Human papillomavirus-driven repression of NRF2 signalling confers chemo-radio sensitivity and predicts prognosis in head and neck squamous cell carcinoma.

PURPOSE

To investigate the role of NRF2 signalling in conferring superior prognosis in patients with HPV positive (HPV) head & neck squamous cell carcinomas (HNSCC) compared to HPV negative (HPV) HNSCC and develop molecular markers for selection of HPV HNSCC patients for treatment de-escalation trials.

METHODS

NRF2 activity (NRF2, KEAP1, and NRF2-transcriptional targets), p16, and p53 levels between HPV HNSCC and HPV HNSCC in prospective and retrospective tumor samples as well as from TCGA database were compared. Cancer cells were transfected with HPV-E6/E7 plasmid to elucidate if HPV infection represses NRF2 activity and sensitizes to chemo-radiotherapy.

RESULTS

Prospective analysis revealed a marked reduction in expression of NRF2, and its downstream genes in HPV tumors compared to HPV tumors. A retrospective analysis by IHC revealed significantly lower NQO1 in p16 tumors compared to p16 tumors and the NQO1 expression correlated negatively with p16 and positively with p53. Analysis of the TCGA database confirmed low constitutive NRF2 activity in HPV HNSCC compared to HPV HNSCC and revealed that HPV HNSCC patients with 'low NQO1' expression showed better overall survival compared to HPV HNSCC patients with 'high NQO1' expression. Ectopic expression of HPV-E6/E7 plasmid in various cancer cells repressed constitutive NRF2 activity, reduced total GSH, increased ROS levels, and sensitized the cancer cells to cisplatin and ionizing radiation.

CONCLUSION

Low constitutive NRF2 activity contributes to better prognosis of HPV HNSCC patients. Co-expression of p16, NQO1, and p53 could serve as a predictive biomarker for the selection of HPV  HNSCC patients for de-escalation trials.