Combinatorial Natural Killer Cell-based Immunotherapy Approaches Selectively Target Chordoma Cancer Stem Cells

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.

Targeting sinonasal undifferentiated carcinoma with a combinatory immunotherapy approach

PURPOSE

Sinonasal undifferentiated carcinoma (SNUC) is a rare, aggressive malignancy of the sinonasal cavity with poor prognosis and limited treatment options. To investigate the potential for SNUC sensitivity to combinatory immunotherapy, we performed in vitro studies with SNUC cell lines and used multi-spectral immunofluorescence to characterize the in vivo patient SNUC tumor immune microenvironment (TIME).

EXPERIMENTAL DESIGN

Human-derived SNUC cell lines were used for in vitro studies of tumor cell susceptibility to natural killer (NK) cell-based immunotherapeutic strategies. Tumor samples from 14 treatment naïve SNUC patients were examined via multi-spectral immunofluorescence and clinical correlations assessed.

RESULTS

Anti-PD-L1 blockade enhanced NK cell lysis of SNUC cell lines ∼5.4 fold (P ≤ 0.0001). This effect was blocked by a CD16 neutralizing antibody demonstrating activity through an antibody-dependent cellular cytotoxicity (ADCC) mediated pathway. ADCC-dependent lysis of SNUC cells was further enhanced by upregulation of PD-L1 on tumor cells by exogenous interferon-gamma (IFN-γ) administration or interleukin-15 (IL-15) stimulated IFN-γ release from NK cells. Combination treatment with anti-PD-L1 blockade and IL-15 superagonism enhanced NK-cell killing of SNUC cells 9.6-fold (P ≤ 0.0001). Untreated SNUC patient tumor samples were found to have an NK cell infiltrate and PD-L1+ tumor cells at a median of 5.4 cells per mm2. A striking 55.7-fold increase in CKlow tumor cell/NK cell interactions was observed in patients without disease recurrence after treatment (P = 0.022). Patients with higher CD3+CD8+ in the stroma had a significantly improved 5-year overall survival (P = 0.0029) and a significant increase in CKlow tumor cell/CD8+ cytotoxic T cell interactions was noted in long-term survivors (P = 0.0225).

CONCLUSION

These data provide the pre-clinical rationale for ongoing investigation into combinatory immunotherapy approaches for SNUC.

Augmentation of tumor expression of HLA-DR, CXCL9, and CXCL10 may improve olfactory neuroblastoma immunotherapeutic responses

BACKGROUND

Olfactory neuroblastoma is a rare malignancy of the anterior skull base typically treated with surgery and adjuvant radiation. Although outcomes are fair for low-grade disease, patients with high-grade, recurrent, or metastatic disease oftentimes respond poorly to standard treatment methods. We hypothesized that an in-depth evaluation of the olfactory neuroblastoma tumor immune microenvironment would identify mechanisms of immune evasion in high-grade olfactory neuroblastoma as well as rational targetable mechanisms for future translational immunotherapeutic approaches.

METHODS

Multispectral immunofluorescence and RNAScope evaluation of the tumor immune microenvironment was performed on forty-seven clinically annotated olfactory neuroblastoma samples. A retrospective chart review was performed and clinical correlations assessed.

RESULTS

A significant T cell infiltration was noted in olfactory neuroblastoma samples with a stromal predilection, presence of myeloid-derived suppressor cells, and sparse natural killer cells. A striking decrease was observed in MHC-I expression in high-grade olfactory neuroblastoma compared to low-grade disease, representing a mechanism of immune evasion in high-grade disease. Mechanistically, the immune effector stromal predilection appears driven by low tumor cell MHC class II (HLA-DR), CXCL9, and CXCL10 expression as those tumors with increased tumor cell expression of each of these mediators correlated with significant increases in T cell infiltration.

CONCLUSION

These data suggest that immunotherapeutic strategies that augment tumor cell expression of MHC class II, CXCL9, and CXCL10 may improve parenchymal trafficking of immune effector cells in olfactory neuroblastoma and augment immunotherapeutic responses.

Chordoma cancer stem cell subpopulation characterization may guide targeted immunotherapy approaches to reduce disease recurrence

Introduction

Cancer stem cells (CSCs), a group of tumor-initiating and tumor-maintaining cells, may be major players in the treatment resistance and recurrence distinctive of chordoma. Characterizing CSCs is crucial to better targeting this subpopulation.

Methods

Using flow cytometry, six chordoma cell lines were evaluated for CSC composition. In vitro, cell lines were stained for B7H6, HER2, MICA-B, ULBP1, EGFR, and PD-L1 surface markers. Eighteen resected chordomas were stained using a multispectral immunofluorescence (mIF) antibody panel to identify CSCs in vivo. HALO software was used for quantitative CSC density and spatial analysis.

