Integrin dependent protein tyrosine phosphorylation is a key regulatory event in collagen IV mediated adhesion and proliferation of human lung tumor cell line, Calu-1

Background The clinical phenomenon of lung cancer metastasis to specific target organs is believed to be a direct interaction between tumor cells and extracellular matrix components. During invasion, tumor cells attach to the basement membrane protein, collagen type IV, degrade it, migrate through blood vessels, and adhere to extracellular matrix proteins. Methods Four nonsmall-cell lung cancer cells were tested for adhesion, proliferation, migration and morphologic alterations on collagen type IV matrix by immunoprecipitation, Western blotting, phase contrast and time lapse video microscopy. Results Collagen type IV promoted Calu-1 cell adhesion (< 15 minutes) and motility (< 6 hours) without any significant effect on proliferation. β1-integrin is essential for collagen type IV adhesion and 8 to 10 fold higher expression of β1-integrin on the surface of Calu-1 cells was identified. A protein tyrosine phosphatase inhibitor, peroxyvanadate, caused 50% inhibition in the adhesion process within 5 minutes but exposure to 60 μmol/L genistein for 72 hours, a protein tyrosine kinase inhibitor, drastically inhibits Calu-1 cell proliferation (> 70%). We examined the influence of β1-integrin, peroxyvanadate and genistein on the spreading morphogenesis of Calu-1 cells on Collagen type IV. Use of either 1 μg of anti β1-integrin inhibitory antibody (P5D2), 100 μmol/L peroxyvanadate or 60 μmol/L genistein had dramatic influence on the spreading of Calu-1 cells. Finally, Focal adhesion kinase was identified as a phosphoprotein target. Conclusions We have characterized an in vitro model of matrix-specific binding of a lung cancer cell line, Calu-1 to Coll IV. Calu-1 cells use primarily a β1-integrin mediated intracellular tyrosine phosphorylation phenomenon as the key regulatory mechanism for its binding advantage to Coll IV matrix.