title: Tumor suppressors miR-143 and miR-145 and predicted target proteins API5, ERK5, K-RAS, and IRS-1 are differentially expressed in proximal and distal colon.
abstract: The colon differs regionally in local luminal environment, excretory function, and gene expression. Polycistronic microRNA (miR)-143 and miR-145 are downregulated early in colon cancer. We asked if these microRNAs (miRNAs) might be differentially expressed in the proximal vs. the distal colon, contributing to regional differences in protein expression. Primary transcripts and mature miR-143 and miR-145 were quantified by real-time PCR, putative targets were measured by Western blotting, and DNA methylation was assessed by sequencing bisulfite-treated DNA in proximal and distal normal colonic mucosa as well as colon cancers. Putative targets of these miRNAs were assessed following transfection with miR-143 or miR-145. Mean expression of mature miR-143 and miR-145 was 2.0-fold (P < 0.001) and 1.8-fold (P = 0.03) higher, respectively, in proximal than distal colon. DNA methylation or primary transcript expression of these miRNAs did not differ by location. In agreement with increased expression of miR-143 and miR-145 in proximal colon, predicted targets of these miRNAs, apoptosis inhibitor 5 (API5), ERK5, K-RAS, and insulin receptor substrate 1 (IRS-1), which are cell cycle and survival regulators, were expressed at a lower level in proximal than distal colon. Transfection of HCA-7 colon cancer cells with miR-145 downregulated IRS-1, and transfection of HT-29 colon cancer cells with miR-143 decreased K-RAS and ERK5 expression. In conclusion, miR-143 and miR-145 and the predicted target proteins API5, ERK5, K-RAS, and IRS-1 display regional differences in expression in the colon. We speculate that differences in these tumor suppressors might contribute to regional differences in normal colonic gene expression and modulate site-specific differences in malignant predisposition.
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and jpekow@medicine.bsd.uchicago.edu.
authors.forename: Joel
authors.initials: J
authors.lastname: Pekow
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and.
authors.forename: Katherine
authors.initials: K
authors.lastname: Meckel
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and.
authors.forename: Urszula
authors.initials: U
authors.lastname: Dougherty
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and.
authors.forename: Fatma
authors.initials: F
authors.lastname: Butun
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and.
authors.forename: Reba
authors.initials: R
authors.lastname: Mustafi
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and.
authors.forename: John
authors.initials: J
authors.lastname: Lim
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and.
authors.forename: Charis
authors.initials: C
authors.lastname: Crofton
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and.
authors.forename: Xindi
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Pathology, University of Chicago, Chicago, Illinois.
authors.forename: Loren
authors.initials: L
authors.lastname: Joseph
authors.affiliation: Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, Illinois; and.
authors.forename: Marc
authors.initials: M
authors.lastname: Bissonnette
mesh_terms: D000328:Adult; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D003106:Colon / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism*; D035683:MicroRNAs / Q000378:metabolism*; D048054:Mitogen-Activated Protein Kinase 7 / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D055815:Young Adult; D018631:ras Proteins / Q000378:metabolism*
chemical_list: C108386:API5 protein, human; D051017:Apoptosis Regulatory Proteins; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; C117307:KRAS protein, human; C542359:MIRN143 microRNA, human; C541010:MIRN145 microRNA, human; D035683:MicroRNAs; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D048054:Mitogen-Activated Protein Kinase 7; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins
keywords: colon; colon cancer; distal colon; miR-143; miR-145; proximal colon; regional variation