To assess whether our IS-PRM assay could quantify NRF2 pathway activation, we engineered HPV(+) HNSCC cell lines SCC90, SCC152, and SCC154 to stably express NRF2E79Q, a common cancer-associated activating NRF2 mutation (Fig. 3A) (60). Here, NFE2L2 is linked to head and neck squamous cell carcinoma.