title: The noncoding RNA, miR-126, suppresses the growth of neoplastic cells by targeting phosphatidylinositol 3-kinase signaling and is frequently lost in colon cancers.
abstract: MicroRNAs (miRNA/miR) are a class of small noncoding RNAs implicated in the pathogenesis of various malignancies. In the current study, using micro(RNA) arrays, we found a ubiquitous loss of miR-126 expression in colon cancer lines when compared to normal human colon epithelia. Reconstitution of miR-126 in colon cancer cells resulted in a significant growth reduction as evidenced in clonogenic assays. A search for miR-126 gene targets revealed p85beta, a regulatory subunit involved in stabilizing and propagating the phosphatidylinositol 3-kinase (PI3K) signal, as one of the potential substrates. Restoration of miR-126 in cancer cells induced a > or =3-fold reduction in p85beta protein levels, with no concomitant change in p85alpha, a gene that is functionally related to p85beta but not a supposed target of miR-126. Additionally, using reporter constructs, we show that the p85beta-3' untranslated region is directly targeted by miR-126. Furthermore, this miR-126 mediated reduction of p85beta was accompanied by a substantial reduction in phosphorylated AKT levels in the cancer cells, suggesting an impairment in PI3K signaling. Finally, in a panel of matched normal colon and primary colon tumors, each of the tumors demonstrated miR-126 down-regulation together with an increase in the p85beta protein level. Taken together, we propose that miR-126 regulates PI3K signaling partly by targeting p85beta, and that the loss of miR-126 may provide a selective growth advantage during colon carcinogenesis.
authors.affiliation: Department of Medicine and Ireland Cancer Center, Case Medical Center and Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Chunguang
authors.initials: C
authors.lastname: Guo
authors.forename: Jerome F
authors.initials: JF
authors.lastname: Sah
authors.forename: Lydia
authors.initials: L
authors.lastname: Beard
authors.forename: James K V
authors.initials: JK
authors.lastname: Willson
authors.forename: Sanford D
authors.initials: SD
authors.lastname: Markowitz
authors.forename: Kishore
authors.initials: K
authors.lastname: Guda
mesh_terms: D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D035683:MicroRNAs; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D021122:Protein Subunits; C527111:MIRN126 microRNA, human