Effects of integrins on laminin chemotaxis by hepatocellular carcinoma cells

To quantitatively evaluate the effects of integrins alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 4 beta 1, alpha 5 beta 1, and alpha 6 beta 1 on the chemotaxis of hepatocelluar carcinoma (HCC) cell line SMMC-7721 to laminin (LN). A modified dual-micropipette system was used to dynamically and quantitatively monitor the formation of pseudopod protrusion of HCC cells toward LN in the presence or absence of specific antibodies against integrins alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, and beta 1. Additionally, the expression levels of different integrin subunits on the surface of the cells were determined via flow cytometry analysis. In response to equal concentrations of LN in both micropipettes, HCC cells form symmetrical pseudopod protrusions on both sides. Addition of antibodies against alpha 3, alpha 6, or beta 1 into one micropipette leads to significant reduction of pseudopod formation on that side, while antibodies against alpha 1, alpha 2, alpha 4, and alpha 5 do not affect the symmetrical formation of pseudopods in either micropipette. The percentages of HCC cells positive for expression of integrins alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, and beta 1 were 95.07, 23.17, 95.55, 2.47, 34, 14.29, and 95.78%, respectively. Integrins alpha 3 beta 1 and alpha 6 beta 1 are important cell surface receptors that mediate the chemotaxis of HCC cells toward LN.