At the molecular level, Rab2A regulates endocytic recycling of MT1-MMP, transport of E-cadherin to the Golgi complex and promotes Erk signalling in breast cancer cells (Kajiho et al., 2016), enabling their mesenchymal invasion and increasing the population of breast cancer stem cells (CSCs) (Luo et al., 2015; Kajiho et al., 2016; 2018). The gene discussed is MAPK1; the disease is breast carcinoma.