IRX4 and head and neck squamous cell carcinoma: Kostareli et al. performed DNA methylation analysis using a human CpG-island tiling array for five HPV (+) and 10 HPV (−) HNSCC cases and reported that ALDH1A2, OSR2, GATA4, GRIA4, and IRX4 were significantly hypermethylated in the HPV (+) HNSCC samples [85].