The invention generally features compositions and methods that are useful for treating or diagnosing a neoplasia, in particular breast neoplasia. The invention is based in part on the observation that the basic helix loop helix transcription factor HEYL was found to be overexpressed in breast cancer cells. Accordingly, the invention provides therapeutic compositions and methods for altering the levels and expression of HEYL of the invention, thereby treating a neoplasia, as well as compositions and methods for diagnosing a neoplasia.
