B7-H3 targeted antibody-based immunotherapy of malignant diseases

The AURKA inhibitor alters the immune microenvironment and enhances targeting B7-H3 immunotherapy in glioblastoma

Glioblastoma (GBM) is one of the most lethal adult brain tumors with limited effective therapeutic options. Immunotherapy targeting B7-H3 (CD276) has shown promising efficacy in the treatment of gliomas. However, the response to this treatment varies among glioma patients due to individual differences. It's necessary to find an effective strategy to improve the efficacy of targeting B7-H3 immunotherapy for nonresponders. In this study, we demonstrated a strong correlation between aurora kinase A (AURKA) and CD276 expression in glioma tissue samples. Additionally, both AURKA knockdown and overexpression resulted in parallel changes in B7-H3 expression levels in glioma cells. Mechanistically, AURKA elevated B7-H3 expression by promoting epidermal growth factor receptor (EGFR) phosphorylation, which was validated in glioma cell lines and primary GBM cells. What's more, the combination of AURKA inhibitor (alisertib) and anti-B7-H3 antibody markedly reduced tumor size and promoted CD8+ T cell infiltration and activation in mouse orthotopic syngeneic glioma models. To our knowledge, this study is the first to demonstrate AURKA-mediated B7-H3 upregulation in glioma cells; moreover, it proposes a promising therapeutic strategy combining the AURKA inhibitor alisertib with B7-H3-specific blocking mAbs.

TBK1 Targeting Is Identified as a Therapeutic Strategy to Enhance CAR T-Cell Efficacy Using Patient-Derived Organotypic Tumor Spheroids

Novel therapeutic strategies are needed to improve the efficacy of chimeric antigen receptor (CAR) T cells as a treatment of solid tumors. Multiple tumor microenvironmental factors are thought to contribute to resistance to CAR T-cell therapy in solid tumors, and appropriate model systems to identify and examine these factors using clinically relevant biospecimens are limited. In this study, we examined the activity of B7-H3-directed CAR T cells (B7-H3.CAR-T) using 3D microfluidic cultures of patient-derived organotypic tumor spheroids (PDOTS) and then confirmed the activity of B7-H3.CAR T cells in PDOTS. Although B7-H3 expression in PDOTS was associated with B7-H3.CAR-T sensitivity, mechanistic studies revealed dynamic upregulation of co-inhibitory receptors on CAR T-cells following target cell encounter that led to CAR T-cell dysfunction and limited efficacy against B7-H3-expressing tumors. PD-1 blockade restored CAR T-cell activity in monotypic and organotypic tumor spheroids with improved tumor control and upregulation of effector cytokines. Given the emerging role of TANK-binding kinase 1 (TBK1) as an immune evasion gene, we examined the effect of TBK1 inhibition on CAR T-cell efficacy. Similar to PD-1 blockade, TBK1 inhibition restored CAR T-cell activity in monotypic and organotypic tumor spheroids, prevented CAR T-cell dysfunction, and enhanced CAR T-cell proliferation. Inhibition or deletion of TBK1 also enhanced the sensitivity of cancer cells to immune-mediated killing. Taken together, our results demonstrate the feasibility and utility of ex vivo profiling of CAR T cells using PDOTS and suggest that targeting TBK1 could be used to enhance CAR T-cell efficacy by overcoming tumor-intrinsic and -extrinsic resistance mechanisms.

B7-H3 CAR-T cell therapy combined with irradiation is effective in targeting bulk and radiation-resistant chordoma cancer cells

BACKGROUND

Chordoma is a slow-growing, primary malignant bone tumor that arises from notochordal tissue in the midline of the axial skeleton. Surgical excision with negative margins is the mainstay of treatment, but high local recurrence rates are reported even with negative margins. High-dose radiation therapy (RT), such as with proton or carbon ions, has been used as an alternative to surgery, but late local failure remains a problem. B7-H3 is an immune checkpoint, transmembrane protein that is dysregulated in many cancers, including chordoma. This study explores the efficacy of B7-H3 chimeric antigen receptor T (CAR-T) therapy in vitro and in vivo.

METHODS

Chordoma cancer stem cells (CCSCs) were identified using flow cytometry, sphere formation, and western blot analysis. The expression of B7-H3 in paraffin-embedded chordoma tissue was determined by immunohistochemical staining, and the expression of B7-H3 in chordoma cells was measured by flow cytometry. Retroviral particles containing either B7-H3 or CD19 CAR-expressing virus were transduced into T cells derived from peripheral blood mononuclear cells isolated from healthy human donor blood to prepare CAR-T cells. Animal bioluminescent imaging was used to evaluate the killing effect of CAR-T cells on chordoma cells in vivo. An irradiator was used for all irradiation (IR) experiments.

