Polycomb group proteins (PcG), proteins that act to regulate transcription, have been implicated in numerous aspects of malignancies especially the ones with an aggressive phenotype and in stem cell biology. Misregulation of Polycomb protein levels often leads to either a block or unscheduled activation of developmental pathways, thereby enhancing the proliferation capability of a cell. Polycomb proteins form at least two distinct complexes, the Polycomb-repressive complexes 1 and 2 (PRC1 and PRC2). There is increasing evidence that PRC complexes have a role in tumor progression and development by blocking differentiation …