生物学过程,例如细胞...     

ING1基因与肿瘤关系的研究

1996年,Garkavtsev等采用改良的eDNA消减杂交法（subtractive hybridization）并结合体内选择技术,克隆出一个新基因。该基因在正常情况下对细胞生长具有抑制作用;而用反义mRNA可以阻断其作用,促进细胞生长和恶性转化,故命名为生长抑制基因（inhibitor of growth,ING）,考虑到这个基因可能是该家族的第一个成员,因此称为ING1。已证实该基因与多种肿瘤的发生发展有关,本文就ING1基因抑癌的机制和途径以及与肿瘤关系作一综述。     

Ras癌基因及nm23抑癌基因对细胞膜磷脂酶D活性的影响

目的为研究ras癌基因和nm23抑癌基因的高表达对细胞膜磷脂酶D (PLD)活性的影响.方法用ras癌基因和nm23抑癌基因构建的重组质粒,分别转染人肝癌细胞株7721,建立了高表达ras癌基因和nm23抑癌基因的H-ras/7721和nm23-H/7721细胞株,测定7721、mock细胞(空载体转染的7721细胞)、H-ras/7721和nm23-H/7721四种细胞中,细胞膜PLD酶活性和PLD酶蛋白表达量.结果在H-ras/7721细胞中,PLD酶活性比7721、mock细胞中PLD酶活性显著升高.nm23-H/7721细胞中,酶活性却显著降低.但在两种细胞中,PLD酶蛋白的量未见显著变化.结论 ras癌基因和nm23抑癌基因的高表达对PLD酶活性的影响,可能主要是通过影响PLD酶活性的调节因素来实现的.     

p73基因与乳腺癌关系研究进展

p73基因是新近发现的p53基因家族成员之一,其编码的蛋白在结构和功能上与p53基因编码蛋白相似,因此人们认为它是一个候选的抑癌基因。     

P16基因与肿瘤

众所周知，癌基因的结构或表达异常以及抑癌基因缺失或失活可以引起细胞癌变而致肿瘤的发生。因而，癌基因和抑癌基因的研究是近年来研究的热门课题。有关抑癌基因，继Rb、P53之后，新近又发现了一种肿瘤抑制基因P16，此基因的缺失或失活与多种肿瘤的发生有密切关系，所以又称多种肿瘤抑制基因（Multipletu-morsuppressor1，MTS1），其编码蛋白质P16蛋白可与细胞周期蛋白依赖性激酶4（CDK4）结合，从而抑制CyclinD／CDK4复合物的活性，所以也叫作CDK4抑制因子（CDK4I或P16INK4）[1，2]。通过对P16基因的研究将有助于进一步了解…     

抑癌基因ARHI与全身各系统肿瘤相关性及机制的研究进展

抑癌基因 ARHI（aplasia ras homologue I）是1999年新发现的母源性印迹基因。最近研究发现ARHI 具有抑制肿瘤细胞增殖、转移、侵袭,调控肿瘤细胞自噬等作用。另外,学者们还发现 ARHI 不仅与卵巢癌、乳腺癌、胰腺癌密切相关,而且还与其他生殖、消化、内分泌等全身各系统肿瘤具有相关性。本文就最近几年国内外对 ARHI 与全身各系统肿瘤的相关性及其机制的最新研究进展进行综述。     

Effects of ARHI on breast cancer cell biological behavior regulated by microRNA-221

The aplysia ras homolog member I (ARHI) is a tumor suppressor gene and is downregulated in various cancers. The downregulation of ARHI was regulated by miR-221 in prostate cancer cell lines. However, it has not been reported whether ARHI is regulated by miR-221 in breast cancer. Here, we reported that the ARHI protein level was downregulated in breast cancer tissues and breast cancer cell lines. The overexpression of ARHI could inhibit cell proliferation and invasion and induce cell apoptosis. To address whether ARHI is regulated by miR-221 in breast cancer cell lines, the results in this study showed that a significant inverse correlation existed between ARHI and miR-221. MiR-221 displayed an upregulation in breast cancer tissues and breast cancer cell lines. The inhibition of miR-221 induced a significant upregulation of ARHI in MCF-7 cells. To prove a direct interaction between miR-221 and ARHI mRNA, ARHI 3′UTR, which includes the potential target site for miR-221, was cloned downstream of the luciferase reporter gene of the pMIR-REPORT vector to generate the pMIR-ARHI-3′UTR vector. The results confirmed a direct interaction of miR-221 with a target site on the 3′UTR of ARHI. In conclusion, ARHI is a tumor suppressor gene that is downregulated in breast cancer. The overexpression of ARHI could inhibit breast cancer cell proliferation and invasion and induce cell apoptosis. This study demonstrated for the first time that the downregulation of ARHI in breast cancer cells could be regulated by miR-221.     

