MKI67 and pancreatic ductal adenocarcinoma: Furthermore, high levels of CD5 indicated elevated Ki-67 and activated tumor cell proliferation.[68] Another study on pancreatic ductal adenocarcinoma indicated that Bruton's tyrosine kinase promoted the proliferation of cancer cells by activating CD1dhiCD5+ regulatory B cells, which accumulated in the stroma of pancreatic lesions of mice.[69]