The ron receptor tyrosine kinase: a key regulator of inflammation and cancer progression.

Numerous studies have documented abnormal expression and activation of the Ron receptor tyrosine kinase in a variety of human malignancies. Here we review the literature regarding the molecular mechanisms governing Ron regulation, the biological functions of Ron, the effect of Ron on cancer development, and potential therapeutic implications. In epithelial cells, activation of Ron by its ligand, macrophage stimulating protein, mediates a number of biological events including cell growth, motility, and epithelial to mesenchymal transition. Overexpression and/or activation of Ron has been implicated in the progression and metastasis of diverse epithelial cancers, where it plays a causal role in tumor development by promoting growth, survival, and motility of tumor cells. As a crucial regulator of inflammation, Ron inhibits classic macrophage activation and promotes alternative activation of macrophages, resulting in the resolution of inflammation and tissue repair. In addition, Ron alleviates antitumor immunity by promoting the alternative activation of tumor-associated macrophages, and Ron expression in the tumor microenvironment promotes the outgrowth of metastatic colonies. Hence, Ron is a promising therapeutic target for the treatment of epithelial cancers.