DNA methylation regulates constitutive expression of Stat6 regulatory genes SOCS-1 and SHP-1 in colon cancer cells.
OBJECTIVE
Stat6 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.


METHODS
Stat6 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 5-aza-2'-deoxycytidine.


RESULTS
Compared with Stat6(null) Caco-2 cells, Stat6(high) 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.


CONCLUSIONS
These findings suggest that DNA methylation controls the constitutive expression of negative Stat6 regulatory genes, which may affect Stat6 activities.
Xu
Shuang Bing
SB
Laboratory of Xinjiang Endemic and Ethnic Diseases, Shihezi University School of Medicine, 832002 Shehezi, Xinjiang, China.
Liu
Xiao Hong
XH
Li
Ben Hui
BH
Zhang
Yan
Y
Yuan
Jia
J
Yuan
Qin
Q
Li
Pin Dong
PD
Yang
Xian Zi
XZ
Li
Feng
F
Zhang
Wen Jie
WJ
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D018938:Caco-2 Cells; D003110:Colonic Neoplasms / Q000235:genetics*; D019175:DNA Methylation / Q000187:drug effects / Q000502:physiology*; D000077209:Decitabine; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D015847:Interleukin-4 / Q000494:pharmacology; D010641:Phenotype; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000235:genetics*; D050800:STAT6 Transcription Factor / Q000502:physiology*; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics*
D000964:Antimetabolites, Antineoplastic; C508598:IL4 protein, human; C108944:SOCS1 protein, human; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015847:Interleukin-4; D000077209:Decitabine; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D001374:Azacitidine