title: Significance of KRAS/PAK1/Crk pathway in non-small cell lung cancer oncogenesis.
abstract: BACKGROUND
  Key effector(s) of mutated KRAS in lung cancer progression and metastasis are unknown. Here we investigated the role of PAK1/Crk axis in transduction of the oncogenic KRAS signal in non-small cell lung cancer (NSCLC).
  
  
  METHODS
  We used NSCLC clinical specimens to examine the correlation among KRAS mutations (codon 12, 13 and 61); PAK1/Crk axis activation [p-PAK1(Thr423), p-Crk(Ser41)]; and adhesion molecules expression by immunohistochemistry. For assessing the role of proto-oncogene c-Crk as a KRAS effector, we inhibited KRAS in NSCLC cells by a combination of farnesyltransferase inhibitor (FTI) and geranylgeranyltransferase inhibitor (GGTI) and measured p-Crk-II(Ser41) by western blotting. Finally, we disrupted the signaling network downstream of KRAS by blocking KRAS/PAK1/Crk axis with PAK1 inhibitors (i.e., IPA-3, FRAX597 or FRAX1036) along with partial inhibition of all other KRAS effectors by prenylation inhibitors (FTI + GGTI) and examined the motility, morphology and proliferation of the NSCLC cells.
  
  
  RESULTS
  Immunohistochemical analysis demonstrated an inverse correlation between PAK1/Crk phosphorylation and E-cadherin/p120-catenin expression. Furthermore, KRAS mutant tumors expressed higher p-PAK1(Thr423) compared to KRAS wild type. KRAS prenylation inhibition by (FTI + GGTI) completely dephosphorylated proto-oncogene c-Crk on Serine 41 while Crk phosphorylation did not change by individual prenylation inhibitors or diluent. Combination of PAK1 inhibition and partial inhibition of all other KRAS effectors by (FTI + GGTI) dramatically altered morphology, motility and proliferation of H157 and A549 cells.
  
  
  CONCLUSIONS
  Our data provide evidence that proto-oncogene c-Crk is operative downstream of KRAS in NSCLC. Previously we demonstrated that Crk receives oncogenic signals from PAK1. These data in conjunction with the work of others that have specified the role of PAK1 in transduction of KRAS signal bring forward the importance of KRAS/PAK1/Crk axis as a prominent pathway in the oncogenesis of KRAS mutant lung cancer.
authors.affiliation: Division of Hematology/Oncology, West Los Angeles VA, Los Angeles, CA, USA. fredmortazavi@ucla.edu.|Department of Medicine, University of California, Los Angeles, CA, USA. fredmortazavi@ucla.edu.|Jonsson Comprehensive Cancer Center, Los Angeles, CA, USA. fredmortazavi@ucla.edu.
authors.forename: Fariborz
authors.initials: F
authors.lastname: Mortazavi
authors.affiliation: Department of Microbiology Immunology & Molecular Genetics, University of California|, Los Angeles, CA, USA. jielu@ucla.edu.
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Pathology, West Los Angeles VA, Los Angeles, CA, USA. Ryan.Phan@va.gov.
authors.forename: Ryan
authors.initials: R
authors.lastname: Phan
authors.affiliation: Department of Pathology, West Los Angeles VA, Los Angeles, CA, USA. Michael.Lewis8@va.gov.
authors.forename: Michael
authors.initials: M
authors.lastname: Lewis
authors.affiliation: Division of Hematology/Oncology, West Los Angeles VA, Los Angeles, CA, USA. Kenny.Trinidad@va.gov.
authors.forename: Kenny
authors.initials: K
authors.lastname: Trinidad
authors.affiliation: Division of Hematology/Oncology, West Los Angeles VA, Los Angeles, CA, USA. Amir.Aljilani@cshs.org.
authors.forename: Amir
authors.initials: A
authors.lastname: Aljilani
authors.affiliation: Department of Pathology, West Los Angeles VA, Los Angeles, CA, USA. Gholamhossein.Pezeshkpour@va.gov.
authors.forename: Gholamhossein
authors.initials: G
authors.lastname: Pezeshkpour
authors.affiliation: Jonsson Comprehensive Cancer Center, Los Angeles, CA, USA. fuyut@microbio.ucla.edu.|Department of Microbiology Immunology & Molecular Genetics, University of California|, Los Angeles, CA, USA. fuyut@microbio.ucla.edu.
authors.forename: Fuyuhiko
authors.initials: F
authors.lastname: Tamanoi
mesh_terms: D015820:Cadherins; D063646:Carcinogenesis; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism*; D051177:Catenins; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D054876:Prenylation; D000090063:Proto-Oncogene Mas; D050737:Proto-Oncogene Proteins c-crk / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*; D000095002:Delta Catenin
chemical_list: C485285:CRK protein, human; D015820:Cadherins; D051177:Catenins; C117307:KRAS protein, human; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D050737:Proto-Oncogene Proteins c-crk; C515903:PAK1 protein, human; D054462:p21-Activated Kinases; D016283:Proto-Oncogene Proteins p21(ras); D000095002:Delta Catenin; C000722347:CTNND1 protein, human