title: The insulin-like growth factor-I (IGF-I) receptor kinase inhibitor NVP-ADW742, in combination with STI571, delineates a spectrum of dependence of small cell lung cancer on IGF-I and stem cell factor signaling.
abstract: Stem cell factor (SCF)/Kit and insulin-like growth factor-I (IGF-I)/IGF-I receptor (IGF-IR) autocrine loops play a prominent role in the growth of small cell lung cancer (SCLC). Previous data suggested that IGF-I protects cells from apoptosis induced by STI571, an efficient inhibitor of Kit signal transduction, by activating the critical phosphatidylinositol 3-kinase-Akt pathway. To determine if inhibition of IGF-IR signaling would be therapeutically relevant in SCLC, the activity of a novel kinase inhibitor of IGF-IR, NVP-ADW742 (Novartis Pharma AG, Basel, Switzerland), was characterized. Pretreatment of the H526 cell line with NVP-ADW742 inhibited IGF-IR signaling and growth with IC(50) values between 0.1 and 0.4 micro M. SCF-mediated Kit phosphorylation and Akt activation were inhibited with IC(50) values in the 1-5 micro M range. However, NVP-ADW742 affected neither hepatocyte growth factor-mediated Akt activation nor activity of constitutively active Akt. The therapeutic potential of NVP-ADW742 was assessed by determining its effect on growth of several SCLC cell lines in serum. These studies clearly delineated two populations of cell lines as determined by differential sensitivity to NVP-ADW742. One population, which lacks active SCF/Kit autocrine loops, was inhibited with IC(50) values between 0.1 and 0.5 micro M. A second population, which has active SCF/Kit autocrine loops, was inhibited with IC(50) values in the 4-7 micro M range. When these cell lines were treated with a combination of STI571 and NVP-ADW742, no advantage was seen in the former group, whereas, in the latter group, a clearly synergistic response to the combination was seen when growth, apoptosis, or Akt activation was assessed. These data demonstrate that NVP-ADW742 is a potent and selective IGF-IR kinase inhibitor that can efficiently inhibit the growth of cells that are highly dependent on IGF-I signaling. However, for optimal growth inhibition of SCLC cells with an active SCF/Kit autocrine loop, a combination of a Kit inhibitor (STI571) and an IGF-IR inhibitor (NVP-ADW742) appears to be necessary. These observations suggest that, in tumors in which critical signal transduction pathways can be activated by alternative receptors, optimal therapy may require inhibition of multiple receptors.
authors.affiliation: Department of Medicine, Virginia Commonwealth University and McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249, USA.
authors.forename: G Sakuntala
authors.initials: GS
authors.lastname: Warshamana-Greene
authors.forename: Julie
authors.initials: J
authors.lastname: Litz
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Buchdunger
authors.forename: Francesco
authors.initials: F
authors.lastname: Hofmann
authors.forename: Carlos
authors.initials: C
authors.lastname: García-Echeverría
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Krystal
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001549:Benzamides; D018288:Carcinoma, Small Cell / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D004357:Drug Synergism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D000068877:Imatinib Mesylate; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000494:pharmacology* / Q000502:physiology; D008175:Lung Neoplasms / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D044967:Serum; D015398:Signal Transduction / Q000187:drug effects; D019089:Stem Cell Factor / Q000494:pharmacology* / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D006133:Growth Substances; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines; D019089:Stem Cell Factor; D007334:Insulin-Like Growth Factor I; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D017526:Receptor, IGF Type 1; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases