A microRNA signature defines chemoresistance in ovarian cancer through modulation of angiogenesis

Epithelial ovarian cancer is the most lethal gynecologic malignancy; it is highly aggressive and causes almost 125,000 deaths yearly. Despite advances in detection and cytotoxic therapies, a low percentage of patients with advanced stage disease survive 5 y after the initial diagnosis. The high mortality of this disease is mainly caused by resistance to the available therapies. Here, we profiled microRNA (miR) expression in serous epithelial ovarian carcinomas to assess the possibility of a miR signature associated with chemoresistance. We analyzed tumor samples from 198 patients (86 patients as a training set and 112 patients as a validation set) for human miRs. A signature of 23 miRs associated with chemoresistance was generated by array analysis in the training set. Quantitative RT-PCR in the validation set confirmed that three miRs (miR-484, -642, and -217) were able to predict chemoresistance of these tumors. Additional analysis of miR-484 revealed that the sensitive phenotype is caused by a modulation of tumor vasculature through the regulation of the VEGFB and VEGFR2 pathways. We present compelling evidence that three miRs can classify the response to chemotherapy of ovarian cancer patients in a large multicenter cohort and that one of these three miRs is involved in the control of tumor angiogenesis, indicating an option in the treatment of these patients. Our results suggest, in fact, that blockage of VEGF through the use of an anti-VEGFA antibody may not be sufficient to improve survival in ovarian cancer patients unless VEGFB signaling is also blocked.Ovarian cancer is the leading cause of gynecological cancer-related death in the developed world (1). Although progress has been made in its treatment by improved debulking surgery and the introduction of platinum–taxane regimens (2), the overall 5-y survival is only 29% in advanced stage disease (1), mostly because of diagnosis at an advanced stage and intrinsic and acquired resistance to platinum-based chemotherapy. Identifying molecular markers of ovarian cancer chemoresistance is, therefore, of crucial importance. Successful translation of findings at the molecular level will lead to individualized treatment regimens, improved chemotherapeutic response rates, and avoidance of unnecessary treatments.MicroRNAs (miRs) are a class of small noncoding RNAs that modulate gene expression by causing translational repression, mRNA cleavage, or destabilization (3). They are involved in numerous physiological cellular processes (4–7). Most importantly, accumulating evidence indicates that many miRs are aberrantly expressed in human cancers (8–10), and their expression profiles can classify stage, subtype, and prognosis of some cancers (11–14).In this report, we describe an miR signature that defines chemoresistant ovarian carcinoma. We show that some miRs are deregulated in most patients with resistant ovarian carcinomas, and we show that miR-484 exerts its action through the regulation of angiogenic factors. We postulate that this miR signature of drug resistance could be used to develop strategies for targeted therapies in chemorefractive ovarian carcinoma patients.     

A microRNA DNA methylation signature for human cancer metastasis

MicroRNAs (miRNAs) are small, noncoding RNAs that can contribute to cancer development and progression by acting as oncogenes or tumor suppressor genes. Recent studies have also linked different sets of miRNAs to metastasis through either the promotion or suppression of this malignant process. Interestingly, epigenetic silencing of miRNAs with tumor suppressor features by CpG island hypermethylation is also emerging as a common hallmark of human tumors. Thus, we wondered whether there was a miRNA hypermethylation profile characteristic of human metastasis. We used a pharmacological and genomic approach to reveal this aberrant epigenetic silencing program by treating lymph node metastatic cancer cells with a DNA demethylating agent followed by hybridization to an expression microarray. Among the miRNAs that were reactivated upon drug treatment, miR-148a, miR-34b/c, and miR-9 were found to undergo specific hypermethylation-associated silencing in cancer cells compared with normal tissues. The reintroduction of miR-148a and miR-34b/c in cancer cells with epigenetic inactivation inhibited their motility, reduced tumor growth, and inhibited metastasis formation in xenograft models, with an associated down-regulation of the miRNA oncogenic target genes, such as C-MYC, E2F3, CDK6, and TGIF2. Most important, the involvement of miR-148a, miR-34b/c, and miR-9 hypermethylation in metastasis formation was also suggested in human primary malignancies (n = 207) because it was significantly associated with the appearance of lymph node metastasis. Our findings indicate that DNA methylation-associated silencing of tumor suppressor miRNAs contributes to the development of human cancer metastasis.     

