ZEB1 and neoplasm: We also observed that, as a consequence of chemotherapy treatment, while proliferating CD44+ cells lose the expression of ZEB1 [23] they gain expression of the differentiation-associated marker the MUC1 protein [24] and acquire morphological characteristics of a more differentiated tumor, suggesting a loss of the EMT and favoring the Mesenchimal to Ephitelial Transition (MET).