MST1R and breast cancer: Indeed, experimental models, in which MSP or RON is overexpressed or the RON receptor is inhibited or genetically deleted, show that the MSP–RON axis drives mammary tumor progression and metastasis (Andrade et al., 2017; Benight et al., 2015; Cunha et al., 2014; Ekiz et al., 2018; Eyob et al., 2013; Faham et al., 2018; Liu et al., 2011; Welm et al., 2007; Zinser et al., 2006).