MERTK and breast cancer: For example, PROS1 secreted by melanoma, breast cancer, and prostate cancer cells binds to MERTK and TYRO3 receptors on macrophages, inhibiting M1 polarization and supporting tumor growth, thereby promoting tumor progression.[39] Myeloid‐derived PROS1 also alleviates peripheral inflammation and suppresses lung cancer invasion and metastasis.[40] Multiple immunofluorescence assays, Western blot analyses, and dot blot assays confirmed the expression of PROS1 and MERTK in CAFs and PTC tumor cells.