Cancer/testis (CT) antigens are considered promising target molecules for immunotherapy for patients with various cancers.
To identify CT antigens or CT-like antigens, we performed serological identification of antigens by recombinant expression cloning (SEREX) analysis that screened a testicular cDNA library with serum obtained from a patient with gastric adenocarcinoma. We isolated 4 genes with testis specific profiles in the database, including G kinase anchoring protein 1 (GKAP1). RT-PCR analysis showed that the
mRNA expression levels of
GKAP1 were restricted to the testis in normal adult tissues. In malignant tissues,
GKAP1 was aberrantly expressed in a variety of cancers, particularly oral squamous cell carcinoma (OSCC).
mRNA expression analysis of other CT antigens revealed that
MAGE-A4 was expressed in 32%,
MAGE-A3 in 24%,
MAGE-A1 in 13%,
CCDC62-2 in 12%,
SSX-2 in 11%,
XAGE-1b in 7 %, and
NY-ESO-1 in 3 % of OSCC. 52.5% of OSCC expressed at least one of these antigens. Of 15 sera from cancer patients with OSCC, 2 sera were reactive with GKAP1 protein on ELISA analysis. None of the healthy donor serum was reactive.
These findings suggested that GKAP1 is immunogenic in OSCC and demonstrated its potential as a diagnostic marker for patients with OSCC in combination with other CT antigens such as MAGE-A4, MAGE-A3, and CCDC62-2.
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