For example, although cancer cell specificity of the ERE73s-ARF (−13) constructs was higher than that of commonly used E2F1 and hTERT promoters, the promoter activity of the artificial promoters in cancer cell lines was lower than that of the E2F1 promoter, likely due to low basal activity of ARF (−13) core promoter. This evidence concerns the gene E2F1 and cancer.