ABCB5 and melanoma: Several findings documented that tumorigenic heterogeneity within the melanoma VGP is the definition of a subpopulation of human melanoma cells that express the multidrug resistance transporter known as adenosine triphosphate–binding cassette subfamily B, ABCB5 (Frank et al., 2005; Klein et al., 2007; Schatton et al., 2008; Laga et al., 2010).