RESULTS

The combination of B7-H3 CAR-T cell therapy and IR has a greater killing effect on killing radiation-resistant CCSCs and bulk chordoma cells compared with CAR-T cell or IR monotherapy. Additionally, increased expression of B7-H3 antigens on CCSCs and bulk tumor cells is associated with enhanced CAR-T cell killing in vitro and in vivo xenograft mouse models. Upregulation of B7-H3 expression by IR increases CCSCs sensitivity to B7-H3 CAR-T cell-mediated killing.

CONCLUSIONS

Our preliminary data show that IR and B7-H3 CAR-T cell therapy is synergistically more effective than either IR or CAR-T cell monotherapy in killing chordoma cells in vitro and in a xenograft mouse model. These results provide preclinical evidence for further developing this combinatorial RT and B7-H3 CAR-T cell therapy model in chordoma.

Emerging druggable targets for immune checkpoint modulation in cancer immunotherapy: the iceberg lies beneath the surface

The immune system serves as a fundamental defender against the initiation and progression of cancer. Failure of the immune system augments immunosuppressive action that leading to cancer manifestation. This immunosuppressive effect causes from significant alterations in immune checkpoint expression associated with tumoral progression. The tumor microenvironment promotes immune escape mechanisms that further amplifying immunosuppressive actions. Notably, substantial targeting of immune checkpoints has been pragmatic in the advancement of cancer research. This study highlights a comprehensive review of emerging druggable targets aimed at modulating immune checkpoint co-inhibitory as well as co-stimulatory molecules in response to immune system activation. This modulation has prompted to the development of newer therapeutic insights, eventually inducing immunogenic cell death through immunomodulatory actions. The study emphasizes the role of immune checkpoints in immunogenic regulation of cancer pathogenesis and explores potential therapeutic avenues in cancer immunotherapy.Modulation of Immunosuppressive and Immunostimulatory pathways of immune checkpoints in cancer immunotherapy.

Engineered oncolytic virus expressing B7H3-targeting BiTE enhances antitumor T-cell immune response

BACKGROUND

Bispecific T-cell engagers (BiTEs) are recombinant bispecific proteins designed to stimulate polyclonal T-cell immunity. In recent years, B7H3, a pan-cancer antigen, has been considered a promising target for future immunotherapy. However, the B7H3-targeting BiTE faces the challenge of systemic toxicity. Oncolytic viruses (OVs) represent a new class of cancer immunotherapeutics and serve as an appropriate platform for locoregional delivery of therapeutic genes. In this study, we designed an oncolytic adenovirus (OAd) encoding BiTE targeting human B7H3. We hypothesized that OVs encoding B7H3 BiTE deliver this molecule persistently to the tumor site while mediating polyclonal T-cell activation and redirecting it to tumor cells.

METHODS

B7H3-targeting BiTE was constructed by linking a single-chain variable fragment (scFv) that recognizes human B7H3 to an scFv that recognizes human CD3. B7H3 BiTE was inserted into OAd to construct OAd-B7H3-BiTE. The function of the OV-delivered B7H3 BiTE was detected via co-culturing B7H3+ target cells and peripheral blood mononuclear cells. A humanized immune system mouse model was used to evaluate the therapeutic effects in vivo.

RESULTS

B7H3 is highly expressed in a high proportion of human malignancies. OV-delivered BiTEs bind to T cells and target cells. We observed a series of phenomena reflecting T-cell activation induced by OAd-B7H3-BiTE, including cell clustering, cell size, activation markers, cytokine secretion, and proliferation. Furthermore, T-cell activation was mirrored by the corresponding cytotoxicity against B7H3+ tumor cells. In vivo, B7H3 BiTE was persistently expressed in tumors and enhanced the antitumor T-cell immune response.

CONCLUSIONS

Using an OV for the local expression of B7H3 BiTE maximizes the local concentration of BiTE while reducing systemic exposure. OV also provides a relatively "hot" T-cell immune environment for the function of BiTE. Because of its capacity to activate polyclonal T cells, BiTE has the potential to redirect virus-specific T cells to tumors. Our study provides new opportunities for the exploitation of B7H3-BiTE-armed OVs as therapeutic agents for the treatment of B7H3-positive malignancies.

