Journal of Clinical Endocrinology & Metabolism, Vol 81, 2653-2662, Copyright © 1996 by Endocrine Society

ARTICLES

Insulin-like growth factors stimulate the release of insulin-like growth factor-binding protein-3 (IGFBP-3) and degradation of IGFBP-4 in nonsmall cell lung cancer cell lines

K Noll, BR Wegmann, K Havemann and G Jaques
Department of Internal Medicine, Philipps University Marburg, Germany.

Insulin-like growth factors (IGFs) are potent mitogens for lung cancer cells. Their proliferative activity is influenced by their binding proteins (IGFBPs). We report here on the regulatory effects of IGF-I and IGF-II on the production and release of IGFBPs by nonsmall cell lung cancer cell lines (NSCLC). The nine NSCLC cell lines used in this study showed messenger ribonucleic acid (mRNA) expression of all six IGFBPs known, as determined by PCR, and protein secretion of IGFBP-1, - 2, -3, -4, and -5, as analyzed by Western immunoblots. The addition of IGFs to a serum-free medium showed divergent effects on IGFBP-3 and IGFBP-4 levels in a conditioned medium (CM). IGF-I and IGF-II, but not insulin, led to a much higher concentration of IGFBP-3 in the CM of all tested NSCLC cell lines, whereas the level of immunologically detected membrane-associated IGFBP-3 was decreased. Furthermore, Northern analysis of mRNA isolated from A549 revealed that IGFBP-3 specific mRNA was not changed by IGF-I or IGF-II, suggesting that the IGF-induced effects on IGFBP-3 depend on the release of cell-associated IGFBP-3. In contrast, IGFBP-4 levels were diminished by increasing concentrations of IGFs in the CM of the NSCLCs A549, NCI-H157, and U1752, with no response to insulin or the IGF-I analog, whereas IGFBP-4-specific mRNA was not changed by IGF-I or IGF-II, as determined by Northern analysis. The same effects were seen in a cell-free system after incubation of the CM with IGFs. The decrease in IGFBP-4 concentrations was prevented by coincubation of the CM with the IGFs and either ethylenediamine tetraacetate or 1,10-phenanthrolene, but not with other protease inhibitors. We suggest that IGFs may either activate an IGFBP-4- specific metalloprotease present in NSCLC CM or that the binding of IGFs to IGFBP-4 may enhance the susceptibility of IGFBP-4 to proteolytic degradation. Based on these data, we present evidence that IGFs may regulate their own availability both by releasing IGFBP-3 from cell membrances and through proteolytic degradation of IGFBP-4.

This article has been cited by other articles:

				Y. S. Chang, K. Gong, S. Sun, D. Liu, A. K. El-Naggar, F. R. Khuri, W. K. Hong, and H.-Y. Lee Clinical Significance of Insulin-like Growth Factor-binding Protein-3 Expression in Stage I Non-Small Cell Lung Cancer Clin. Cancer Res., December 1, 2002; 8(12): 3796 - 3802. [Abstract] [Full Text] [PDF]

				Y. Kodama, R. C. Baxter, and J. L. Martin Insulin-Like Growth Factor-I Inhibits Cell Growth in the A549 Non-Small Lung Cancer Cell Line Am. J. Respir. Cell Mol. Biol., September 1, 2002; 27(3): 336 - 344. [Abstract] [Full Text] [PDF]

				X. Wu, H. Yu, C. I. Amos, W. K. Hong, and M. R. Spitz Joint Effect of Insulin-Like Growth Factors and Mutagen Sensitivity in Lung Cancer Risk J Natl Cancer Inst, May 3, 2000; 92(9): 737 - 743. [Abstract] [Full Text] [PDF]

				S. Mazerbourg, J. Zapf, R. S. Bar, D. R. Brigstock, C. Lalou, M. Binoux, and P. Monget Insulin-Like Growth Factor Binding Protein-4 Proteolytic Degradation in Ovine Preovulatory Follicles: Studies of Underlying Mechanisms Endocrinology, September 1, 1999; 140(9): 4175 - 4184. [Abstract] [Full Text]

				H. Yu, M. R. Spitz, J. Mistry, J. Gu, W. K. Hong, and X. Wu Plasma Levels of Insulin-Like Growth Factor-I and Lung Cancer Risk: a Case-Control Analysis J Natl Cancer Inst, January 20, 1999; 91(2): 151 - 156. [Abstract] [Full Text] [PDF]

				T. L. Bushman and J. F. Kuemmerle IGFBP-3 and IGFBP-5 production by human intestinal muscle: reciprocal regulation by endogenous TGF-beta 1 Am J Physiol Gastrointest Liver Physiol, December 1, 1998; 275(6): G1282 - G1290. [Abstract] [Full Text] [PDF]

				J. T. Allen, C. A. Bloor, R. A. Knight, and M. A. Spiteri Expression of Insulin-like Growth Factor Binding Proteins in Bronchoalveolar Lavage Fluid of Patients with Pulmonary Sarcoidosis Am. J. Respir. Cell Mol. Biol., August 1, 1998; 19(2): 250 - 258. [Abstract] [Full Text]

				M. M. Rechler Editorial: Growth Inhibition by Insulin-Like Growth Factor (IGF) Binding Protein-3--What's IGF Got To Do with It? Endocrinology, July 1, 1997; 138(7): 2645 - 2647. [Full Text] [PDF]