Although we have not been able to assess the highly cell type-specific physical interaction between EcR and Rbf/E2F1, because of the small number of SCs in each male, it seems likely that this part of the Rbf/E2F1-dependent regulation of EcR that controls its hormone-independent signalling involves physical interaction between the EcR and at least E2F1, as reported in prostate cancer cells. This evidence concerns the gene E2F1 and Familial prostate cancer.