Epigenetic regulation of microRNA-370 by interleukin-6 in malignant human cholangiocytes.
Interleukin-6 (IL-6) is overexpressed and contributes to tumor cell growth in cholangiocarcinoma. Enforced IL-6 production can alter the expression of specific microRNAs (miRNAs) involved in tumor growth, and moreover can modulate expression of methylation-dependent genes. Thus, we assessed the methylation-dependent regulation of miRNA expression in human malignant cholangiocytes stably transfected to overexpress IL-6. The expression of the methyltransferases DNA methyltransferase enzyme-1 and HASJ4442 was increased by IL-6 overexpression, but was decreased by the methylation inhibitor 5-aza-2'-deoxycytidine (5-aza-CdR). Expression profiling identified seven miRNAs that were significantly downregulated by IL-6 overexpression (<0.4-fold) and upregulated (>2-fold) by 5-aza-CdR. One of these, miR-370, is embedded in a CpG island. Although 5-aza-CdR increased miR-370 expression by 2.1-fold in malignant cells, the expression in nonmalignant cells was unchanged. The oncogene mitogen-activated protein kinase kinase kinase 8 (MAP3K8) was identified as a target of miR-370, and its expression was decreased by 5-aza-CdR in cholangiocarcinoma cells. Overexpression of IL-6 reduced miR-370 expression and reinstated MAP3K8 expression in vitro as well as in tumor cell xenografts in vivo. Thus, IL-6 may contribute to tumor growth by modulation of expression of selected miRNAs, such as miR-370. These studies define a mechanism by which inflammation-associated cytokines can epigenetically modulate gene expression and directly contribute to tumor biology.
Meng
F
F
Department of Internal Medicine, Scott and White Clinic, Texas A&M University System Health Science Center College of Medicine, Temple, TX, USA.
Wehbe-Janek
H
H
Henson
R
R
Smith
H
H
Patel
T
T
D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D001650:Bile Duct Neoplasms / Q000235:genetics*; D001653:Bile Ducts, Intrahepatic / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018281:Cholangiocarcinoma / Q000235:genetics*; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D044127:Epigenesis, Genetic; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism
D015850:Interleukin-6; C526503:MIRN370 microRNA, human; D035683:MicroRNAs; D011518:Proto-Oncogene Proteins; D000077209:Decitabine; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D020930:MAP Kinase Kinase Kinases; C069937:MAP3K8 protein, human; D001374:Azacitidine