beta 1-integrins regulate the formation and adhesion of ovarian carcinoma multicellular spheroids

Ovarian carcinoma multicellular spheroids are an in vitro model of micromet astasis whose adhesive abilities have not been elucidated. In this study, w e identified adhesion molecules that mediate the formation of ovarian carci noma spheroids and their subsequent adhesion to extracellular matrix protei ns. The NIH; OVCAR5, but not the SKOV3, ovarian carcinoma cell fine formed spheroids similar to multicellular aggregates isolated from patient ascitic fluid. NIH:OVCAR5 spheroid formation was augmented by a beta1-integrin-sti mulating monoclonal antibody or exogenous fibronectin, but was inhibited by blocking monoclonal antibodies against the alpha5- or beta1-integrin subun its. By immunohistochemical staining, alpha2-, alpha3-, alpha5-, alpha6-, a nd beta1-integrin subunits, CD44, and fibronectin were detected in NIH:OVCA R5 spheroids. NIH:OVCAR5 spheroids adhered to fibronectin, laminin, and typ e IV collagen, and this adhesion was partially inhibited by blocking antibo dies against the alpha5-, alpha6-, and alpha2-integrin subunits, respective ly. A blocking monoclonal antibody against the beta1-integrin subunit compl etely inhibited adhesion of the spheroids to all three proteins. These resu lts suggest that interactions between the alpha5 beta1-integrin and fibrone ctin mediate the formation of ovarian carcinoma spheroids and that their ad hesion to extracellular matrix proteins at sites of secondary tumor growth may be mediated by a complex interaction between multiple integrins; and th eir ligands.