E2F1 and cancer: Similarly to the results in Saos-2 cells, although the ERE73 (1 + 2)-ARF (−13) and ERE73 (3 + 4)-ARF (−13) promoters showed comparable to or lower activity than E2F1, hTERT, ARF, and E2WT-ARF (−13) constructs (Figure 1E), they exhibited higher cancer cell specificity than E2F1, hTERT, and ARF promoters and the E2WT-ARF (−13) construct across all three cancer cell lines (Figure 1E).