The MM SP cells show high tumourigenic potential and self-renewal capability and are further characterized by up-regulation of polycomb-related genes, such as EZH2 and EPC1. As bortezomib can reduce levels of p-histone H3 and EZH2, it effectively increased apoptosis and induced G2/M arrest in MM SP [66]. Here, EPC1 is linked to Miyoshi myopathy.