Increased extracellular pressure enhances cancer cell integrin-binding affinity through phosphorylation of {beta}1-integrin at threonine 788/789

David H. Craig,1 Christopher P. Gayer,1,3 Keri L. Schaubert,4 Yanzhang Wei,5,6 Jinhua Li,5 

Yasmina Laouar,4 and Marc D. Basson1,2,3 

Departments of 1Surgery, 2Anesthesiology, and 3Anatomy and Cell Biology, John D. Dingell VA Medical Center and Wayne 

State University, Detroit, Michigan; 4Department of Immunology and Microbiology, University of Michigan, Ann Arbor, 

Michigan; 5Oncology Research Institute, Greenville Hospital System, Greenville, South Carolina; and 6Department 

of Biological Sciences, Clemson University, Clemson, South Carolina 

Submitted 8 July 2008; accepted in final form 11 November 2008

Summary:

The adhesion of integrin-mediated tumor cells to extracellular matrix is important in the development of metastatic cancer. Integrin-binding affinity is regulated by the activation state of the appropriate integrin receptor. However, some tumor defy this law by maintaining adhesion to the ECM while reducing overall integrin expression. For this reason, this study analyzed how external mechanical stimuli affects the affinity and adhesion ability of cancerous cells.

This study used SW620 colon cancer cells, and pressure was applied to the cells using an airtight Lucite box with an inlet and outlet valve for gas application. After being pressurized, a cell-adhesion assay was performed under ambient conditions, and the adhesion was measured by relative fluorescence of each well (pressurized, not-pressurized) using a fluorescence microplate reader. Next, a Western blot analysis was done (using a beta-1-integrin antibody) to determine the activation state of the cell surface integrins.

Results revealed that increased extracellular pressure enhances integrin-binding affinity and cell-adhesion. The reason for this is that pressure influences beta-1-integrin conformational activation.

Significance:

Knowing how pressure affects a cancer cell's ability to adhere to ECM has many clinical implications for preventing cancer metastasis. For example, if we know that a given pressure (from shear forces in blood, for example) is beyond that of a tumor cell's adhesion limit, we that the cancer can metastasize at any moment, and must be removed. Furthermore, once a cancer has spread, we can determine the likelihood of a tumor cell re-binding to the ECM in another location and growing a secondary tumor based on the pressure conditions. This knowledge can help stem the growth of metastatic cancer.

Kiran Sekhon