Abstract
Abstract B57 UBE3A (E6AP) auto antibodies in hepatocellular carcinoma 1Gebreselassie, D., 1Lan, R., 1Loffredo, C.A., 2Abdel-Hamid, M., 1Goldman, R. 1Lombardi Comprehensive Cancer Center Georgetown University Washington, D.C. & 2National Hepatology and Tropical Medicine Research Institute, Cairo, Egypt Patients with cancer produce auto antibodies that could serve as biomarkers for detection and classification of the disease. To identify auto antibodies associated with hepatocellular carcinoma (HCC), we used a protein array of 5,000 human proteins (Invitrogen) to compare sera of ten cancer free controls and ten patients with HCC matched on age, gender, and viral infection. Thirty six proteins significantly associated with HCC (p<0.05) were spotted on a custom array. The array experiments confirmed increased auto antibodies in HCC for 20 of the 36 candidates. The frequency of increase was as high as 45% for some of the auto antibodies in a comparison of 20 HCC cases and 10 matched controls. To further validate the observed auto antibody response to Ubiquitin protein ligase E3A (UBE3A), we fused cDNA for the protein, with an N-terminal FLAG tag and an enzyme reporter gene, humanized Renilla luciferase (hRluc). The construct was expressed in the Cos-1 mammalian cell line and crude cell lysates were used for quantification of auto antibodies in serum of the same individuals used in the protein array experiment. The assay is based on immunoprecipitation (IP) of the antigenic protein-construct on protein G beads followed by the quantification of hRluc chemiluminescence. Antibodies to the FLAG tag and the antigen of interest were used to optimize the assay. We found that HCC patient sera contain significantly elevated auto antibodies to UBE3A (t-test P<0.01). The autoantibody response to UBE3A was observed in approximately 20% of the HCC patients and correlates with the results of the protein array experiment. Citation Information: Cancer Prev Res 2008;1(7 Suppl):B57.
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