Results

In vitro, chordoma CSCs express more B7H6, MICA-B, and ULBP1, assessed by percent positivity and mean fluorescence intensity (MFI), as compared to non-CSCs in all cell lines. PD- L1 percent positivity is increased by >20% in CSCs compared to non-CSCs in all cell lines except CH22. In vivo, CSCs comprise 1.39% of chordoma cells and most are PD-L1+ (75.18%). A spatial analysis suggests that chordoma CSCs cluster at an average distance of 71.51 mm (SD 73.40 mm) from stroma.

Discussion

To our knowledge, this study is the first to identify individual chordoma CSCs and describe their surface phenotypes using in vitro and in vivo methods. PD-L1 is overexpressed on CSCs in chordoma human cell lines and operative tumor samples. Similarly, potential immunotherapeutic targets on CSCs, including B7H6, MICA-B, ULBP1, EGFR, and HER2 are overexpressed across cell lines. Targeting these markers may have a preferential role in combating CSCs, an aggressive subpopulation likely consequential to chordoma's high recurrence rate.

Unraveling molecular signatures in rare bone tumors and navigating the cancer pathway landscapes for targeted therapeutics

Rare cancers (RCs), which account for over 20% of cancer cases, face significant research and treatment challenges due to their limited prevalence. This results in suboptimal outcomes compared to more common malignancies. Rare bone tumors (RBTs) constitute 5-10% of rare cancer cases and pose unique diagnostic complexities. The therapeutic potential of anti-cancer drugs for RBTs remains largely unexplored. Identifying molecular alterations in cancer-related genes and their associated pathways is essential for precision medicine in RBTs. Small molecule inhibitors and monoclonal antibodies targeting specific RBT-associated proteins show promise. Ongoing clinical trials aim to define RBT biomarkers, subtypes, and optimal treatment contexts, including combination therapies and immunotherapeutic agents. This review addresses the challenges in diagnosing, treating, and studying RBTs, shedding light on the current state of RBT biomarkers, potential therapeutic targets, and promising inhibitors. Rare cancers demand attention and innovative solutions to improve clinical outcomes.

Natural killer cell therapy targeting cancer stem cells: Old wine in a new bottle

A small proportion of cancer cells that have stem cell-like properties are known as cancer stem cells (CSCs). They can be used to identify malignant tumor phenotypes and patients with poor prognosis. Targeting these cells has been shown to improve the effectiveness of cancer therapies. Owing to the nature of CSCs, they are resistant to conventional treatment methods such as radio- and chemotherapy. Therefore, more effective anti-CSC therapies are required. Immunotherapy, including natural killer (NK) and T cell therapy, has demonstrated the ability to eliminate CSCs. NK cells have demonstrated superior anti-CSC capabilities compared to T cells in recognizing low levels of major histocompatibility complex (MHC) class I expression. However, CSC escape also occurs during NK cell therapy. It is important to determine CSC-specific immune evasion mechanisms and find out potential solutions to optimize NK cell function. Therefore, this review discusses promising strategies that can improve the efficiency of NK cell therapy in treating CSCs, and aims to provide a reference for future research.

Exploiting an Interleukin-15 Heterodimeric Agonist (N803) for Effective Immunotherapy of Solid Malignancies

Identifying effective immunotherapies for solid tumors remains challenging despite the significant clinical responses observed in subsets of patients treated with immune checkpoint inhibitors. Interleukin-15 (IL-15) is a promising cytokine for the treatment of cancer as it stimulates NK and CD8⁺ lymphocytes. However, unfavorable pharmacokinetics and safety concerns render recombinant IL-15 (rIL-15) a less attractive modality. These shortcomings were addressed by the clinical development of heterodimeric IL-15 agonists, including N803. In preclinical tumor models, N803 elicited significant Th1 immune activation and tumor suppressive effects, primarily mediated by NK and CD8⁺ T lymphocytes. In addition, multiple clinical studies have demonstrated N803 to be safe for the treatment of cancer patients. The combination of N803 with the immune checkpoint inhibitor nivolumab demonstrated encouraging clinical responses in nivolumab-naïve and nivolumab-refractory patients with non-small cell lung cancer. In a recent Phase II/III clinical study, most Bacillus Calmette-Guerin (BCG)-refractory bladder cancer patients treated with N803 plus BCG experienced durable complete responses. Currently, N803 is being evaluated preclinically and clinically in combination with various agents, including chemotherapeutics, immune checkpoint inhibitors, vaccines, and other immuno-oncology agents. This report will review the mechanism(s) of action of N803 and how it relates to the preclinical and clinical studies of N803.

Immunotherapy as a Promising Option for the Treatment of Advanced Chordoma: A Systemic Review

OBJECTIVE

To summarize the function and efficacy of immunotherapy as an adjunctive therapy in the treatment of advanced chordoma.

