Immune profiles of desmoplastic small round cell tumor and synovial sarcoma suggest different immunotherapeutic susceptibility upfront compared to relapse specimens

Fate control engagement augments NK cell responses in LV/hu-IL-12 transduced sarcoma

INTRODUCTION

NK cells are an untapped resource for cancer therapy. Sarcomas transduced with lentiviruses to express human IL-12 are only cleared in mice bearing mature human NK cells. However, systemic inflammation limits IL-12 utilization. Fate control a.k.a. "suicide mechanisms" regulate unchecked systemic inflammation caused by cellular immunotherapies. Despite increasing utilization, there remains limited data on immune consequences or tumor-directed effects of fate control.

OBJECTIVES

We sought to engage the mutant thymidylate kinase (mTMPK) metabolic fate control system to regulate systemic inflammation and assess the impact on NK cell effector functions.

METHODS

Primary human sarcoma short-passage samples and cell lines were transduced with LV/hu-IL-12_mTMPK engineering expression of IL-12 and an AZT-associated fate control enzyme. We assessed transduced sarcoma responses to AZT engagement and subsequent modulation of NK cell functions as measured by inflammatory cytokine production and cytotoxicity.

RESULTS

AZT administration to transduced (LV/hu-IL-12_mTMPK) short-passage primary human sarcomas and human Ewing sarcoma, osteosarcoma, and rhabdomyosarcoma cell lines, abrogated the robust expression of human IL-12. Fate control activation elicited a specific dose-dependent cytotoxic effect measured by metabolic activity (WST-1) and cell death (Incucyte). NK effector functions of IFN-γ and cytotoxic granule release were significantly augmented despite IL-12 abrogation. This correlated with preferentially induced expression of NK cell activation ligands.

CONCLUSIONS

mTMPK fate control engagement terminates transduced sarcoma IL-12 production and triggers cell death, but also augments an NK cell-mediated response coinciding with metabolic stress activating surface ligand induction. Fate control engagement could offer a novel immune activation method for NK cell-mediated cancer clearance.

Desmoplastic small round cell tumor: from state of the art to future clinical prospects

INTRODUCTION

Desmoplastic small round cell tumor (DSRCT) is an extremely rare and highly aggressive soft tissue sarcoma, presenting mainly in male adolescents and young adults with multiple nodules disseminated within the abdominopelvic cavity. Despite a multimodal approach including aggressive cytoreductive surgery, intensive multi-agent chemotherapy, and postoperative whole abdominopelvic radiotherapy, the prognosis for DSRCT remains dismal. Median progression-free survival ranges between 4 and 21 months, and overall survival between 17 and 60 months, with the 5-year overall survival rate in the range of 10-20%.

AREA COVERED

This review discusses the treatment strategies used for DSRCT over the years, the state of the art of current treatments, and future clinical prospects.

EXPERT OPINION

The unsatisfactory outcomes for patients with DSRCT warrant investigations into innovative treatment combinations. An international multidisciplinary and multi-stakeholder collaboration, involving both pediatric and adult sarcoma communities, is needed to propel preclinical model generation and drug development, and innovative clinical trial designs to enable the timely testing of treatments involving novel agents guided by biology to boost the chances of survival for patients with this devastating disease.

Identification of immunotherapy and radioimmunotherapy targets on desmoplastic small round cell tumors

Background

Development of successful antibody-based immunotherapeutic and radioimmunotherapeutic strategies rely on the identification of cell surface tumor-associated antigens (TAA) with restricted expression on normal tissues. Desmoplastic small round cell tumor (DSRCT) is a rare and generally neglected malignancy that primarily affects adolescent and young adult males. New therapies capable of treating disseminated disease are needed for DSRCT, which is often widespread at diagnosis.

Methods

We used immunohistochemistry (IHC) on fresh frozen surgical specimens and patient-derived xenograft (PDX) tumors and flow cytometry on DSRCT cell lines to evaluate expression of TAAs in these tumors. In vitro cytotoxicity assays were used to evaluate the efficacy of T cell-engaging bispecific antibodies (T-BsAbs) directed at these targets. In vivo, we used an intraperitoneal xenograft mouse model of DSRCT to test T-BsAbs against several TAAs.

