Induction of protective and therapeutic antitumor immunity by a DNA vaccine with a glioma antigen, SOX6

Advance of SOX Transcription Factors in Hepatocellular Carcinoma: From Role, Tumor Immune Relevance to Targeted Therapy

Simple Summary

Hepatocellular carcinoma (HCC) is one of the deadliest human health burdens worldwide. However, the molecular mechanism of HCC development is still not fully understood. Sex determining region Y-related high-mobility group box (SOX) transcription factors not only play pivotal roles in cell fate decisions during development but also participate in the initiation and progression of cancer. Given the significance of SOX factors in cancer and their ‘undruggable’ properties, we summarize the role and molecular mechanism of SOX family members in HCC and the regulatory effect of SOX factors in the tumor immune microenvironment (TIME) of various cancers. For the first time, we analyze the association between the levels of SOX factors and that of immune components in HCC, providing clues to the pivotal role of SOX factors in the TIME of HCC. We also discuss the opportunities and challenges of targeting SOX factors for cancer.

Abstract

Sex determining region Y (SRY)-related high-mobility group (HMG) box (SOX) factors belong to an evolutionarily conserved family of transcription factors that play essential roles in cell fate decisions involving numerous developmental processes. In recent years, the significance of SOX factors in the initiation and progression of cancers has been gradually revealed, and they act as potential therapeutic targets for cancer. However, the research involving SOX factors is still preliminary, given that their effects in some leading-edge fields such as tumor immune microenvironment (TIME) remain obscure. More importantly, as a class of ‘undruggable’ molecules, targeting SOX factors still face considerable challenges in achieving clinical translation. Here, we mainly focus on the roles and regulatory mechanisms of SOX family members in hepatocellular carcinoma (HCC), one of the fatal human health burdens worldwide. We then detail the role of SOX members in remodeling TIME and analyze the association between SOX members and immune components in HCC for the first time. In addition, we emphasize several alternative strategies involved in the translational advances of SOX members in cancer. Finally, we discuss the alternative strategies of targeting SOX family for cancer and propose the opportunities and challenges they face based on the current accumulated studies and our understanding.

The Role of Neurodevelopmental Pathways in Brain Tumors

Disruptions to developmental cell signaling pathways and transcriptional cascades have been implicated in tumor initiation, maintenance and progression. Resurgence of aberrant neurodevelopmental programs in the context of brain tumors highlights the numerous parallels that exist between developmental and oncologic mechanisms. A deeper understanding of how dysregulated developmental factors contribute to brain tumor oncogenesis and disease progression will help to identify potential therapeutic targets for these malignancies. In this review, we summarize the current literature concerning developmental signaling cascades and neurodevelopmentally-regulated transcriptional programs. We also examine their respective contributions towards tumor initiation, maintenance, and progression in both pediatric and adult brain tumors and highlight relevant differentiation therapies and putative candidates for prospective treatments.

The circRNA_102911/miR-129-5p/SOX6 axis is involved with T lymphocyte immune function in elderly patients with laparoscopic left hepatectomy for hepatolithiasis

The aim of the present study was to investigate the impact of laparoscopic left hepatectomy (LLH) for hepatolithiasis on the T lymphocyte immune changes of elderly patients and to analyze underlying mechanisms of action behind these changes. A total of 164 patients who underwent LLH due to left-sided hepatolithiasis were recruited. In terms of T lymphocyte immune changes, it was found that firstly, the basic quantity of peripheral lymphocytes in the elderly group was significantly lower than that in a younger preoperative group. Secondly, after surgical trauma, the immune function of T lymphocytes had a significant decline and lasted longer when compared with younger patients, which was reflected by the perioperative changes in the T lymphocyte proliferative ability, levels of IL-2 secreted by T lymphocytes and the percentage of CD3⁺/CD4⁺ T lymphocytes in the peripheral blood. Circular RNA (circRNA) 102911 (102911) was upregulated and microRNA (miR)-129-5p was downregulated in CD3⁺/CD4⁺ T lymphocytes from elderly patients with LLH for hepatolithiasis. Furthermore, the overexpression of 102911 inhibited the proliferation of CD3⁺/CD4⁺ T lymphocytes as well as promoting cell apoptosis, with the opposite effects being observed on knockdown of 102911. miR-129-5p is involved in the proliferation and apoptosis of CD3⁺/CD4⁺ T lymphocytes and may be a promising target of 102911. Moreover, SOX6 is a downstream molecule of miR-129-5p. Immune function and number of T lymphocytes decreased significantly after surgical trauma compared to younger patients, and this decline lasted longer in older patients treated with LLH for hepatolithiasis. The 102911/miR-129-5p/SOX6 axis was found to be involved in T lymphocytes immune function, which provided a novel insight for the treatment of elderly patients with hepatolithiasis.

