The analysis of microRNA-34 family expression in human cancer studies comparing cancer tissues with corresponding pericarcinous tissues

Recently many studies have focused on the microRNA-34 (miR-34) family expression in various cancers; nevertheless, the controversial results of these studies still exist in identifying miR-34 members as new biomarkers of cancers. Therefore, we carried out this comprehensive meta-analysis of published studies that compared the miR-34 family expression profiles between cancer tissues and paired neighboring noncancerous tissues to systemically evaluate the findings globally and address the inconsistencies of pertinent literatures. The data included in this article were collected from Embase, PubMed and Web of Science up to December 2013. To overcome the difficulties that many raw data were unavailable and study methods were different, a vote-counting strategy was adopted to identify consistent markers in our analysis. Ultimately, a total of 23 cancers were reported in the 61 eligible studies, of which 46 studies provided fold-change value information. In the consistently reported cancer types, non-small cell lung cancer (NSCLC), glioma and nasopharyngeal carcinoma (NPC) ranked at the top with down-regulated feature. Cervical neoplasm was consistently reported to be over-expressed in the panel of each member of miR-34s. Subgroup analysis of miR-34 family expression demonstrated that colorectal cancer (CRC), gastric cancer (GC), hepatocellular carcinoma (HCC) and prostate cancer (PCa) were most frequently reported with inconsistent regulations. Our meta-analysis showed that miR-34 family members could be expected to become potential diagnostic and prognostic biomarkers in some types of human cancers. Further well-designed and larger sample studies are surely warranted to identify the role of the miR-34 family in the occurrence and development of tumors.