AXL and B-cell chronic lymphocytic leukemia: In adult normal cells, such as normal brain tissue, hippocampus, heart and liver, AXL expression is relatively low (27, 28); however, in certain malignant cells such as breast cancer, chronic lymphocytic leukemia, non-small cell lung cancer, melanoma, and prostate cancer cells, AXL is abnormally overexpressed (29–40), promotes tumor progression and reduces overall survival.