E2F1 and ovarian cancer: For example, KLF5 increased the resistance of ovarian cancer cells to drug treatment,7 and DEC1 increased the expression of survivin via Sp1 sites in kidney and lung adenocarcinomas.8 A recent study reported that HH/GLI via GLI1 and GLI2 transcription factors activated the E2F1 promoter in melanoma cells, and E2F1 contributed to the increase of melanoma cell growth,9 constituting a positive feedback loop.