Upregulation of microRNA-31 associates with a poor prognosis of malignant pleural mesothelioma with sarcomatoid component

Malignant pleural mesothelioma (MPM) is a neoplastic disease with a poor prognosis. The complete resection of tumor with extra-pleural pneumonectomy is effective only for early stage epithelioid-type MPM. An accurate pathological diagnosis including the histological subtype and also clinical staging are crucial to decide on the therapeutic approach. However, the pathological diagnosis is difficult when the amount of biopsy sample is small. We performed a comparative analysis of the miR-31 expression in MPM and reactive mesothelial proliferations (RMPs), by RT-qPCR of formaldehyde-fixed paraffin-embedded samples, and compared the expression levels of miR-31 with the results of a survival analysis for the diagnosis and prognosis of MPM. The expression of miR-31 was found to be significantly reduced in MPMs compared with RMPs (P < 0.01). The pathological subtype of four among five cases with upregulated miR-31 levels was MPM with a sarcomatoid component. (i.e., biphasic or sarcomatoid type). Furthermore, these four cases were significantly associated with a worse prognosis compared with the five cases of biphasic or sarcomatoid MPM without upregulated miR-31 expression (P = 0.0027). In conclusion, the analysis of miR-31 expression levels may be a good biomarker for diagnosis of MPM histological typing and predicting the prognosis.