α1-microglobulin (HC protein) in human hepatocellular carcinoma

Abstract

al -Microglobulin (cx1-m) is a highly glycosylated polypeptide of 182 amino acids associated with a brown chromophore (Ekstr6m et al., 1975; Lopez Otin et al., 1984). The molecule is heterogeneous in charge and was described as HC protein (Tejler & Grubb, 1976) or acl-microglycoprotein (Seon & Pressmann, 1978). It occurs in biological fluids as a 31 kDa monomer and as a 90kDa component covalently associated to one a chain of monomeric immunoglobulin A (IgA) (Grubb et al., 1983; Vincent et al., 1985). The al-m gene is associated with a gene coding for the HI-30 domain of interax-trypsin inhibitor, one of the acute phase proteins (Kaumeyer et al., 1986). The human 31 kDa al-m was shown to be synthesised by fetal liver explants (Tejler et al., 1978) and we recently reported that the molecule was produced in vitro by several human hepatoma cell lines but not by lymphoma or plasmocytoma cell lines (Vincent et al., 1987). For these reasons we have determined serum levels of al-m in a large series of patients suffering from primary hepatocellular carcinoma in order to evaluate the possible use of this molecule as an additional tumour marker. The data show that 31 kDa al-m levels are usually not increased in this disease, whereas the 90kDa component levels are elevated in some cases. Our study involved a hundred South African Blacks with histologically proven hepatocellular carcinoma. They included 11 women and 89 men whose ages ranged from 20 to 73 years (median 39). Seventy-seven healthy South African Black subjects served as controls. All serum samples were sent frozen in dry ice from South Africa and were stored at -40°C until use. The differential quantitation of 31 kDa and IgA-associated 90 kDa ocl-m in unfractionated sera was performed by