乳腺癌组织中NOEY2基因的mRNA表达及其与临床病理的关系

目的：观察乳腺癌组织中NOEY2基因的mRNA表达情况,并探讨其与临床病理及其他分子指标的关系。方法：以RT－PCR法和反义RNA探针原位杂交法,检测乳腺良恶性病变组织中NOEY2基因的mRNA表达,以免疫组化法检测乳腺癌石蜡标本中的雌激素受体（ER)状态,Ki67标记指数以及p27和p21WAF1的表达。结果：RT－PCR法检测显示,24例冻存乳腺组织中,6例良性病变NOEY2均为阳性;18例乳腺癌中,13例（72．2％）NOEY2为阳性,原位杂交法检测显示,10例乳腺良性病变NOEY2均为阳性;而60例乳腺侵袭性癌中,仅有31例NOEY2为阳性,占51．7％,良恶性病变NOEY2阳性率差异有显著性（P＜0．025）,NOEY2的阳性率有随组织学分级升高而递减的趋势。淋巴结阴性者阳性率为76．7％,而阳性者仅为26．7％,两者差异有显著性（P＜0．001）,NOEY2基因mRNA表达与其他临床病理指标以及免疫组化指标均无显著相关性。结论：NOEY2基因可能在一定程度上参与乳腺癌的发生和发展。该基因的失表达可能与乳腺癌的转移机制有关。     

抑癌基因ARHI研究进展

ARHI（aplasia ras homologue member I）/NOEY2是1999年新发现的一个母源性抑癌印迹基因,位于人染色体1p31,编码一个相对分子量为26kD的小GTP结合蛋白。ARHI属ras/rap超家族成员,与该家族成员有50%～60%的同源性并且两者具有相似的GTP/GDP结合域,但与该家族其它成员不同,ARHI发挥抑癌基因作用,是该家族第一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,而该基因在人卵巢癌、乳腺癌、胰腺癌、肝癌等多种肿瘤中表达下调或缺失,提示其与上述肿瘤的发生、发展密切相关。ARHI可能通过作用于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期来参与细胞周期调控;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;另外,该基因可通过抑制STAT3的激活而发挥抑癌基因功能,也可以调节自体吞噬和肿瘤细胞休眠。目前研究显示,ARHI基因的表达缺失主要通过遗传事件和表观遗传学机制发生,包括DNA甲基化异常、杂合性丢失,乙酰化组蛋白的低水平表达及基因突变有关,但有待进一步深入研究。可以预见,ARHI基因的深入研究必将为早期肿瘤的基因诊治提供新的思路和理论依据。      

ARHI基因与肿瘤的关系

近年来研究表明，一种新的抑癌印迹基因ARHI(NOEY2)的异常参与了一些肿瘤的发生。该文就ARHI(NOEY2)的结构、功能及其与某些肿瘤的关系进行综述。     

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。     

The expression of ARHI in pT2a and pT2b stage gastric cancer and its clinical significance

ARHI is a novel tumor suppressor gene located on chromosome 1p31. Downregulation of ARHI expression has been detected in many types of cancer. However, the effects of ARHI in gastric cancer remain unclear. The aim of this study was to identify the relationship between ARHI expression and gastric cancer clinicopathological features. In this study, 81 pT2 stage gastric cancer specimens were subclassified by pT2a and pT2b stage. ARHI mRNA and protein levels were evaluated by real-time PCR and western blot analysis, respectively. Methylation plays an important role in suppressor gene silencing. We utilized methylation-specific PCR to identify the status of CpG islands in the ARHI gene. We used immunohistochemistry to determine the expression of the protein and analyzed clinicopathological features. The levels of ARHI mRNA in gastric cancer were lower compared to normal tissues (P<0.01). Similarly, the levels of ARHI protein in the cancer specimens were lower (P<0.05). DNA hypermethylation was identified in 79.1% of gastric cancer specimens without ARHI expression. Immunohistochemistry results were significantly correlated with the pT2 category (P<0.05). The cumulative survival rate of patients with ARHI expression was significantly higher compared to those without ARHI expression (P<0.05). ARHI as a suppressor is not only an important factor in the pathogenesis of gastric cancer, but also a potential factor for tumor aggravation. ARHI expression in gastric cancer can be employed to indicate favorable prognosis for the disease.     

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.     

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.     

Expression of the tumor suppressor gene ARHI in epithelial ovarian cancer is associated with increased expression of p21WAF1/CIP1 and prolonged progression-free survival.

