Homozygous deletions of UGT2B17 modifies effects of smoking on TP53-mutations and relapse of head and neck carcinoma.

BACKGROUND: Smoking induces oncogenic TP53-mutations in head and neck squamous cell carcinomas (HNSCCs). Disruptive mutations of TP53-gene and expression of p16 protein [p16 (+)] in tumor tissue associate with worse and better prognosis, respectively. UDP-glucuronosyltransferase 2 family, polypeptide B17 (UGT2B17) detoxifies smoking-related metabolites. Differences among ethnic groups in UGT2B17 are extremely high. Homozygous deletions of UGT2B17 gene (UGT2B17-deletion) are a common copy number variant (CNV) among Japanese, but not a common CNV among Africans and Europeans. Thus, we examined Japanese patients with HNSCC to explore if UGT2B17-deletion and/or p16 (+) modify effects of smoking on TP53-mutations and affect relapse. METHODS: We conducted a posthoc analysis of a prospective cohort. Polymerase chain reaction, immunohistochemistry, and direct sequencing were used to determine UGT2B17-deletion, p16 (+), and detailed TP53-mutations, respectively. RESULTS: UGT2B17-deletion was observed in 80% of this study population. For this 80%, TP53-mutations were significantly more common among smokers than non-smokers (P = 0.0016), but this difference between smokers and nonsmokers was not significant for the 20% with UGT2B17. In patients with UGT2B17-deletion and p16 (+), simultaneously, TP53-mutations were much more common among smokers than among non-smokers (81% versus 17%; P = 0.0050). Patients with both UGT2B17-deletion and disruptive TP53-mutations had higher relapse rates than other patients (hazard ratio, 2.22; 95% confidence interval, 1.30 to 3.80, P = 0.004) in a stepwise method. CONCLUSIONS: These results suggest that UGT2B17-deletion interacting with p16 (+) may modify effects of smoking on TP53-mutations and may further interact with the disruptive TP53-mutations to raise relapse rates among Japanese patients with HNSCC.