miR-31 displays subtype specificity in lung cancer.

miRNA rarely possess pan-oncogenic or tumor suppressive properties. Most miRNA function under tissue-specific contexts, acting as either tumor suppressors in one tissue, promoting oncogenesis in another, or having no apparent role in the regulation of processes associated with the hallmarks of cancer. What has been less clear is the role of miRNAs within cell types of the same tissue and the ability within each cell type to contribute to oncogenesis. In this study, we characterize the role of one such tissue-specific miRNA, miR-31, recently identified as the most oncogenic miRNA in lung adenocarcinoma, across the histological spectrum of human lung cancer. Compared to normal lung tissue, miR-31 was overexpressed in patient lung adenocarcinoma, squamous cell carcinoma, and large cell neuroendocrine carcinoma, but not small cell carcinoma or carcinoids. miR-31 promoted tumor growth in mice of xenografted human adenocarcinoma and squamous cell carcinoma cell lines, but not in large or small cell carcinoma lines. While miR-31 did not to promote primary tumor growth of large and small cell carcinoma, it did promote spontaneous metastasis. Mechanistically, miR-31 altered distinct cellular signaling programs within each histological subtype, resulting in distinct phenotypic differences. This is the first report distinguishing diverse functional roles for this microRNA across the spectrum of lung cancers and suggests that miR-31 has broad clinical value in human lung malignancy.