title: Ras-GTPase activating protein inhibition specifically induces apoptosis of tumour cells.
abstract: Oncogenes and tumour suppressor genes control the balance between apoptotic death and anti-apoptotic survival signals determining whether a cell proliferates or dies. Through which effectors might oncoproteins generate sensitivity to apoptosis remains to be determined. Ras GTPase activating protein (Ras-GAP) is a key element in the Ras signalling pathway, being both a negative regulator and possibly an effector of Ras. Ras-GAP acts as a regulator of transcription, and possibly connects Ras to stress-activated protein kinases. A role for Ras-GAP in cell survival has been suspected from the study of knock-out mouse embryos. In search for selective killing of tumour cells, we asked whether Ras-GAP inhibition by other means would lead to apoptosis in established cell lines. We injected a monoclonal antibody directed against the SH3 domain of Ras-GAP (mAb200) that has been shown to block Ras-GAP downstream signalling into various human normal and tumour cell lines. We show that inhibition of Ras-GAP induces apoptosis specifically in tumour, but not in normal cells, therefore pointing at a specific role for Ras-GAP in tumour cell survival. MAb200-induced apoptosis is largely prevented by coinjection of activated RhoA or Cdc42 proteins, by injection of a constitutively activated mutant of phosphoinositide 3-OH kinase (PI3-K), but not by injection of v-Raf. These results show that targeting of Ras-GAP could represent a novel anticancer approach.
authors.affiliation: ExonHit Therapeutics, 65 Bld Massena, 75013 Paris, France.
authors.forename: V
authors.initials: V
authors.lastname: Leblanc
authors.forename: I
authors.initials: I
authors.lastname: Delumeau
authors.forename: B
authors.initials: B
authors.lastname: Tocqué
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D001943:Breast Neoplasms / Q000473:pathology / Q000503:physiopathology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002470:Cell Survival; D003110:Colonic Neoplasms / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005347:Fibroblasts; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D020690:GTPase-Activating Proteins; D006367:HeLa Cells; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000503:physiopathology*; D008845:Microinjections; D018715:Microscopy, Video; D027384:Oncogene Proteins v-raf; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000276:immunology; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology; D020764:cdc42 GTP-Binding Protein; D020703:ras GTPase-Activating Proteins; D020742:rhoA GTP-Binding Protein; D018909:src Homology Domains / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D018797:Cell Cycle Proteins; D020690:GTPase-Activating Proteins; D011506:Proteins; D015682:Retroviridae Proteins, Oncogenic; D020703:ras GTPase-Activating Proteins; D019869:Phosphatidylinositol 3-Kinases; D027384:Oncogene Proteins v-raf; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein