Sato et al. assessed the correlation between the expression level of CEA and the antitumor efficacy of anti-CEA-CAR-T through a functional assay involving various pancreatic ductal adenocarcinoma (PDAC) cell lines and proved the correlation between tumor heterogeneity and the intensity of CEA immunostaining. The gene discussed is CEACAM5; the disease is pancreatic ductal adenocarcinoma.