cis-polyunsaturated fatty acids stimulate beta(1) integrin-mediated adhesion of human breast carcinoma cells to type IV collagen by activating protein kinases C-epsilon and -mu

We have investigated the effects of various fatty acids (FAs) on integrin-m ediated MDA-MB-435 breast carcinoma cell adhesion to type IV collagen (coll agen IV) in vitro. Arachidonic acid (AA) and linoleic acid both induced a d ose-dependent increase in cell adhesion to collagen IV with no significant increase in nonspecific adhesion to polylysine and BSA. Oleic acid (a monou nsaturated FA), AA methyl ester, and linoelaidic acid (a trans-isomer of li noleic acid) failed to stimulate adhesion to collagen IV, suggesting that t hese effects required cis-polyunsaturation and a free carboxylic moiety and that they were not due to membrane perturbations. Calphostin C, a protein kinase C (PKC) inhibitor, blocked cis-polyunsaturated FA (cis-PUFA)-induced cell adhesion in a dose-dependent manner, suggesting a role for a calcium- dependent PKC in this signal transduction pathway. Immunoblotting revealed that cis-PUFAs induced the translocation of PKC epsilon and PKC mu, two of the novel PKC isozymes, from the cytosol to the membrane. In contrast, a co nventional PKC isozyme, PKC alpha, as well as the atypical isozymes, PKC ze ta and PKC iota, did not translocate after cis-PUFA treatment. Function-blo cking antibodies specific for alpha (1), alpha (2), and beta (1) integrin s ubunits inhibited cell adhesion to collagen IV, whereas antibodies to alpha (3) and alpha (5) did not. No increase in the expression of these integrin s on the cell surface was detected after the incubation of cells with cis-P UFAs, suggesting that there is an increase in the activity, but not in the amount, of these beta (1) integrins. Altogether, these data suggest that ci s-PUFAs enhance human breast cancer cell adhesion to collagen IV by selecti vely activating specific PKC isozymes, which leads to the activation of bet a (1) integrins.