In the present study, we compared the protein levels of P-gp and CYP3A4 in duodenum tissues between patients with PaC with/without DM and found that P-gp, but not CYP3A4, was significantly upregulated in the DM group vs the non-DM group, suggesting a possible positive correlation between duodenal expression of P-gp and the presence of DM in patients with PaC. The gene discussed is CYP3A4; the disease is diabetes mellitus.