Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) is transcription coregulator and modulates functions of several hormonal receptors and transcription factors. PELP1 plays essential roles in hormonal signaling, cell cycle progression, and ribosomal biogenesis. PELP1 expression is upregulated in several cancers; its deregulation contributes to hormonal therapy resistance and metastasis; therefore, PELP1 represents a novel therapeutic target for many cancers.