SSTR1 and pancreatic insulinoma: PDX-1 also was overexpressed in mouse insulinoma (β TC-6) cells (Fig. 1c) and in both islet and acinar cells of the pancreata of somatostatin receptor subtypes 1 and 5 knock-out mice (SSTR1/5−/−) (Fig. 1e, f, respectively) as compared to that of wild type mice (Fig. 1d).