Overexpression of the DNA methyltransferase 3B (DNMT3B) gene and its effect on 
carcinogenesis has been demonstrated for various types of cancer. Recently, 
three single nucleotide polymorphisms (SNPs) of the DNMT3B promoter region, 
C46359T (-149C>T), -283T>C, and -579G>T have also been reported to be 
stratification markers that can predict an individual's susceptibility to 
cancers. In this study, we analyzed expression of DNMT3B in nasopharyngeal 
carcinoma (NPC) specimens and did not find elevated levels of DNMT3B in tumors 
using cDNA microarray analysis and RT-PCR. Meanwhile, 259 NPC patients and 250 
controls were genotyped for the above three SNPs using a MALDI-TOF based 
mini-sequencing method. For C46359T (-149C>T), only the T/T genotype was found 
to be present in both patient and control groups (100% frequency). The frequency 
of the genotypes, -283CC, -283CT and -283TT, amongst NPC patients versus 
controls was, respectively, 86.1% versus 84.0%, 13.5% versus 15.6%, and 0.4% 
versus 0.4% (P=0.589). The allele frequency, -597TT, -597GT and -597GG, for 
patients versus controls was, respectively, 87.3% versus 84.8%, 12.0% versus 
15.2%, and 0.8% versus 0 (P=0.501). The distribution of SNPs among cancer 
patients either featuring or not featuring cervical metastasis also did not 
reveal any significant difference. In conclusion, our data indicate that neither 
overexpression of DNMT3B nor the presence of three DNMT3B SNPs are associated 
with NPC, which suggests that DNMT3B might not play a role in hypermethylation 
of many tumor suppressor genes during carcinogenesis of NPC.