Monoclonal antibody 57B stains tumor tissues that express gene MAGE-A4

Monoclonal antibody (Mab) 57B, which was raised against a recombinant MAGE- A3 protein, was tested for its ability to stain cells expressing various me mbers of the MAGE-A gene family. COS-7 cells transfected with cDNAs encodin g MACE A1, A2, A3, A4, A6, or A12 were stained, whereas those transfected w ith MAGE-A8, A9, A10, or A11 cDNAs were not. However, in tissue sections, w e observed a different pattern of staining: the antibody effectively staine d the tumors that expressed MAGE-A4 and only these tumors, regardless of th e expression of the other MAGE-A genes. It seems, therefore, that at the le vel of MAGE gene expression found in tumors, a level clearly lower than tha t observed in transfected COS cells, only the MAGE-A4 protein can be reliab ly detected. We conclude that the 57B Mab should be useful for tumor diagno sis related to therapeutic vaccination involving MAGE-A4. (C) 2000 Wiley-Li ss, Inc.