ABCB1 and neoplasm: To demonstrate proof of principle of this semi-synthetic Salmonella nanoparticle mimic, we employed a colorectal carcinoma model since this type of cancer is known to be one of the tumours with the highest expression of the MDR1 gene (encoding for P-gp)42 and in addition, acquires high expression of P-gp in the course of carcinogenesis.