title: Gab1 but not Grb2 mediates tumor progression in Met overexpressing colorectal cancer cells.
abstract: Hepatocyte growth factor receptor (Met) plays an important role in the progression of multiple cancer types. The overexpression of Met in DLD-1 colon carcinoma cells with kirsten rat sarcoma oncogene homolog (KRAS) oncogene activation resulted in enhanced subcutaneous and orthotopic tumor growth rate and increased metastatic potential. To elucidate the mechanism of this effect, we stably expressed kinase-inactive Met(K1110A), Src homology 2 (SH2)-binding domain-inactive Met(Y1349/1356F), growth factor receptor-bound protein 2 (Grb2) non-binding Met(N1358H) and mutant receptors with ability to selectively recruit signaling proteins Grb2, src homology domain c-terminal adaptor homolog (Shc), phospholipase c-gamma (PLCgamma) and p85 phosphatidyl inositol 3 kinase. As subcutaneous implants, DLD-1 cells that expressed the majority of these receptor constructs failed to recapitulate the tumor growth-enhancing effect of the wild-type Met receptor. The Grb2- and Shc-recruiting Met mutants demonstrated slight but consistent tumor-suppressive activity, whereas the expression of N1358H mutant stimulated tumor growth rate comparable with the wild-type receptor. This suggests that direct Grb2/Shc binding does not contribute to the tumor progression activity of Met receptor. The tumors expressing Grb2- and Shc-recruiting Met receptors demonstrated a marked loss in Grb2-associated adaptor protein 1 (Gab1) protein levels, which was not observed in the cell lines, consistent with a post-translationally regulated process. Moreover, a moderate level of Gab1 overexpression stimulated tumor growth. The findings suggest a delicate balance for intact Y1349/1356 SH2-binding domain to mediate the tumor progression activity of the coactivated Met-rat sarcoma oncogene homolog (RAS) pathways. Selectivity for specific adaptor protein involvement may be the key that determines the tissue- and cell-type specificity of Met-mediated tumorigenicity in human cancers.
authors.affiliation: Ontario Cancer Institute and Princess Margaret Hospital, University Health Network, 610 University Avenue, Toronto, Ontario, Canada.
authors.forename: Isolde
authors.initials: I
authors.lastname: Seiden-Long
authors.forename: Roya
authors.initials: R
authors.lastname: Navab
authors.forename: Warren
authors.initials: W
authors.lastname: Shih
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Jane
authors.initials: J
authors.lastname: Chow
authors.forename: Chang Qi
authors.initials: CQ
authors.lastname: Zhu
authors.forename: Nikolina
authors.initials: N
authors.lastname: Radulovich
authors.forename: Caroline
authors.initials: C
authors.lastname: Saucier
authors.forename: Ming-Sound
authors.initials: MS
authors.lastname: Tsao
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D001483:Base Sequence; D014408:Biomarkers, Tumor / Q000378:metabolism; D002460:Cell Line; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology*; D017931:DNA Primers; D018450:Disease Progression; D051380:GRB2 Adaptor Protein / Q000502:physiology*; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019859:Proto-Oncogene Proteins c-met; D017978:Receptors, Growth Factor / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D014408:Biomarkers, Tumor; D017931:DNA Primers; C098587:GAB1 protein, human; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D011518:Proto-Oncogene Proteins; D017978:Receptors, Growth Factor; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met