Lack of tumor recognition by cytolytic T lymphocyte clones recognizing peptide 195-203 encoded by gene MAGE-A3 and presented by HLA-A24 molecules.

So T., Hanagiri T., Chapiro J., Colau D., Brasseur F., Yasumoto K., Boon T., Coulie PG.
Cancer Immunol Immunother., 56 (2007), 259-269.

Gene MAGE-A3 encodes tumor-specific antigenic peptides recognized by T cells on many tumors. MAGE-A3 peptides presented by HLA class I molecules have been identified using CD8 lymphocytes stimulated with cells that either expressed gene MAGE-A3 or were pulsed with candidate peptides. One antigen identified with the latter method is peptide MAGE-A3(195-203) IMPKAGLLI, presented by HLA-A24 molecules. It has been used to vaccinate advanced cancer patients. Here, we have used HLA/peptide tetramers to detect T cells recognizing this peptide. Their frequency was estimated to be 2 x 10(-8) of the blood CD8 cells in non-cancerous HLA-A24(+) individuals, which is tenfold lower than the reported frequencies of T cells against other MAGE peptides. In the blood of a patient vaccinated with MAGE-A3, the estimated frequency was 5 x 10(-7). Anti-MAGE-3.A24 cytolytic T cell clones were derived, that lysed peptide-pulsed cells with half-maximal effect at the low concentration of 500 pM. However, these CTL did not recognize a panel of HLA-A24(+) tumor cells that expressed MAGE-A3 at levels similar to those found in HLA-A1(+) tumor cells recognized by anti-MAGE-3.A1 CTLs. Furthermore, 293-EBNA cells transfected with MAGE-A3 and HLA-A24 constructs were hardly recognized by the anti-MAGE-3.A24 CTL clones. These results suggest that peptide MAGE-A3(195-203) is poorly processed and is not an appropriate target for cancer immunotherapy.

URL: http://www.springerlink.com/content/d30n0h7n77k82355/

Pub Med: http://www.ncbi.nlm.nih.gov/pubmed/16758204

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