Laminin mediates tethering and spreading of colon cancer cells in physiological sheer flow

Under the physiological shear condition, cultured colon cancer cells bound to laminin (LM), but not to fibronectin or vitronectin. Most of the tethered cells did not roll, but arrested immediately and spread within 10-30 min on LM under the continuous presence of shear flow. The tethering of Colo201 was partially inhibited by monoclonal antibodies (mAbs) to alpha 6 integrin and a combination of mAbs to beta 1 and beta 4 integrins, but not by mAb to 67KD laminin receptor. Some Colo201 cells still tethered at 4 degrees C. This suggests that alpha 6 beta 1 and alpha 6 beta 4 integrins participate in Colo201 tethering on LM, although other non-integrin molecules play roles. In contrast, the spread of Colo201 was effectively inhibited by the mAbs to integrin alpha 2, alpha 6 and beta 1 chains. The effect of anti-alpha 2 plus anti-alpha 6 mAbs was almost equal to anti-beta 1, suggesting that Colo201 cells mainly use alpha 2 beta 1 and alpha 6 beta 1 integrins for spreading on LM. When the cells were perfused on subconfluent endothelial cells (HUVEC) cultured on LM, they did not tether on HUVEC but did on coated LM exposed at intercellular gap area. Immunohistochemistry revealed that LM abundantly existed in the cytosol of human portal and hepatic vein endothelial cells. These data suggest that LM can mediate from tethering to spreading of colon cancer cells under the blood flow and plays an essential role in haematogeneous metastasis.