Absence of central tolerance in Aire-deficient mice synergizes with immune-checkpoint inhibition to enhance antitumor responses

Immunotherapy for Thymomas and Thymic Carcinomas: Current Status and Future Directions

Thymic epithelial tumors are a histologically diverse group of cancers arising from the epithelial compartment of the thymus. These tumors are characterized by a low tumor mutation burden, a lack of actionable genomic changes, and, especially with thymomas, defects in immune tolerance. Surgery is the mainstay of the management of resectable disease, whereas advanced, unresectable tumors are treated with platinum-based chemotherapy. Disease recurrence can occur months to years after frontline treatment. Although several options are available for conventional treatment of recurrent thymic tumors, response rates are generally low, and treatment-related toxicity can affect quality of life. A subset of patients benefit from biologic therapies, but there remains an unmet need for the development of new treatments. Immune checkpoint inhibitors are safe, clinically active, and have contributed to an improvement in survival for patients with a wide variety of cancers. However, the application of these revolutionary treatments for thymic cancers is limited to their use for the management of recurrent thymic carcinoma because of the risk of immune toxicity. In this paper, we review the current uses of immunotherapy for the management of thymic epithelial tumors and highlight potential strategies to improve safety and broaden the application of these treatments for patients with thymic cancers.

AIRE is expressed in breast cancer TANs and TAMs to regulate the extrinsic apoptotic pathway and inflammation

The autoimmune regulator (AIRE) is a transcriptional regulator expressed in the thymus and is necessary for maintaining immunological self-tolerance. Extrathymic AIRE expression is rare, and a role for AIRE in tumor-associated innate immune cells has not yet been established. In this study, we show that AIRE is expressed in human pro-tumor neutrophils. In breast cancer, AIRE was primarily located to tumor-associated neutrophils (TANs), and to a lesser extent to tumor-associated macrophages (TAMs) and tumor cells. Expression of AIRE in TAN/TAMs, but not in cancer cells, was associated with an adverse prognosis. We show that the functional role for AIRE in neutrophils and macrophages is to regulate expression of immune mediators and the extrinsic apoptotic pathway involving the Fas/TNFR death receptors and cathepsin G. Here, we propose that the role for AIRE in TAN/TAMs in breast tumors is to regulate cell death and inflammation, thus promoting tumor progression.

MYCBP2 expression correlated with inflammatory cell infiltration and prognosis immunotherapy in thyroid cancer patients

Introduction

Immune checkpoint inhibitors (ICIs) have shown promising results for the treatment of multiple cancers. ICIs and related therapies may also be useful for the treatment of thyroid cancer (TC). In TC, Myc binding protein 2 (MYCBP2) is correlated with inflammatory cell infiltration and cancer prognosis. However, the relationship between MYCBP2 expression and ICI efficacy in TC patients is unclear.

Methods

We downloaded data from two TC cohorts, including transcriptomic data and clinical prognosis data. The Tumor Immune Dysfunction and Exclusion (TIDE) algorithm was used to predict the efficacy of ICIs in TC patients. MCPcounter, xCell, and quanTIseq were used to calculate immune cell infiltration scores. Gene set enrichment analysis (GSEA) and single sample GSEA (ssGSEA) were used to evaluate signaling pathway scores. Immunohistochemical (IHC) analysis and clinical follow up was used to identify the MYCBP2 protein expression status in patients and associated with clinical outcome.

Results

A higher proportion of MYCBP2-high TC patients were predicted ICI responders than MYCBP2-low patients. MYCBP2-high patients also had significantly increased infiltration of CD8+ T cells, cytotoxic lymphocytes (CTLs), B cells, natural killer (NK) cells and dendritic cells (DC)s. Compared with MYCBP2-low patients, MYCBP2-high patients had higher expression of genes associated with B cells, CD8+ T cells, macrophages, plasmacytoid dendritic cells (pDCs), antigen processing and presentation, inflammatory stimulation, and interferon (IFN) responses. GSEA and ssGSEA also showed that MYCBP2-high patients had significantly increased activity of inflammatory factors and signaling pathways associated with immune responses.In addiation, Patients in our local cohort with high MYCBP2 expression always had a better prognosis and greater sensitivity to therapy while compared to patients with low MYCBP2 expression after six months clinic follow up.

Conclusions

In this study, we found that MYCBP2 may be a predictive biomarker for ICI efficacy in TC patients. High MYCBP2 expression was associated with significantly enriched immune cell infiltration. MYCBP2 may also be involved in the regulation of signaling pathways associated with anti-tumor immune responses or the production of inflammatory factors.

