Expression of IGF system genes during T-antigen driven pituitary tumorigenesis.

Expression of IGF-I, IGF-II, the Type-I IGF receptor and six IGF binding proteins were examined in three different T-ag-driven mouse tumors. Unlike the widespread expression of IGF-II in pancreatic beta-cell tumors, IGF-II was not widely expressed in the two different pituitary tumors examined indicating that a mechanism independent of focal IGF-II expression can also drive T-antigen tumorigenesis. In addition, multiple IGF binding proteins were expressed in all three tumor types. This expression, however, was generally heterogeneous with no specific changes to indicate a required role for any IGF binding protein in T-antigen tumorigenesis.