AR and prostate cancer: In contrast to the oncogenic potential of p48, the short isoform of Ebp1, p42, has been considered a tumor suppressor because it binds to the tumor suppressor retinoblastoma protein (Rb), thus inhibiting E2F-1–mediated transcription8, 9, and strongly suppresses both androgen receptor (AR)-mediated transcription and tumorigenesis of prostate cancer cells and salivary adenoid carcinoma cell metastasis in mice10, 11.