B7-H3 in acute myeloid leukemia: From prognostic biomarker to immunotherapeutic target

ABSTRACT

B7-H3 (CD276), an immune checkpoint protein of the B7 family, exhibits significant upregulation in solid tumors and hematologic malignancies, exerting a crucial role in their pathophysiology. The distinct differential expression of B7-H3 between tumors and normal tissues and its multifaceted involvement in tumor pathogenesis position it as a promising therapeutic target for tumors. In the context of acute myeloid leukemia (AML), B7-H3 is prominently overexpressed and closely associated with unfavorable prognoses, yet it has remained understudied. Despite various ongoing clinical trials demonstrating the potential efficacy of immunotherapies targeting B7-H3, the precise underlying mechanisms responsible for B7-H3-mediated proliferation and immune evasion in AML remain enigmatic. In view of this, we comprehensively outline the current research progress concerning B7-H3 in AML, encompassing in-depth discussions on its structural attributes, receptor interactions, expression profiles, and biological significance in normal tissues and AML. Moreover, we delve into the protumor effects of B7-H3 in AML, examine the intricate mechanisms that underlie its function, and discuss the emerging application of B7-H3-targeted therapy in AML treatment. By juxtaposing B7-H3 with other molecules within the B7 family, this review emphasizes the distinctive advantages of B7-H3, not only as a valuable prognostic biomarker but also as a highly promising immunotherapeutic target in AML.

Interleukin-7 expression by CAR-T cells improves CAR-T cell survival and efficacy in chordoma

Chordoma is a rare bone tumor that frequently recurs after surgery, and the prognosis is poor with current treatments. This study aimed to identify potential novel immunotherapeutic targets for chordomas by identifying target proteins in clinical samples as well as tumor microenvironmental factors to enhance efficacy. Fourteen chordoma samples were analyzed by single-cell RNA sequencing, and B7-H3 and IL-7 were identified as potential targets and potentiators, respectively. B7-H3-targeted chimeric antigen receptor T (CAR-T) cells and B7-H3 CAR-T cells expressing IL-7 were synthesized and their anti-tumor activity evaluated in vitro, including in primary chordoma organoid models. The B7-H3 CAR-T/IL-7 therapy showed enhanced cytotoxicity and prolonged duration of action against tumor cells. Additionally, IL-7 modulated favorable subpopulations of cultured CAR-T cells, diminished immune checkpoint expression on T-cell surfaces, and enhanced T-cell functionality. The incorporation of IL-7 molecules into the B7-H3 CAR structure augmented CAR-T-cell function and improved CAR-T-cell efficacy, thus providing a novel dual therapeutic strategy for chordoma treatment.

Expression and Prognostic Value of a Novel B7-H3 (CD276) Antibody in Acute Myeloid Leukemia

Despite recent advances in immunophenotyping, the prognosis of acute myeloid leukemia (AML) is still mainly estimated using age and genetic markers. As the genetic heterogeneity of AML patients is high, flow cytometry-based classification with appropriate biomarkers can efficiently complement risk stratification and treatment selection. An increased expression of B7-H3 (CD276), an immune checkpoint protein, has been reported and associated with poor prognosis. However, the available data are limited and heterogeneous. Here, we used a novel, proprietary murine anti-B7-H3 8H8 antibody for the flow cytometric analysis of B7-H3 expression in AML blasts from 77 patients. Our antibody reliably detected substantial B7-H3 expression in 62.3% of AML patients. B7-H3 expression was higher in the monocytic French-American-British (FAB) M5 group and in intermediate and poor risk patients according to the European Leukemia Network. Using receiver operating characteristics (ROCs), we identified a specific fluorescence intensity cut-off of 4.45 to discriminate between B7-H3high and B7-H3low expression. High B7-H3 expression was associated with shorter overall survival (OS) and progression-free survival (PFS). In conclusion, we have developed a novel B7-H3 antibody that serves as a new tool for the detection of B7-H3 expression in AML and may help to facilitate risk stratification and treatment selection in AML patients.

Non-immune functions of B7-H3: bridging tumor cells and the tumor vasculature

B7-H3 (CD276), an immune checkpoint molecule, is overexpressed in various types of cancer and their tumor vasculature, demonstrating significant associations with adverse clinical outcomes. In addition to its well-known immune functions, B7-H3 exhibits dual co-stimulatory/co-inhibitory roles in normal physiology and the tumor microenvironment. The non-immune functions of B7-H3 in tumor cells and the tumor vasculature, including promoting tumor cell anti-apoptosis, proliferation, invasion, migration, drug resistance, radioresistance, as well as affecting cellular metabolism and angiogenesis, have increasingly gained attention from researchers. Particularly, the co-expression of B7-H3 in both tumor cells and tumor endothelial cells highlights the higher potential and clinical utility of therapeutic strategies targeting B7-H3. This review aims to summarize the recent advances in understanding the non-immune functions of B7-H3 in tumors and provide insights into therapeutic approaches targeting B7-H3, focusing on its co-expression in tumor cells and endothelial cells. The aim is to establish a theoretical foundation and practical reference for the development and optimization of B7-H3-targeted therapies.

