Lack of efficacy of dasatinib may be due to multiple factors; including unselective properties as a multi-kinase inhibitor, lack of predictive biomarker data, variability of Src biology and role in CRC tumorigenesis, and efflux of dasatinib from CRC cells via activation of p-glycoprotein (p-gp), a member of the ABC transporter family (Ekblad 2010). The gene discussed is ABCB1; the disease is colorectal carcinoma.