ABSTRACT: PurposeStat6 signaling is active in cancer cells and IL-4-induced Stat6 activities or Stat6 activational phenotypes vary among cancer
cells. This study aimed at investigating possible mechanism(s) involved in the formation of varying Stat6 activities/phenotypes.
MethodsStat6 regulatory genes, SOCS-1 and SHP-1, were examined for mRNA expression using RT-PCR, and their promoter DNA methylation
was assayed by methylation-specific PCR in Stat6-phenotyped colon cancer cell lines. DNA methylation was then verified by
sequencing. RT-PCR assay and Western blotting were used to detect the expression of SOCS-1 and SHP-1 after demethylation using
ResultsCompared with Stat6null Caco-2 cells, Stat6high HT-29 cells showed decreased constitutive expression of SOCS-1 and SHP-1, which correlated with DNA hypermethylation in these
genes’ promoters. Interestingly, demethylation in HT-29 cells recovered the constitutive expression of SOCS-1 and SHP-1.
ConclusionsThese findings suggest that DNA methylation controls the constitutive expression of negative Stat6 regulatory genes, which
may affect Stat6 activities.
Journal of Cancer Research and Clinical Oncology 04/2012; 135(12):1791-1798. · 2.56 Impact Factor
ABSTRACT: PurposeTo investigate potential differences in the expression of Stat6 regulatory genes that may influence IL-4/Stat6 activities
(phenotypes) in colon cancer cells.
MethodsRT-PCR method was employed to examine the constitutive mRNA expression of Stat6 negative regulators SOCS-1 and SHP-1, and positive regulator PP2A in colon cancer cell lines HT-29 and Caco-2. Stat6 protein expression and nuclear phosphorylation were detected using Western
ResultsCaco-2 cells carrying inactive Stat6null phenotype showed normal constitutive expression of Stat6 but decreased phosphorylation of nuclear Stat6 compared with HT-29
cells carrying active Stat6high phenotype. Stat6null Caco-2 cells expressed increased levels of mRNA and protein of SOCS-1 and SHP-1, and decreased mRNA expression of PPP2CA and PPP2CB, encoding two critical subunits of PP2A.
ConclusionsConstitutively increased expression of Stat6 negative regulators SOCS-1 and SHP-1, together with decreased expression of positive regulator PP2A, may play a role in forming the inactive Stat6null phenotype in colon cancer cells.
Journal of Cancer Research and Clinical Oncology 12/2008; 135(1):131-140. · 2.56 Impact Factor
ABSTRACT: IL-4-induced Stat6 signaling is active in a variety of cell types and plays a role in cell proliferation/growth and resistance to apoptosis. Using EMSA, we identified differential IL-4/Stat6 activities in colorectal cancer cell lines, HT-29 being active Stat6(high) phenotype and Caco-2 being defective Stat6(null) phenotype, respectively. Active Stat6(high) HT-29 cells exhibited resistance to apoptosis by flowcytometry and aggressive metastasis by Transwell assay compared with defective Stat6(null) Caco-2 cells. Comparing one another using RT-PCR, Stat6(high) HT-29 cells expressed more mRNA of anti-apoptotic and pro-metastatic genes Survivin, MDM2, and TMPRSS4, while Stat6(null) Caco-2 cells expressed more mRNA of pro-apoptotic and anti-metastatic genes BAX, CAV1, and P53, respectively. This is the first study describing correlations of IL-4/Stat6 activities with apoptosis and metastasis in colon cancer. These findings, together with the observation of constitutive Stat6 activation in many human malignancies, suggest that Stat6 activities could be a biomarker for cancer cell's invasive/metastatic capability.
Biochemical and Biophysical Research Communications 06/2008; 369(2):554-60. · 2.48 Impact Factor
ABSTRACT: IL-4-induced Stat6 signaling is active in a variety of cell types, including immune cells and cancer cells, and plays an important role in the regulation of gene expression. Using EMSA gel shift assay and an antibody to Stat6, we phenotyped two breast cancer cell lines, ZR-75-1 being active Stat6(high) phenotype and BT-20 being defective Stat6(null) phenotype, respectively. Breast cancer cells carrying Stat6(null) phenotype exhibited increased spontaneous apoptosis compared with those carrying Stat6(high) phenotype. Expression microarray analyses demonstrated that IL-4 upregulated CCL26, SOCS1, CISH, EGLN3, and SIDT1, and downregulated DUSP1, FOS, and FOSB, respectively, in these breast cancer cells. Among those genes, CCL26 and SOCS1 were known genes regulated by IL-4/Stat6 pathway, but CISH, EGLN3, SIDT1, DUSP1, FOS, and FOSB were novel genes demonstrated to be IL-4 responsive for the first time. IL-4 also upregulated 38 genes unique to Stat6(null) BT-20 cells and 23 genes unique to Stat6(high) ZR-75-1 cells, respectively. Furthermore, Stat6(high) and Stat6(null) cells showed very different profiles of constitutively expressed genes relevant to apoptosis and metastasis among others, which serve as a valuable expression database and warrant for detailed studies of IL-4/Stat6 pathway in breast cancer.
Cytokine 05/2008; 42(1):39-47. · 3.02 Impact Factor
ABSTRACT: Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory diseases with unsolved pathogenesis. Imbalanced Th1/Th2 may play a role in the sustained inflammation of IBD. In China, CD is rare but the incidence of UC has been rising steadily in the last two decades. We investigated the expression of IL-12 (p40) and IFN-gamma, and the activational state of Stat4 signaling in mucosal tissues at the site of disease from 30 active UC patients in comparison with 30 healthy controls. RT-PCR analyses revealed increased mRNA expression of IL-12 (p40) but not IFN-gamma in UC patients. Western blot analyses discovered, for the first time, increased levels of constitutive Stat4 in the cytoplasm and phosphorylated Stat4 in the nucleus of mucosal cells from UC patients. We conclude that a heightened, perhaps persistent, activational state of IL-12/Stat4, and/or IL-23/Stat4 signaling may be present in active Chinese UC patients, and possibly involved in chronic inflammation in UC.
Cellular Immunology 09/2007; 248(2):115-20. · 1.97 Impact Factor