The Comprehensive Characterization of B7-H3 Expression in the Tumor Microenvironment of Lung Squamous Cell Carcinoma: A Retrospective Study

Lung squamous cell carcinoma (LSCC) is refractory to various therapies for non-small cell cancer; therefore, new therapeutic approaches are required to improve the prognosis of LSCC. Although immunotherapies targeting B7 family molecules were explored as treatments for several cancer types, the expression and significance of B7-H3 in the tumor microenvironment (TME) and its relationship with other immune checkpoint molecules have not yet been investigated in detail. We used high-throughput quantitative multiplex immunohistochemistry to examine B7-H3 expression in the TME. We investigated the relationship between B7-H3 expression and prognosis as well as changes in the TME with B7-H3 expression using 110 surgically resected pathological specimens retrospectively. We examined the correlation between B7-H3 and programmed cell death-ligand 1 (PD-L1) expression in single cells. High B7-H3 expression in tumor cells was associated with a better prognosis and a significant increase in the number of CD163+PD-L1+ macrophages. Quantitative analysis revealed that there is a positive correlation between B7-H3 and PD-L1 expression in tumor and stromal cells, as well as in intratumoral tumor-infiltrating lymphocytes and tumor-associated macrophages in the same cells. CD68+, CD163+, and CK+ cells with PD-L1+ phenotypes had higher B7-H3 expression compared to PD-L1- cells. Our findings demonstrate a correlation between B7-H3 and PD-L1 expression in the same cells, indicating that therapies targeting B7-H3 could provide additional efficacy in patients refractory to PD-L1-targeting therapies.

Fully human anti-B7-H3 recombinant antibodies inhibited tumor growth by increasing T cell infiltration

Mortality due to malignant tumors is one of the major factors affecting the life expectancy of the global population. Therapeutic antibodies are a cutting-edge treatment method for restricting tumor growth. B7-H3 is highly expressed in tumor tissues, but rarely in normal tissues. B7-H3 is closely associated with poor prognosis in patients with tumors. B7-H3 is an important target for antitumor therapy. In this study, the fully human anti-B7H3 single-chain antibodies (scFvs) were isolated and screened from the fully human phage immune library with B7H3 as the target. The antibodies screened from a fully human phage library had low immunogenicity and high affinity, which was more beneficial for clinical application. Leveraging B7-H3 scFvs as a foundation, we constructed two distinct recombinant antibody formats, scFv-Fc and IgG1, characterized by elevated affinity and a prolonged half-life. The results demonstrated that the recombinant antibodies had high specificity and affinity for the B7-H3 antigen and inhibited tumor cell growth by enhancing the ADCC. After treatment with anti-B7H3 recombinant antibody, the number of infiltrating T cells in the tumor increased and the secretion of IFN- γ by infiltrating T cells increased in vivo. Additionally, the use of pleural fluid samples obtained from tumor-afflicted patients revealed the ability of anti-B7-H3 recombinant antibodies to reverse CD8+ T cell exhaustion. In summary, we screened the fully human anti-B7H3 recombinant antibodies with specificity and high affinity that increase immune cell infiltration and IFN-γ secretion, thereby inhibiting tumor cell growth to a certain extent. This finding provides a theoretical basis for the development of therapeutic tumor antibodies and could help promote further development of antibody-based drugs.

Improved antitumor effects elicited by an oncolytic HSV-1 expressing a novel B7H3nb/CD3 BsAb

Oncolytic viruses have emerged as a promising modality for cancer treatment due to their unique abilities to directly destroy tumor cells and modulate the tumor microenvironment. Bispecific T-cell engagers (BsAbs) have been developed to activate and redirect cytotoxic T lymphocytes, enhancing the antitumor response. To take advantage of the specific infection capacity and carrying ability of exogenous genes, we generated a recombinant herpes simplex virus type 1 (HSV-1), HSV-1dko-B7H3nb/CD3 or HSV-1dko-B7H3nb/mCD3, carrying a B7H3nb/CD3 or B7H3nb/mCD3 BsAb that replicates and expresses BsAb in tumor cells in vitro and in vivo. The new generation of oncolytic viruses has been genetically modified using CRISPR/Cas9 technology and the cre-loxp system to increase the efficiency of HSV genome editing. Additionally, we used two fully immunocompetent models (GL261 and MC38) to assess the antitumor effect of HSV-1dko-B7H3nb/mCD3. Compared with the HSV-1dko control virus, HSV-1dko-B7H3nb/mCD3 induced enhanced anti-tumor immune responses and T-cell infiltration in both GL261 and MC38 models, resulting in improved treatment efficacy in the latter. Furthermore, flow cytometry analysis of the tumor microenvironment confirmed an increase in NK cells and effector CD8+ T cells, and a decrease in immunosuppressive cells, including FOXP3+ regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and CD206+ macrophages (M2). Overall, our study identified a novel camel B7H3 nanobody and described the genetic modification of the HSV-1 genome using CRISPR/Cas9 technology and the cre-loxp system. Our findings indicate that expressing B7H3nb/CD3 BsAb could improve the antitumor effects of HSV-1 based oncolytic virus.