PURPOSE: ARHI, an imprinted putative tumor suppressor gene, is expressed in normal ovarian epithelial cells, but its expression is down-regulated or lost in most ovarian cancer cell lines. Reexpression of ARHI in cancer cells induces p21(WAF1/CIP1), down-regulates cyclin D1 promoter activity and inhibits growth in cell culture and in heterografts. To determine the relevance of these observations to clinical cancer, we have now measured ARHI expression in normal, benign and malignant ovarian tissues using immunohistochemistry and in situ hybridization. EXPERIMENTAL DESIGN: Paraffin embedded tissues from 7 normal ovaries, 22 cystadenomas and 42 borderline lesions were analyzed using standard immunoperoxidase and in situ hybridization techniques to assess ARHI expression. In addition, immunohistochemistry against ARHI was performed on a tissue microarray containing 441 consecutive cases of ovarian carcinoma. RESULTS: Strong ARHI expression was found in normal ovarian surface epithelial cells, cysts and follicles using immunohistochemistry and in situ hybridization. Reduced ARHI expression was observed in tumors of low malignant potential as well as in invasive cancers. ARHI expression was down-regulated in 63% of invasive ovarian cancer specimens and could not be detected in 47%. When immunohistochemistry and in situ hybridization were compared, ARHI protein expression could be down-regulated in the presence of ARHI mRNA. ARHI expression was correlated with expression of p21(WAF1/CIP1) (P = 0.0074) but not with cyclin D1 and associated with prolonged disease free survival (P = 0.001). On multivariate analysis, ARHI expression, grade and stage were independent prognostic factors. ARHI expression did not correlate with overall survival. CONCLUSIONS: Persistence of ARHI expression in epithelial ovarian cancers correlated with prolonged disease free survival and expression of the cyclin dependent kinase inhibitor p21(WAF1/CIP1).     

NOEY2基因对人乳腺癌细胞体外生长的影响

目的：构建NOEY2基因真核表达载体。研究其对人乳腺癌细胞系MDA-MB-231生长的影响。方法：RT-PCR获得目的基因编码区,经T/A策略克隆后,再亚克隆至pcDNA3,获得真核表达载体。用lipofectAMINE辅助转染MDA-MB-231细胞,经G418长期筛选而获得稳定转染细胞克隆。Western印迹检测NOEY2蛋白水平的表达。通过记录生长曲线和流式细胞分析术观察转染细胞的生长和细胞周期变化。结果：NOEY2真核表达载体pcDNA3/NOEY2-CR构建成功。被稳定转染该载体的MDA-MB-231细胞有明显NOEY2蛋白表达,而对照细胞无表达。NOEY2转染细胞的生长抑制率可达46.3%,在细胞周期改变上可见明显的S期分数和G2/M期分数下降,而G0/G1期比例上升。结论：NOEY2基因转染对体外培养的人乳腺癌细胞生长具有一定的抑制作用。支持其人微言轻一个抑癌基因的推测,本研究为进一步探索NOEY2作为治疗基因的价值创造了条件。     

Clinical significance of CYLD downregulation in breast cancer

Cylindromatosis (CYLD) is a tumor suppressor gene that is mutated in familial cylindromatosis, a rare autosomal dominant disorder associated with numerous benign skin adnexal tumors. CYLD is now known to regulate various signaling pathways, including transforming growth factor-β signaling, Wnt/β-catenin signaling, and NF-κB signaling by deubiquitinating upstream regulatory factors. Downregulation of CYLD has been reported in several malignancies; however, the clinical significance of CYLD expression in many malignancies, including breast cancer, remains to be elucidated. This study investigated the clinical significance of CYLD in breast cancer and its roles in tumor progression. We evaluated CYLD expression in matched normal breast tissue samples and tumor breast tissue samples from 26 patients with breast cancer and in a series of breast cancer cell lines. In addition, by means of immunohistochemistry, we investigated CYLD protein expression and its clinical significance in 244 breast cancer cases. We also analyzed the effects of CYLD repression or overexpression on breast cancer cell viability, cell migration, and NF-κB activity with or without receptor activator of NF-κB ligand (RANKL) stimulation. Breast cancer tissues demonstrated significantly reduced CYLD mRNA expression compared with normal breast tissues. Downregulation of CYLD promoted cell survival and migratory activities through NF-κB activation, whereas CYLD overexpression inhibited those activities in MDA-MB-231 cells. As an important finding, CYLD overexpression also inhibited RANKL-induced NF-κB activation. Our immunohistochemical analysis revealed that reduced CYLD protein expression was significantly correlated with estrogen receptor negativity, high Ki-67 index, high nuclear grade, decreased disease-free survival, and reduced breast cancer-specific survival in primary breast cancer. Moreover, reduced CYLD expression was an independent factor for poor prognosis in breast cancer. CYLD downregulation may promote breast cancer metastasis via NF-κB activation, including RANKL signaling.     

