DDR2 and melanoma: The examination of public gene expression datasets of the melanoma differentiation signature confirmed that DDR1 and DDR2 levels were increased in the undifferentiated (U) and neural crest‐like (NC) cell subpopulations from the TSOI signature (Fig 3F; Tsoi et al, 2018) and in the invasive MITFlow cells from the HOEK signature (Appendix Fig S4; Widmer et al, 2012).