Development of a Human B7-H3-Specific Antibody with Activity against Colorectal Cancer Cells through a Synthetic Nanobody Library

Nanobodies have emerged as promising tools in biomedicine due to their single-chain structure and inherent stability. They generally have convex paratopes, which potentially prefer different epitope sites in an antigen compared to traditional antibodies. In this study, a synthetic phage display nanobody library was constructed and used to identify nanobodies targeting a tumor-associated antigen, the human B7-H3 protein. Combining next-generation sequencing and single-clone validation, two nanobodies were identified to specifically bind B7-H3 with medium nanomolar affinities. Further characterization revealed that these two clones targeted a different epitope compared to known B7-H3-specific antibodies, which have been explored in clinical trials. Furthermore, one of the clones, dubbed as A6, exhibited potent antibody-dependent cell-mediated cytotoxicity (ADCC) against a colorectal cancer cell line with an EC50 of 0.67 nM, upon conversion to an Fc-enhanced IgG format. These findings underscore a cost-effective strategy that bypasses the lengthy immunization process, offering potential rapid access to nanobodies targeting unexplored antigenic sites.

Interplay between B7-H3 and HLA class I in the clinical course of pancreatic ductal adenocarcinoma

Human leukocyte antigen (HLA) class I defects are associated with cancer progression. However, their prognostic significance is controversial and may be modulated by immune checkpoints. Here, we investigated whether the checkpoint B7-H3 modulates the relationship between HLA class I and pancreatic ductal adenocarcinoma (PDAC) prognosis. PDAC tumors were analyzed for the expression of B7-H3, HLA class I, HLA class II molecules, and for the presence of tumor-infiltrating immune cells. We observed defective HLA class I and HLA class II expressions in 75% and 59% of PDAC samples, respectively. HLA class I and B7-H3 expression were positively related at mRNA and protein level, potentially because of shared regulation by RELA, a sub-unit of NF-kB. High B7-H3 expression and low CD8+ T cell density were indicators of poor survival, while HLA class I was not. Defective HLA class I expression was associated with unfavorable survival only in patients with low B7-H3 expression. Favorable survival was observed only when HLA class I expression was high and B7-H3 expression low. Our results provide the rationale for targeting B7-H3 in patients with PDAC tumors displaying high HLA class I levels.

Efficacy of the induced pluripotent stem cell derived and engineered CD276-targeted CAR-NK cells against human esophageal squamous cell carcinoma

Introduction

Chimeric antigen receptor natural killer (CAR-NK) cells have been found to be successful in treating hematologic malignancies and present potential for usage in solid tumors.

Methods

In this study, we created CD276-targeted CAR-expressing NK cells from pluripotent stem cells (iPSC CD276-targeted CAR-NK cells) and evaluated their cytotoxicity against esophageal squamous cell carcinoma (ESCC) using patient-specific organoid (PSO) models comprising of both CD276-positive and CD276-negative adjacent epithelium PSO models (normal control PSO, NC PSO) as well as primary culture of ESCC cell models. In addition, in vitro and in vivo models such as KYSE-150 were also examined. iPSC NK cells and NK-free media were used as the CAR-free and NK-free controls, respectively.

Results

The positive CD276 staining was specifically detected on the ESCC membrane in 51.43% (54/105) of the patients of all stages, and in 51.35% (38/74) of stages III and IV. The iPS CD276-targeted CAR-NK cells, comparing with the iPS NK cells and the NK-free medium, exhibited specific and significant cytotoxic activity against CD276-positive ESCC PSO rather than CD276-negative NC PSO, and exhibited significant cytotoxicity against CD276-expressing cultured ESCC cells, as well as against CD276-expressing KYSE-150 in vitro and in BNDG mouse xenograft.

Discussion

The efficacy of the iPSC CD276-targeted CAR-NK cells demonstrated by their successful treatment of CD276-expressing ESCC in a multitude of pre-clinical models implied that they hold tremendous therapeutic potential for treating patients with CD276-expressing ESCC.

B7-H3/CD276 and small-cell lung cancer: What's new?

