Curcuphenol possesses an unusual histone deacetylase enhancing activity that counters immune escape in metastatic tumours

Curcuphenol, a common component of the culinary spices, naturally found in marine invertebrates and plants, has been identified as a novel candidate for reversing immune escape by restoring expression of the antigen presentation machinery (APM) in invasive cancers, thereby resurrecting the immune recognition of metastatic tumours. Two synthetic curcuphenol analogues, were prepared by informed design that demonstrated consistent induction of APM expression in metastatic prostate and lung carcinoma cells. Both analogues were subsequently found to possess a previously undescribed histone deacetylase (HDAC)-enhancing activity. Remarkably, the H3K27ac ChIPseq analysis of curcuphenol-treated cells reveals that the induced epigenomic marks closely resemble the changes in genome-wide pattern observed with interferon-γ, a cytokine instrumental for orchestrating innate and adaptive immunity. These observations link dietary components to modifying epigenetic programs that modulate gene expression guiding poised immunity.

Erratum: A novel cell-based screen identifies chemical entities that reverse the immune-escape phenotype of metastatic tumours

[This corrects the article DOI: 10.3389/fphar.2023.1119607.].

A novel cell-based screen identifies chemical entities that reverse the immune-escape phenotype of metastatic tumours

Genetic and epigenetic events have been implicated in the downregulation of the cellular antigen processing and presentation machinery (APM), which in turn, has been associated with cancer evasion of the immune system. When these essential components are lacking, cancers develop the ability to subvert host immune surveillance allowing cancer cells to become invisible to the immune system and, in turn, promote cancer metastasis. Here we describe and validate the first high-throughput cell-based screening assay to identify chemical extracts and unique chemical entities that reverse the downregulation of APM components in cell lines derived from metastatic tumours. Through the screening of a library of 480 marine invertebrate extracts followed by bioassay-guided fractionation, curcuphenol, a common sesquiterpene phenol derived from turmeric, was identified as the active compound of one of the extracts. We demonstrate that curcuphenol induces the expression of the APM components, TAP-1 and MHC-I molecules, in cell lines derived from both metastatic prostate and lung carcinomas. Turmeric and curcumins that contain curcuphenol have long been utilized not only as a spice in the preparation of food, but also in traditional medicines for treating cancers. The remarkable discovery that a common component of spices can increase the expression of APM components in metastatic tumour cells and, therefore reverse immune-escape mechanisms, provides a rationale for the development of foods and advanced nutraceuticals as therapeutic candidates for harnessing the power of the immune system to recognize and destroy metastatic cancers.

Human Leukocyte Antigen Class I Antigen-Processing Machinery Upregulation by Anticancer Therapies in the Era of Checkpoint Inhibitors: A Review

IMPORTANCE

Although typically impressive, objective responses to immune checkpoint inhibitors (ICIs) occur in only 12.5% of patients with advanced cancer. The majority of patients do not respond due to cell-intrinsic resistance mechanisms, including human leukocyte antigen (HLA) class I antigen-processing machinery (APM) defects. The APM defects, which have a negative effect on neoantigen presentation to cytotoxic T lymphocytes (CTLs), are present in the majority of malignant tumors. These defects are caused by gene variations in less than 25% of cases and by dysregulated signaling and/or epigenetic changes in most of the remaining cases, making them frequently correctable. This narrative review summarizes the growing clinical evidence that chemotherapy, targeted therapies, and, to a lesser extent, radiotherapy can correct HLA class I APM defects in cancer cells and improve responses to ICIs.

OBSERVATIONS

Most chemotherapeutics enhance HLA class I APM component expression and function in cancer cells, tumor CTL infiltration, and responses to ICIs in preclinical and clinical models. Despite preclinical evidence, radiotherapy does not appear to upregulate HLA class I expression in patients and does not enhance the efficacy of ICIs in clinical settings. The latter findings underscore the need to optimize the dose and schedule of radiation and timing of ICI administration to maximize their immunogenic synergy. By increasing DNA and chromatin accessibility, epigenetic agents (histone deacetylase inhibitors, DNA methyltransferase inhibitors, and EZH2 inhibitors) enhance HLA class I APM component expression and function in many cancer types, a crucial contributor to their synergy with ICIs in patients. Furthermore, epidermal growth factor receptor (EGFR) inhibitors and BRAF/mitogen-activated protein kinase kinase inhibitors are effective at upregulating HLA class I expression in EGFR- and BRAF-variant tumors, respectively; these changes may contribute to the clinical responses induced by these inhibitors in combination with ICIs.

