Genetic Polymorphisms of XPC, XPD, XPG Genes and their Association with Radiotherapy Induced Toxicity among Head and Neck Cancer Patients: A Hospital Based Study from Maharashtra

Background: The present study was planned to investigate possible association of single nucleotide polymorphisms (SNPs) of nucleotide excision repair (NER) genes such as XPC, XPD, XPG with acute radiation induced toxicities such as skin reactions and oral mucositis in normal tissue from head and neck cancer (HNC) patients receiving radiotherapy. Methods: Two hundred and fifty HNC patients receiving radiotherapy were enrolled in this study and the acute toxicity reactions and radiation response were recorded. Association of SNPs rs2228001 of XPC, rs238406, rs13181 of XPD and rs17655 of XPG gene with normal tissue reactions in the form of dermatitis and mucositis were studied by PCR-RFLP and direct DNA sequencing.

Results: The results of univariate analysis of SNPs of XPC, XPD and XPG showed that XPC polymorphism at codon 939 of exon 15 (A>C) was not associated with dermatitis (OR=0.30, 95% CI: 0.06-1.39; p=0.125), or oral mucositis (OR=1.14, 95% CI: 0.41-3.20; p=0.793). The XPD codon 156 of exon 6 (C>A) and codon 751 of exon-23 A>C) polymorphism showed no association with radiosensitivity in HNC patients (OR=1.50, 95% CI: 0.60-3.71; p=0.080) for dermatitis, (OR=1.54, 95% CI: 0.66-3.61; p=0.312) for oral mucositis. The 1104 Asp variant genotype or allele of XPG (OR=1.35 95% CI: 0.50-3.64; p=0.541) showed no association with degree of radiotherapy associated dermatitis or mucositis (OR=0.80, 95% CI: 0.32-2.03; p=0.648) in HNC patients. The variant C allele of 2920 A/C genotype of XPC gene at codon 939 of exon 15, found protective with developing skin reactions with grade >1 (OR=0.60, 95% CI: 0.36-0.97; p=0.039) in HNC patients treated with radiotherapy.

Conclusion: The results obtained in this study concluded that the SNPs rs2228001of XPC, rs238406, rs13181 SNPs of XPD and rs17655 SNP of XPG are not associated with normal tissue toxicity in HNC patients treated with radiotherapy. Radiotherapy with high radiation dose was significantly associated with oral mucositis in response to radiotherapy.