SRY-related high-mobility-group box 6 suppresses cell proliferation and is downregulated in breast cancer

Breast cancer is one of the most common cancers endangering women's health. SRY-related high-mobility-group box 6 (SOX6) is associated with many cancers, though its role has not been reported in breast cancer. Here, we aimed to explore the expression and function of SOX6 in breast cancer. On the basis of the analysis of SOX6 in The Cancer Genome Atlas, Cancer Cell Line Encyclopedia and Genotype-Tissue Expression databases, we revealed that SOX6 was downregulated in breast cancer, and we verified the results at the cellular level by means of western blotting and quantitative real-time PCR. When SOX6 was overexpressed, the proliferation of breast cancer cells was inhibited, and apoptosis was promoted. Moreover, the methylation level of the SOX6 promoter in breast cancer was significantly higher than that in normal tissues. 5'-Aza-2'-deoxycytidine reversed the high level of methylation that was caused by decreased expression of SOX6. This evidence suggests that SOX6 is a tumor suppressor gene associated with breast cancer. This study could provide a new target for breast cancer treatment.

Novel role of the SRY-related high-mobility-group box D gene in cancer

The SRY-related high-mobility-group box (Sox) gene family encodes a set of transcription factors and is defined by the presence of highly conserved domains. The Sox gene can be divided into 10 groups (A-J). The SoxD subpopulation consists of Sox5, Sox6, Sox13 and Sox23, which are involved in the transcriptional regulation of developmental processes, including embryonic development, nerve growth and cartilage formation. Recently, the SoxD gene family was recognized as important transcriptional regulators associated with many types of cancer. In addition, Sox5 and Sox6 are representatives of the D subfamily, and there are many related studies; however, there are few reports on Sox13 and Sox23. In this review, we first introduce the structures of the SoxD genes. Next, we summarize the latest research progress on SoxD in various types of cancer. Finally, we discuss the potential direction of future SoxD research. In general, the information reviewed here may contribute to future experimental design and increase the potential of SoxD as a cancer treatment target.

The role of SOX family members in solid tumours and metastasis

Cancer is a heavy burden for humans across the world with high morbidity and mortality. Transcription factors including sex determining region Y (SRY)-related high-mobility group (HMG) box (SOX) proteins are thought to be involved in the regulation of specific biological processes. The deregulation of gene expression programs can lead to cancer development. Here, we review the role of the SOX family in breast cancer, prostate cancer, renal cell carcinoma, thyroid cancer, brain tumours, gastrointestinal and lung tumours as well as the entailing therapeutic implications. The SOX family consists of more than 20 members that mediate DNA binding by the HMG domain and have regulatory functions in development, cell-fate decision, and differentiation. SOX2, SOX4, SOX5, SOX8, SOX9, and SOX18 are up-regulated in different cancer types and have been found to be associated with poor prognosis, while the up-regulation of SOX11 and SOX30 appears to be favourable for the outcome in other cancer types. SOX2, SOX4, SOX5 and other SOX members are involved in tumorigenesis, e.g. SOX2 is markedly up-regulated in chemotherapy resistant cells. The SoxF family (SOX7, SOX17, SOX18) plays an important role in angio- and lymphangiogenesis, with SOX18 seemingly being an attractive target for anti-angiogenic therapy and the treatment of metastatic disease in cancer. In summary, SOX transcription factors play an important role in cancer progression, including tumorigenesis, changes in the tumour microenvironment, and metastasis. Certain SOX proteins are potential molecular markers for cancer prognosis and putative potential therapeutic targets, but further investigations are required to understand their physiological functions.

Expression of cancer/testis antigens is correlated with improved survival in glioblastoma

Background

Glioblastoma (GBM) confers a dismal prognosis despite advances in current therapy. Cancer-testis antigens (CTA) comprise families of tumor-associated antigens that are immunogenic in different cancers. The aim of this study was to determine the expression profile of a large number of CTA genes in GBM.

Methods

We selected, from 153 CTA genes, those genes potentially expressed in GBM. The expression pattern of 30 CTA was then evaluated by RT-PCR in a series of 48 GBM and 5 normal brain samples. The presence of CTCFL protein was also evaluated by immunohistochemical staining.

