A small molecular inhibitor of E2F (HLM006474) was identified using a computer-based virtual screen and the known crystal structure of the DNA bound E2F4/DP2 heterodimer. Treatment of multiple cell lines resulted in the loss of intracellular E2F4 DNA-binding activity. Overnight exposure to HLM006474 resulted in down regulation of total E2F4 protein as well as several known E2F targets. The effects of treatment on different cell lines included a reduction in cell proliferation and an increase in apoptosis. Apoptosis was induced in a manner distinct from cisplatin and doxorubicin. E2F4-null MEFs (mouse embryo fibroblasts) were less sensitive than wildtype counterparts to the apoptosis-inducing activity of the compound revealing its biological specificity. A375 cells were extremely sensitive to the apoptosis-inducing activity of the compound in two-dimensional culture and HLM006474 was a potent inhibitor of melanocytes proliferation and subsequent invasion in a three-dimensional tissue culture model system.
