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

Abstract

Serological analysis of recombinant cDNA expression libraries (SEREX) using tumor mRNA and autologous patient serum provides a powerful approach to identify immunogenic tumor antigens. We have applied this methodology to a case of esophageal squamous cell carcinoma and identified several candidate tumor targets. One of these, NY-ESO-1, showed restricted mRNA expression in normal tissues, with high-level mRNA expression found only in testis and ovary tissues. Reverse transcription-PCR analysis showed NY-ESO-1 mRNA expression in a variable proportion of a wide array of human cancers, including melanoma, breast cancer, bladder cancer, prostate cancer, and hepatocellular carcinoma. NY-ESO-1 encodes a putative protein of Mr 17,995 having no homology with any known protein. The pattern of NY-ESO-1 expression indicates that it belongs to an expanding family of immunogenic testicular antigens that are aberrantly expressed in human cancers in a lineage-nonspecific fashion. These antigens, initially detected by either cytotoxic T cells (MAGE, BAGE, GAGE-1) or antibodies [HOM-MEL-40(SSX2), NY-ESO-1], represent a pool of antigenic targets for cancer vaccination.

Figures

Figure 1

RT-PCR analysis of NY-ESO-1 (A) and NY-ESO-4 (B) mRNA expression. Total RNA was extracted from the original esophageal cancer (lane 1) and from normal colon (lane 2), kidney (lane 3), testis (lane 4), liver (lane 5), and brain (lane 6). Negative control with no RNA was included (lane 7). NY-ESO-1 PCR primer sequences were: ESO1A, 5′-CACACAGGATCCATGGATGCTGCAGATGCGG-3′ and ESO1B, 5′-CACACAAAGCTTGGCTTAGCGCCTCTGCCCTG.

Figure 2

Northern blot analysis of NY-ESO-1, showing NY-ESO-1 mRNA in testis and SK-MEL-19, but not in uterus, small intestine, liver, placenta, brain, and SK-MEL-30. The major mRNA species is 0.8–0.9 kb, with minor higher molecular weight species seen in SK-MEL-19.

Figure 3

Nucleotide and amino acid sequences of NY-ESO-1, indicating potential N-myristoylation (Myr) and phosphorylation (P) sites. The potential transmembrane domain at the carboxyl end is italicized. (GenBank database accession number: U87459U87459.)

Figure 4

Hydrophilicity plot of NY-ESO-1, indicating hydrophilic domain (positive value) in the amino terminus, and a long hydrophobic stretch (negative value) close to the carboxyl end of the putative protein sequence.