Immunohistochemical detection of PcG expression in H/RS cells. Neoplastic cells in HL express various members of the PRC1/HPC-HPH PcG complex (BMI-1, MEL-18, RING1, HPH1, HPC2, and CtBP) and the PRC2/EED-EZH complex (EED, EZH2, and YY1). HPC1, a member of the PRC1/HPH-HPC PcG complex, was undetectable in H/RS cells by immunohistochemistry.