We have shown that exposure to arachidonic acid, followed by its metabolism through a lipoxygenase pathway, leads to a rapid increase in human breast cell adhesion to vitronectin and collagen type IV. We have now identified the critical integrin complex involved in this adhesion as alpha2beta1, an integrin known to bind collagen type IV, and have shown that the activity, but not the surface expression, of these integrins is up-regulated. We also showed that the arachidonic acid-mediated adhesion is inhibited by the tyrosine kinase inhibitor, genistein, as well as by calphostin C, an inhibitor of various protein kinase C isozymes. These results suggest that serine/threonine and tyrosine protein kinases play an important role in the induction of integrin-mediated adhesion by fatty acids.We have found that arachidonic acid specifically activates MAP kinase activated protein kinase 2 (MAPKAPK2) through the MAP kinase family protein, p38. Although the extracellular signal-regulated kinases, ERK1 and ERK2, are also activated by arachidonic acid, cell adhesion to collagen type IV was not highly sensitive to a MEK1 inhibitor which blocks activation of the ERKs. In contrast, treatment with a specific p38 inhibitor completely abrogated arachidonic acid-mediated cell adhesion to collagen type IV. Together, these data suggest a novel role for p38 in regulating adhesion of breast cancer cells to collagen type IV.We have also examined cytoskeletal components of MDA-MB-435 cells and have found that arachidonic acid induces both a decrease in stress fibers and an increase in filopodia when cells are plated on collagen type IV. These changes are accompanied by an increase in the number of focal contacts in these breast tumor cells, as measured by staining for vinculin. Furthermore, arachidonic acid-treated cells have an increased ability to spread and are more motile on collagen type IV. We have now observed a number of changes in various cytoskeletal proteins that may help explain the observed changes in cell behavior following arachidonic acid exposure.
