MiR-145 Affects Proliferation Of Nasopharyngeal Carcinoma Cells By Regulating C-Myc Expression

Objective: The aim of this study is to explore the possible regulatory mechanism of miR-145 affects the proliferation of nasopharyngeal carcinoma cells.Methods : To determine the relative expression of miR-145 and c-Myc in nasopharyngeal carcinoma, quantitative real-time PCR(qRT-PCR) and Western blot were initially performed in 3 nasopharyngeal carcinoma cell lines(CNE-1,CNE-2 and CNE-2Z) and normal nasopharyngeal NP69 cell line. MiR-145 mimics(or miR-NC) were transfected into CNE-1 cells, and the expression of miR–145 was detected by qRT-PCR. Cell Counting Kit-8 assay was used to evaluate the cell proliferation, and propyliodide organism(PI) staining was used to detect the cell cycle. Meanwhile we evaluated the cell proliferation and cell cycle after we transfected si-c-Myc(or si-NC)into CNE-1 cells. Then we performed dual-luciferase assay to explore the relationship between c-Myc and miR-145 in nasopharyngeal carcinoma cells.Results : The expression of miR-145 was significantly decreased in 3 nasopharyngeal carcinoma compare with that in NP69 cells, and the expression of c-Myc was higher in 3 nasopharyngeal carcinoma than NP69 cells. After transfected miR-145 mimics into CNE-1 cells, CNE-1 cells showed significant growth-suppressing effect by inhibiting cell proliferation(3d:1.03±0.02, P<0.05;4d:1.79±0.02, P<0.01), and cells were accumulated in G1 phase((74.43±1.55)% vs(69.98±1.16)%,P<0.001). Knock down of c-Myc inhibits the proliferation of CNE-1(3d:0.80±0.02, P<0.01;4d:1.68±0.4, P<0.01), and cells were accumulated in G1 phase((69.77± 0.87)% vs(54.10±2.26)%,P<0.01). miR-145 can down regulate c-Myc expression by directly targeting the seed sequence of c-Myc 3’UTR in CNE-1.Conclusion:MiR-145 inhibits nasopharyngeal carcinoma proliferation by targeting c-Myc,and this maybe provide a new direction for the diagnose and treatment of nasopharyngeal carcinoma.