ZEB1 and neoplasm: While different studies used ZEB2 and ZEB1 as additional markers to define the proliferative (MITFhigh/AXLlow) or invasive (MITFlow/AXLhigh) phenotypes, respectively [55,56], our data further demonstrated that EMT-TFs are major regulators of melanoma cell plasticity that fuel intra-tumor heterogeneity.