CBX5 and cancer: Three known HP1 isoforms, HP1α (CBX5), HP1β (CBX1), and HP1γ (CBX3), are critical for regulating gene expression networks that are crucial for normal embryonic development1 and cancer associated processes, including differentiation,2, 3 cell proliferation,4, 5 cell cycle control,4, 6, 7, 8, 9 apoptosis,8, 10 and DNA damage response.11, 12, 13, 14, 15, 16, 17, 18 In fact, a conservation in sequence, structure, and function among these proteins in organisms ranging from Drosophila melanogaster to human reflects the biological importance and biomedical implications of their alterations.