On the other hand, P-gp probably also plays a role in regulating cell death, differentiation, and proliferation, as well as in immune response.4 It is found that P-gp is highly expressed on the atypical surface of differentiated tubular structures in CRC and the expression of P-gp is associated with the progression of CRC.5,6 The ABCB1 gene is polymorphic and to date approximately 48 SNPs have been identified.7 SNPs probably change the functional expression of the ABCB1 gene so that predisposing to diseases. This evidence concerns the gene ABCB1 and colorectal carcinoma.