MST1 and breast cancer: In particular, the expression of the receptor tyrosine kinase RON on macrophages inhibits the anti-tumor immune response enhancing the PDL-1 expression on TAMs as well as the Macrophage stimulating protein (MSP)-Macrophage Stimulating-1 Receptor (RON) signaling up-regulates the binding of CD80 and CTLA-4 to inhibit T cell activation, reducing the effectiveness of immune checkpoint inhibitors in the BC treatment (73).