EXPRESSION OF THE MAGE GENE FAMILY IN HUMAN LYMPHOCYTIC-LEUKEMIA

The MAGE gene family, encoding tumor-rejection antigens recognized by cytotoxic T lymphocytes, is frequently expressed in human solid cancer s. However, its expression in leukemia has not been well studied. We h ave investigated MAGE gene expression at the mRNA level in human leuke mia. The MAGE gene family was expressed in 17 of 34 (50%) examples of T cell leukemia (12/21 patients' peripheral blood mononuclear cells an d 5/13 cell lines), in 7 of 16 (44%) cases of B cell leukemia (1/8 and 6/8 respectively), but in none of 23 myelomonocytic leukemia cases (0 /16 and 0/7), as evaluated by the primers common to the MAGE-1, -3, -4 (-4a and/or -4b), and -6 genes and the semi-quantificative reverse tr anscription/polymerase chain reaction method. None of a panel of norma l lymphoid cells expressed the MAGE gene family. As revealed by the pr imers specific for each of the MAGE genes, the MAGE-1, -2, -3, -4 or - 6 gene was expressed in 8, 8, 6, 2, or 6 respectively out of 23 types of leukemia cell lines. Expression of the MAGE-1 protein in both the c ell lines and patients' cells was confirmed by immunoblot analysis wit h the polyclonal antibody to recombinant MAGE-1 protein. Cellular MAGE -4 protein in the cell lines was measured by an enzyme-linked immunoso rbent assay with the polyclonal and monoclonal antibodies to recombina nt MAGE-4b protein. In summary, the MAGE gene family was found to be e xpressed in the substantial proportion of T cell leukemias, but in no case of myelomonocytic leukemia. Antigens coded by the MAGE gene famil y could be important molecules for understanding specific immunity aga inst lymphocytic leukemia.