In a previous study in melanoma xenografts, ADC was shown to be inversely related to hypoxic fraction determined by pimonidazole staining.31 The relationship between CAIX and ADC has been explored previously but no relationship was found,32 possibly because CAIX is a downstream marker of hypoxia which can be regulated by other factors whereas pimonidazole represents a more direct measure. The gene discussed is CA9; the disease is melanoma.