Results

Among the genes with no expression in normal brain, ACTL8 (57%), OIP5 (54%), XAGE3 (44%) and CTCFL (15%) were frequently expressed in GBM, while over 85% of the tumors expressed at least 1 of these four CTA. Coexpression of two or more CTA occurred in 49% of cases. CTCFL protein expression was detected in 13% of the GBM and was negative in normal brain samples. GBM expressing 3-4 CTA was associated with significantly better overall survival (OS) rates (P = 0.017). By multivariate analysis, mRNA positivity for 3-4 CTA (P = 0.044), radiotherapy (P = 0.010) and chemotherapy (P = 0.001) were independent prognostic factors for OS.

Conclusions

GBM frequently express ACTL8, OIP5, XAGE3 and CTCFL. A relatively high percentage of tumors expressed at least one of these four CTA, opening the perspective for their utility in antigen-specific immunotherapy. Furthermore, mRNA positivity for 3-4 CTA is an independent predictor of better OS for GBM patients.

Improvement of cancer immunotherapy by combining molecular targeted therapy

In human cancer cells, a constitutive activation of MAPK, STAT3, β-catenin, and various other signaling pathways triggers multiple immunosuppressive cascades. These cascades result in the production of immunosuppressive molecules (e.g., TGF-β, IL-10, IL-6, VEGF, and CCL2) and induction of immunosuppressive immune cells (e.g., regulatory T cells, tolerogenic dendritic cells, and myeloid-derived suppressor cells). Consequently, immunosuppressive conditions are formed in tumor-associated microenvironments, including the tumor and sentinel lymph nodes. Some of these cancer-derived cytokines and chemokines impair immune cells and render them immunosuppressive via the activation of signaling molecules, such as STAT3, in the immune cells. Thus, administration of signal inhibitors may inhibit the multiple immunosuppressive cascades by acting simultaneously on both cancer and immune cells at the key regulatory points in the cancer-immune network. Since common signaling pathways are involved in manifestation of several hallmarks of cancer, including cancer cell proliferation/survival, invasion/metastasis, and immunosuppression, targeting these shared signaling pathways in combination with immunotherapy may be a promising strategy for cancer treatment.

Glioma antigen

Because several antigenic peptides of human tumors that are recognized by T-lymphocytes have been identified, immune responses against cancer can now be artificially manipulated. Furthermore, since T-lymphocytes have been found to play an important role in the rejection of tumors by the host and also to have antigen-specific proliferative potentials and memory mechanisms, T-lymphocytes are thought to play a central role in cancer vaccination. Although multidisciplinary therapies have been attempted for the treatment of gliomas, the results remain unsatisfactory. For the development of new therapies against gliomas, it is required to identify tumor antigens as targets for specific immunotherapy. In this chapter, recent progress in research on glioma antigens is described.

CD4+ and CD8+ T cells can act separately in tumour rejection after immunization with murine pneumotropic virus chimeric Her2/neu virus-like particles

Background

Immunization with murine pneumotropic virus virus-like particles carrying Her2/neu (Her2MPtVLPs) prevents tumour outgrowth in mice when given prophylactically, and therapeutically if combined with the adjuvant CpG. We investigated which components of the immune system are involved in tumour rejection, and whether long-term immunological memory can be obtained.

Methodology and Results

During the effector phase in BALB/c mice, only depletion of CD4⁺ and CD8⁺ in combination, with or without NK cells, completely abrogated tumour protection. Depletion of single CD4⁺, CD8⁺ or NK cell populations only had minor effects. During the immunization/induction phase, combined depletion of CD4⁺ and CD8⁺ cells abolished protection, while depletion of each individual subset had no or negligible effect. When tumour rejection was studied in knock-out mice with a C57Bl/6 background, protection was lost in CD4^−/−CD8^−/− and CD4^−/−, but not in CD8^−/− mice. In contrast, when normal C57Bl/6 mice were depleted of different cell types, protection was lost irrespective of whether only CD4⁺, only CD8⁺, or CD4⁺ and CD8⁺ cells in combination were eradicated. No anti-Her2/neu antibodies were detected but a Her2/neu-specific IFNγ response was seen. Studies of long-term memory showed that BALB/c mice could be protected against tumour development when immunized together with CpG as long as ten weeks before challenge.

Conclusion

Her2MPtVLP immunization is efficient in stimulating several compartments of the immune system, and induces an efficient immune response including long-term memory. In addition, when depleting mice of isolated cellular compartments, tumour protection is not as efficiently abolished as when depleting several immune compartments together.

