Chromobox homolog 7 (CBX7) is a chromobox family protein which belongs to polycomb repressive complex 1 (PRC1). In cooperation with other polycomb group (PcG) proteins, CBX7 maintain target genes, which participate in stem cell self-renewal and developmental regulation, in a silenced state [1–4]. CBX7 recognizes H3K27me3, which is catalyzed by enhancer of zeste homolog 2 (EZH2). Then, CBX7 recruits other PRC1 proteins to the target chromatin marked by H3K27me3 and represses gene transcription consequently [5–7]. Besides the PRC-dependent mechanism, recent studies found that CBX7 epigenetically regulates gene expression via the interaction with histone deacetylase 2 (HADC2) [8, 9]. However, the precise role of CBX7 in tumorigenesis and tumor progression is still controversial.