title: Modulation of the c-Met/hepatocyte growth factor pathway in small cell lung cancer.
abstract: The c-Met receptor tyrosine kinase and its ligand HGF (hepatocyte growth factor) have been shown to be involved in angiogenesis, cellular motility, growth, invasion, and differentiation. The role of c-Met/HGF axis in small cell lung cancer (SCLC) has not been reported previously. We have determined the expression of p170(c-Met) precursor and p140(c-Met) beta-chain in seven SCLC cell lines by immunoblotting. We used the SCLC cell line H69, which expressed an abundant amount of c-Met to study the function and downstream effects of c-Met activation. Stimulation of H69 cells with HGF (40 ng/ml, 6-h stimulation) significantly altered cell motility of the SCLC cells with increased formation of filopodia and membrane ruffling, characterized as membrane blebbing, as well as increased migration of the cellular clusters were seen. We have further studied the signal transduction pathways of HGF/c-Met in the H69 cell line. The stimulation of H69 with HGF (40 ng/ml, >24 h, maximal at 1 h) increased the amount of reactive oxygen species formed by 34%. HGF stimulation (40 ng/ml, 7.5-min stimulation) of H69 cells showed increased tyrosine phosphorylated bands identified at M(r) 68,000, 120,000-140,000, and 200,000. Some of these tyrosine-phosphorylated bands were identified as the focal adhesion proteins paxillin, FAK, PYK2, and the c-Met receptor itself. Phospho-specific antibodies show that tyrosines at amino acid (a.a.) 31 of paxillin, and autophosphorylation sites at a.a. 397 of p125FAK, and a.a. 402 of PYK2 are phosphorylated in response to HGF/c-Met signaling. We also demonstrate that the Hsp90 inhibitor geldanamycin, which also affects c-Met, reduced the growth and viability of four of four SCLC cell lines by 25% to 85%, over a 72-h time period. Geldanamycin caused apoptosis of SCLC cells, as well as led to increased levels of Hsp70 but not Hsp90. These results demonstrate that c-Met/HGF pathway is functional in SCLC, and it would be useful to target this pathway toward novel therapy.
authors.affiliation: Department of Adult Oncology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA.
authors.forename: Gautam
authors.initials: G
authors.lastname: Maulik
authors.forename: Takashi
authors.initials: T
authors.lastname: Kijima
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Ma
authors.forename: Sudip K
authors.initials: SK
authors.lastname: Ghosh
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Lin
authors.forename: Geoffrey I
authors.initials: GI
authors.lastname: Shapiro
authors.forename: Erik
authors.initials: E
authors.lastname: Schaefer
authors.forename: Elena
authors.initials: E
authors.lastname: Tibaldi
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Johnson
authors.forename: Ravi
authors.initials: R
authors.lastname: Salgia
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D016227:Benzoquinones; D018288:Carcinoma, Small Cell / Q000378:metabolism*; D002453:Cell Cycle; D002465:Cell Movement; D003599:Cytoskeleton / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D017228:Hepatocyte Growth Factor / Q000096:biosynthesis / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047029:Lactams, Macrocyclic; D008175:Lung Neoplasms / Q000378:metabolism*; D010766:Phosphorylation; D019859:Proto-Oncogene Proteins c-met / Q000096:biosynthesis / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; D016227:Benzoquinones; D004791:Enzyme Inhibitors; D047029:Lactams, Macrocyclic; D011809:Quinones; D017382:Reactive Oxygen Species; D014443:Tyrosine; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; C001277:geldanamycin