胃癌相关microRNA及其作用靶点的研究进展

microRNA(miRNA)是近年来发现的一类非编码单链小分子RNA,它的发现揭示了一种新的基因表达调控方式。其功能具有多样性,通过参与对靶基因的调控而影响细胞的生理及病理过程。近年发现许多miRNA与多种肿瘤的发生、发展及预后关系密切。胃癌是消化系统常见的恶性肿瘤之一,目前已发现一些miRNA及其相应的作用靶点与胃癌细胞的增殖、侵袭、转移、凋亡、对放射化学疗法的敏感性及DNA甲基化有密切关系,为对胃癌的研究提供新的途径。此文就近年胃癌相关miRNA及其作用靶点的研究作一综述。     

Studied microRNA gene expression in human hepatocellular carcinoma by microRNA microarray techniques

AIM: To achieve a better understanding of the molecular mechanisms of micro RNA expression changes involved in hepatocellular carcinoma.METHODS: In this research process, patients were not treated with antivirals, immunosuppressants or immunomodulators for at least 6 mo before collecting serum. The study population was composed of 35 outpatient hepatitis B virus(HBV) cases and 12 healthy control cases from the Affiliated Hospital of Inner Mongolia Medical University(Inner Mongolia, China) from July 2013 to April 2014. The 35 HBV cases were divided into two groups: a hepatocirrhosis group with 20 cases and a liver cancer group with 15 cases. All 35 cases carried HBs Ag. The diagnostic criteria followed the European Association for the Study of the Liver 2012(EASL2012) standards. Micro RNA(mi RNA) was extracted from a control group of patients, a group with hepatocirrhosis and a group with liver cancer and its quality was analyzed using the human V2 micro RNA expression beadchip. Cluster analysis and a radar chart were then applied to the mi RNA changes.RESULTS: The mi RNA-qualified rate of human serum samples was 93%. The concentration of a single sample was 200 ng/μL and the volume was 5 μL.All mi RNA serum samples were uncontaminated by the genome. The Mann-Whitney test showed significant differences in mi RNA between each group, with a detection P-value of 0.05. Illumina software was set up with Diff Score set to ± 13, meaning that P = 0.001.There were significant changes in mi RNA expression between the three groups. mi RNA-183 was the most up-regulated, followed by mi RNA-373. mi RNA-129 and mi RNA-188 were both strongly down-regulated and mi RNA-378 was down-regulated a small amount. The liver cancer group had greater changes, which indicated that changes in mi RNA expression levels were caused by hepatocirrhosis. The liver cancer disease course then further increased these changes. In the pentagon created by these five mi RNAs, three groups showed significant deviation. The liver cancer group had a bigger deviation trend. The chart indicated that mi RNA expression changes occurred in the hepatocirrhosis group, which increased in the liver cancer disease course and were irreversible.CONCLUSION: There was a significant relationship between the irreversible up-regulation of mi RNA-183/373 and down-regulation of mi RNA-129/188/378 and incidences of hepatocirrhosis and liver cancer.     

Transforming growth factor-beta gene expression signature in mouse hepatocytes predicts clinical outcome in human cancer

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world. The clinical heterogeneity of HCC, and the lack of good diagnostic markers and treatment strategies, has rendered the disease a major challenge. Patients with HCC have a highly variable clinical course, indicating that HCC comprises several biologically distinctive subgroups reflecting a molecular heterogeneity of the tumors. Transforming growth factor beta (TGF-beta) is known to exhibit tumor stage dependent suppressive (that is, growth inhibition) and oncogenic (that is, invasiveness) properties. Here, we asked if a TGF-beta specific gene expression signature could refine the classification and prognostic predictions for HCC patients. Applying a comparative functional genomics approach we demonstrated that a temporal TGF-beta gene expression signature established in mouse primary hepatocytes successfully discriminated distinct subgroups of HCC. The TGF-beta positive cluster included two novel homogeneous groups of HCC associated with early and late TGF-beta signatures. Kaplan-Meier plots and log-rank statistics indicated that the patients with a late TGF-beta signature showed significantly (P < 0.005) shortened mean survival time (16.2 +/- 5.3 months) compared to the patients with an early (60.7 +/- 16.1 months) TGF-beta signature. Also, tumors expressing late TGF-beta-responsive genes displayed invasive phenotype and increased tumor recurrence. We also showed that the late TGF-beta signature accurately predicted liver metastasis and discriminated HCC cell lines by degree of invasiveness. Finally, we established that the TGF-beta gene expression signature possessed a predictive value for tumors other than HCC. CONCLUSION: These data demonstrate the clinical significance of the genes embedded in TGF-beta expression signature for the molecular classification of HCC.     

Identification of a risk dependent microRNA expression signature in myelodysplastic syndromes

The myelodysplastic syndromes (MDS) display both haematological and biological heterogeneity with variable leukaemia potential. MicroRNAs play an important role in tumour suppression and the regulation of self-renewal and differentiation of haematopoietic progenitors. Using a microarray platform, we evaluated microRNA expression from 44 patients with MDS and 17 normal controls. We identified a thirteen microRNA signature with statistically significant differential expression between normal and MDS specimens (P < 0·01), including down-regulation of members of the leukaemia-associated MIRLET7 family. A unique signature consisting of 10 microRNAs was closely associated with International Prognostic Scoring System (IPSS) risk category permitting discrimination between lower (Low/Intermediate-1) and higher risk (Intermediate-2/High) disease (P < 0·01). Selective overexpression of MIR181 family members was detected in higher risk MDS, indicating pathogenetic overlap with acute myeloid leukaemia. Survival analysis of an independent cohort of 22 IPSS lower risk MDS patients revealed a median survival of 3·5 years in patients with high expression of MIR181 family compared to 9·3 years in patients with low MIR181 expression (P = 0·002). Our pilot study suggested that analysis of microRNA expression profile offers diagnostic utility, and provide pathogenetic and prognostic discrimination in MDS.     

microRNA在人类恶性肿瘤中的研究进展

微小核糖核酸(microRNA,miRNA)与恶性肿瘤的相互关系是目前肿瘤分子生物学研究的热点领域,涉及恶性肿瘤的发生、发展、诊断、治疗、预后判断等各个方面,该文就microRNA在人类恶性肿瘤领域的研究进展作一综述。     

A biochemical approach to identifying microRNA targets

Identifying the downstream targets of microRNAs (miRNAs) is essential to understanding cellular regulatory networks. We devised a direct biochemical method for miRNA target discovery that combined RNA-induced silencing complex (RISC) purification with microarray analysis of bound mRNAs. Because targets of miR-124a have been analyzed, we chose it as our model. We honed our approach both by examining the determinants of stable binding between RISC and synthetic target RNAs in vitro and by determining the dependency of both repression and RISC coimmunoprecipitation on miR-124a seed sites in two of its well characterized targets in vivo. Examining the complete spectrum of miR-124 targets in 293 cells yielded both a set that were down-regulated at the mRNA level, as previously observed, and a set whose mRNA levels were unaffected by miR-124a. Reporter assays validated both classes, extending the spectrum of mRNA targets that can be experimentally linked to the miRNA pathway.     

Differential expression of microRNA species in human gastric cancer versus non-tumorous tissues

Background and Aim:  MicroRNAs (miRNAs) play important roles in carcinogenesis. The global miRNA expression profile of gastric cancer has not been reported. The purpose of the present study was to determine the miRNA expression profile of gastric cancer.
Methods:  Total RNA were first extracted from primary gastric cancer tissues and adjacent non-tumorous tissues and then small isolated RNAs (< 300 nt) were 3'-extended with a poly(A) tail. Hybridization was carried out on a μParaflo™ microfluidic chip (LC Sciences, Houston, TX, USA). After hybridization detection by fluorescence labeling using tag-specific Cy3 and Cy5 dyes, hybridization images were collected using a laser scanner and digitized using Array-Pro image analysis software (Media Cybernetics, Silver Spring, MD, USA). To validate the results and investigate the biological meaning of differential expressed miRNAs, immunohistochemistry was used to detect the differential expression of target genes.
Results:  The most highly expressed miRNAs in non-tumorous tissues were miR-768-3p, miR-139-5p, miR-378, miR-31, miR-195, miR-497 and miR-133b. Three of them, miR-139-5p, miR-497 and miR-768-3p, were first found in non-tumorous tissues. The most highly expressed miRNAs in gastric cancer tissues were miR-20b, miR-20a, miR-17, miR-106a, miR-18a, miR-21, miR-106b, miR-18b, miR-421, miR-340*, miR-19a and miR-658. Among them, miR-340*, miR-421 and miR-658 were first found highly expressed in cancer cells. The expression of some target genes (such as Rb and PTEN ) in cancer tissues was found to be decreased.
Conclusion:  To our knowledge, this is the first report about these miRNAs associated with gastric cancer. This new information may suggest the potential roles of these miRNAs in the diagnosis of gastric cancer.