Pioneer factors in hormone-dependent cancers.

Pioneer factors are a special class of transcription factor that can associate with compacted chromatin to facilitate the binding of additional transcription factors. The function of pioneer factors was originally described during development; more recently, they have been implicated in hormone-dependent cancers, such as oestrogen receptor-positive breast cancer and androgen receptor-positive prostate cancer. We discuss the importance of pioneer factors in these specific cancers, the discovery of new putative pioneer factors and the interplay between these proteins in mediating nuclear receptor function in cancer.