Hormone responsiveness of a transplantable rat chondrosarcoma. II. Evidence for in vivo hormone dependence.

We have previously demonstrated that the Swarm rat chondrosarcoma responds to GH-dependent serum factors in vitro by increasing amino acid transport and macromolecular synthesis. The question of in vivo hormone dependence was evaluated by studying the growth of the tumor in hypophysectomized rats. Tumor-bearing hypophysectomized rats were treated with saline, T4, cortisone, bovine GH (bGH), or combinations of these hormones. Tumor growth was assessed in terms of tumor weight. Histological appearance was studied to ascertain the viability of the tumors and the relative contributions of cellularity vs. cartilage matrix to the weight of the chondrosarcoma. The weight of tumors grown in saline-treated hypophysectomized rats was less than 10% of the weight attained by tumors grown in normal rats for a comparable period of time. There was a greater relative cellularity in tumors grown in normal and hormone-treated hypophysectomized rats compared to that in tumors grown in saline-treated hypophysectomized rats. Tumors from saline-treated hypophysectomized rats had an atrophic appearance. Treatment of the hypophysectomized rats with bGH or cortisone increased the rate of tumor growth 5- to 6-fold and restored the histological appearance toward that of tumors grown in normal rats. A greater rate of tumor growth was effected by treatment with a combination of bGH and cortisone. T4 by itself did not stimulate chondrosarcoma growth in the hypophysectomized rat. Withdrawal of bGH and cortisone treatment from hypophysectomized rats after tumors were hormone stimulated caused a loss of the apparent exponential rate of growth observed in hypophysectomized rats treated through the full 38-day observation period. These data indicate that bGH and cortisone act in concert to stimulate the growth of the Swarm rat chondrosarcoma in vivo and that the tumor is hormone dependent.