NRF2 in HNSCC: Implications for Immune Response and Angiogenesis

Introduction: Hypoxia and oxidative stress are hallmarks of solid tumor microenvironment. The nuclear factor erythroid 2-related factor (NRF2) is the key transcription factor involved in the oxidative stress response to reactive oxygen species and electrophilic stresses as seen under hypoxic conditions. Alterations in the NRF2 pathway are reported in up to 22% of head and neck squamous cell carcinoma (HNSCC) and are associated with treatment resistance, antitumor immune dysregulation, and poor prognosis. This study investigates the relationship between NRF2 expression, angiogenesis and anti-tumor immunity.

Methods: Publicly available RNAseq data from the HNSCC TCGA project (N = 523) was analyzed using standard pipelines. The relationships between NRF2 pathway mutations (NFE2L2, KEAP1, and CUL3), and several key factors were examined through cBioPortal. These factors included hypoxia-induced factor 1-alpha (HIF-1alpha), a key mediator of hypoxia-induced angiogenesis; T-cell lymphocyte markers (CD4 and CD8A); and CD31, a marker for microvessels and leukocyte transmigration.

Results: NRF2 pathway mutations were present in 32% (N=166) of HNSCC examined in the TCGA cohort. NRF2 expression was positively correlated with HIF-1alpha expression (Spearman’s correlation = 0.1, p = 0.0241) and negatively correlated with CD31 (Spearman’s coefficient = -0.13, p = 0.0029), CD4 (Spearman’s coefficient = -0.11, p = 0.00164), and CD8A (Spearman’s coefficient = -0.11, p = 0.0142). No statistically significant difference was present in the expression of HIF-1alpha, CD4, CD8A, and CD31 between the NRF2 pathway mutants and wild-type groups (all p-values > 0.05).

Conclusions: The present study highlights the complex interplay between the NRF2, hypoxia-mediated angiogenesis, and antitumor immunity in HNSCC. Further work is underway to validate these findings in HNSCC cell lines with constitutive NRF2 expression, and in an internal cohort of patient-derived NRF2 mutant HNSCC specimens by employing microvessels density quantification and T-cell lymphocytes count.