KLK4 and neoplasm: Comparison of expression profiles of ET (≤40 years) and LT (≥55 years) yielded few genes that are unique between the two groups, 7 genes B4GALNT1, S100P, KLK4, HIST3H2A, DRD4, PCSK1N, and BAPX1 were significantly overexpressed in early-onset tumours compared to late-onset tumours.