CD4 and pancreatic ductal adenocarcinoma: This suggests that Treg cells play a role in the progression and metastasis of various malignant tumors.[13] In a study of pancreatic ductal adenocarcinoma by Hiraoka et al, the prevalence of Treg cells in CD4+ T cells was significantly increased in the ductal adenocarcinomas compared with that in the stroma of nonneoplastic inflammation.