CTLA-4 on thymic epithelial cells complements Aire for T cell central tolerance

Medullary thymic epithelial cells (mTECs) are essential for the establishment of T cell central tolerance. The transcription factor Aire plays a key role in this process, but other factors remain understudied. We found that a small population of mTECs expressed the coinhibitory receptor cytotoxic T lymphocyte-associated protein 4 (CTLA-4). These CTLA-4⁺ cells were detectable in perinates, peaked around young adulthood and expanded sixfold in the absence of Aire. Single-cell transcriptomics revealed CTLA-4⁺ mTECs to express a distinct gene signature encoding molecules associated with antigen presentation and interferon-gamma signaling. Mice conditionally lacking CTLA-4 in thymic epithelial cells had no major immunological deficiencies but displayed a mildly increased inflammatory tone and a partial defect in the generation of Foxp3⁺CD4⁺ regulatory T cells. Consequently, these mice developed modest levels of autoantibodies and lymphocytic infiltration of peripheral tissues. Thus, CTLA-4 expression in mTECs complements Aire to establish T cell central tolerance.

Immunotherapy for Management of Thymic Epithelial Tumors: A Double-Edged Sword

Simple Summary

Immunotherapy has a rapidly expanding role for the treatment of several cancers due to durable clinical activity and favorable tolerability. However, the unique biology of thymic epithelial tumors (TETs) increases the risk of immune-mediated toxicity. In this paper we review the biology of thymic cancers and its impact on the potential benefits and risks of immunotherapy. We describe the results of completed clinical trials of immune checkpoint inhibitors for advanced TETs and provide an overview of potential biomarkers of response or toxicity of immunotherapy that might influence future development of immunotherapeutic modalities for the treatment of advanced thymoma and thymic carcinoma.

Abstract

Thymic epithelial tumors (TETs) are rare thoracic cancers that are broadly classified as thymomas and thymic carcinomas. Surgery is the cornerstone of management for early-stage disease. There are a limited number of effective treatment options for patients with advanced or recurrent disease. The occurrence of paraneoplastic autoimmune disorders in patients with TETs, especially thymomas, creates significant challenges for the development of immunotherapy, including immune checkpoint inhibitors, as a feasible treatment option. In addition, patients with TETs are at increased risk for the development of immune-mediated toxicity with a predilection for musculoskeletal and neuromuscular adverse events upon treatment with immunotherapy. The identification of biomarkers of response and toxicity is expected to play a key role in harnessing the benefits of immunotherapy for patients with TETs. In this paper we review the biology of TETs and the potential effects on the tolerability of immunotherapy. The results of clinical trials of immune checkpoint inhibitors for the treatment of advanced TETs are described to understand the potential risks and benefits of immunotherapy. We also provide an overview of future avenues for treatment with novel immunotherapeutic modalities and opportunities to develop biomarkers to improve the safety and tolerability of immunomodulatory treatments in patients with TETs.

The role of immunotherapy for management of advanced thymic epithelial tumors: a narrative review

The emergence of immunotherapy as a modern pillar of cancer treatment has changed the treatment landscape for various cancers. Immune checkpoint inhibitors directed at programed death-1 (PD-1) or its ligand (PD-L1), in particular, have found widespread clinical applications and have resulted in durable responses and an improvement in survival of patients with advanced or metastatic disease. Tumor cell PD-L1 expression and tumor mutation burden (TMB) are biomarkers of response and efforts are underway to identify other biomarkers that might predict benefit with these drugs. Most patients tolerate immunotherapy well, although a subset of patients develop immune-mediated toxicity due to excessive immune stimulation. Thymic epithelial tumors (TETs) have a unique biology which can predispose to development of autoimmune paraneoplastic disease, especially in patients with thymoma. Due to defects in immunological self-tolerance, the use of immunotherapy in TET patients is associated with an increased risk of immune-mediated adverse events, which can be potentially life-threatening. Development of biomarkers of response and toxicity is particularly important for the treatment of TETs since it is important to identify patients who might benefit from treatment and be at low risk for development of severe immune toxicity. The use of immunotherapy in patients with autoimmune disorders and those who have previously experienced immune-mediated toxicity is currently an area of active research. Various risk mitigation strategies are under evaluation in prospective clinical trials, including trials of immune checkpoint inhibitors in patients with thymic cancers.