Somatostatin inhibits both in-vitro and in-vivo carcinoembryonic antigen secretion by human colon cancer.

This study investigated the effect of SMS 201.995 on CEA secretion of human colon cancer cell lines in vitro and as xenografts in nude mice. Using the two cell lines which secreted significant amounts of CEA in the media, there was a 40% and 54% decrease in CEA level at 2e-10M and 2e-9M concentrations of SMS 201.995, respectively, after five days of incubation for LIM 2412 cell line (P < 0.05, both). There was a 13% decrease in CEA at 2e-9M concentration of SMS with the LoVo cell line (P > 0.05). In vivo, there was a direct correlation between the mean volume of the LIM 2412 xenografts and serum CEA level (r = 0.92). When the growth of xenografts was inhibited by SMS, there was a corresponding drop in serum CEA. On the other hand, when tumor sizes remained unchanged, whether after a short duration of SMS treatment or with the oral route, serum CEA was unaffected. Thus, CEA concentration reflected cell number in vitro and tumor size in vivo as a response to treatment with SMS 201.995. The CEA level may therefore be a useful marker during somatostatin treatment to monitor tumor response.