Tissue microRNA expression profiling in hepatic and pulmonary metastatic melanoma

Malignant melanoma has a propensity for the development of hepatic and pulmonary metastases. MicroRNAs (miRs) are small, noncoding RNA molecules containing about 22 nucleotides that mediate protein expression and can contribute to cancer progression. We aim to identify clinically useful differences in miR expression in metastatic melanoma tissue. RNA was extracted from formalin-fixed, paraffin-embedded samples of hepatic and pulmonary metastatic melanoma, benign, nevi, and primary cutaneous melanoma. Assessment of miR expression was performed on purified RNA using the NanoString nCounter miRNA assay. miRs with greater than twofold change in expression when compared to other tumor sites (P value ≤ 0.05, modified t-test) were identified as dysregulated. Common gene targets were then identified among dysregulated miRs unique to each metastatic site. Melanoma metastatic to the liver had differential expression of 26 miRs compared to benign nevi and 16 miRs compared to primary melanoma (P < 0.048). Melanoma metastatic to the lung had differential expression of 19 miRs compared to benign nevi and 10 miRs compared to primary melanoma (P < 0.024). Compared to lung metastases, liver metastases had greater than twofold upregulation of four miRs, and 4.2-fold downregulation of miR-200c-3p (P < 0.0081). These findings indicate that sites of metastatic melanoma have unique miR profiles that may contribute to their development and localization. Further investigation of the utility of these miRs as diagnostic and prognostic biomarkers and their impact on the development of metastatic melanoma is warranted.