PCNA and cancer: Additionally, previous studies reported (12, 33–38) that ESCC-associated proteins, including PCNA, SLC7A5, CTTN, RB1, EGFR, TP63, and PRMT1, exhibited increased expression in S-III; among these proteins, SLC7A5 and EGFR were FDA-approved drug targets for cancer treatment (Figure 3F).