Cancer Biology, University of Wisconsin Comprehensive Cancer Center, 7007 Wisconsin Institutes for Medical Research, 1111 Highland Ave., Madison, WI, 53705, United States.
Recent FDA approval of the first immunotherapy for prostate cancer encourages efforts to improve immune targeting of this disease. The synovial sarcoma X chromosome breakpoint (SSX) proteins comprise a set of cancer-testis antigens (CTA) that are upregulated in MHC class I-deficient germline cells and in various types of advanced cancers with a poor prognosis. Humoral and cell-mediated immune responses to the SSX family member SSX2 can arise spontaneously in prostate cancer patients. Thus, SSX2 and other proteins of the SSX family may offer useful targets for tumor immunotherapy. In this study, we evaluated the expression of SSX family members in prostate cancer cell lines and tumor biopsies to identify which members might be most appropriate for immune targeting. We found that SSX2 was expressed most frequently in prostate cell lines, but that SSX1 and SSX5 were also expressed after treatment with the DNA demethylating agent 5-aza-2'-deoxycytidine. Immunohistochemical analysis of microarrayed tissue biopsies confirmed a differential level of SSX protein expression in human prostate cancers. Notably, SSX expression in patient tumor samples was restricted to metastatic lesions (5/22; 23%) and no expression was detected in primary prostate tumors examined (0/73; p < 0.001). We determined that cross-reactive immune responses to a dominant HLA-A2-specific SSX epitope (p103-111) could be elicited by immunization of A2/DR1 transgenic mice with SSX vaccines. Our findings suggest that multiple SSX family members are expressed in metastatic prostate cancers which are amenable to simultaneous targeting.
Written by:
Smith HA, Cronk RJ, Lang JM, McNeel DG. Are you the author?
Reference: Cancer Res. 2011 Sep 7. Epub ahead of print.
doi: 10.1158/0008-5472.CAN-11-2127
PubMed Abstract
PMID: 21880588
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