Targeting histone methyltransferase EZH2 as cancer treatment

It is widely accepted that epigenetic alterations are associated with different stages of tumour formation and progression in many cancers. Therefore, epigenetic abnormalities in cancers are emerging as important biomarkers and may have therapeutic potential. The polycomb repressive complex 2 (PRC2) is a key epigenetic regulator that catalyses trimethylation of lysine 27 on histone H3 (H3K27me3) via the histone methyltransferase, EZH2, which confers stemness and regulates differentiation during embryonic development. Given these roles of EZH2 and H3K27me3, plastic and dynamic features of cancer cells, especially cancer stem cells (CSCs), may be closely associated with this epigenetic mechanism. In addition, recent sequencing technology revealed that there are many recurrent mutations in polycomb-related genes, including EZH2, in different types of cancers. Therefore, researchers focused on targeting EZH2 as a novel cancer treatment and identified small compounds that inhibit EZH2 activity. Some of them are now under clinical trial in B-cell lymphoma. However, the underlying mechanisms by which PRC2 precisely regulate epigenetic alterations at certain genomic loci under different cellular conditions remain unclear. In this review, I focus on the recent advancements in EZH2 research, especially its dynamic regulation of epigenetic alterations in tumour cells, including the CSC population, and discuss perspectives and challenges for cancer treatment in the near future.