Accumulating studies have indicated that Gas6 is critical for the progression of prostate cancer and renal cell carcinoma in the urinary system.12, 14, 16, 89, 90, 91, 92, 93 The Gas6–Axl interaction promotes mitogenic activity in undifferentiated metastatic human prostatic cancer cell lines by inducing the phosphorylation of Akt and MAPK.14 Bone is the preferred metastatic site of advanced prostate cancer. Here, AXL is linked to hereditary clear cell renal cell carcinoma.