METHODS

Literature search was conducted by two reviewers independently. Case reports, case series and clinical trials of immunotherapy for chordoma were retrieved systematically from Pubmed, Web of Science, Scoupus and Cochrane Library. Clinical outcome data extracted from the literature included median progression-free survival (PFS), median overall survival (OS), clinical responses and adverse events (AEs).

RESULTS

All studies were published between 2015 and 2022. Twenty-two eligible studies were selected for systemic review. PD-1/PD-L1 immune checkpoint inhibitors (ICIs) were the most common used immunotherapy agents in chordoma, among which Pembrolizumab was the most frequently prescribed. CTLA-4 antibody was only used as combination therapy in chordoma. Dose Limiting Toxicity (DLT) was not observed in any vaccine targeting brachyury, and injection site response was the most frequent AV. The response evaluation criteria in solid tumors (RECIST) were the most generally used evaluation standard in chordoma immunotherapy, and none of the included studies employed the Choi criteria.

CONCLUSIONS

No clinical data have demonstrated that CTLA-4 ICIs combined with PD-1/PD-L1 ICIs is more effective than ICIs monotherapy in treating chordoma, and ICIs in combination with other therapies exhibit more toxicity than monotherapy. PD-1/PD-L1 ICIs monotherapy is recommended as an immunotherapy in patients with advanced chordoma, which may even benefit PD-L1-negative patients. The brachyury vaccine has shown good safety in chordoma patients, and future clinical trials should focus on how to improve its therapeutic efficacy. The use of immunomodulatory agents is a promising therapeutic option, though additional clinical trials are required to evaluate their safety and effectiveness. RECIST does not seem to be an appropriate standard for assessing medications of intratumoral immunotherapy.

Emerging target discovery and drug repurposing opportunities in chordoma

The development of effective and personalized treatment options for patients with rare cancers like chordoma is hampered by numerous challenges. Biomarker-guided repurposing of therapies approved in other indications remains the fastest path to redefining the treatment paradigm, but chordoma's low mutation burden limits the impact of genomics in target discovery and precision oncology efforts. As our knowledge of oncogenic mechanisms across various malignancies has matured, it's become increasingly clear that numerous properties of tumors transcend their genomes - leading to new and uncharted frontiers of therapeutic opportunity. In this review, we discuss how the implementation of cutting-edge tools and approaches is opening new windows into chordoma's vulnerabilities. We also note how a convergence of emerging observations in chordoma and other cancers is leading to the identification and evaluation of new therapeutic hypotheses for this rare cancer.

Multi-spectral immunofluorescence evaluation of the myeloid, T cell, and natural killer cell tumor immune microenvironment in chordoma may guide immunotherapeutic strategies

Background

Chordoma is a rare, invasive, and devastating bone malignancy of residual notochord tissue that arises at the skull base, sacrum, or spine. In order to maximize immunotherapeutic approaches as a potential treatment strategy in chordoma it is important to fully characterize the tumor immune microenvironment (TIME). Multispectral immunofluorescence (MIF) allows for comprehensive evaluation of tumor compartments, molecular co-expression, and immune cell spatial relationships. Here we implement MIF to define the myeloid, T cell, and natural killer (NK) cell compartments in an effort to guide rational design of immunotherapeutic strategies for chordoma.

Methods

Chordoma tumor tissue from 57 patients was evaluated using MIF. Three panels were validated to assess myeloid cell, T cell, and NK cell populations. Slides were stained using an automated system and HALO software objective analysis was utilized for quantitative immune cell density and spatial comparisons between tumor and stroma compartments.

Results

Chordoma TIME analysis revealed macrophage infiltration of the tumor parenchyma at a significantly higher density than stroma. In contrast, helper T cells, cytotoxic T cells, and T regulatory cells were significantly more abundant in stroma versus tumor. T cell compartment infiltration more commonly demonstrated a tumor parenchymal exclusion pattern, most markedly among cytotoxic T cells. NK cells were sparsely found within the chordoma TIME and few were in an activated state. No immune composition differences were seen in chordomas originating from diverse anatomic sites or between those resected at primary versus advanced disease stage.

Conclusion

This is the first comprehensive evaluation of the chordoma TIME including myeloid, T cell, and NK cell appraisal using MIF. Our findings demonstrate that myeloid cells significantly infiltrate chordoma tumor parenchyma while T cells tend to be tumor parenchymal excluded with high stromal infiltration. On average, myeloid cells are found nearer to target tumor cells than T cells, potentially resulting in restriction of T effector cell function. This study suggests that future immunotherapy combinations for chordoma should be aimed at decreasing myeloid cell suppressive function while enhancing cytotoxic T cell and NK cell killing.