PSMB4 and melanoma: Notably, PSMB4 (proteasome subunit beta type-4), a protein of the ubiquitin-proteasome degradation pathway, has been identified as the first proteasomal subunit with oncogenic properties and associated to poor prognosis in several tumors including melanoma, breast, and ovarian cancers (Liu et al., 2016; Zhang et al., 2017; Zheng et al., 2015; Lee et al., 2014).