Inhibitory effect of a long-acting somatostatin analogue on EGF-stimulatedcell proliferation in Capan-2 cells

Numerous studies have reported diverse effects of gut-derived regulatory pe ptides on growth of the normal pancreas, pancreatic neoplasms induced exper imentally in animals, and pancreatic cancer cell lines, but the results of these investigations are rather controversial. The stimulatory effect of ep idermal growth factor (EGF) on cell proliferation of pancreatic cell lines is well established. Whether this action can be modulated by somatostatin i s not clear. Furthermore, it is not certain whether another regulatory pept ide, cholecystokinin (CCK), affects the proliferation of these cells. In th e present study we investigated the presence of CCK-A and CCK-B, as well as somatostatin-2 (SSTR2) receptors by RT-PCR, and studied the actions of EGF , CCK and octreotide on DNA synthesis in the human pancreatic adenocarcinom a cell line Capan-2. Octreotide, a long-acting somatostatin analogue was us ed as somatostatin agonist. Cells were cultured in RPMI-1640 medium. They w ere incubated in serum free medium containing 0.2% BSA in the absence (cont rol) or the presence of the peptides. [H-3]-thymidine incorporation into DN A was measured after 48 h of incubation. By means of RT-PCR analysis we wer e able to demonstrate SSTR2 expression, but not CCK-A or CCK-B receptor mRN A in Capan-2 cells. DNA synthesis evaluated by [H-3]-thymidine incorporatio n was found to be increased by 45.2 +/- 5.6% in response to EGF (10(-8) M) and decreased by 11.7 +/- 2.6% to octreotide (10(-8) M) compared to control s (P < 0.01). The increase in [H-3]-thymidine incorporation was significant ly lower when EGF treatment was combined with octreotide administration (10 .1 +/- 2.5% over control). In the concentration range of 10(-11)-10(-8) M, CCK did not alter significantly the incorporation of [H-3]-thymidine into D NA in Capan-2 cells. In conclusion, these data support a role for EGF as a growth factor for the human pancreatic cancer cell Capan-2. Somatostatin ma y play an important role in regulating cell proliferation in Capan-2 cells both under basal, and growth factor-stimulated conditions. Our results sugg est, however, that CCK receptors are not expressed, and CCK does not affect cell proliferation in this transformed pancreatic cell line. (C) 2000 Else vier Science Ltd. Published by Editions scientifiques et medicales Elsevier SAS.