MAGE‐1 gene product is a cytoplasmic protein

Abstract

MAGE-1 gene encodes a human melanoma antigen, recognized by syngeneic cytotoxic T lymphocytes (CTL). MAGE-1 transcripts are also detectable in breast cancers, in non-small-cell lung carcinomas and in central nervous system tumors. In order to identify, in cellular preparations, the protein encompassing the antigenic peptide, we generated a panel of monoclonal antibodies (MAbs) against the MAGE-1 gene product by using, as immunogen, a full-length recombinant preparation (rMAGE-1), obtained through expression cloning of the relevant gene in E. coli. Four reagents were obtained recognizing both rMAGE-1 and the 46-kDa native protein in cell lines expressing MAGE-1 mRNA. No positivity could be detected in MAGE-1-mRNA-negative melanoma lines. No surface labelling of MAGE-1-positive cell lines could be observed. In contrast, on permeabilization of MZ2 melanoma cells, all 4 MAbs induced efficient staining, as detected by cytofluorography. Fluorescence microscopy shows that MAGE-1 gene product is a cytoplasmic protein clustered in paranuclear organelle-like structures. Thus, MAGE-1 protein location closely resembles that of P91A and P198 murine-tumor antigens.

Cancer-Testis Antigens: Expression and Correlation with Survival in Human Urothelial Carcinoma

“…Because CTAs have high homology, the possibility of cross-reactivity of the mAbs to related antigens cannot be excluded. This point is exemplified by discussions about the specificity of mAb 57B, which was generated to MAGE-A3 but is now considered to be reactive to MAGE-A4 (25,27,28). The high percentage of congruent mRNA expression and mAb reactivity suggest that the present antibodies did in fact detect their target antigen.…”

A testicular antigen aberrantly expressed in human cancers detected by autologous antibody screening

“…Through cell fractionation and immunohistochemical studies (31,32), it has been shown that MAGE-1 is a cytoplasmic protein, and there is no structural evidence for a transmembrane domain in MAGE, BAGE, GAGE, or SSX2. NY-ESO-1, in contrast, contains a hydrophobic segment at its carboxyl end.…”

MAGE‐A10 is a nuclear protein frequently expressed in high percentages of tumor cells in lung, skin and urothelial malignancies

“…Although 77B mAb only recognized its MAGE-A1 putative target protein, 57B mAb recognized, in addition to its putative MAGE-A3 target, also MAGE-A1 and MAGE-A11. 13,18 Neither reagent was able to identify MAGE-A10. In contrast, a number of antibodies produced during our study only identified MAGE-A10, as shown, for GA11.1 representative mAb in Figure 2.…”