Table 5. Genetic risk for NPC: carcinogen metabolism.
| Enzyme(s) | Function | Study | Results |
| CYP2E1 | Carcinogen metabolism | 50 NPC cases and 50 controls & 364 NPC cases and 320 controls in Taiwan were analyzed by PCR-RFLP | Increased NPC risk for homozygous variant genotype[142],[143] |
| Carcinogen metabolism | 2,499 subjects from 546 NPC families were genotyped547 NPC cases and 755 controls in Guangzhou | Association of SNP and increased NPC risk for individuals <46 years and with smoking history[144] | |
| CYP2A6 | Carcinogen metabolism | 74 NPC cases and 137 controls in Thailand were analyzed by PCR-RFLP | 5-fold increase in NPC risk with mutant allele[145] |
| CYP2A13 | Carcinogen metabolism | The CYP2A13 gen from 45 NPC patients in Guangzhou were PCR-amplified and sequenced | Identified novel SNPs, but no correlation between SNPs and NPC risk[146] |
| CYPE2B6, CYPE2E1, PRKDC, PCNA, CHEK2, NQ01 | DNA repair, nitrosamine metabolism | 31 NPC cases and 10 controls in Taiwan compared in a microarray targeting biological pathways for carcinogen metabolism, DNA repair, and chromosomal regions of interest | Differential expression in genes for DNA repair, nitrosamine metabolism, chromosomes 4p15-4q12 and 14q32[147] |
| CYP2E1, GSTP1, NQO1, MPO | Carcinogen metabolism | 358 NPC cases and 629 controls in Guangzhou and Guangxi studied with Taqman genotyping and Tag SNPs | No significant difference between cases and controls[148] |
| GSTM1 (glutathione S-transferase M1) | Carcinogen metabolism | 83 NPC cases and 114 controls in the US | No association with NPC risk, but absence of GSTM1 is associated with moderately increased NPC risk[149] |
| GSTM1, GSTT1 (glutathione S-trans-ferase theta-1) | Carcinogen metabolism | 350 NPC cases and 622 controls in Beijing studied with multiplex PCR | No significant association with NPC risk, but males with double null genotype had increased NPC risk[150] |
| GSTM1, GSTT1 | Carcinogen metabolism | Meta-analysis of 85 published papers and selected 8 case-control studies of NPC | GSTM1 deletion is a risk factor for NPC; no association of GSTT1 with NPC risk[151] |
Abbreviation as in Table 4.