Similar to what has been found in pancreatic cancer, activation of RON is also associated with tumorigenicity and metastasis of various other forms of human malignancy, such as bladder cancer, head and neck squamous cell carcinomas, breast cancer, ovarian cancer, and colorectal cancer (Chen et al., 2000; Zhou et al., 2003; Lin et al., 2004; Cheng et al., 2005; Lee et al., 2005). Here, MST1R is linked to breast cancer.