MicroRNA-224 targets SMAD family member 4 to promote cell proliferation and negatively influence patient survival.
MicroRNA-224 (miR-224) is frequently over-expressed in liver and colorectal cancers. We and others have previously described the role of miR-224 over-expression in cell proliferation in vitro but we have yet to identify the relevant miR-224 direct target. In this study, we further demonstrated that miR-224 up-regulation promotes cell proliferation using both in vitro assays and in vivo tumor growth models. We systematically screened for high confidence miR-224 targets by overlapping in silico predicted targets from multiple algorithms and significantly down-regulated genes in miR-224-expressing cells from whole genome expression microarrays. A total of 72 high confidence miR-224 targets were identified and found to be enriched in various cancer-related processes. SMAD family member 4 (SMAD4) is experimentally validated as the direct cellular target through which miR-224 promotes cell proliferation. The clinical relevance of our experimental observations was supported by a statistically significant inverse correlation between miR-224 and SMAD4 transcript expression in tumor versus paired adjacent non-tumorous tissues from HCC patients (p<0.001, r= -0.45, R(2) =0.122). Furthermore, miR-224 up-regulation and SMAD4 down-regulation is significantly associated with poorer patient survival (p<0.05). In summary, miR-224/SMAD4 pathway is a clinically relevant pathway to provide new insights in understanding HCC. (191 words).
Division of Medical Sciences, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, Singapore, Singapore.
Yu
Y
Wang
Jianwei
J
Ren
Yun
Y
Gao
Joel Z I
JZ
Ma
Han Chong
HC
Toh
Pierce
P
Chow
Alexander Y F
AY
Chung
London L P J
LL
Ooi
Caroline G L
CG
Lee
D000818:Animals; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000473:pathology; D049109:Cell Proliferation; D015536:Down-Regulation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D063990:Gene Ontology; D045325:HCT116 Cells; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D051901:Smad4 Protein / Q000378:metabolism*; D016019:Survival Analysis
C546140:MIRN224 microRNA, human; D035683:MicroRNAs; C497796:SMAD4 protein, human; D051901:Smad4 Protein