Identification of HLA-A2- and A24-restricted T-cell epitopes derived from SOX6 expressed in glioma stem cells for immunotherapy

Malignant gliomas are the most aggressive human primary brain tumors and are currently incurable. Immunotherapies have the potential to target glioma and glioma stem cells (GSCs) that are resistant to conventional therapies. We previously identified SOX6 as a human glioma antigen and demonstrated that vaccination with SOX6 DNA induced cytotoxic T lymphocytes (CTLs) specific for glioma, thereby exerting therapeutic antitumor responses in glioma-bearing mice. In this study, we attempted to identify SOX6-derived peptides as specific targets for effective and safe T-cell-mediated immunotherapy targeting SOX6-positive glioma and GSCs. In vitro stimulation with human leukocyte antigen (HLA)-A*2402 (A24)-restricted peptides, RFENLGPQL (SOX6(504)) and PYYEEQARL (SOX6(628)) or the HLA-A*0201 (A2)-restricted peptide, ALFGDQDTV (SOX6(447)) was capable of inducing SOX6 peptide-specific CTLs in peripheral blood mononuclear cells derived from healthy donors and glioma patients. These CTLs were able to lyse a majority of glioma cell lines and a GSC line derived from human glioblastoma in an HLA Class I-restricted and an antigen-dependent manner. Furthermore, peptide vaccines of SOX6(628), which was conserved in the murine SOX6 protein and expected to bind to major histocompatibility complex (MHC) H-2(d), induced CTLs specific for SOX6(628) in H-2(d) mice. Normal autologous cells from mice, in which SOX6-specific immune responses were generated, were not destroyed. These results suggest that these SOX6 peptides are potnetially immunogenic in HLA-A24 or -A2 positive glioma patients and should be considered as a promising strategy for safe and effective T-cell-based immunotherapy of patients with gliomas.

Systemic inhibition of transforming growth factor-beta in glioma-bearing mice improves the therapeutic efficacy of glioma-associated antigen peptide vaccines

PURPOSE

A variety of cancers, including malignant gliomas, overexpress transforming growth factor-beta (TGF-beta), which helps tumors evade effective immune surveillance through a variety of mechanisms, including inhibition of CD8(+) CTLs and enhancing the generation of regulatory T (T(reg)) cells. We hypothesized that inhibition of TGF-beta would improve the efficacy of vaccines targeting glioma-associated antigen (GAA)-derived CTL epitopes by reversal of immunosuppression.

EXPERIMENTAL DESIGN

Mice bearing orthotopic GL261 gliomas were treated systemically with a TGF-beta-neutralizing monoclonal antibody, 1D11, with or without s.c. vaccinations of synthetic peptides for GAA-derived CTL epitopes, GARC-1 (77-85) and EphA2 (671-679), emulsified in incomplete Freund's adjuvant.

RESULTS

Mice receiving the combination regimen exhibited significantly prolonged survival compared with mice receiving either 1D11 alone, GAA vaccines alone, or mock treatments alone. TGF-beta neutralization enhanced the systemic induction of antigen-specific CTLs in glioma-bearing mice. Flow cytometric analyses of brain-infiltrating lymphocytes revealed that 1D11 treatment suppressed phosphorylation of Smad2, increased GAA-reactive/IFN-gamma-producing CD8(+) T cells, and reduced CD4(+)/FoxP3(+) T(reg) cells in the glioma microenvironment. Neutralization of TGF-beta also upregulated plasma levels of interleukin-12, macrophage inflammatory protein-1 alpha, and IFN-inducible protein-10, suggesting a systemic promotion of type-1 cytokine/chemokine production. Furthermore, 1D11 treatment upregulated plasma interleukin-15 levels and promoted the persistence of GAA-reactive CD8(+) T cells in glioma-bearing mice.

CONCLUSIONS

These data suggest that systemic inhibition of TGF-beta by 1D11 can reverse the suppressive immunologic environment of orthotopic tumor-bearing mice both systemically and locally, thereby enhancing the therapeutic efficacy of GAA vaccines.

Immunotherapeutic approaches for glioma

The development of effective immunotherapy strategies for glioma requires adequate understanding of the unique immunological microenvironment in the central nervous system (CNS) and CNS tumors. Although the CNS is often considered to be an immunologically privileged site and poses unique challenges for the delivery of effector cells and molecules, recent advances in technology and discoveries in CNS immunology suggest novel mechanisms that may significantly improve the efficacy of immunotherapy against gliomas. In this review, we first summarize recent advances in the CNS and CNS tumor immunology. We address factors that may promote immune escape of gliomas. We also review advances in passive and active immunotherapy strategies for glioma, with an emphasis on lessons learned from recent early-phase clinical trials. We also discuss novel immunotherapy strategies that have been recently tested in non-CNS tumors and show great potential for application to gliomas. Finally, we discuss how each of these promising strategies can be combined to achieve clinical benefit for patients with gliomas.