Insulin-like growth factor II in human adrenal pheochromocytomas and Wilms tumors: expression at the mRNA and protein level.

Two forms of insulin-like growth factor (IGF) II with molecular masses of 10 and 7.5 kDa, respectively, were found in tumor tissue from human adrenal pheochromocytomas. The tumors contained 5.3-7.1 micrograms of immunoreactive IGF-II per g of tissue, which is about 20 times more than in adrenal medulla. The total bioactive IGF in the pheochromocytomas exceeded that in normal liver or kidney, which contained only the 7.5-kDa IGF-II species, by a factor of approximately equal to 100. By contrast, the amount of IGF-I was just measurable and did not vary significantly between tumor and normal tissue. The high amounts of IGF-II in the pheochromocytomas were not reflected, however, by a corresponding increase of mRNA. The opposite situation was found in Wilms tumors, where IGF-II content was in the same range as in nontumor tissues despite increased expression of IGF-II mRNA.