ZNRF1 and head and neck squamous cell carcinoma: Furthermore, although there were differences in age at initial diagnosis among the low-tobacco, medium-tobacco, and high-tobacco exposed HNSCC, the additional analysis indicated that the differential expression of hsa-miR-499a, AEBP2, and ZNRF1 in HNSCC with low, medium, and high tobacco exposure was due to the different lifetime tobacco exposure value, rather than the different age at initial diagnosis.