Tumor associated antigen PRAME exhibits dualistic functions that are targetable in diffuse large B-cell lymphoma

T cell exhaustion initiates tertiary lymphoid structures and turbocharges cancer-immunity cycle

Immune therapies represented by immune checkpoint blockade (ICB) have significantly transformed cancer treatment. However, the effectiveness of these treatments depends on the status of T cells. T cell exhaustion, characterized by diminished effector function, increased expression of co-inhibitory receptors, and clonal deletion, emerges as a hypofunctional state resulting from chronic exposure to antigens, posing an obstacle to ICB therapy. Several studies have deeply explored T cell exhaustion, providing innovative insights and correlating T cell exhaustion with tertiary lymphoid structures (TLS) formation. TLS, lymphocyte aggregates formed in non-lymphoid tissues amid chronic inflammation, serve as pivotal reservoirs for anti-tumour immunity. Here, we underscore the pivotal role of T cell exhaustion as a signalling mechanism in reinvigorating anti-tumour immunity by turbocharging cancer-immunity (CI) cycle, particularly when tumour becomes unmanageable. Building upon this concept, we summarize emerging immunotherapeutic strategies aimed at enhancing the response rate to ICB therapy and improving patient prognosis.

Targeting PRAME for acute myeloid leukemia therapy

Despite significant progress in targeted therapy for acute myeloid leukemia (AML), clinical outcomes are disappointing for elderly patients, patients with less fit disease characteristics, and patients with adverse disease risk characteristics. Over the past 10 years, adaptive T-cell immunotherapy has been recognized as a strategy for treating various malignant tumors. However, it has faced significant challenges in AML, primarily because myeloid blasts do not contain unique surface antigens. The preferentially expressed antigen in melanoma (PRAME), a cancer-testis antigen, is abnormally expressed in AML and does not exist in normal hematopoietic cells. Accumulating evidence has demonstrated that PRAME is a useful target for treating AML. This paper reviews the structure and function of PRAME, its effects on normal cells and AML blasts, its implications in prognosis and follow-up, and its use in antigen-specific immunotherapy for AML.

PRAME Expression: A Target for Cancer Immunotherapy and a Prognostic Factor in Uveal Melanoma

Purpose

Uveal melanoma (UM) is a rare disease with a high mortality, and new therapeutic options are being investigated. Preferentially Expressed Antigen in Melanoma (PRAME) is a cancer testis antigen, expressed in the testis, but also in cancers, including uveal melanoma. PRAME is considered a target for immune therapy in several cancers, and PRAME-specific T cell clones have been shown to kill UM cells.

Methods

We studied the literature on PRAME expression in hematological and solid malignancies, including UM, and its role as a target for immunotherapy. The distribution of tumor features was compared between PRAME-high and PRAME-low UM in a 64-patient cohort from the Leiden University Medical Center (LUMC) and in the Cancer Genome Atlas (TCGA) cohort of 80 cases and differential gene expression analysis was performed in the LUMC cohort.

Results

PRAME is expressed in many malignancies, it is frequently associated with a negative prognosis, and can be the target of T cell receptor (TCR)-transduced T cells, a promising treatment option with high avidity and safety. In UM, PRAME is expressed in 26% to 45% of cases and is correlated with a worse prognosis. In the LUMC and the TCGA cohorts, high PRAME expression was associated with larger diameter, higher Tumor-Node-Metastasis (TNM) stage, more frequent gain of chromosome 8q, and an inflammatory phenotype.

Conclusions

We confirm that PRAME is associated with poor prognosis in UM and has a strong connection with extra copies of 8q. We show that PRAME-specific immunotherapy in an adjuvant setting is promising in treatment of malignancies, including UM.