CONCLUSIONS AND RELEVANCE

This narrative review summarizes evidence indicating that chemotherapy and targeted therapies are effective at enhancing HLA class I APM component expression and function in cancer cells. The resulting increased immunogenicity and recognition and elimination of cancer cells by cognate CTLs contributes to the antitumor activity of these therapies as well as to their synergy with ICIs.

Tumor Microenvironment, HLA Class I and APM Expression in HPV-Negative Oral Squamous Cell Carcinoma

Simple Summary

Oral squamous cell carcinoma has developed different strategies to escape from T-cell-mediated immune surveillance, which is mediated by changes in the composition of cellular and soluble components of the tumor microenvironment as well as an impaired expression of molecules of the antigen processing machinery leading to a downregulation of HLA class I surface antigens. In depth characterization of these escape mechanisms might help to develop strategies to overcome this tolerance. In this study, human papilloma virus negative oral squamous cell carcinoma lesions were analyzed regarding the protein expression of major components of the HLA class I antigen processing/presentation pathway in correlation to the intra-tumoral immune cell composition, IFN-γ signaling and clinical parameters, which was further confirmed by bioinformatics analyses of datasets obtained from The Cancer Genome Atlas. This novel knowledge could be used for optimizing the design of immunotherapeutic approaches of this disease.

Abstract

Progression of oral squamous cell carcinoma (OSCC) has been associated with an escape of tumor cells from the host immune surveillance due to an increased knowledge of its underlying molecular mechanisms and its modulation by the tumor microenvironment and immune cell repertoire. In this study, the expression of HLA class I (HLA-I) antigens and of components of the antigen processing machinery (APM) was analyzed in 160 pathologically classified human papilloma virus (HPV)-negative OSCC lesions and correlated to the intra-tumoral immune cell response, IFN-γ signaling and to the patient’s outcome. A heterogeneous but predominantly lower constitutive protein expression of HLA-I APM components was found in OSCC sections when compared to non-neoplastic cells. Tumoral HLA-I APM component expression was further categorized into the three major phenotypes HLA-I^high/APM^high, HLA-I^low/APM^low and HLA-I^{discordant high/low}/APM^high. In the HLA-I^high/APM^high group, the highest frequency of intra-tumoral CD8⁺ T cells and lowest number of CD8⁺ T cells close to FoxP3⁺ cells were found. Patients within this group presented the most unfavorable survival, which was significantly evident in stage T2 tumors. Despite a correlation with the number of intra-tumoral CD8⁺ T cells, tumoral JAK1 expression as a surrogate marker for IFN-γ signaling was not associated with HLA-I/APM expression. Thus, the presented findings strongly indicate the presence of additional factors involved in the immunomodulatory process of HPV-negative OSCC with a possible tumor-burden-dependent complex network of immune escape mechanisms beyond HLA-I/APM components and T cell infiltration in this tumor entity.

ASTX660, an antagonist of cIAP1/2 and XIAP, increases antigen processing machinery and can enhance radiation-induced immunogenic cell death in preclinical models of head and neck cancer

Inhibitor of apoptosis protein (IAP) antagonists have shown activity in preclinical models of head and neck squamous cell carcinoma (HNSCC), and work across several cancer types has demonstrated diverse immune stimulatory effects including enhancement of T cell, NK cell, and dendritic cell function. However, tumor-cell-intrinsic mechanisms for this immune upregulation have been largely unexplored. In this study, we show that ASTX660, an antagonist of cIAP1/2 and XIAP, induces expression of immunogenic cell death (ICD) markers in sensitive HNSCC cell lines in vitro. Experiments in syngeneic mouse models of HNSCC showed that ASTX660 can also enhance radiation-induced ICD in vivo. On a functional level, ASTX660 also enhanced killing of multiple murine cell lines by cytotoxic tumor-infiltrating lymphocytes, and when combined with XRT, stimulated clonal expansion of antigen-specific T lymphocytes and expression of MHC class I on the surface of tumor cells. Flow cytometry experiments in several human HNSCC cell lines showed that MHC class I (HLA-A,B,C) was reliably upregulated in response to ASTX660 + TNFα, while increases in other antigen processing machinery (APM) components were variable among different cell lines. These findings suggest that ASTX660 may enhance anti-tumor immunity both by promoting ICD and by enhancing antigen processing and presentation.