Cancer-testis Antigen Expression is Shared Between Epithelial Ovarian Cancer Tumors

Objectives: Cancer-testis (CT) antigens have been proposed as potential targets for cancer immunotherapy. Our objective was to evaluate the expression of a panel of CT antigens in epithelial ovarian cancer (EOC) tumor specimens, and to determine if antigen sharing occurs between tumors.

Methods: RNA was isolated from EOC tumor specimens, EOC cell lines and benign ovarian tissue specimens. Real time-PCR analysis was performed to determine the expression level of 20 CT antigens.

Results: A total of 62 EOC specimens, 8 ovarian cancer cell lines and 3 benign ovarian tissues were evaluated for CT antigen expression. The majority of the specimens were: high grade (62%), serous (68%) and advanced stage (74%). 58 (95%) of the EOC tumors analyzed expressed at least one of the CT antigens evaluated. The mean number of CT antigen expressed was 4.5 (0-17). The most frequently expressed CT antigen was MAGE A4 (65%). Antigen sharing analysis showed the following: 9 tumors shared only one antigen with 62% of the evaluated specimens, while 37 tumors shared 4 or more antigens with 82%. 5 tumors expressed over 10 CT antigens, which were shared with 90% of the tumor panel.

Conclusion: CT antigens are expressed in 95% of EOC tumor specimens. However, not a single antigen was universally expressed across all samples. The degree of antigen sharing between tumors increased with the total number of antigens expressed. These data suggest a multi-epitope approach for development of immunotherapy for ovarian cancer treatment.