H-2Kb and H-2Db gene transfections in B16 melanoma differently affect non-immunological properties relevant to the metastatic process. Involvement of integrin molecules

Modification of non-immunological cell adhesion properties plays a major role in the decrease in metastatic ability observed after transfection of the H-2K^b gene in H-2-negative B16-derived melanoma clone cells. To investigate the role played by different class-I major histocompatibility complex (MHC) genes on non-immunological properties relevant for metastasis, transfection with the H-2D^b gene alone or in conjunction with the H-2K^b gene was performed. H-2D^b gene transfection did not modify either metastatic potential or non-immunological cell adhesion properties. Double K^bD^b transfectants showed a decreased metastatic ability when compared to control clones and to D^b transfectants; a decrease in homotypic adhesive ability was also observed, even though not in all clones studied: therefore expression of the D^b gene is also relevant. The mechanisms of homotypic cell adhesion were studied and found to be dependent upon temperature and divalent cations. Adhesion was partially inhibited by an antiserum directed against the β₁ integrin subunit, whereas anti-α(IIb)β₃ was ineffective. Cell pre-treatment with anti β₁ serum reduced metastatic ability. A decreased expression of α₄ and α₆, integrin subunits was observed in K^b clones, whereas no difference in the levels of some homophilic cell adhesion molecules, such as N-CAM and α(IIb)β₃, was found. Adhesion required the activity of tyrosine kinases, as suggested by the decreased adhesive properties and impaired metastatic ability of cells pre-treated with the tyrosine-kinaseinhibitor genistein. These results are compatible with involvement of integrin molecules of the β₁ family in the adhesive ability of these cells. Our data show that: (a) immunological and non-immunological effects of MHC transfection are correlated and depend on the class-I gene used, suggesting that MHC gene therapy can be highly successful only if appropriate MHC genes are transfected; (b) non-immunological cell-adhesion properties modified after MHC transfection could be related to an impairment of integrin-mediated adhesive interactions.