A direct plasma assay of circulating microRNA-210 of hypoxia can identify early systemic metastasis recurrence in melanoma patients

Circulating cell-free(cf) microRNAs (miRNAs) have been reported to exist in plasma. MicroRNA-210(miR-210) is known to play important roles in the tumor hypoxic state. We hypothesized that the expression levels of cf-miR-210 in plasma would predict early clinical recurrence in melanoma patients. A direct miRNA assay on plasma (RT-qPCR-DP) was developed to improve cf-miRNA assay logistics, eliminate RNA extraction, and reduce specimen amount required. RNA was extracted from formalin-fixed paraffin-embedded (FFPE) melanoma tissues (n = 108) and assessed by RT-qPCR. Plasma (10 μl; n = 264) was procured from AJCC Stage III/IV patients in phase III clinical trials. A RT-qPCR-DP was performed to detect cf-miR-210. MiR-210 was significantly higher in metastatic tumors compared to primary tumors. Cf-miR-210 was significantly higher in melanoma patients versus healthy donor controls. In serial bloods within individual patients, cf-miR-210 < 3 months prior to disease recurrence significantly increased compared to baseline levels (p = 0.012). ROC curve analysis demonstrated that patients with elevated cf-miR-210 were more likely to have disease recurrence. Moreover, cf-miR-210 increase significantly correlated with poorer prognosis (p < 0.001). Lactate dehydrogenase (LDH) level was also assessed within patients, and the AIC values for proportional hazards regression models of cf-miR-210(120.01) and LDH (122.91) demonstrated that cf-miR-210 is a better recurrence indicator. We concluded enhanced cf-miR-210 provides identification of early systemic melanoma recurrence.