To investigate the role of NRF2 signaling in conferring superior prognosis in patients with HPV positive (HPV+ ve) head & neck squamous cell carcinomas (HNSCC) compared to HPV negative (HPV− ve) HNSCC and develop molecular markers for selection of HPV+ ve HNSCC patients for treatment de-escalation trials.
We compared NRF2 activity (NRF2, KEAP1, and NRF2-transcriptional targets), p16, and p53 levels between HPV+ ve HNSCC and HPV− ve HNSCC in prospective and retrospective tumor samples. Cancer cells were transfected with HPV E6/E7 plasmid to elucidate if HPV infection repress NRF2 activity and sensitize to an anticancer drug.
Prospective analysis revealed a marked reduction in expression of NRF2, and its target antioxidant genes (NQO1, HMOX-1, GCLC, and GCLM) in HPV+ ve tumors compared to HPV− ve tumors. A retrospective analysis by IHC revealed significantly lower NQO1 in p16high tumors compared to p16low 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+ ve HNSCC compared to HPV− ve HNSCC and revealed that HPV+ ve HNSCC patients with ‘low NQO1’ expression showed better overall survival compared to HPV+ ve HNSCC patients with ‘high NQO1’ expression. Ectopic expression of HPV E6/E7 plasmid in cancer cells repressed constitutive NRF2 activity, increased KEAP1, reduced total GSH levels, and enhanced cytotoxic effects of cisplatin.
Low constitutive NRF2 activity contributes to better prognosis in patients with HPV+ ve HNSCC compared to HPV− ve HNSCC. Co-expression of p16high, NQO1low, and p53low could serve as a predictive biomarker for the selection of HPV+ ve HNSCC patients for de-escalation trials.