In the context of the inconsistent profiles between tissue-based and plasma-based result, however, some consistently reported miRNAs in tissue-based profiling studies, for example, a panel of miR-21, miR-210 and miR-486-5p, have been validated in plasma-based eFT508 mouse studies to confirm their diagnostic value in the diagnosis LEE011 research buy of lung cancer with solitary pulmonary nodules [39]. Future studies that based on parallel plasma and tissue samples may provide more solid evidence. For the included profiling studies in which adjacent corresponding normal lung tissue served as an expression baseline, we need to know that adjacent appearing

morphologically normal tissue may contain molecular changes associated with cancer [40, 41]. Third, rigorous validation and demonstration of reproducibility

in an independent population are necessary to confirm the predictive value of miRNAs. One of the most frequently investigated miRNAs is miR-21, it ranks second among consistently reported up-regulated miRNAs in this meta-analysis, it has been also reported to be associated with prognosis in several kinds of cancer [42–44]. From the prognostic point of view, see more over expression of miR-21 has been reported to be independently associated with reduced survival of pancreatic ductal adenocarcinoma [43]. High miR-21 expression was also associated with poor survival of colon adenocarcinoma in both the training cohort (US test cohort of 84 patients with incident colon adenocarcinoma, recruited between 1993 and 2002) and validation cohort (independent Chinese cohort of 113 patients recruited between 1991 and 2000) [44]. However, when expression of miR-21, miR-29b, miR-34a/b/c, miR-155, and let-7a was determined by quantitative real-time PCR in formalin-fixed paraffin-embedded tumor specimens from 639 patients who participated in the International Adjuvant Lung Cancer Trial (IALT), there was a deleterious borderline prognostic Ribonucleotide reductase effect of lowered miR-21 expression [45]. Conclusions In conclusion, the top

two most consistently reported up-regulated miRNAs were miR-210 and miR-21. The results of this meta-analysis of human lung cancer miRNA expression profiling studies might provide some clues of the potential biomarkers in lung cancer. Further mechanistic and external validation studies are needed for their clinical significance and role in the development of lung cancer. Acknowledgements This work was supported by Key Laboratory Project, Liaoning Provincial Department of Education (No. LS2010168) and the National Natural Science Foundation of China (No. 81102194). The funding sources had no role in the study design, data collection, analysis and interpretation, or in the writing of this manuscript. References 1.