OBJECTIVETo screen the microRNAs involved in colon cancer proliferation and to investigate the expression and regulating function of target miRNA in colon cancer.

METHODSMitochondrial transcription factor A(TFAM), which was proved to be an oncogene to colon cancer in prior study, was used as target gene. The microRNAs involved in colon cancer proliferation were screened with miRWalk 2.0 software. The expression of screened miRNAs was examined in 30 samples of colon cancer tissue, para-cancer tissue, normal colon cell strain, and 3 colon cancer strains (SW480, HT-29, and HCT116) by real-time PCR. MiR-204 presenting lowest expression was selected to further study in SW480 cells. Dual luciferase reporter assays was performed to examine the association of TFAM with miR-204. Anti-miR-204 lentivirus and miR-240 lentivirus were used to down-regulate and up-regulate miR-204 expression respectively. Change of TFAM protein expression in SW480 cells was detected by Western blotting, and change of SW480 cells proliferation was detected by MTT and BrdU assay after lentivirus transfection.

RESULTSAfter screening, the candidate miRNAs were miR-204, miR-211, miR-214, miR-381 and miR-590-3p. Expressions of miR-204, miR-211, miR-214 and miR-381 were lower, but miR-590-3p expression was higher, in colon cancer tissues than those in para-cancer tissues(all P<0.05). Meanwhile expressions of above 4 miRNAs(miR-204, miR-211, miR-214 and miR-381) were also lower, but miR-590-3p expression was higher as well, in SW480, HT-29 and HCT116 cells compared to normal colon cells(all P<0.05). Among above 4 miRNAs, miR-204 showed the lowest expression in both colon cancer tissues and cell lines. Expression of miR-204 was negatively correlated with TFAM expression in colon cancer tissues(P<0.05). Dual luciferase reporter assays revealed TFAM could be integrated with miR-204 directly, suggesting TFAM as the direct target of miR-204. After up-regulating miR-204 by lentivirus, expression of TFAM decreased and proliferation increased in SW480 cells(all P<0.05). After down-regulating miR-204 by lentivirus, expression of TFAM increased and proliferation decreased in SW480 cells(all P<0.05).

CONCLUSIONMiR-204 inhibits TFAM expression and up-regulates the proliferation of colon cancer cells SW480.