title: Haplotype insufficiency for suppressor of cytokine signaling-2 enhances intestinal growth and promotes polyp formation in growth hormone-transgenic mice.
abstract: GH may improve intestinal growth or function in patients with short bowel syndrome. Excessive trophic effects of GH or IGF-I may contribute to neoplastic growth or increased colorectal cancer risk in acromegaly. Identification of mechanisms that limit the tumorigenic potential of GH and IGF-I is desirable. Suppressor of cytokine signaling-2 (SOCS2) limits GH action on body and organ growth, but its role in GH action on intestine is unknown. We tested the hypothesis that SOCS2 limits GH-induced intestinal growth or neoplasia in vivo. GH-transgenic (GH-TG) mice were crossed with SOCS2 null mice to generate wild-type (WT) or transgenic (TG) mice with zero (HO-WT; HO-TG), one (HT-WT; HT-TG), or two (WT-WT; WT-TG) functional SOCS2 genes. No HO-TG mice were derived from crossbreeding. WT-WT, HT-WT, WT-TG, and HT-TG were compared. Body weight, small intestine and colon growth, and levels of jejunal IGF-I and sucrase-isomaltase mRNAs were assessed. Colon was analyzed for abnormal lesions. HT-WT did not differ from WT-WT. Compared with WT-TG, HT-TG had significantly increased body weight, small intestine growth, and local IGF-I expression and decreased sucrase-isomaltase expression. HT-TG colon spontaneously developed multiple hyperplastic and lymphoid polyps. GH-induced activation of STAT5 DNA binding activity was enhanced in intestine of SOCS2 null mice compared with WT control. Haplotype insufficiency for SOCS2 promotes trophic actions of GH in small intestine and promotes preneoplastic growth in colon during excess GH. Small variations in SOCS2 expression levels may significantly influence the outcome of therapeutic GH or acromegaly in intestine.
authors.affiliation: Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, 27599-7545, USA. carmen_michaylira@med.unc.edu
authors.forename: Carmen Z
authors.initials: CZ
authors.lastname: Michaylira
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Ramocki
authors.forename: James G
authors.initials: JG
authors.lastname: Simmons
authors.forename: C Kirby
authors.initials: CK
authors.lastname: Tanner
authors.forename: Kirk K
authors.initials: KK
authors.lastname: McNaughton
authors.forename: John T
authors.initials: JT
authors.lastname: Woosley
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Greenhalgh
authors.forename: P Kay
authors.initials: PK
authors.lastname: Lund
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D003106:Colon / Q000473:pathology; D005260:Female; D013006:Growth Hormone / Q000502:physiology*; D006239:Haplotypes; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007413:Intestinal Mucosa / Q000473:pathology*; D007417:Intestinal Polyps / Q000209:etiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D012333:RNA, Messenger / Q000032:analysis; D050799:STAT5 Transcription Factor / Q000378:metabolism; D013394:Sucrase-Isomaltase Complex / Q000235:genetics; D050826:Suppressor of Cytokine Signaling Proteins / Q000172:deficiency / Q000235:genetics* / Q000502:physiology
chemical_list: D012333:RNA, Messenger; D050799:STAT5 Transcription Factor; C491409:Socs2 protein, mouse; D050826:Suppressor of Cytokine Signaling Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013394:Sucrase-Isomaltase Complex