A new strategy for the diagnosis of MAGE-expressing cancers

The expression of melanoma antigen gene (MAGE), coding for tumor antigens recognized by cytotoxic T cell, is highly specific to cancer cells, but their use in the detection of a few cancer cells by reverse transcription-polymerase chain reaction (RT-PCR) has been limited by the low frequency of expression of individual MAGE genes. In order to increase MAGE detection rate in RT-PCR assay, here, we designed multiple MAGEs recognizing primers (MMRPs) that can bind to the sequences of cDNA of MAGE-1, -2, -3, -4a, -4b, -5a, -5b and-6 (MAGE 1-6) together. The nested RT-PCR assay using MMRPs, MAGE 1-6 assay, detected MAGE messages of 1 to 5 SNU484 cells in a background of 10(7) SNU638 cells. MAGE detection rate of MAGE 1-6 assay in cancers was higher than that of nested RT-PCR that detects single MAGE gene expression. The expressions of MAGE genes was detected by MAGE 1-6 assay in 70.4% (19/27) of head and neck cancer tissues, 91.7% (11/12) of breast cancer tissues, 75% (9/12) of lung cancer tissues. However, they were not detected in 18 benign lesions and 20 normal head and neck tissues and 30 blood samples from healthy donor. In conclusions, MAGE 1-6 assay can detect any cancer cells that express at least one of eight MAGE subtype genes, and this method may be very useful for the diagnosis of MAGE-expressing cancers.