Insulin-like growth factor binding protein-3 inhibits the growth of non-small cell lung cancer.
Insulin-like growth factors (IGFs) have mitogenic and antiapoptotic properties and have been implicated in the development of lung cancer. The effects of IGFs are modulated by insulin-like growth factor binding proteins (IGFBPs). This study explored the effects of IGFBP-3 on non-small cell lung cancer (NSCLC) cells after infection with an adenovirus constitutively expressing IGFBP-3 under the control of the cytomegalovirus promoter (Ad5CMV-BP3). We found that IGFs, especially IGF-I, stimulated the growth of NSCLC cells, and Ad5CMV-BP3 suppressed this IGF-I-induced NSCLC cell growth. We also found that the clonogenicity of H1299 cells in soft agar was markedly reduced by Ad5CMV-BP3. Furthermore, direct injection of Ad5CMV-BP3 into H1299 NSCLC xenografts s.c. established in athymic nude mice induced massive destruction of the tumors. Ad5CMV-BP3 did not induce detectable cytotoxicity on normal human bronchial epithelial cells, suggesting therapeutic efficacy of this virus. Ad5CMV-BP3 infection was accompanied by apoptotic cell death in vitro as detected by flow cytometry, DNA fragmentation analysis, and Western blot analysis on the expression of Bcl-2 and on the cleavage of poly(ADP-ribose) polymerase, a substrate of caspase 3. Immunofluorescence confocal microscopy was also used to show the apoptotic effect of Ad5CMV-BP3 in H1299 tumors established in nude mice. These findings indicated that IGFBP-3 was a potent inducer of apoptosis in NSCLC cells in vitro and in vivo. To delineate the underlying mechanism, we examined the effect of IGFBP-3 on Akt/protein kinase B and glycogen synthase kinase-3beta, downstream mediators of the phosphatidylinositol 3-kinase pathway, and on mitogen-activated protein kinase (MAPK), all three of which are activated by IGF-mediated signaling pathways and have important roles in cell survival. IGFBP-3 overexpression inhibited the phosphorylation of Akt and glycogen synthase kinase-3beta and the activity of MAPK. Furthermore, IGF-I rescued the NSCLC cells from serum depletion-induced apoptosis, and this rescue was blocked in Ad5CMV-BP-3-infected H1299 NSCLC cells. Transient transfection with activated Akt or constitutively active MAPK kinase-1, an upstream activator of MAPK, partially blocked IGFBP-3-induced apoptosis of NSCLC cells. These findings suggested that the growth-regulatory effect of IGFBP-3 on NSCLC cells was attributable in part to the inhibition of the IGF-induced survival pathway. These data demonstrate the importance of IGFBP-3 in the regulation of NSCLC cell proliferation, clonogenicity, and tumor growth, suggesting that IGFBP-3 is a target for the treatment of lung cancer and that Ad5CMV-BP3 is a potential therapeutic agent.
Lee
Ho-Young
HY
Department of Thoracic/Head and Neck Medical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston 77030, USA. hlee@mdanderson.org
Chun
Kyung-Hee
KH
Liu
Bingrong
B
Wiehle
Sandra A
SA
Cristiano
Richard J
RJ
Hong
Waun Ki
WK
Cohen
Pinchas
P
Kurie
Jonathan M
JM
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002455:Cell Division / Q000502:physiology; D005260:Female; D018014:Gene Transfer Techniques; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D048369:MAP Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D008819:Mice, Nude; D020929:Mitogen-Activated Protein Kinase Kinases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt
D018972:Insulin-Like Growth Factor Binding Protein 3; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C494918:AKT1 protein, human; C482125:MAP2K1 protein, human; C482127:Map2k1 protein, mouse