Characterization of tumor-associated antigens in colon cancer

A Line, MSc,a Z Slucka,a A Stengrevics, MD,b K Silina, a G Li, PhD, c E Jankevics, PhD, a RC Rees, PhD, c

aBiomedical Research and Study Centre,University of Latvia, Riga, Latvia, bLatvian Oncology Center, Riga, Latvia, cDepartment of Life Sciences, Nottingham Trent University, Nottingham, UK

AIMS: In order to search for clinically relevant cancer-associated genes and to define further the spectrum of immunogenic proteins, we applied a serological screening method, called SEREX, to colon adenocarcinoma. METHODS: Colon cancer cDNA expression library was screened with autologous patient serum and reactive cDNA clones were isolated and identified. Full-length cDNA sequences were obtained by RLM-RACE analysis. mRNA expression of selected antigens was analyzed in a panel of normal tissues and the expression levels were compared between colon cancer and adjacent tissue samples of 15 patients by comparative RT-PCR. RESULTS: Eight different serum-reactive cDNA clones were isolated by immunoscreening from colon cancer-derived expression library. With regard to immunogenicity, three antigens did not react with any of sera from 35 healthy individuals, while others had similar reactivity with sera from patients and controls. RHAMM (receptor for hyaluronan mediated motility) and AD034 mRNA showed differential tissue distribution pattern but comparison of the relative mRNA amounts revealed that RHAMM, AD034 and NAP1L1 are overexpressed in tumors versus adjacent tissues. Direct sequencing and RT-PCR analysis showed that RHAMM mRNA is alternatively spliced and the isoform lacking 48-bp alternative exon is predominantly expressed in colon cancer. 5’RLM-RACE analysis of AD034 - a sequence with tyrosine kinase motif revealed a frameshifting insertion of 32 nucleotides, presumably generated by use of cryptic splice site. CONCLUSIONS: This study has revealed several new cancer candidate genes, including alternatively spliced and overexpressed genes, but additional studies are required to evaluate their role in tumorigenesis and their potential as therapeutic targets.

KEY WORDS: Tumor antigens, .

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Molecular Pathology.