AXL and renal cell carcinoma: Axl overexpression has been detected in a majority of human cancers, including acute myeloid leukemia (Rochlitz et al., 1999; Hong et al., 2008), breast cancer (Berclaz et al., 2001; Zhang et al., 2008; Gjerdrum et al., 2010), gastric (Wu et al., 2002) and lung cancer (Shieh et al., 2005), melanoma (Quong et al., 1994), osteosarcoma (Han et al., 2013), renal cell carcinoma (Gustafsson et al., 2009), etc. Therefore, targeting the Axl to inhibit its function might be a promising strategy for the treatment of various malignant tumors.