Alpha6beta4 integrin crosslinking induces EGFR clustering and promotes EGF-mediated Rho activation in breast cancer.
BACKGROUND
The alpha6beta4 integrin is overexpressed in the basal subtype of breast cancer and plays an important role in tumor cell motility and invasion. EGFR is also overexpressed in the basal subtype of breast cancer, and crosstalk between alpha6beta4 integrin and EGFR appears to be important in tumor progression.


METHODS
We evaluated the effects of alpha6beta4 crosslinking on the distribution and function of EGFR in breast carcinoma cell line MDA-MB-231. Receptor distribution was evaluated by fluorescence microscopy and multispectral imaging flow cytometry, and ligand-mediated EGFR signaling was evaluated using Western blots and a Rho pull-down assay.


RESULTS
Antibody-mediated crosslinking of alpha6beta4 integrin was sufficient to induce cell-surface clustering of not only alpha6beta4 but also EGFR in nonadherent cells. The induced clustering of EGFR was observed minimally after 5 min of integrin crosslinking but was more prominent after 15 min. EGFR clustering had minimal effect on the phosphorylation of Akt or Erk1,2 in response to EGF in suspended cells or in response to HB-EGF in adherent cells. However, EGFR clustering induced by crosslinking alpha6beta4 had a marked effect on Rho activation in response to EGF.


CONCLUSIONS
Crosslinking alpha6beta4 integrin in breast carcinoma cells induces EGFR clustering and preferentially promotes Rho activation in response to EGF. We hypothesize that this integrin-EGFR crosstalk may facilitate tumor cell cytoskeletal rearrangements important for tumor progression.
Gilcrease
Michael Z
MZ
Department of Pathology, The University of Texas M,D, Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, USA. mgilcrease@mdanderson.org
Zhou
Xiao
X
Lu
Xiaolin
X
Woodward
Wendy A
WA
Hall
Brian E
BE
Morrissey
Phillip J
PJ
D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D003432:Cross-Linking Reagents; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D047468:Immunoprecipitation; D039161:Integrin alpha6beta4 / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
D003432:Cross-Linking Reagents; D039161:Integrin alpha6beta4; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors; D020741:rho GTP-Binding Proteins