For example, the distribution of the biomarker JARID1B (a histone demethylase) in populations of melanoma cells is indicative of an intra-clonal heterogeneity that is important for tumour progression [7], biomarkers CD24 and CD133 can distinguish rare cells that persist anti-cancer drug treatments [10] and multiplexed markers of signalling response can reveal patterns of population heterogeneity that predict drug sensitivity [48]. Here, KDM5B is linked to melanoma.