Cell proliferation was significantly decreased in Terc null, TRF2 null, and K14Cre;TRF2f/f;Terc-/- cancers compared to control SCC as determined by PCNA immunohistochemistry (9%, 5%, and 20% vs. 45%; P < 0.001; Figure 4H-4J; Supplementary Figure 1I-K). This evidence concerns the gene PCNA and cancer.