Alteration of properties of cell contacts during progression of hepatomas

Mechanical, electrical and physicochemical properties of the cell contacts in normal, regenerating liver and nine hepatoma strains were examined. Three patterns of contact alteration were found in tumours. They coincide with definite steps in tumour progression. Only some contact destabilization is found in hepatomas with minimal deviations. Contact stability can be restored to an almost normal degree by addition of macromolecular adhesive factor washed out from the normal liver by Ca²⁺-free solution. This factor does not act on the cell contacts of the hepatomas during the further steps of progression. The decrease in mutual adhesiveness and the non-divergence of the daughter cells play an important role during the next steps of tumour progression. Possible mechanisms of contact alteration and the significance of these alterations for tumour progression are discussed.