MicroRNA-21 in lung cancer: overexpression in metastasis of pulmonary adenocarcinomas and squamous cell carcinomas

Abstract

MicroRNAs (miRNAs) are a class of naturally occurring small non-coding RNAs that target protein-coding mRNAs at the post-transcriptional level. Expression profiling has identified miRNA signatures in cancers that associate with diagnosis, staging, progression, prognosis, and response to treatment. MiRNAs are ideal biomarkers in FFPE-tissue because, unlike mRNA, miRNA integrity is affected very little by formalin fixation. Previous studies have shown that miR-21 overexpression correlated with poor prognosis in NSCLC patients. In this study we investigated the expression of mir-21 in primary carcinoma and metastasis and near non-tumor parenchyma. FFPE samples from surgical specimens and biopsies of 7 pulmonary adenocarcinomas and 5 squamous cell carcinomas and respective metastasis together with normal lung tissue from the same case; these areas were separated by laser-capture microdissection prior to miRNA analysis. The expression level of miR-21 by qRT-PCR was significantly higher in tumor tissues than in adjacent normal tissues (p = 0.005). The overexpression in the metastasis samples compared to adjacent normal tissue was almost satistically significant (p = 0.051). MiR-21 was overexpressed in tumor tissues relative to adjacent non-tumor tissues. We found an increase in miR-21 expression in primary carcinoma and metastasis in pulmonary adenocarcinomas when compared with miR-21 lower expression in squamous cell carcinoma. Despite the small sample studied, further investigation may indicate therapeutic and prognostic relevance of this determination, previous studies suggest that miR-21 and has a role in tumor growth, invasion and metastasis by targeting multiple suppressor genes [1]. Therefore, suppression of miR-21 may provide a novel approach for the treatment of advanced cancers through regulation of tumour suppressor genes.