Results

In DSRCT specimens we found widespread expression of B7-H3, EGFR, GD2, HER2, mesothelin, and polysialic acid, clinical targets for which specific antibody therapeutics are available. The expression of B7-H3, EGFR, HER2, and mesothelin was confirmed on the cell surface of DSRCT cell lines. In vitro cytotoxicity assays confirmed the efficacy of T cell-engaging bispecific antibodies (T-BsAbs) directed at these targets against DSRCT cells. Remarkably, a HER2xCD3 T-BsAb was capable of completely shrinking established tumors in an intraperitoneal mouse model of DSRCT.

Conclusions

We propose that these TAAs should be further investigated in preclinical models as targets for immunotherapy and radioimmunotherapy with the hope of providing a rationale to extend these therapies to patients with advanced DSRCT.

Small round cell sarcomas

Undifferentiated small round cell sarcomas (SRCSs) of bone and soft tissue comprise a heterogeneous group of highly aggressive tumours associated with a poor prognosis, especially in metastatic disease. SRCS entities mainly occur in the third decade of life and can exhibit striking disparities regarding preferentially affected sex and tumour localization. SRCSs comprise new entities defined by specific genetic abnormalities, namely EWSR1-non-ETS fusions, CIC-rearrangements or BCOR genetic alterations, as well as EWSR1-ETS fusions in the prototypic SRCS Ewing sarcoma. These gene fusions mainly encode aberrant oncogenic transcription factors that massively rewire the transcriptome and epigenome of the as yet unknown cell or cells of origin. Additional mutations or copy number variants are rare at diagnosis and, depending on the tumour entity, may involve TP53, CDKN2A and others. Histologically, these lesions consist of small round cells expressing variable levels of CD99 and specific marker proteins, including cyclin B3, ETV4, WT1, NKX3-1 and aggrecan, depending on the entity. Besides locoregional treatment that should follow standard protocols for sarcoma management, (neo)adjuvant treatment is as yet ill-defined but generally follows that of Ewing sarcoma and is associated with adverse effects that might compromise quality of life. Emerging studies on the molecular mechanisms of SRCSs and the development of genetically engineered animal models hold promise for improvements in early detection, disease monitoring, treatment-related toxicity, overall survival and quality of life.

The Role of Immunotherapy in the Management of Soft Tissue Sarcomas: Current Landscape and Future Outlook

Soft tissue sarcomas (STS) are a subset of sarcoma, a rare group of heterogeneous malignancies of mesenchymal origin. Current standard of care involves surgical resection with systemic chemotherapy used to treat high-risk localized and metastatic disease. Though classically thought to be immunologically quiet tumors, STS interact with the immune system, undergoing immunoediting that alters tumor immunogenicity and the tumor microenvironment. Recent advances with immune checkpoint inhibition have led to clinical trials exploring the efficacy of immunotherapy in treating STS. Results from these trials point to histologic subtype-specific clinical activity of immune checkpoint blockade. In addition, combinatorial strategies adding immune checkpoint inhibition to local or systemic therapies for STS have further increased their efficacy. Targeted immunotherapies using engineered T-cell receptor-based approaches also show increasing promise as treatment options for some patients with STS. Adoptive transfer of autologous T cells targeting NY-ESO-1 and MAGE-A4 have high response rates in sarcomas expressing these antigens, although recurrence is often seen in responding patients. Future work must focus on identifying primary and acquired mechanisms of resistance to these therapies, and extend T-cell receptor discovery to other tumor-associated antigens.

Targeting cancer testis antigens in synovial sarcoma

Synovial sarcoma (SS) is a rare cancer that disproportionately affects children and young adults. Cancer testis antigens (CTAs) are proteins that are expressed early in embryonic development, but generally not expressed in normal tissue. They are aberrantly expressed in many different cancer types and are an attractive therapeutic target for immunotherapies. CTAs are expressed at high levels in SS. This high level of CTA expression makes SS an ideal cancer for treatment strategies aimed at harnessing the immune system to recognize aberrant CTA expression and fight against the cancer. Pivotal clinical trials are now underway, with the potential to dramatically alter the landscape of SS management and treatment from current standards of care. In this review, we describe the rationale for targeting CTAs in SS with a focus on NY-ESO-1 and MAGE-A4, the current state of vaccine and T-cell receptor-based therapies, and consider emerging opportunities for future development.

