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Growth characteristics of human Wilms' tumor in nude mice.

Ten Wilms' tumors (WT) were heterotransplated into athymic (nude) mice. Eight of the tumors (80%) grew and were serially passaged as many as 20 times. The histology of the primary heterotransplants resembled that of the surgically excised tumors (seven classical and one anaplastic). Histological examination of serial passages of the classical WT demonstrated the tendency of the stromal and tubular components to disappear. The anaplastic tumor, however, maintained histological features identical to the primary tumor through all passages examined. One WT cell line that exhibited a prominent skeletal muscle component failed to grow beyond the third passage. Spontaneous glomerular differentiation was noted in several heterotransplants. The site of transplantation (subcutaneous, peritoneal, or renal capsule) had no effect on the differentiation of the tumors, and attempts to produce intravenous metastases were unsuccessful. Unilateral nephrectomy of WT-bearing mice gave a transient increase in pulse labeling of the tumors with bromodeoxyuridine, a thymidine analogue, compared with sham-operated controls or mice bearing Ewings' sarcoma heterotransplants. The increased labeling of tumor nuclei reached a maximum at 48 h. Similar increased labeling was observed in the remaining kidney following unilateral nephrectomy. These data show that although WT is a malignant neoplasm, its cells retain the capacity to respond to physiological signals resulting from nephrectomy and that differentiation cannot be modulated by the site of heterotransplantation or serial passage in athymic mice.