TRANSFERRIN AND TRANSFERRIN RECEPTOR IN HUMAN HYPOPHYSIS AND PITUITARY-ADENOMAS

Transferrin (Tf), a major transport protein for iron in the blood and an essential growth factor in some tissues, acts via specific transfer rin receptor (TfR). We studied the cellular distribution of Tf and TfR gene expression in 50 human nontumorous autopsy pituitaries and 42 su rgically removed pituitary adenomas, Tf and TfR mRNA accumulation was correlated with Ki-67 proliferation marker. In nontumorous pituitaries without iron deposits Tf immunoreactivity was localized in some growt h hormone, prolactin, adrenocorticotropin, thyrotropin, and luteinizin g hormone cells. Most adenohypophysial cells were immunopositive for T fR. In pituitaries with iron deposits, Tf and TfR were localized only in iron-free cells. Tf mRNA and protein were present in 27 and 32 aden omas, respectively; Ki-67 labeling index of tumors positive for Tf mRN A was significantly higher than in those without transcript (0.94% ver sus 0.51%; P < 0.025). A positive linear correlation between tumor gro wth fraction and Tf mRNA signal intensity was evident (r = 0.32; P = 0 .04). TfR mRNA and encoded protein were demonstrated in 26 and 31 aden omas, respectively; Ki-67 immunoreactivities were not correlated with the presence of TfR transcripts and signal intensities. These data sug gest that Tf may act as a growth-promoting factor for pituitary tumors .