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.