Expression of Somatostatin Receptor Subtypes and Growth Inhibition in Human Exocrine Pancreatic Cancers

The antiproliferative effects of somatostatin and its analogs on human pancreatic cancers were studied: (1) by evaluating the gene expression of somatostatin receptor (sstr) subtypes in human pancreatic cancer cell lines and cancer tissue specimens, (2) by evaluating the antiproliferative effects of somatostatin analogs, and (3) by evaluating the effect of sstr-2 cDNA transduction. Using a reverse transcriptase polymerase chain reaction (RT-PCR), the gene expression of five sstr subtypes (sstr-1 to -5) was examined in eight cell lines, and in ten pancreatic cancer tissues and in the normal surrounding pancreatic tissues. The antiproliferative effects of somatostatin (SS) -14 and its two analogs (SMS 201-995, RC-160) were examined by means of an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (thiazolyl blue)) assay on three cell lines and Panc-1 transfectants with human sstr (hsstr)-2A cDNA. Sstr-2 was expressed in all samples tested. All examined cell lines simultaneously expressed sstr-2 and -5, while most of the examined pancreatic cancer tissues did not express both of these subtypes simultaneously. Somatostatin analogs inhibited epidermal growth factor (EGF)-stimulated pancreatic cancer cell proliferation. The cell proliferation was further and significantly inhibited by 14% in stable transfectants of Panc-1 cells with hsstr-2A. Based on these findings, it is concluded that somatostatin analogs with their antiproliferative effects mediated by sstr-2 could be potentially useful in the treatment of pancreatic cancers.