Somatostatin analogue rc‐160 inhibits the growth of transplanted colon cancer in rats

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Abstract
The effect of somatostatin analogue RC‐160 on the growth of DHD/K12 rat colon cancer has been investigatedin vivoas well asin vitro.Twenty syngeneic BDIX rats with s.c. implanted tumors were divided randomly into 2 groups. The rats from each group received a daily s.c. injection of either RC‐160 (100 μg/kg/day) or injection vehicle as control for 37 days starting from the day of tumor inoculation. Tumor volumes were measured every 3‐4 days. At the end of the treatment, the mean tumor volume was 504.5 ± 97.0 mm3in the control group and 177.8 ± 60.5 mm3in the RC‐160 treated group (p< 0.01). The tumor volume doubling time was calculated to be 11 days in the control group and 13.5 days in the RC‐160 group, respectively. The tumor growth delay time was 18 days. Using bromodeoxyuridine labellingin vivo, the mean labelling index in the tumors was decreased by 35% (pp< 0.05) and 68.7% (p< 0.05), respectively. The data indicate that somatostatin analogue RC‐160 inhibits the growth of DHD/K12 colon cancerin vivo.In 2 studiesin vitro, DHD/K12 cells were cultured for 72 hr with RC‐160 and natural somatostatin‐14 (S‐S‐14) at concentrations ranging from 62.5 ng/ml to 2,000 ng/ml. Tumor‐cell growth was measured spectrophotometrically by the crystal violet staining assay. No direct effect on tumor cell growthin vitrowas observed with either RC‐160 or S‐S‐14, possibly because of the loss of somatostatin receptors in previous passages of the DHD/K12 cell line.
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