Up-regulation of DNA methyltransferase 3B expression in endometrial cancers.
OBJECTIVE
To understand the role of epigenetic regulation in the pathogenesis of endometrial cancer, we have characterized DNA methyltransferase 3B (DNMT3B) gene expression in normal, Grade I and Grade III endometrioid cancers, and examined DNMT3B promoter activities in endometrial cancer cell lines.


METHODS
DNMT3B expression was measured in normal, Grade I, and Grade III endometrioid cancer samples. Real-time PCR and Western blot analysis were performed to compare DNMT3B mRNA and protein levels. DNMT3B levels were also compared among endometrial cell lines including those for Ishikawa, KLE, AN3, RL-95, HEC-1A, and HEC-1B. DNMT3B promoter reporter plasmids were constructed. Promoter activities in well and poorly differentiated cell lines were compared by in vitro reporter gene transfection.


RESULTS
DNMT3B was significantly up-regulated in both Grade I and Grade III cancers as compared to normal controls. Western blot analysis confirmed the increased DNMT3B protein expression in cancer tissues. It was also found that the well-differentiated endometrial cell line, Ishikawa, expressed lower levels of DNMT3B than the poorly differentiated KLE cells, the expression patterns similar to those observed in tumor specimens.


CONCLUSIONS
The results suggest that DNMT3B overexpression may play a significant role in endometrial cancer development. In addition, the transfection experiments indicated that DNMT3B promoters are more active in the poorly differentiated endometrial cancer cell lines, suggesting that the in vitro assay provides a useful model for studying the DNMT3B transactivation mechanism related to tumor transformation.
Jin
Fan
F
Department of Obstetrics and Gynecology, Mayo Clinic and Foundation, 200 First Street SW, Rochester, MN 55905, USA.
Dowdy
Sean C
SC
Xiong
Yuning
Y
Eberhardt
Norman L
NL
Podratz
Karl C
KC
Jiang
Shi-Wen
SW
D018269:Carcinoma, Endometrioid / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000096:biosynthesis* / Q000235:genetics; D016889:Endometrial Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation; D000097584:DNA Methyltransferase 3B
D004248:DNA (Cytosine-5-)-Methyltransferases; D012333:RNA, Messenger; D000097584:DNA Methyltransferase 3B