title: Defective interleukin-4/Stat6 activity correlates with increased constitutive expression of negative regulators SOCS-3, SOCS-7, and CISH in colon cancer cells.
abstract: Interleukin-4 (IL-4)-induced Stat6 activities (phenotypes) vary among human cancer cells, of which the HT-29 cell line carries an active Stat6(high) phenotype, while Caco-2 carries a defective Stat6(null) phenotype, respectively. Cancer cells with Stat6(high) show resistance to apoptosis and exaggerated metastasis, suggesting the clinical significance of Stat6 phenotypes. We previously showed that Stat6(high) HT-29 cells exhibited low constitutive expression of Stat6-negative regulators SOCS-1 and SHP-1 because of gene hypermethylation. This study further examined the constitutive expression of other closely related SOCS family numbers including SOCS-3, SOCS-5, SOCS-7, and CISH using RT-PCR. Similar to SOCS-1 and SHP-1, Stat6(high) HT-29 cells expressed low constitutive mRNA of SOCS-3, SOCS-7, and CISH than Stat6(null) Caco-2 cells. Interestingly, DNA demethylation using 5-aza-2'-deoxycytidine in HT-29 cells up-regulated mRNA expression of the above genes, indicating a hypermethylation status, which was confirmed by methylation-specific sequencing in selected SOCS-3 gene. Furthermore, defective Stat6(null) Caco-2 exhibited impaired phosphorylation of Stat6 after IL-4 stimulation by flow cytometry, in keeping with the notion of an over-performed negative regulation. The findings that IL-4/Stat6 phenotypes show differential expression of multiple negative regulators suggest a model that a collective force of powerful negative regulators, directly and indirectly, acts on Stat6 activation, which may result in differential Stat6 phenotypes.
authors.affiliation: Department of Medical Oncology, Zhongnan Hospital and Cancer Research Center, Wuhan University, Wuhan, Hubei, People's Republic of China.
authors.forename: Xiao Hong
authors.initials: XH
authors.lastname: Liu
authors.forename: Shuang Bing
authors.initials: SB
authors.lastname: Xu
authors.forename: Jia
authors.initials: J
authors.lastname: Yuan
authors.forename: Ben Hui
authors.initials: BH
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Qin
authors.initials: Q
authors.lastname: Yuan
authors.forename: Pin Dong
authors.initials: PD
authors.lastname: Li
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.forename: Wen Jie
authors.initials: WJ
authors.lastname: Zhang
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D018938:Caco-2 Cells; D019175:DNA Methylation / Q000187:drug effects / Q000502:physiology; D000077209:Decitabine; D019073:HT29 Cells; D006801:Humans; D015847:Interleukin-4 / Q000378:metabolism / Q000494:pharmacology; D009369:Neoplasms / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000819:agonists / Q000378:metabolism; D050800:STAT6 Transcription Factor / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D001374:Azacitidine; D000077209:Decitabine; D015847:Interleukin-4; D009687:Nuclear Proteins; D012333:RNA, Messenger; D050800:STAT6 Transcription Factor; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C106644:SOCS3 protein, human; C408990:SOCS5 protein, human; C108775:SOCS7 protein, human; C494101:STAT6 protein, human