Double null tumors exhibited extreme aneuploidy (modal chromosome number = 151 vs. 49 for K14Cre;TRF2+/+;Terc+/+ SCC; P < 0.00003) and dramatic shortening of most chromosomes (Figure 6A, 6B) which was significantly greater than that observed in Terc null and TRF2 null cancers (52 and 77; P < 0.004; Supplementary Figure 4A, 4B). Here, TERC is linked to cancer.