[The genetic polymorphism of melanoma-associated antigen 1 in Chinese normal donors and hepatoma patients].

OBJECTIVES

To investigate the expression of melanoma-associated antigen 1 (MAGE-1) in Chinese hepatocellular carcinoma (HCC) patients and to determine the existence and distribution of single nucleotide polymorphisms (SNP) of MAGE-1 gene.

METHODS

Total RNA was extracted from cancer tissues and adjacent tissues from 19 HCC patients and the expression of MAGE-1 mRNA was examined by using RT-PCR. The PCR products were sequenced to analysis the gene variation. Genomic DNA was extracted from cancer tissues, adjacent tissues and peripheral blood cells of 19 HCC patients, as well as from peripheral blood cells of 23 healthy donors. The PCR product of MAGE-1 DNA was sequenced to determine the existence and distribution of SNPs of MAGE-1 gene.

RESULTS

9 of 19 (47.4%) tumor tissues and none of adjacent tissue from HCC patients expressed MAGE-1 mRNA. There were three kinds of gene variations of cDNA in 9 MAGE-1 mRNA positive patients. One type was named type I including 1 patient, which sequence is as same as that of the GenBank M77481. The other was named TGA type including 5 patients, which involved three nucleotide changes (C159T, A272G and G393A) and result in two amino acid changes (T32A and R72Q). Another one was named GTG type including 3 patients, which involved three nucleotide changes (A272G, C991T, A1125G) and result in only one amino acid changes (T32A). According to the analysis of genomic DNA, above three types were not specific mutations of tumor tissue, but were SNPs. These SNPs types were distributed in HCC patients and normal donors with the frequencies of 26.3% (5/19) and 60.9% (14/23) for type I, 57.9% (11/19) and 47.8% (11/23) for TGA type, and 21.1% (4/19) and 21.7% (5/23) for GTG type, respectively. The sequences of two new SNPs had been deposited in GenBank with the accession numbers of AF463515 and AY148486. In male population, the distributions of SNPs were not correlated to HCC suffering or MAGE-1 expression. Several new HLA-restricted epitopes were probably resulted from SNPs existing. The three-dimensional models of MAGE-1 proteins of type I and TGA type was established by using computer software.

CONCLUSION

The expression rate of MAGE-1 gene in Chinese HCC patients is high. Three SNP types of MAGE-1 gene exist in Chinese population. The three-dimensional models of MAGE-1 proteins were obtained by computer processing. These results will be helpful to developing MAGE-1 peptide-vaccine for HCC immunotherapy.