In order to enforce a negative selection pressure against DH5α E. coli, the transformed human colon adenocarcinoma cell line DLD-1 was transduced with a pLVX-IRES-ZsGreen1 lentiviral vector in which a C-terminal poly-His tagged Colicin M (Cma) coding sequence optimised for human codon usage was cloned upstream of the IRES sequence (pLVX-Cma-ZsG1) [20]. Here, SGCZ is linked to colon adenocarcinoma.