Mouse homologue of the human SART3 gene encoding tumor-rejection antigen

Antitumor activity of antibody against cytotoxic T lymphocyte epitope peptide of lymphocyte-specific protein tyrosine kinase

Although humoral responses against CTL epitope peptides from lymphocyte‐specific protein tyrosine kinase (Lck) antigen have been observed in the majority of healthy donors and cancer patients, the biological activity of the antibody has not been determined. We investigated the biological activity of mAb against CTL epitope peptide of Lck antigen at positions 486‐494 (anti‐Lck‐486 mAb). This mAb induced dendritic cell maturation from murine bone marrow cells by the immune complex form in vitro, and inhibited tumor growth in association with a suppression of tumor‐infiltrating T cells, including T regulatory cells in a murine model using female BALB/cCrlCrlj mice (H‐2K^d). More potent tumor inhibition was observed when this mAb was given prior to peptide vaccination. These results may help to unveil the biological activity of anti‐Lck peptide antibodies against CTL epitope peptides.

Identification of gene expression models for laryngeal squamous cell carcinoma using co-expression network analysis

One of the most common head and neck cancers is laryngeal squamous cell carcinoma (LSCC). LSCC exhibits high mortality rates and has a poor prognosis. The molecular mechanisms leading to the development and progression of LSCC are not entirely clear despite genetic and therapeutic advances and increased survival rates. In this study, a total of 116 differentially expressed genes (DEGs), including 11 upregulated genes and 105 downregulated genes, were screened from LSCC samples and compared with adjacent noncancerous. Statistically significant differences (log 2-fold difference > 0.5 and adjusted P-value < .05) were found in this study in the expression between tumor and nontumor larynx tissue samples. Nine cancer hub genes were found to have a high predictive power to distinguish between tumor and nontumor larynx tissue samples. Interestingly, they also appear to contribute to the progression of LSCC and malignancy via the Jak-STAT signaling pathway and focal adhesion. The model could separate patients into high-risk and low-risk groups successfully when only using the expression level of mRNA signatures. A total of 4 modules (blue, gray, turquoise, and yellow) were screened for the DEGs in the weighted co-expression network. The blue model includes cancer-specific pathways such as pancreatic cancer, bladder cancer, nonsmall cell lung cancer, colorectal cancer, glioma, Hippo signaling pathway, melanoma, chronic myeloid leukemia, prostate cancer, and proteoglycans in cancer. Endocrine resistance (CCND1, RAF1, RB1, and SMAD2) and Hippo signaling pathway (CCND1, LATS1, SMAD2, and TP53BP2) could be of importance in LSCC, because they had high connectivity degrees in the blue module. Results from this study provide a powerful biomarker discovery platform to increase understanding of the progression of LSCC and to reveal potential therapeutic targets in the treatment of LSCC. Improved monitoring of LSCC and resulting improvement of treatment of LSCC might result from this information.

Tip110: Physical properties, primary structure, and biological functions

HIV-1 Tat-interacting protein of 110kDa (Tip110), also referred to as squamous cell carcinoma antigen recognized by T cells 3 (Sart3), p110 or p110(nrb), was initially identified as a cDNA clone (KIAA0156) without annotated functions. Over the past twenty years, several functions have been attributed to this protein. The proposed biological functions include roles for Tip110 in pre-mRNA splicing, gene transcription, stem cell biology, and development. Dysregulation of Tip110 is also a contributing factor in the development of cancer and other human diseases. It is clear that our understanding of this protein is rapidly evolving. In this review, we aimed to provide a summary of all the existing literature on this gene/protein and its proposed biological functions.

Intraperitoneal administration of a tumor-associated antigen SART3, CD40L, and GM-CSF gene-loaded polyplex micelle elicits a vaccine effect in mouse tumor models

Polyplex micelles have demonstrated biocompatibility and achieve efficient gene transfection in vivo. Here, we investigated a polyplex micelle encapsulating genes encoding the tumor-associated antigen squamous cell carcinoma antigen recognized by T cells-3 (SART3), adjuvant CD40L, and granulocyte macrophage colony-stimulating factor (GM-CSF) as a DNA vaccine platform in mouse tumor models with different types of major histocompatibility antigen complex (MHC). Intraperitoneally administrated polyplex micelles were predominantly found in the lymph nodes, spleen, and liver. Compared with mock controls, the triple gene vaccine significantly prolonged the survival of mice harboring peritoneal dissemination of CT26 colorectal cancer cells, of which long-term surviving mice showed complete rejection when re-challenged with CT26 tumors. Moreover, the DNA vaccine inhibited the growth and metastasis of subcutaneous CT26 and Lewis lung tumors in BALB/c and C57BL/6 mice, respectively, which represent different MHC haplotypes. The DNA vaccine highly stimulated both cytotoxic T lymphocyte and natural killer cell activities, and increased the infiltration of CD11c⁺ DCs and CD4⁺/CD8a⁺ T cells into tumors. Depletion of CD4⁺ or CD8a⁺ T cells by neutralizing antibodies deteriorated the anti-tumor efficacy of the DNA vaccine. In conclusion, a SART3/CD40L+GM-CSF gene-loaded polyplex micelle can be applied as a novel vaccine platform to elicit tumor rejection immunity regardless of the recipient MHC haplotype.

