NY-ESO-1 tumour associated antigen is a cytoplasmic protein detectable by specific monoclonal antibodies in cell lines and clinical specimens

NY-ESO-1 gene encodes a novel member of the cancer/testis (CT) family of hu man tumour-associated antigens (TAA). Specific monoclonal antibodies (mAb) have identified the corresponding gene product in lysates of tumour cell li nes as a 22 kDa protein but no data are available concerning its intracellu lar location or distribution within neoplastic tissues. We have generated N Y-ESO-1 specific mAbs recognizing the target molecule in cytospin preparati ons and in sections from clinical tumour specimens. These reagents identify NY-ESO-1 TAA in melanoma cell lines expressing the specific gene as a cyto plasmic protein, sharing the intracellular location of most MAGE TAA. In a series of 12 melanoma specimens, specific staining, limited to neoplastic c ells, was detectable in the five cases where NY-ESO-1 gene expression was o bserved. In two of them over 90% of tumour cells showed evidence of positiv e staining. Lower percentages of positive neoplastic cells ranging between single cells and 50% were observed in the remaining tumours. These data sug gest that active specific immunotherapies targeting NY-ESO-1, alone or in c ombination with other TAA could be of high clinical relevance in sizeable s ubgroups of melanoma patients. (C) 2000 Cancer Research Campaign.