Lysophosphatidic acid induces a migratory phenotype through a crosstalk between RhoA-Rock and Src-FAK signalling in colon cancer cells

Lysophosphatidic acid (LPA) acts as a potent stimulator of tumorigenesis. Cell-cell adhesion disassembly, actin cytoskeletal alterations, and increased migratory potential are initial steps of colorectal cancer progression. However, the role that LPA plays in these events in this cancer type is still unknown. We explored this question by using Caco-2 cells, as colon cancer model, and treatment with LPA or pretreatment with different cell signalling inhibitors. Changes in the location of adherent junction proteins were examined by immunofluorescence and immunoblotting. The actin cytoskeleton organisation and focal adhesion were analysed by confocal microscopy. Rho-GTPase activation was analysed by the pull-down assay. FAK and Src activation by immunoblotting, and cell migration by the wound healing technique. We show that LPA induced adherent junction disassembly, perijunctional actin cytoskeletal reorganisation, and increased cell migration. These events were dependent on Src, Rho and Rock because their chemical inhibitors PP2, toxin A and Y27632, respectively, abrogated the effects of LPA. Moreover, we showed that Src acts upstream of RhoA in this signalling cascade and that LPA induces focal adhesion formation and FAK redistribution and activation in confluent monolayers. Focal adhesion formation was also observed in the front of migrating cells in response to LPA, and Rock inhibitor abolished this effect. In conclusion, our findings show that LPA modulates adherent junction disassembly, actin cytoskeletal disorganisation, and focal adhesion formation, conferring a migratory phenotype in colon tumour cells. We suggest a functional regulatory cascade that integrates RhoA-Rock and Src-FAK signalling to control these events during colorectal cancer progression. (C) 2011 Elsevier B.V. All rights reserved.