Epigenetics, microRNAs, and carcinogenesis: functional role of microRNA-137 in uveal melanoma.
OBJECTIVE
MicroRNAs (miRNAs) can contribute to tumorigenesis by acting as either oncogenes or tumor suppressor genes. The authors' previous studies on miR-34a showed that miRNA can influence the growth of uveal melanoma cells. In this study, they investigated the role of miR-137 in the pathogenesis of uveal melanoma.


METHODS
Real-time RT-PCR was used to screen the expression levels of miR-137 in uveal melanocytes and uveal melanoma cell lines. Cell proliferation was examined by MTS assay and cell cycle was analyzed by flow cytometry. The target genes of miR-137 were predicted by bioinformatics and confirmed using a luciferase reporter assay. The expression of MITF, CDK6, and cell cycle regulatory proteins was determined by Western blot analysis. The ability to increase miR-137 expression by epigenetic drugs was tested using real-time RT-PCR.


RESULTS
miR-137 expression was lower in uveal melanoma cell lines than in uveal melanocytes. Ectopic transfection of miR-137 into uveal melanoma cells induced G1 cell cycle arrest, leading to a significant decrease in cell growth. Overexpression of miR-137 downregulated MITF, a transcription factor with oncogenic activity. Moreover, the introduction of miR-137 downregulated the oncogenic tyrosine kinase protein receptor c-Met and cell cycle-related proteins, including CDK6. One avenue to increase the expression levels of miR-137 was through treatment with a DNA hypomethylating agent, 5-aza-2'-deoxycytidine, and a histone deacetylase inhibitor, trichostatin A.


CONCLUSIONS
The results showed that miR-137 can act as a tumor suppressor in uveal melanoma cell proliferation through downregulation of the targets MITF and CDK6. miR-137 may be epigenetically silenced during uveal melanoma tumorigenesis.
School of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China.
Xiaoyan
X
Chen
Jiao
J
Wang
Huanjun
H
Shen
Juan
J
Lu
Canxia
C
Li
Dan-Ning
DN
Hu
Xiang Da
XD
Dong
Dongsheng
D
Yan
Lili
L
Tu
D015153:Blotting, Western; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D049109:Cell Proliferation; D051361:Cyclin-Dependent Kinase 6 / Q000378:metabolism; D015536:Down-Regulation; D057890:Epigenomics; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D035683:MicroRNAs / Q000502:physiology*; D051739:Microphthalmia-Associated Transcription Factor / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014604:Uveal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology
D018797:Cell Cycle Proteins; C545567:MIRN137 microRNA, human; C497234:MITF protein, human; D035683:MicroRNAs; D051739:Microphthalmia-Associated Transcription Factor; C495911:CDK6 protein, human; D051361:Cyclin-Dependent Kinase 6