GENE-EXPRESSION AND PROTEIN DISTRIBUTION OF INTER-ALPHA-TRYPSIN INHIBITOR IN 3 HUMAN HEPATOMA-CELL LINES

In standard culture conditions, three human hepatoma cell lines, Hep3B , PLC/PRF/5 and HepG2, were characterised by a predominant transcripti on of only two (H2 and L) among the four genes involved in the synthes is of inter-alpha-trypsin inhibitor (ITI)-related proteins. Pulse-chas e experiments followed by immunoprecipitation with specific anti-L and anti-H ITI antisera showed that the proteins synthesised displayed a restricted L and/or H2 antigenic reactivity. Furthermore, while Hep3B and PLC/PRF/5 lines only synthesised ITI precursors (mainly the L-form ), HepG2 cells were able to secrete art ITI-like protein. Immunocytoch emical analyses substantiated these results with uneven distribution o f heavy and light-chain polypeptide reactivity among the cells. The us e of hepatoma cell models for the study of protein synthesis and assem bly must therefore be considered cautiously.