Progesterone Receptor Levels in Estrogen-induced Renal Carcinomas after Serial Passage beneath the Renal Capsule of Syrian Hamsters¹ Free

Elevated concentrations of progesterone receptor, a sensitive indicator of estrogen responsiveness, have been measured in this study during early serial transplan tation of estrogen-induced renal adenocarcinoma tissue in hamsters. A new approach of tumor transplantation beneath the renal capsule has been used. Fragments of primary tumor tissue transplanted subpannicularly in estrogen-treated hamsters increased less than 10% in mass during a 2-month period; however, transplantation of primary tumor tissue beneath the renal capsule resulted in a 20- to 30-fold increase in tumor mass after 2 months. There was no statistically significant difference in tumor concentration of progesterone receptor after the first or second serial passage relative to the concentration found in primary tumor tissue. Although the concentration of progesterone receptor was not significantly decreased after the second serial passage, there was a slower growth rate of tumors during this period. In addition to the reduced growth rate of the tumors, a lower concentration of progesterone receptor was found in untransformed kidney areas of hosts bearing second-serial-passage tumors relative to those with first-passage or primary tumors. The serum concentration of diethylstilbestrol in tumor-bearing hosts was 2 to 4 × 10^-8 m and apparently was not a factor in the change in growth rate of the tumors. The results are discussed in terms of a possible alteration in invasiveness or surface properties of estrogen-induced renal adenocarcinoma cells during early transplantation.