miRNAs expression profiling to distinguish lung squamous-cell carcinoma from adenocarcinoma subtypes.

Purpose: We investigated whether miRNA expression profiles can distinguish and predict outcome of non-small-cell lung carcinoma (NSCLC) patients with different histological subtypes.

Methods: High-throughput microarray was used to measure miRNA expression levels in six NSCLC samples. Subsequently, quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to verify findings in an independent set of 54 squamous-cell lung carcinomas (SCC), 51 lung adenocarcinomas (AD), and paired adjacent non-neoplastic lung tissue.

Results: We showed that, compared to adjacent non-neoplastic lung tissues, the expressions of miR-125a-5p and let-7e were decreased in AD and SCC samples, while increased expressions of miR-93, miR-205, and miR-221 were observed in SCC samples. In addition, miR-205 expression was significantly higher in SCC patients with lymph node metastasis. Lower let-7e expression was associated with lymph node metastasis, >3 cm tumor size, and differentiation of the NSCLC AD subtype. High levels of miR-100 expression also correlated with the AD subtype in current smokers. Moreover, induction of miR-93 and miR-205 expressions and reduction of let-7e were strongly associated with shorter overall survival in SCC patients, whereas AD patient survival was only associated with reduced let-7e.

Conclusions: We identified differential expression profiles of miRNAs in AD and SCC. More importantly, in addition to morphology and immunocytochemistry approaches, we report that miR-93, miR-205, miR-221, and let-7e may represent novel biomarkers for differential diagnosis and prognosis of certain NSCLC subtypes or be new targets of histology-specific treatments. Furthermore, our results suggest a strong correlation between high expression of miR-100 and AD patients with history of heavy smoking.