Reexpression of the tumor suppressor gene ARHI induces apoptosis in ovarian and breast cancer cells through a caspase-independent calpain-dependent pathway

ARHI, an imprinted putative tumor suppressor gene, encodes a M(r) 26,000 GTP-binding protein that is 60% homologous to ras and rap but has a dramatically different function. ARHI expression is down-regulated in a majority of breast and ovarian cancers. Using a dual adenovirus system, we have reexpressed ARHI in ovarian cancer and breast cancer cells that have lost ARHI expression. Reexpression of ARHI inhibited growth, decreased invasiveness, and induced apoptosis. At 5 days after infection with ARHI adenovirus, 30-45% of MDA-MB-231 breast cancer cells and 5-11% of SKOv3 ovarian cancer cells were apoptotic as judged by a terminal deoxynucleotidyl transferase-mediated nick end labeling assay and by Annexin V staining with flow cytometric analysis. Although poly(ADP-ribose) polymerase could be detected immunohistochemically in the nuclei of apoptotic cells, no activation of the effector caspases (caspase 3, 6, 7, or 12) or the initiator caspases (caspase 8 or 9) could be detected in cell lysates using Western blotting. When gene expression was analyzed on a custom cDNA array that contained 2304 known genes, infection with ARHI adenovirus up-regulated 15 genes relative to control cells infected with LacZ adenovirus. The greatest degree of mRNA up-regulation was observed in a Homo sapiens calpain-like protease. On Western blot analysis, calpain protein was increased 2-3-fold at 3-5 days after infection with ARHI adenovirus. No increase in calpain protein was observed after LacZ adenovirus infection. Calpain cleavage could be detected after ARHI reexpression, and inhibitors of calpain, but not inhibitors of caspase, partially prevented ARHI-induced apoptosis. Consequently, reexpression of ARHI in breast and ovarian cancer cells appears to induce apoptosis through a caspase-independent, calpain-dependent mechanism.     

ARHI/NOEY2 inactivation may be important in breast tumor pathogenesis

Allelic loss frequently occurs on the short arm of chromosome 1 in human breast carcinoma, suggesting that the ARHI/NOEY2 gene, an imprinted putative tumor suppressor gene, is involved in the pathogenesis of the tumor entity. To clarify the clinical importance of ARHI/NOEY2 mRNA in breast cancer, we studied whether ARHI/NOEY2 inactivation might contribute to tumors arising in the breast. An ARHI/NOEY2 message was detected by real-time PCR analysis in all noncancerous breast tissues, but was not detected in 2 of 26 breast cancer tissue samples. In 10 of 26 breast cancer tissue samples ARHI/NOEY2 mRNA was substantially reduced. ARHI/NOEY2 expression was lost or markedly reduced in 12 of 26 (46.15%) breast cancer tissue samples. In summary, we conclude that decreased ARHI/NOEY2 mRNA expression may play an important role in the pathogenesis of breast cancer.     

转化生长因子βⅢ型受体在人类肿瘤发生发展中作用的研究进展

转化生长因子βⅢ型受体(TGFBR3,也称为betaglycan),作为肿瘤抑制和肿瘤促进基因,在肿瘤发生发展中起着调节细胞迁移、侵袭、增殖和血管生成的作用。近年来的研究结果证实TGFBR3与人类肿瘤的发生发展密切相关。TGFBR3在肿瘤中的作用多样,在乳腺癌和胰腺癌等恶性肿瘤中可作为抑癌基因,抑制细胞的增殖和分化,但在结肠癌中则可促进肿瘤的侵袭和转移。本文中,我们回顾了目前已知的文献,作为TGF-β超家族中的一员,TGFBR3扮演着上皮表型守护者的角色,其表达能抑制人类肿瘤的发生发展。     

ARHI is a Ras-related small G-protein with a novel N-terminal extension that inhibits growth of ovarian and breast cancers