Clinical and immunological characteristics of sarcomas patients with clonogenic tumors

Tumorigenesis is related to the generation of heterogeneous tumor cell population, which is the result of genetic and epigenetic alterations followed by clonal selections and subsequent expansion. In basic studies genetic, histological and morphological diversity of different clones within a patient's neoplasm and specifics of their interrelation with patient's immune system are investigated mostly on the models of tumors of epithelial origin. Mesenchymal tumors such as soft tissue and bone-derived sarcomas (STBS) have been poorly studied in this regard. The molecular genetic methods used to examine intratumoral heterogeneity do not currently provide insight into which portion of the identified subclones are able to grow autonomously. Limiting dilution cloning demonstrates the existence of self-regulating tumor cells in the population and can serve as an independent prognostic predictor of poor prognosis. Intratumoral heterogeneity results not only in differences in growth dynamics, gene expression, and phenotypic markers, but also in the resistance to treatment, especially immunotherapy, thus causing tumor eluding immune escape. The changes that accompany this process can be affected by the cellular immune system, resulting in an imbalance between populations. The variations in the population composition of immune system cells are now widely debated as a predictor of response to immunotherapy, which is of obvious interest for sarcomas, where the effectiveness of chemotherapy is low and the prognosis is unfavorable, especially in case of metastatic disease development. The search for new predictive markers of disease prognosis and treatment efficacy is an important task, to which this study is focused. Our results demonstrate that clonogenic tumor characteristics such as clonogenic potential is independent predictor of unfavorable prognosis in cases of cancer and correlate with the clinical characteristics of the tumor such as overall survival (OS) and progression free survival (PFS). It was found that patients with clonogenic sarcomas had a lower content of activated cytotoxic T-lymphocytes (CTL) with the CD3⁺CD8⁺HLA^-DR⁺ phenotype and an increased number of natural NK killers (p < 0.05) compared to nonclonogenic tumors. In addition, according to our data, a high neutrophil to lymphocyte ratio (NLR), a low value of major T-lymphocyte populations, and a higher number of natural killer cells (NK) in the blood can be negative prognostic factors for the immunotherapy of this disease.

Sarcomas: Immune biomarker expression and checkpoint inhibitor trials

Sarcomas are a heterogenous group of mesenchymal cancers comprising over 100 subtypes. Current chemotherapy for all but a very few subtypes has limited efficacy, resulting in 5-year relative survival rates of 16% for metastatic patients. While sarcomas have often been regarded as an "immune cold" tumor category, recent biomarker studies have confirmed a great deal of immune heterogeneity across sarcoma subtypes. Reports from the first generation of clinical trials treating sarcomas with immunotherapy demonstrate a few positive responses, supporting efforts to stratify patients to optimize response rates. This review summarizes recent advances in knowledge around immune biomarker expression in sarcomas, the potential use of new technologies to complement these study results, and clinical trials particularly of immune checkpoint inhibitor therapy in sarcomas. Each of the immune biomarkers assessed was reviewed for subtype-specific expression patterns and correlation with prognosis. Overall, there is extensive heterogeneity of immune biomarker presence across sarcoma subtypes, and no consensus on the prognostic effect of these biomarkers. New technologies such as multiplex immunohistochemistry and high plex in situ profiling may offer more insights into the sarcoma microenvironment. To date, clinical trials using immune checkpoint inhibitor monotherapy have not shown compelling clinical benefits. Combination therapy with dual checkpoint inhibitors or in combinations with other agents has yielded more promising results in dedifferentiated liposarcoma, undifferentiated pleomorphic sarcoma, angiosarcoma and alveolar soft-part sarcoma. Better understanding of the sarcoma immune status through biomarkers may help decipher the reasons behind differential responses to immunotherapy.

Immune profiling of pediatric solid tumors

Pediatric cancers, particularly high-risk solid tumors, urgently need effective and specific therapies. Their outlook has not appreciably improved in decades. Immunotherapies such as immune checkpoint inhibitors offer much promise, but most are only approved for use in adults. Though several hundred clinical trials have tested immune-based approaches in childhood cancers, few have been guided by biomarkers or clinical-grade assays developed to predict patient response and, ultimately, to help select those most likely to benefit. There is extensive evidence in adults to show that immune profiling has substantial predictive value, but few studies focus on childhood tumors, because of the relatively small disease population and restricted use of immune-based therapies. For instance, only one published study has retrospectively examined the immune profiles of pediatric brain tumors after immunotherapy. Furthermore, application and integration of advanced multiplex techniques has been extremely limited. Here, we review the current status of immune profiling of pediatric solid tumors, with emphasis on tumor types that represent enormous unmet clinical need, primarily in the context of immune checkpoint inhibitor therapy. Translating optimized and informative immune profiling into standard practice and access to personalized combination therapy will be critical if childhood cancers are to be treated effectively and affordably.