Immunotherapy revolutionized the treatment landscape of several cancers, including small-cell lung cancer (SCLC), with a huge number of practice-changing trials, and becoming a new frontier for their management. The addition of an anti-PD-L1, atezolizumab or durvalumab, to platinum/etoposide regimen became the standard of care for first-line therapy of extensive-stage (ES)-SCLC with the 12 months median survival exceeded for the first time. Nevertheless, most patients show primary or acquired resistance to anti-PD-L1 therefore new promising therapeutic immune-targets are under clinical investigation in several solid tumors. Among these, B7-H3, also known as CD276, is a member of the B7 family overexpressed in tumor tissues, including SCLC, while showing limited expression in normal tissues becoming an attractive and promising target for cancer immunotherapy. B7-H3 plays a dual role in the immune system during the T-cell activation, acting as a T-cell costimulatory/coinhibitory immunoregulatory protein, and promoting pro-tumorigenic functions such as tumor migration, invasion, metastases, resistance, and metabolism. Immunohistochemistry, flow cytometry, and immunofluorescence were the most used methods to assess B7-H3 expression levels and validate a possible relationship between B7-H3 staining patterns and clinicopathological features in lung cancer patients. To date, there are no clinically available therapeutics/drugs targeting B7-H3 in any solid tumors. The most promising preliminary clinical results have been reported by DS7300a and HS-20093, both are antibody-drug conjugates, that are under investigation in ongoing trials for the treatment of pretreated SCLC. This review will provide an overview of B7-H3 and corresponding inhibitors and the clinical development in the management of SCLC.

Alternative immune checkpoints in immunoregulatory profile of cancer stem cells

Tumor-mediated bypass of immune checkpoint inhibitor (ICI) therapy with anti-programmed death-1 (PD-1), anti-programmed death-ligand 1 (PD-L1, also called B7-H1 or CD274) or anti-cytotoxic T lymphocyte associated antigen-4 (CTLA-4) is a challenge of current years in the area of cancer immunotherapy. Alternative immune checkpoints (AICs) are molecules beyond the common PD-1, PD-L1 or CTLA-4, and are upregulated in patients who show low/no ICI responses. These are members of B7 family including B7-H2 (ICOS-L), B7-H3 (CD276), B7-H4 (B7x), V-domain immunoglobulin suppressor of T cell activation (VISTA), B7-H6, HHLA2 (B7-H5/B7-H7) and catabolic enzymes like indoleamine 2,3-dioxygenase 1 (IDO1), and others that are also contributed to the regulation of tumor immune microenvironment (TIME). There is also strong evidence supporting the implication of AICs in regulation of cancer stemness and expanding the population of cancer stem cells (CSCs). CSCs display immunoregulatory capacity and represent multiple immune checkpoints either on their surface or inside. Besides, they are active promoters of resistance to the common ICIs. The aim of this review is to investigate interrelations between AICs with stemness and differentiation profile of cancer. The key message of this paper is that targeted checkpoints can be selected based on their impact on CSCs along with their effect on immune cells. Studies published so far mainly focused on immune cells as a target for anti-checkpoints. Ex vivo engineering of extracellular vesicles (EVs) equipped with CSC-targeted anti-checkpoint antibodies is without a doubt a key therapeutic target that can be under consideration in future research.

Development of a MMAE-based antibody-drug conjugate targeting B7-H3 for glioblastoma

B7-H3 (immunoregulatory protein B7-homologue 3) is overexpressed in many cancer cells with limited expression in normal tissues, considered to be a promising target for tumor therapeutics. Clinical trials of antibody-drug conjugates (ADCs) against different targets for glioblastoma have been investigated and showed potent efficacies. In this study, we developed a homogeneous ADC 401-4 with a drug-to-antibody ratio (DAR) of 4, which was prepared by conjugation of Monomethyl auristatin E (MMAE) to a humanized anti-B7-H3 mAb 401, through a divinylsulfonamide-mediated disulfide re-bridging approach. In vitro studies, 401-4 displayed specific killing against B7-H3-expressing tumors and was more effective in cells with higher levels of B7-H3 for different glioblastoma cells. 401-4 was furthered labeled with Cy5.5 to yield a fluorescent conjugate 401-4-Cy5.5. The in vivo imaging studies showed that the conjugate accumulated in tumor regions and exhibited the ability to target-specific delivery. In addition, significant antitumor activities for 401-4 was observed against U87-derived tumor xenografts in a dose dependent manner.

Computational and Experimental Evaluation of Linker Peptides and Thioredoxin Fusion Tag in CD20-rituximab Specific Interactions

Background

Overexpression of CD20 protein on the surface of B cells in lymphoma can be targeted by several anti-CD20 molecules. The development of accessible interactive epitopes is more favorable than the full-length transmembrane CD20 in the affinity assessment of anti-CD20 monoclonal antibodies (mAbs).

Methods

The sequence of these epitopes was extracted, and the effects of different linker peptides and the location of histidine (His)-tag were computationally analyzed. The impact of thioredoxin (Trx)-tag on the folding of the selected construct and its interaction with rituximab was further investigated. The two final expression cassettes were expressed in Escherichia coli after optimization of culture conditions for incubation temperature, post-induction time, optical density at the induction time, and concentration of the inducer. ELISA evaluated the binding affinity of rituximab towards the recombinant proteins.

