MiRNALet-7a mediates prostate cancer PC-3 cell invasion, migration by inducing epithelial-mesenchymal transition through CCR7/MAPK pathway

Prostate cancer is one of the most common malignancies in older men. Recent evidence has demonstrated microRNA (miRNA) Let-7a expression decreased in prostate cancer, while the expression of CC chemokine receptor type 7 (CCR7) increased. In this study, we investigated whether CCR7 overexpression was associated with a decrease in the expression of miRNA Let-7a in invasion and metastasis of prostate cancer cell. Synthetic Let-7a mimics and Let-7a inhibitors were transfected into prostate cancer PC-3 cells, respectively. Then Western blot was used to detect the expression of CCR7, ERK, p38, MMP-9, and Epithelial-Mesenchymal Transition (EMT)-related proteins. Matrigel invasion assays were performed to assess the migratory and invasive activities of PC3 cells. To confirm the fact that 3UTR of CCR7 is a direct target of Let-7a, a luciferase assay for the reporter gene expressing the Let-7a binding sites of CCR7 3UTR was used. Synthetic Let-7a mimics decreased prostate cancer cell migration and invasion, as well as the expression of CCR7, phospho-p38, phospho-ERK1/2, MMP-9, N-cadherin, and Snail in PC-3 cells. The Let-7a inhibitors reversed the effects of Let-7a on PC-3 cells. The 3UTR of CCR7 was confirmed as a direct target of Let-7a by using the luciferase assay. All findings demonstrated that Let-7a/CCR7 axis regulated EMT progress in prostate cancer cells and mediated the tumor cell invasion and migration process via activation of P38/ERK signal pathway. Our results suggested that the therapeutic potential of Let-7a as an antitumor and antimetastatic manager in prostate cancer and CCR7 may be regarded as a therapeutic target for the prostate cancer treatment.