Expression of the SART-1 antigens in uterine cancers

Expression of a newly defined tumor-rejection antigen SART3 in musculoskeletal tumors and induction of HLA class I-restricted cytotoxic T lymphocytes by SART3-derived peptides

We recently reported that a SART3 tumor-rejection antigen possessing tumor epitopes is capable of inducing HLA class 1-restricted and tumor-specific cytotoxic T lymphocytes in cancer patients. We studied the expression of the SART3 protein in musculoskeletal tumors to find a molecule for potential use in tumor-specific immunotherapy. The SART3 was detected at protein levels in 100% of the osteosarcoma cell lines (n = 20), in 50% of the musculoskeletal tumor tissue specimens (n = 32), and at notable levels in 67% of osteosarcoma tissues (n = 9) and malignant fibrous histiocytosis tissues (n = 9), respectively. SART3-derived peptides at positions 109-118 and 315-323 induced HLA-A24-restricted tumor-specific cytoxic T lymphocytes from peripheral blood mononuclear cells of patients with osteosarcoma or malignant fibrous histiocytosis. These peptide-induced cytotoxic T lymphocytes recognized HLA-A24+ SART3+ osteosarcoma cells but not HLA-A24 or SART3 cells. These results suggest that the SART3 protein and its derived peptides could be molecules appropriate for use in specific immunotherapies for approximately 60% of HLA-A24+ patients with osteosarcoma or malignant fibrous histiocytosis.

Expression of tumor-rejection antigens in gynecologic cancers

We recently reported the four tumor-rejection antigens (SART1(259), SART2, SART3, and ART4) that possess tumor epitopes capable of inducing HLA-A2402-restricted cytotoxic T lymphocytes (CTLs) in cancer patients. This study investigated the expression of these tumor antigens in gynecologic cancers, including 33 ovarian cancers, 38 cervical cancers, and 40 endometrial cancers. SART1(259) antigen was detected in 56%, 35%, and 30% of ovarian, cervical and endometrial cancers, while SART2 antigen was detected in 46%, 66%, and 30% of these cancers, respectively. Both SART3 and ART4 antigens were detectable in the majority of these gynecologic cancers tested. In contrast, none of these antigens was detectable in any of the normal ovarian and uterine tissues tested. Peripheral blood mononuclear cells (PBMCs) of HLA-A24(+) patients with gynecologic cancers were found to produce significant levels of interferon-gamma in response to HLA-A24(+) SART3(+) gynecologic cancer cells after having been stimulated three times in vitro with either SART3(109 - 118) or SART3(315 - 323) peptide. These PBMCs lysed HLA-A24(+) SART3(+) gynecologic cancer cells, but not HLA-A24(-) SART3(+) gynecologic cancer cells or HLA-A24(+) normal cells. Therefore, these four antigens and their peptides, including SART3 peptides, would be appropriate molecules for use in specific immunotherapy of HLA-A24(+) gynecologic cancer patients.

Expression of the SART3 tumor-rejection antigen in brain tumors and induction of cytotoxic T lymphocytes by its peptides

The authors recently reported on the SART3 tumor-rejection antigen, which possesses epitopes that can induce cytotoxic T lymphocytes (CTLs) in patients with epithelial cancer. To explore a new modality for treatment of patients with brain tumors, this study investigated the expression of the SART3 antigen in patients with brain tumors and the ability of SART3 peptides to induce CTLs from peripheral blood mononuclear cells (PBMCs) of these patients. The SART3 antigen was detected in the cytoplasmic fraction of all 18 glioma cell lines examined and in the majority (31 of 34; 91%) of brain tumor tissues irrespective of their histologies. It was also expressed in the nuclear fraction of all 18 glioma cell lines and in the majority (26 of 34; 76%) of brain tumor tissues. In contrast, the SART3 was not expressed in nontumorous brain tissues. Cytotoxic T lymphocytes were induced in patients with glioma by stimulation with two epitope peptides of SART3. These CTLs could eliminate glioma cells in a HLA-A24-restricted manner. Therefore, the SART3 peptides may be appropriate molecules for use in peptide-based specific immunotherapy of HLA-A24+ patients with brain tumors.

Induction of human leukocyte antigen-A26-restricted and tumor-specific cytotoxic T lymphocytes by a single peptide of the SART1 antigen in patients with cancer with different A26 subtypes

Peptide antigens available for use in specific immunotherapy of patients with cancer have not been fully determined. Although the authors have reported the SART1 gene encoding epitopes recognized by HLA-A2601-restricted and tumor-specific cytotoxic T lymphocytes (CTLs), the HLA-A26 allele is mainly subdivided into A2601, A2602, and A2603 subtypes. In this study, the authors attempted to determine whether the SART1-derived peptide at position 736-744 (KGSGKMKTE) is suitable to induce HLA-A26-restricted and tumor-specific CTLs in patients with cancer who have these subtypes. This peptide induced the HLA-A26 subtype-restricted and tumor-specific CTLs in HLA-A2601+ or HLA-A2603+ peripheral blood mononuclear cells, respectively. It also induced the HLA-A26-restricted CTL activity in HLA-A2602+ peripheral blood mononuclear cells. Therefore, this peptide could be useful for specific immunotherapy of patients with cancer who have any of the three HLA-A26 subtypes.