CXCR4 and neoplasm: In the H929-VR20 MM model, selected in vitro as a H929 sub-population resistant to 20 nM bortezomib (Supplementary Fig. 3g), CXCR4 expression is up-regulated (Supplementary Fig. 3h) and ADC 513 caused significant tumour growth inhibition (Fig. 3e,f).