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.

Distinct Involvement of the Gab1 and Grb2 Adaptor Proteins in Signal Transduction by the Related Receptor Tyrosine Kinases RON and MET

“…Gab1 and MET gene knock-out mice have very similar developmental defects (40). Furthermore, Gab1 mediates a wide range of cellular effects downstream of MET, including epithelial morphogenesis, cell transformation, and tumor progression (21,31,41,42). Early studies using the TPR-MET oncoprotein suggested that the cellular effects of MET are dependent on the Grb2 docking site tyrosine Tyr-1356, rather than the Gab1-binding tyrosine Tyr-1349 (19,20,23,32,34,43).…”

Fibroblast Growth Factor Receptor 2 IIIc as a Therapeutic Target for Colorectal Cancer Cells

“…The mice to undergo implantation were subjected to brief general inhalation anesthesia with isoflurane; then, the 2-mm square tumor fragments were sutured on the surface on cecum wall using 7.0 Prolene suture (ref. 27; n ¼ 3 per cell line). The animals were monitored for 9 weeks.…”

“…Subcutaneous tumors from mice were cut into small-sized fragments and sutured on the cecum wall surface of other mice (27). FGFR2IIIc-9 cells formed larger tumors in the cecum, with tumor volume that was significantly higher than that of tumors formed by mock-1 cells (Fig.…”

Targeting Focal Adhesion Kinase with Dominant-Negative FRNK or Hsp90 Inhibitor 17-DMAG Suppresses Tumor Growth and Metastasis of SiHa Cervical Xenografts

“…Migration and invasion were assessed as described (19). Human fibronectin (5 Ag/mL; BD Biosciences) or epidermal growth factor (50 ng/mL; Sigma-Aldrich) served as chemoattractants.…”