Our group recently identified Ras homolog member I (ARHI), a novel maternally imprinted tumor suppressor gene that encodes a 26 kDa GTP-binding protein with high homology to Ras and Rap. Unlike other Ras family members, ARHI exhibits several unusual structural and functional properties. ARHI contains a unique 34 amino-acid extension at the N-terminus, and differs from Ras in residues critical for GTPase activity and in its putative effector domain. Like Ras, ARHI can bind to GTP with high affinity but has low intrinsic GTPase activity. In addition, while Ras is an oncogene, ARHI functions as an inhibitor for cell growth. (32)Phosphorus labeling showed that ARHI is maintained in a constitutively activated GTP-bound state in resting cells, possibly because of impaired GTPase activity. ARHI is associated at the cell membrane through its prenylation at the C-terminal cysteine residue. Mutation of the conserved CAAX box at the C-terminus led to a loss of its membrane association and a decreased ability to inhibit cell growth. Conversion of Ser(51) to Asn decreased GTP binding and reduced ARHI's biological activity. Mutation of Ala(46) to Val increased the ability of ARHI to inhibit cell growth, associated with a further decrease of its intrinsic GTPase activity. Moreover, conversion of residues in ARHI that are conserved in the Ras family for GTPase activity partially restored the GTPase activity in ARHI. Most strikingly, deletion of ARHI's unique N-terminal extension nearly abolished its inhibitory effect on cell growth, suggesting its importance in ARHI's inhibitory function. Thus, ARHI is a unique Ras family member that retains basic small GTPase function, but exhibits many unusual features. In contrast to most other Ras family members, ARHI has a long N-terminal extension, modest GTPase activity, and constitutive GTP binding in resting cells. Furthermore, unlike the Ras oncogene, ARHI inhibits cell growth, and loss of its expression in cells may contribute to the development of breast and ovarian cancers.     

Bin3 deletion causes cataracts and increased susceptibility to lymphoma during aging

Bin3 encodes an evolutionarily conserved and ubiquitously expressed member of the BAR superfamily of curved membrane and GTPase-binding proteins, which includes the BAR, PCH/F-BAR, and I-BAR adapter proteins implicated in signal transduction and vesicular trafficking. In humans, Bin3 maps to chromosome 8p21.3, a region widely implicated in cancer suppression that is often deleted in non-Hodgkin's lymphomas and various epithelial tumors. Yeast studies have suggested roles for this gene in filamentous actin (F-actin) organization and cell division but its physiologic functions in mammals have not been investigated. Here we report that homozygous inactivation of Bin3 in the mouse causes cataracts and an increased susceptibility to lymphomas during aging. The cataract phenotype was marked by multiple morphologic defects in lens fibers, including the development of vacuoles in cortical fibers and a near total loss of F-actin in lens fiber cells but not epithelial cells. Through 1 year of age, no other phenotypes were apparent; however, by 18 months of age, Bin3(-/-) mice exhibited a significantly increased incidence of lymphoma. Bin3 loss did not affect normal cell proliferation, F-actin organization, or susceptibility to oncogenic transformation. In contrast, it increased the proliferation and invasive motility of cells transformed by SV40 large T antigen plus activated ras. Our findings establish functions for Bin3 in lens development and cancer suppression during aging. Further, they define Bin3 as a candidate for an unidentified tumor suppressor that exists at the human chromosome 8p21.3 locus.     

Identification of a putative tumor suppressor gene Rap1GAP in pancreatic cancer

Human chromosome 1p35-p36 has long been suspected to harbor a tumor suppressor gene in pancreatic cancer and other tumors. We found that expression of rap1GAP, a gene located in this chromosomal region, is significantly down-regulated in pancreatic cancer. Only a small percentage of preneoplastic pancreatic intraductal neoplasia lesions lost rap1GAP expression, whereas loss of rap1GAP expression occurred in 60% of invasive pancreatic cancers, suggesting that rap1GAP contributes to pancreatic cancer progression. In vitro and in vivo studies showed that loss of rap1GAP promotes pancreatic cancer growth, survival, and invasion, and may function through modulation of integrin activity. Furthermore, we showed a high frequency of loss of heterozygosity of rap1GAP in pancreatic cancer. Collectively, our data identify rap1GAP as a putative tumor suppressor gene in pancreatic cancer.