Interferon-gamma renders tumors that express low levels of Her-2/neu sensitive to cytotoxic T cells

Her-2/neu is a tumor-associated antigen that has been targeted with both antibodies and cytotoxic T lymphocytes (CTL). Despite the isolation of Her-2/neu-reactive CTL in vaccinated patients, their therapeutic use has been limited by the observation that they often do not robustly recognize Her-2/neu(+) tumors. We sought to determine the mechanism for this escape using Ag201P and Ag201M cells, which are murine osteosarcoma tumor lines that express a functional HLA-A2/K(b) molecule. We now demonstrate that Ag201P and Ag201M express low levels of murine Her-2/neu, and that Ag201M was modestly and inconsistently recognized by an HLA-A2-restricted, Her-2/neu-reactive human CTL clone. In order to determine whether inefficient antigen processing might account for the weak recognition, COS-A2 cells were transfected with a short Her-2/neu minigene coding for the immunodominant Her-2/neu:369 epitope that did not require antigen processing or a long Her-2/neu minigene that did require antigen processing. Her-2/neu-reactive CTL clones only recognized COS-A2 cells transfected with the short minigene, indicating that lack of proper antigen processing could be responsible for the poor recognition of target cells. To confirm these results, it was demonstrated that following treatment with interferon-gamma, both Ag201P and Ag201M robustly and consistently stimulated the CTL clones. Furthermore, CTL clone recognition was enhanced following interferon-gamma treatment using another murine tumor line that expressed low levels of Her-2/neu (B16-A2/K(b)). The enhanced recognition of Ag201P and Ag201M in the presence of interferon-gamma was not due to an upregulation of Her-2/neu protein expression. Collectively, these results suggest that inefficient antigen processing of Her-2/neu can contribute to the lack of tumor recognition by CTL. These results also suggest that even tissues that express low levels of Her-2/neu might become CTL targets under conditions in which antigen processing is enhanced.

p110, a novel human U6 snRNP protein and U4/U6 snRNP recycling factor

During each spliceosome cycle, the U6 snRNA undergoes extensive structural rearrangements, alternating between singular, U4-U6 and U6-U2 base-paired forms. In Saccharomyces cerevisiae, Prp24 functions as an snRNP recycling factor, reannealing U4 and U6 snRNAs. By database searching, we have identified a Prp24-related human protein previously described as p110(nrb) or SART3. p110 contains in its C-terminal region two RNA recognition motifs (RRMs). The N-terminal two-thirds of p110, for which there is no counterpart in the S.cerevisiae Prp24, carries seven tetratricopeptide repeat (TPR) domains. p110 homologs sharing the same domain structure also exist in several other eukaryotes. p110 is associated with the mammalian U6 and U4/U6 snRNPs, but not with U4/U5/U6 tri-snRNPs nor with spliceosomes. Recom binant p110 binds in vitro specifically to human U6 snRNA, requiring an internal U6 region. Using an in vitro recycling assay, we demonstrate that p110 functions in the reassembly of the U4/U6 snRNP. In summary, p110 represents the human ortholog of Prp24, and associates only transiently with U6 and U4/U6 snRNPs during the recycling phase of the spliceosome cycle.

Binding of a SART3 tumor-rejection antigen to a pre-mRNA splicing factor RNPS1: a possible regulation of splicing by a complex formation

We recently reported the identification of a human SART3 gene that encodes a tumor-rejection antigen recognized by cytotoxic T lymphocytes (CTLs). The squamous-cell carcinoma antigen recognized by T cells-3 (SART3) is an RNA-binding protein expressed in the nucleus of the majority of proliferating cells, including normal cells and malignant cells, but not in normal tissues except for the testes and fetal liver. To determine its biologic function, we employed a 2-hybrid screening in yeast for proteins interacting with SART3, and this method yielded a pre-mRNA splicing factor (RNA-binding protein prevalent during the S phase or RNA-binding protein with a serine-rich domain [RNPS1]) that activated both constitutive and alternative splicing of pre-mRNA in vitro. Interaction of SART3 with RNPS1 through the physical association of N-terminal domains of RNPS1 was confirmed by both in vitro pull-down assay and immunoprecipitation assay. Cotransfection of the 2 genes changed the distribution pattern of SART3 from diffuse nucleoplasmic spreading to nuclear speckled regions in which the RNPS1 was colocalized, suggesting a complex formation of the 2 proteins. In cooperation with RNPS1, SART3 stimulated the proximal alternative 3' splicing of a calcitonin-dihydrofolate reductase chimeric minigene pre-mRNA. These results suggest that SART3 is involved in the regulation of mRNA splicing probably via its complex formation with RNPS1.

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.