SMS 201.995 inhibits in vitro and in vivo growth of human colon cancer.

The effect of a long-acting somatostatin analogue SMS 201.995 (SMS; Sandoz) on basal and gastrin-stimulated growth of 4 human colon cancer lines was studied in vitro and in vivo. Proliferation assay was done with overnight [75Se]selenomethionine uptake after 5 days of incubation. Gastrin concentrations used were 5e-10 M and 1e-7 M. SMS concentrations were from 2e-12 M to 2e-7 M. Cell lines LIM 1215, LIM 2405, and LIM 2412 were inhibited dose-dependently in both basal and gastrin-stimulated groups. LIM 1863 was slightly stimulated. Based on in vivo growth characteristics, LIM 2412 and LIM 2405 were selected for xenograft study. The dose of 50 micrograms/kg/day was arrived at after a preliminary experiment showed it to be safe and effective. The LIM 2412 xenografts in the SMS-treated animals were 473.3 +/- 99.9 (SD) versus 838.1 +/- 111.3 mm3 in control (P less than 0.05) after 20 days. The LIM 2405 tumors were also significantly inhibited (81.2 +/- 30.0 versus 245.7 +/- 48.3 mm3, P less than 0.01). The effect of SMS appeared to be reversible. Oral SMS at 200 micrograms/kg/day was not absorbed. This study suggests that SMS may have direct antitumor effects in human colon cancer.