Inhibitory effect of the somatostatin analogue SMS 201-995 and cytokines on the proliferation of human colon adenocarcinoma cell lines

The activity of the synthetic somatostatin analogue SMS 201-995 was investigated in vitro on the growth of SW480 and SW620 human colon adenocarcinoma cell lines. The inhibition of cell proliferation was significant in SW480 cells (-19.6±1.4% at SMS 201-995 10-9 m, P<0.05), but not in SW620 cells (-5.5±0.8% at SMS 201-995 10-8 m) as compared to untreated cultures. Moreover, SMS 201-995 10-8m decreased the mitogenic effect of epidermal growth factor (EGF) on the SW480 cell line (-26.6±3.4% vs. cells exposed to EGF 10 ng ml-1 alone, P<0.05). The effect of combining SMS 201-995 plus the cytokines interleukin-2 (IL-2) or γ-interferon (γ-IFN) on SW480 and SW620 cancer cell growth was also evaluated. The treatment produced a synergistic antiproliferative effect against SW620 cells as compared to untreated cultures, with growth inhibition being -20.2±1.2 and -19.3±1.3%, at SMS 201-995 10-8m plus IL-2 or γ-IFN 100 IU ml-1, respectively, but did not increase the activity of SMS 201-995 against the SW480 cells. In conclusion, the effect of SMS 201-995 on colon cancer cell growth can be enhanced by its combination with cytokines in SW620 but not in SW480 colon adenocarcinoma cells. © 1995 The Italian Pharmacological Society.