MicroRNAs 221/222 and genistein-mediated regulation of ARHI tumor suppressor gene in prostate cancer

ARHI is an imprinted tumor suppressor gene and is downregulated in various malignancies. However, ARHI expression, function, and mechanisms of action in prostate cancer have not been reported. Here, we report that ARHI mRNA and protein levels were downregulated in prostate cancer tissues compared with adjacent normal tissues. Overexpression of ARHI inhibited cell proliferation, colony formation, invasion, and induced apoptosis. Further studies on a new mechanism of ARHI downregulation showed a significant inverse relationship between ARHI and miR-221 and 222, which were upregulated in prostate cancer cell lines. Transfection of miR-221 and 222 inhibitors into PC-3 cells caused a significant induction of ARHI expression. A direct interaction of miR-221 or 222 with a target site on the 3'UTR of ARHI was confirmed by a dual luciferase pMIR-REPORT assay. Finally, we also found that genistein upregulates ARHI by downregulating miR-221 and 222 in PC-3 cells. In conclusion, ARHI is a tumor suppressor gene downregulated in prostate cancer, and overexpression of ARHI can inhibit cell proliferation, colony formation, and invasion. This study demonstrates for the first time that prostate cancer cells have decreased level of ARHI which could be caused by direct targeting of 3'UTR of ARHI by miR221/222. Genistein, a potential nontoxic chemopreventive agent, restores expression of ARHI and may be an important dietary therapeutic agent for treating prostate cancer.     

抑癌基因RASSF1A与乳腺癌发生发展关系的研究

目的 探讨RASSF1A基因在乳腺癌组织中的表达及其对乳腺癌发生发展的作用。方法 采用逆转录-聚合酶链反应(RT-PCR)方法检测51例乳腺癌组织、30例癌旁正常组织、12例乳腺良性肿瘤组织中RASSF1A基因mRNA的表达情况。结果 (1)RASSF1A mRNA在癌旁正常组织、良性肿瘤组织中均有表达,其表达量分别为0.463 03±0.150 69、0.480 64±0.135 69,二者之间的表达无明显差别(P＞0.05)。而该基因在乳腺癌组织中的表达缺失率为51.0%(26/51),其表达量为0.095 50±0.135 69,明显低于癌旁正常组织、良性肿瘤组织(P＜0.01);(2)乳腺癌组织中RASSF1A mRNA的表达低下或缺失与淋巴结转移相关(P＜0.05);(3)RASSF1A mRNA的表达低下或缺失与年龄、肿瘤大小、病理分型、组织学分级、激素受体和HER-2表达情况无显著相关(P＞0.05)。结论 RASSF1A基因表达缺失可能在乳腺癌的发生和发展过程中起重要作用,并影响其预后。     

Aberrant methylation and silencing of ARHI,an imprinted tumor suppressor gene in which the function is lost in breast cancers

ARHI is a maternally imprinted tumor suppressor gene that maps to a site on chromosome 1p31 where loss of heterozygosity has been observed in 40% of human breast and ovarian cancers. ARHI is expressed in normal ovarian and breast epithelial cells, but ARHI expression is lost in a majority of ovarian and breast cancers. Expression of ARHI from the paternal allele can be down-regulated by multiple mechanisms in addition to loss of heterozygosity. This article explores the role of DNA methylation in silencing ARHI expression. There are three CpG islands in the ARHI gene. CpG islands I and II are located in the promoter region, whereas CpG island III is located in the coding region. Consistent with imprinting, we have found that all three CpG islands were partially methylated in normal human breast epithelial cells. Additional confirmation of imprinting has been obtained by studying DNA methylation and ARHI expression in murine A9 cells that carry either the maternal or the paternal copy of human chromosome 1. All three CpG islands were methylated, and ARHI was not expressed in A9 cells that contained the maternal allele. Conversely, CpG islands were not methylated and ARHI was expressed in A9 cells that contained the paternal allele of human chromosome 1. Aberrant methylation was found in several breast cancer cell lines that exhibited decreased ARHI expression. Hypermethylation was detected in 67% (6 of 9) of breast cancer cell lines at CpG island I, 33% (3 of 9) at CpG island II, and 56% (5 of 9) at CpG island III. Hypomethylation was observed in 44% (4 of 9) of breast cancer cell lines at CpG island II. When methylation of CpG islands was studied in 20 surgical specimens, hypermethylation was not observed in CpG island I, but 3 of 20 cases exhibited hypermethylation in CpG island II (15%), and 4 of 20 cases had hypermethylation in CpG island III (20%). Treatment with 5-aza-2'-deoxycytidine, a methyltransferase inhibitor, could reverse aberrant hypermethylation of CpG island I, II and III and partially restore ARHI expression in some, but not all of the cell lines. Treatment with 5-aza-2'-deoxycytidine partially reactivated ARHI expression in cell lines with hypermethylation of CpG islands I and II but not in cell lines with partial methylation or hypomethylation of these CpG islands. To test the impact of CpG island methylation on ARHI promoter activity more directly, constructs were prepared with the ARHI promoter linked to a luciferase reporter and transfected into SKBr3 and human embryo kidney 293 cells. Methylation of the entire construct destroyed promoter activity. Selective methylation of CpG island II alone or in combination with CpG island I also abolished ARHI promoter activity. Methylation of CpG I alone partially inhibited promoter activity of ARHI. Thus, hypermethylation of CpG island II in the promoter region of ARHI is associated with the complete loss of ARHI expression in breast cancer cells. Other epigenetic modifications such as hypermethylation in CpG island III may also contribute to the loss of ARHI expression.