Results

By homology modeling studies, C-terminal His-tagged structures represented more desirable folded structures. Validation of the models revealed that CD20 extracellular domain linked by the G₄S polypeptide had better stereochemical quality and structural compatibility. It was selected due to its more effective interaction with rituximab showing the highest dissociation constant of 5.8E-09M, which improved after the fusion of Trx-tag (7.1E-10M). The most influential parameters in the expression of the two selected proteins were post-induction temperature and optical density at the induction time. Homemade ELISA assays revealed a slightly higher affinity of rituximab towards the Trx-CD20 protein than the CD20/G₄S molecule.

Conclusions

Experimental in vitro studies confirmed the computationally calculated affinity of rituximab towards the two designed CD20 constructs. Also, the cell-based binding assessment of anti-CD20 mAbs could be substituted by the engineered extracellular domain of human CD20 protein.

One Step Nucleic Acid Amplification (OSNA) Lysate Samples Are Suitable to Establish a Transcriptional Metastatic Signature in Patients with Early Stage Hormone Receptors-Positive Breast Cancer

The One Step Nucleic Acid Amplification (OSNA) is being adopted worldwide for sentinel lymph nodes (SLNs) staging in breast cancer (BC). As major disadvantage, OSNA precludes prognostic information based on structural evaluation of SLNs. Our aim is to identify biomarkers related to tumor-microenvironment interplay exploring gene expression data from the OSNA remaining lysate. This study included 32 patients with early stage hormone receptors-positive BC. Remaining OSNA lysates were prepared for targeted RNA-sequencing analysis. Identification of differentially expressed genes (DEGs) was performed by DESeq2 in R and data analysis in STATA. The results show that, in metastatic SLNs, several genes were upregulated: KRT7, VTCN1, CD44, GATA3, ALOX15B, RORC, NECTIN2, LRG1, CD276, FOXM1 and IGF1R. Hierarchical clustering analysis revealed three different clusters. The identified DEGs codify proteins mainly involved in cancer aggressiveness and with impact in immune response. The overexpression of the immune suppressive genes VTCN1 and CD276 may explain that no direct evidence of activation of immune response in metastatic SLNs was found. We show that OSNA results may be improved incorporating microenvironment-related biomarkers that may be useful in the future for prognosis stratification and immunotherapy selection. As OSNA assay is being implemented for SLNs staging in other cancers, this approach could also have a wider utility.

The Heterogeneity of Immune Cell Infiltration Landscape and Its Immunotherapeutic Implications in Hepatocellular Carcinoma

Immunotherapy, closely associated with immune infiltration and tumor mutation burden (TMB), is emerging as a promising strategy for treating tumors, but its low response rate in hepatocellular carcinoma (HCC) remains a major challenge. Herein, we applied two algorithms to uncover the immune infiltration landscape of the immune microenvironment in 491 HCC patients. Three immune infiltration patterns were defined using the CIBERSORT method, and the immune cell infiltration (ICI) scores were established using principal component analysis. In the high ICI score group, the activation of the Wnt/β-catenin pathway was significantly enriched and expressions of immune checkpoint genes increased, which showed a pessimistic outcome. The low ICI score group was characterized by increased TMB and enrichment of metabolism-related pathways. Further analysis found that the ICI score exhibited a significant difference in age ≥65/age <65, grade I/grade II–IV, and response to immunotherapy. Moreover, the CTNNB1 mutation status was found to be closely associated with prognosis and immunotherapeutic efficiency, significantly affecting the ICI score and TMB, which might be regarded as a potential marker for the treatment of HCC. The evaluation of immune infiltration patterns can improve the understanding of the tumor immune microenvironment and provide new directions for the study of individualized immunotherapy strategies for HCC.

Canine Melanoma Immunology and Immunotherapy: Relevance of Translational Research

In veterinary oncology, canine melanoma is still a fatal disease for which innovative and long-lasting curative treatments are urgently required. Considering the similarities between canine and human melanoma and the clinical revolution that immunotherapy has instigated in the treatment of human melanoma patients, special attention must be paid to advancements in tumor immunology research in the veterinary field. Herein, we aim to discuss the most relevant knowledge on the immune landscape of canine melanoma and the most promising immunotherapeutic approaches under investigation. Particular attention will be dedicated to anti-cancer vaccination, and, especially, to the encouraging clinical results that we have obtained with DNA vaccines directed against chondroitin sulfate proteoglycan 4 (CSPG4), which is an appealing tumor-associated antigen with a key oncogenic role in both canine and human melanoma. In parallel with advances in therapeutic options, progress in the identification of easily accessible biomarkers to improve the diagnosis and the prognosis of melanoma should be sought, with circulating small extracellular vesicles emerging as strategically relevant players. Translational advances in melanoma management, whether achieved in the human or veterinary fields, may drive improvements with mutual clinical benefits for both human and canine patients; this is where the strength of comparative oncology lies.

