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Somatostatin analog RC‐160 inhibits the growth of human osteosarcomas in nude mice

We investigated the effects of the potent somatostatin analog RC‐160 on the growth of human osteosarcoma cell lines SK‐ES‐1 and MNNG/HOS, transplanted into nude mice or cultured in vitro. Growth of SK‐ES‐I and MNNG/HOS tumors in nude mice was significantly inhibited after 4 weeks of treatment with daily s.c. injections of 100 μg RC‐160, as measured by a reduction in tumor volume and weight. Histologically, the number of mitotic cells was decreased in the groups treated with RC‐160. In mice bearing either tumor model, administration of RC‐160 significantly decreased serum growth hormone and insulin‐like growth factor I (IGF‐I) levels. Specific high‐affinity receptors for somatostatin and epidermal growth factor were found on membranes of MNNG/HOS tumors but not on SK‐ES‐I tumors. Receptor analyses also demonstrated high‐affinity binding sites for IGF‐I on membranes of both tumors. In cell cultures, the proliferation rate of MNNG/HOS cells, but not of SK‐ES‐I, was significantly suppressed by RC‐160. Our findings demonstrate that RC‐160 can significantly inhibit the growth of SK‐ES‐I and MNNG/HOS osteosarcomas in mice. © 1996 Wiley‐Liss, Inc.