Treatment of liver metastases of human colon cancers in nude mice with somatostatin analogue RC-160.

Hepatic metastases of colon 320 DM and WidR human colon cancers in nude mice were treated by s.c. injections of somatostatin analogue RC-160 for 4 weeks. Chronic administration of RC-160 significantly inhibited the incidence and growth of liver metastases of these 2 colon-cancer cell lines. After RC-160 treatment, the incidence of liver metastases decreased by 25% for colon 320 DM cells and by 37.5% for WidR cells. The mean number of metastatic tumors in each liver decreased by 47.9% for colon 320 DM and 42.6% for WidR. Survival times of mice with liver tumors of colon 320 DM and WidR cells were prolonged by 20 days and 7 days, respectively. The inhibitory effect of RC-160 on the growth of these 2 colon cancers implanted s.c. was also observed. After administration of RC-160 for 4 weeks, the mean tumor volume in the treated groups was only 39.8% of that of controls for the colon 320 DM line and 58% for the WidR line. Tumor-growth rate and final tumor weight were also significantly decreased, while tumor-volume doubling time and tumor-growth delay time were prolonged. The effect of RC-160 on cellular proliferation in the tumors was studied by in vivo labelling with bromodeoxyuridine and immunoperoxidase staining. The mean labelling index in the treatment group was reduced by 14.9% and 19.5%, respectively, for colon 320 DM and WidR tumors. The cytostatic effect of RC-160 was also evident from the apparent reduction in DNA and protein content in the tumor tissues of these cancer lines. Our findings suggest that somatostatin analogue RC-160 may be useful for the treatment of patients with hepatic metastases of colon cancer.