LINC01123 promotes immune escape by sponging miR-214-3p to regulate B7-H3 in head and neck squamous-cell carcinoma

Numerous studies have shown that long noncoding RNAs (LncRNAs) are involved in the development and immune escape of head and neck squamous-cell carcinoma (HNSCC). However, the specific regulatory mechanisms by which LINC01123 regulates HNSCC and its correlation with immunity remain unclear. Therefore, this study’s primary purpose was to explore the mechanisms by which LINC01123 regulates the immune escape and progression of HNSCC. This study confirmed that LINC01123 is competitively bound to miR-214-3p, and miR-214-3p specifically targets B7–H3. The effects of LINC01123, B7–H3, and miR-214-3p on tumor progression, CD8⁺T-cell-mediated immune response, and the tumorigenicity of HNSCC in vitro and in vivo were examined through the downregulation or upregulation of LINC01123, B7–H3, and miR-214-3p. Our results indicated that LINC01123 and B7–H3 were highly expressed in HNSCC and are associated with poor prognosis in patients. Notably, overexpression of LINC01123 or B7–H3 or downregulation of miR-214-3p inhibited the function of CD8⁺T cells and promoted the progression of HNSCC. Therefore, LINC01123 acts as a miR-214-3p sponge to inhibit the activation of CD8⁺T cells and promote the progression of HNSCC by upregulating B7–H3.

Co-immunizing with HMGB1 enhances anti-tumor immunity of B7H3 vaccine in renal carcinoma

Metastatic renal carcinoma is a kind of tumor with high degree of malignancy, but there are no effective treatment methods and strategies at present. In this study, we designed a folate-grafted PEI600-CyD (H1) nanoparticle-mediated DNA vaccine containing an adjuvant of high mobility group box 1 protein (HMGB1) and a tumor-specific antigen of B7H3 (CD276) for renal carcinoma therapy. Mice bearing subcutaneous human B7H3 (hB7H3)-Renca tumor were immunized with H1-pHMGB1/pB7H3, H1-pB7H3, H1-pHMGB1, or Mock vaccine. Compared to other control groups, the growth of the tumor was significantly inhibited in H1-pHMGB1/pB7H3 vaccine group. The increased proportion and mature of CD11c⁺ DCs were observed in the spleen of H1-pHMGB1/pB7H3 treated mice. Likewise, HMGB1 promoted B7H3 vaccine to induce tumor-specific CD8⁺ T cell proliferation and CTL responses. Beyond that, H1-pHMGB1/pB7H3 vaccine strengthened the induction of functional CD8⁺ T cells. With the depletion of CD8⁺ T cells, the anti-tumor effect of H1-pHMGB1/pB7H3 also disappeared, indicating that CD8⁺ T cells are the key factor of the anti-tumor activity of the vaccine. So, to sum up, H1-pHMGB1/pB7H3 vaccine could achieve the desired anti-tumor effect by enhancing the response of tumor-specific functional CD8⁺ T cell responses. H1 nanoparticle-based vaccines may have great potential and prospect in the treatment of primary solid tumors.

B7-H3/CD276: An Emerging Cancer Immunotherapy

Immunotherapy aiming at suppressing tumor development by relying on modifying or strengthening the immune system prevails among cancer treatments and points out a new direction for cancer therapy. B7 homolog 3 protein (B7-H3, also known as CD276), a newly identified immunoregulatory protein member of the B7 family, is an attractive and promising target for cancer immunotherapy because it is overexpressed in tumor tissues while showing limited expression in normal tissues and participating in tumor microenvironment (TME) shaping and development. Thus far, numerous B7-H3-based immunotherapy strategies have demonstrated potent antitumor activity and acceptable safety profiles in preclinical models. Herein, we present the expression and biological function of B7-H3 in distinct cancer and normal cells, as well as B7-H3-mediated signal pathways in cancer cells and B7-H3-based tumor immunotherapy strategies. This review provides a comprehensive overview that encompasses B7-H3’s role in TME to its potential as a target in cancer immunotherapy.

B7 Family Members in Lymphoma: Promising Novel Targets for Tumor Immunotherapy?

T cells play a vital role in the immune responses against tumors. Costimulatory or coinhibitory molecules regulate T cell activation. Immune checkpoint inhibitors, such as programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) have shown remarkable benefits in patients with various tumor, but few patients have displayed significant immune responses against tumors after PD-1/PD-L1 immunotherapy and many have been completely unresponsive. Thus, researchers must explore novel immune checkpoints that trigger durable antitumor responses and improve clinical outcomes. In this regard, other B7 family checkpoint molecules have been identified, namely PD-L2, B7-H2, B7-H3, B7-H4 and B7-H6. The aim of the present article was to address the expression, clinical significance and roles of B7 family molecules in lymphoma, as well as in T and NK cell-mediated tumor immunity. B7 family checkpoints may offer novel and immunotherapeutic strategies for patients with lymphoma.