E2F1 and cancer: In Saos-2 cells, the ERE73 (1 + 2)-ARF (−13) and ERE73 (3 + 4)-ARF (−13) promoters exhibited higher cancer cell specificity than that of the hTERT, ARF, or E2WT-ARF (−13) promoters, and even exceeded that of the E2F1 promoter (Figure 1E).