Targeting CTCFL/BORIS for the immunotherapy of cancer

Cancer vaccines have great potential in the fight against metastatic malignancies. Current anti-tumor immunotherapy is hindered by existing tolerance to tumor-associated antigens (TAA) and tumor escape using various mechanisms, highlighting the need for improved targets for immunotherapy. The cancer-testis antigen CTCFL/BORIS was discovered 16 years ago and possesses all features necessary for an ideal TAA. Recently CTCFL/BORIS has received additional attention as a target expressed in cancer stem cells (CSC). These cells drive tumor growth recurrence, metastasis, and treatment resistance. CTCFL/BORIS silencing leads to senescence and death of CSC. Therefore, an immunotherapeutic strategy that targets CTCFL/BORIS may lead to the selective destruction of CSC and potential eradication of metastatic disease. The high immunotherapeutic potential of CTCFL/BORIS antigen was shown in a stringent 4T1 mouse model of breast cancer. Using these highly metastatic, poorly immunogenic carcinoma cells inoculated into T-helper2 prone mice, we showed that DC fed with recombinant CTCFL/BORIS as an immunogen inhibited tumor growth and reduced the number of metastases in distant organs. About 20% of CTCFL/BORIS immunized animals were tumor free. 50% of animals remained metastasis free. Those having metastasis showed at least tenfold fewer metastases compared to controls. In a rat model of breast cancer, we showed that alphavirus-based CTCFL/BORIS immunotherapy was capable of cancer elimination as we were able to cure 50% of animals. Based on the above data, we believe that translation of CTCFL/BORIS-targeting immunotherapeutic strategies to the clinic will provide new avenues for improving survival of breast cancer patients with advanced metastatic disease.