Sensitive detection of melanoma metastasis using circulating microRNA expression profiles.

Numerous studies have indicated that the serum levels of microRNAs are useful for the diagnosis or evaluation of activity in human diseases. However, determining the level of only one of the nearly 2000 microRNAs identified so far may be less significant. Accordingly, we examined the possibility that the expression pattern of multiple microRNAs in each patient may be a more reliable disease marker for melanoma, especially metastatic disease, focusing on the interaction among microRNAs. Six microRNAs (miR-9, miR-145, miR-150, miR-155, miR-203, and miR-205) were evaluated using real-time PCR in 11 patients with metastatic melanoma and in 16 patients without melanoma. The expression of the six microRNAs was significantly different between the patients with metastasis and those without it. MiR-9 and miR-205 and miR-203 and miR-205 showed significant correlations, and the combination of miR-9, miR-145, miR-150, miR-155, and miR-205 was more sensitive than when each miR was used individually to distinguish the patients with metastasis from those without it. This is the first report demonstrating the expression profiles of multiple microRNAs in melanoma patients. Clarifying the involvement of the microRNA network in the pathogenesis of melanoma may contribute to the development of new diagnostic tools and to advancing the understanding of this disease.