Stat3 up-regulates expression of nicotinamide N-methyltransferase in human cancer cells.
OBJECTIVE
To discover new molecular targets for cancer therapy and diagnosis, we surveyed signal transducers and activators of transcription 3 (Stat3)-regulated genes, because constitutive activation of Stat3 is associated with a wide variety of human malignancies.


METHODS
We investigated the Stat3-regulated genes in 293 cells with cDNA microarray analysis and found that Nicotinamide N-methyltransferase (NNMT) was induced on stimulation of the cells with leukemia inhibitory factor. We examined the expression of NNMT in several types of cancer cells by real-time quantitative RT-PCR. To examine the role of Stat3, Hep-G2 hepatocellular carcinoma cells were transfected with NNMT promoter-luciferase reporter construct together with conditionally active Stat3 (Stat3ER) or dominant-negative Stat3 expression vector and NNMT promoter activity was determined. The expression of NNMT and activated Stat3 in 88 colon cancer tissues and 17 normal colon tissues was examined with immunohistochemical analysis.


RESULTS
In Hep-G2 cells and SW480 colon cancer cells, NNMT expression increased on stimulation of the cells with interleukin 6. NNMT promoter activity in Hep-G2 cells was dependent on the activation of Stat3. MDA-MB-468 breast cancer cells and HT29 colon cancer cells expressed constitutively a high level of NNMT. Treatment of these cells with Stat3 siRNA or curcumin, which inhibited Stat3 phosphorylation, resulted in reduction of the NNMT level. We found a correlation between the expression of NNMT and activated Stat3 (P<0.001) in the colon cancer tissues.


CONCLUSIONS
NNMT is a novel Stat3-regulated gene. Its expression is enhanced with the activation of Stat3 in colon cancer tissues. NNMT may be a potential candidate for a tumor marker of various kinds of cancers.
Tomida
Mikio
M
Research Institute for Clinical Oncology, Saitama Cancer Center, 818 Komuro, Ina, Saitama 362-0806, Japan. tomida@cancer-c.pref.saitama.jp.
Ohtake
Hideki
H
Yokota
Takashi
T
Kobayashi
Yasuhito
Y
Kurosumi
Masafumi
M
D014408:Biomarkers, Tumor / Q000032:analysis*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000502:physiology; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D009369:Neoplasms / Q000201:enzymology*; D050903:Nicotinamide N-Methyltransferase / Q000096:biosynthesis*; D020411:Oligonucleotide Array Sequence Analysis; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D046888:Tissue Array Analysis; D014162:Transfection; D015854:Up-Regulation
D014408:Biomarkers, Tumor; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050903:Nicotinamide N-Methyltransferase