Extinction, retention and induction of serum protein secretion in hepatoma-fibroblast hybrids

The production of four serum proteins has been analysed in several hepatoma-fibroblast hybrids. Extinction of albumin and alpha-foetoprotein production occurs systematically in intra and interspecific (rat X mouse) hybrids derived from mouse hepatoma cells (BW). Similar hybrids derived from two related clones of rat hepatoma cells either do not produce albumin (Fa32-derived hybrids), as the BW-derived hybrids, or retain the capacity to produce it, but at a reduced rate (Fu5-derived hybrids); some differences in the control of albumin production thus seem to exist between clonal hepatoma cell lines. The mouse hepatoma cell hybrids retain the capacity to secrete transferrin at a reduced rate, and C3 (the third component of complement) at a high rate. Further analysis of C3 production in interspecific hybrids showed that both parental genomes actively contribute to C3 production: induction of C3 secretion is thus observed in these hybrids.