INTEGRIN EXPRESSION AND FUNCTION IN HPV16-IMMORTALIZED HUMAN KERATINOCYTES IN THE PRESENCE OR ABSENCE OF V-HA-RAS - COMPARISON WITH CERVICAL INTRAEPITHELIAL NEOPLASIA

Keratinocytes express several receptors of the integrin family which r egulate both adhesion and differentiation. We have investigated whethe r HPV immortalisation, which changes the growth and differentiation pr operties of keratinocytes, is associated with altered integrin express ion or function. We compared two HPV 16-immortalised lines of human ke ratinocytes, up and vp, with the normal keratinocyte strains, u and v, from which they were derived and with upr, obtained by transfection o f up with viral Harvey ras. Immunofluorescence, immunoprecipitation an d flow cytometry demonstrated that up and vp had lower levels of integ rins than u and v, the reduction in up being greater than in vp. Up an d vp also had reduced levels of mRNA encoding the beta(1) integrin sub unit. Reduced expression of the alpha(5) beta(1) and alpha(2) beta(1) integrins was correlated with reduced adhesion to fibronectin and coll agen in up but not in vp and there were no significant differences bet ween the normal and immortalised cells in adhesion to laminin. Reduced integrin expression was correlated with decreased motility, up showin g a greater reduction in motility than vp. Introduction of activated r as into up had no effect on integrin levels, cell motility or tumorige nicity in nude mice; the only difference between up and upr was that u pr showed increased adhesion to fibronectin. Examination of eight biop sies of cervical intraepithelial neoplasias with evidence of HPV infec tion revealed reduced, or discontinuous integrin expression in the mos t severe lesions. We conclude that both in vivo and in cultured kerati nocytes the impaired differentiation that is associated with the prese nce of HPV is correlated with reduced integrin expression.