CLONING AND INCREASED EXPRESSION OF AN INSULIN-RECEPTOR SUBSTRATE-1-LIKE GENE IN HUMAN HEPATOCELLULAR-CARCINOMA

Human insulin receptor substrate-1 (hlRS-1) cDNAs were cloned from a λGT11 expression library using a monoclonal antibody (MAb) produced against a human hepatocellular carcinoma (HCC) cell line (FOCUS). The predicted amino acid sequence derived from both a genomic DNA fragment and the cDNAs showed a 90.5% identity to the previously reported rat IRS-1 cDNA [Sun, X.P. (1991) Nature 352, 73-77]. Multiple potential phosphorylation sites, that suggest an intrinsic function of this molecule in response to insulin action, were highly conserved between the two species. A c.a. 180 kDa hlRS-1 protein was immunoprecipitated and found to be phosphorylated on tyrosine residue(s) following insulin stimulation of HuH-7 HCC cells. Northern blot analysis demonstrated a single c.a. 5 kb transcript in HCC cell lines and tissues. Higher levels of hlRS-1 gene transcripts were observed in HCC tumors compared to adjacent non-involved normal liver. © 1992.