NORMAL HUMAN MESOTHELIAL CELLS AND MESOTHELIOMA CELL-LINES EXPRESS INSULIN-LIKE GROWTH FACTOR-I AND ASSOCIATED MOLECULES

Insulin-like growth factor (IGF) I has important growth regulatory fun ctions in normal growth and development. IGF-I is also a mitogen for a number of cancer cell lines; however, its autocrine effect has not be en well established. In this study, the expression of IGF-I, its recep tor, and its major serum-binding protein were examined in 5 normal hum an mesothelial (NHM) cell samples and 11 pleural mesothelioma cell lin es. All NHM cells and mesothelioma cell lines expressed IGF-I, IGF-bin ding protein 3 (IGFBP-3), and IGF-I receptor mRNA by either Northern b lot or reverse transcription polymerase chain reaction analysis. IGF-I (0.136 +/- 0.024 ng/ml, mean +/- SEM) and IGFBP-3 (18.5 +/- 3.2 ng/ml ) proteins were readily detected in the conditioned medium of mesothel ioma cell lines but were not greater than corresponding measurements i n that of NHM cells (IGF-I, 0.120 +/- 0.080 ng/ml; IGFBP-3, 15.9 +/- 1 .3 ng/ml). Exogenous recombinant IGF-I stimulated cell proliferation o f NHM cells, demonstrating the presence of a functional IGF-I receptor . Our results suggest that IGF-I may function as an autocrine growth s timulus in normal proliferating mesothelial cells. which mav contribut e to their malignant transformation.