Expression of SSX genes in the neoplastic cells of Hodgkin's lymphoma

The cancer/testis antigen (CTA) group of tumor-associated proteins have been reported to be expressed in various cancers and in adult testis but they are essentially not found in any other normal adult nonneoplastic tissues. Prompted by the frequent detection of SSX1 in a previous comprehensive expression profile of the Hodgkin's lymphoma (HL) cell line L428, we analyzed SSX expression by nonnested reverse-transcription polymerase chain reaction (RT-PCR) in 4 HL cell lines (L428, L540, HD-MY-Z, and KM-H2) and 32 tumor samples of HL. The cellular localization of SSX expression in the tumor samples was further analyzed by in situ hybridization (ISH). All 4 HL cell lines were positive by RT-PCR using SSX consensus primers. Using primers specific to individual SSX genes, all 4 cell lines expressed multiple SSX family members. Five tumor samples (15.6%) were positive by RT-PCR using SSX consensus primers and direct sequencing of the RT-PCR products showed that 4 of 5 expressed more than I SSX family member. ISH confirmed that SSX expression originated in HL cells in all 5 RT-PCR-positive tumor samples. Furthermore, ISH demonstrated SSX-positive HL cells in 6 of 11 cases (55%) that were negative by RT-PCR. Our results suggest that members of the SSX family of CTA are expressed in most HL. This subset of HL may be a candidate for immunotherapy approaches directed at SSX proteins.