Defective interleukin-4/Stat6 activity correlates with increased constitutive expression of negative regulators SOCS-3, SOCS-7, and CISH in colon cancer cells.
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.
Liu
Xiao Hong
XH
Department of Medical Oncology, Zhongnan Hospital and Cancer Research Center, Wuhan University, Wuhan, Hubei, People's Republic of China.
Xu
Shuang Bing
SB
Yuan
Jia
J
Li
Ben Hui
BH
Zhang
Yan
Y
Yuan
Qin
Q
Li
Pin Dong
PD
Li
Feng
F
Zhang
Wen Jie
WJ
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
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