MicroRNA-143 targets DNA methyltransferases 3A in colorectal cancer.
BACKGROUND
MicroRNAs (miRNAs) are 19-25-nucleotides regulatory non-protein-coding RNA molecules that regulate the expressions of a wide variety of genes, including some involved in cancer development. In this study, we investigated the possible role of miR-143 in colorectal cancer (CRC).


METHODS
Expression levels of human mature miRNAs were examined using real-time PCR-based expression arrays on paired colorectal carcinomas and adjacent non-cancerous colonic tissues. The downregulation of miR-143 was further evaluated in colon cancer cell lines and in paired CRC and adjacent non-cancerous colonic tissues by qRT-PCR. Potential targets of miR-143 were defined. The functional effect of miR-143 and its targets was investigated in human colon cancer cell lines to confirm miRNA-target association.


RESULTS
Both real-time PCR-based expression arrays and qRT-PCR showed that miR-143 was frequently downregulated in 87.5% (35 of 40) of colorectal carcinoma tissues compared with their adjacent non-cancerous colonic tissues. Using in silico predictions, DNA methyltranferase 3A (DNMT3A) was defined as a potential target of miR-143. Restoration of the miR-143 expression in colon cell lines decreased tumour cell growth and soft-agar colony formation, and downregulated the DNMT3A expression in both mRNA and protein levels. DNMT3A was shown to be a direct target of miR-143 by luciferase reporter assay. Furthermore, the miR-143 expression was observed to be inversely correlated with DNMT3A mRNA and protein expression in CRC tissues.


CONCLUSIONS
Our findings suggest that miR-143 regulates DNMT3A in CRC. These findings elucidated a tumour-suppressive role of miR-143 in the epigenetic aberration of CRC, providing a potential development of miRNA-based targeted approaches for CRC therapy.
Ng
E K O
EK
Department of Medicine and Therapeutics, Institute of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
Tsang
W P
WP
Ng
S S M
SS
Jin
H C
HC
Yu
J
J
Li
J J
JJ
Röcken
C
C
Ebert
M P A
MP
Kwok
T T
TT
Sung
J J Y
JJ
D015153:Blotting, Western; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000235:genetics*; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism*; D000090205:DNA Methyltransferase 3A; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D020868:Gene Silencing; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction
C000717967:DNMT3A protein, human; C542359:MIRN143 microRNA, human; D035683:MicroRNAs; D034741:RNA, Small Interfering; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A