Abstract: ObjectiveTo verify the difference of serum miR-21 levels between patients with melanoma and healthy persons, clarify its role in the apoptosis of melanoma cells, and explore the potential targets for melanoma therapy.MethodsSera were collected from patients with melanoma and healthy control to extract microRNAs. RT-PCR was used to quantify the relative serum level of miR-21. The target gene programmed cell death-4 (PDCD4) was also analyzed as the potential target of miR-21 by ELISA. The miR-21 inhibitory melanoma cells was constructed and its effect on PDCD4 expression was identified. The effect of miR-21 on apoptosis was analyzed by flow-cytometric assay.ResultsCompared with the negative control, the level of miR-21 in sera of melanoma patients was up-regulated (4.62±2.42) and its potential target PDCD4 was down-regulated (0.36±0.21) (both P<0.01). As the expression of miR-21 was inhibited in melanoma cells, the expressions of PDCD4 in A-375 and SK-MEL-1 cells were (1.69±0.39) and (2.20±1.06) times of the negative control group respectively, and the cell apoptosis was increased in miR-21 over expressed melanoma cells compared with negative control (A-375: 2.82±0.24, SK-MEL-1: 2.26±0.23) through target PDCD4 (P<0.01).ConclusionmiR-21 was increased in patients with melanoma and might inhibit tumor cell apoptosis by inducing down-regulation of PDCD4 in melanoma cells, suggesting that miR-21 may be a potential target in melanoma therapy.