Biology of Cancer-Testis Antigens and Their Therapeutic Implications in Cancer

Tumour-specific antigens have been an area of interest in cancer therapy since their discovery in the middle of the 20th century. In the era of immune-based cancer therapeutics, redirecting our immune cells to target these tumour-specific antigens has become even more relevant. Cancer-testis antigens (CTAs) are a class of antigens with an expression specific to the testis and cancer cells. CTAs have also been demonstrated to be expressed in a wide variety of cancers. Due to their frequency and specificity of expression in a multitude of cancers, CTAs have been particularly attractive as cancer-specific therapeutic targets. There is now a rapid expansion of CTAs being identified and many studies have been conducted to correlate CTA expression with cancer and therapy-resistant phenotypes. Furthermore, there is an increasing number of clinical trials involving using some of these CTAs as molecular targets in pharmacological and immune-targeted therapeutics for various cancers. This review will summarise the current knowledge of the biology of known CTAs in tumorigenesis and the regulation of CTA genes. CTAs as molecular targets and the therapeutic implications of these CTA-targeted anticancer strategies will also be discussed.

Transcriptome Analysis of Diffuse Large B-Cell Lymphoma Cells Inducibly Expressing MyD88 L265P Mutation Identifies Upregulated CD44, LGALS3, NFKBIZ, and BATF as Downstream Targets of Oncogenic NF-κB Signaling

During innate immune responses, myeloid differentiation primary response 88 (MyD88) functions as a critical signaling adaptor protein integrating stimuli from toll-like receptors (TLR) and the interleukin-1 receptor (IL-1R) family and translates them into specific cellular outcomes. In B cells, somatic mutations in MyD88 trigger oncogenic NF-κB signaling independent of receptor stimulation, which leads to the development of B-cell malignancies. However, the exact molecular mechanisms and downstream signaling targets remain unresolved. We established an inducible system to introduce MyD88 to lymphoma cell lines and performed transcriptomic analysis (RNA-seq) to identify genes differentially expressed by MyD88 bearing the L265P oncogenic mutation. We show that MyD88L265P activates NF-κB signaling and upregulates genes that might contribute to lymphomagenesis, including CD44, LGALS3 (coding Galectin-3), NFKBIZ (coding IkBƺ), and BATF. Moreover, we demonstrate that CD44 can serve as a marker of the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) and that CD44 expression is correlated with overall survival in DLBCL patients. Our results shed new light on the downstream outcomes of MyD88L265P oncogenic signaling that might be involved in cellular transformation and provide novel therapeutical targets.

Metastatic melanoma and rare melanoma variants: a review

The histopathological diagnosis of melanoma is fraught with potential pitfalls. In the setting of cutaneous metastatic melanoma, it is important to recognise the various histological patterns that can be encountered from the more common to the rare, including epidermotropic, folliculotropic, naevoid, and blue naevus-like. In addition, melanoma is notorious for phenotypic plasticity. Thus, there are many different subtypes and cytomorphological variations that can be difficult to recognise as melanoma, particularly in the recurrent or metastatic setting. Select melanoma variants including primary dermal, clear cell, plasmacytoid, signet ring cell, small cell, myxoid, rhabdoid, and dedifferentiated melanoma will be discussed, in addition to composite melanocytic neoplasms. This review is intended to remind the practitioner of key concepts of metastatic disease and select rare melanoma variants, while providing practical guidelines for accurate diagnosis.

EZH2 interacts with HP1BP3 to epigenetically activate WNT7B that promotes temozolomide resistance in glioblastoma

Glioblastoma (GBM) is the most lethal primary brain tumor in adults and harbors a subpopulation of glioma stem cells (GSCs). Enhancer of Zeste Homolog 2 (EZH2), a histone lysine methyltransferase, deeply involves in the stemness maintenance of GSC. However, the precise mechanism and therapeutic potential remain elusive. We postulated that the interactome of EZH2 in GSC is unique. Therefore, we performed proteomic and transcriptomic research to unveil the oncogenic mechanism of EZH2. Immunoprecipitation and mass spectrometry were used to identify proteins that co-precipitate with EZH2. We show that EZH2 binds to heterochromatin protein 1 binding protein 3 (HP1BP3) in GSCs and impairs the methylation of H3K9. Overexpression of HP1BP3 enhances the proliferation, self-renewal and temozolomide (TMZ) resistance of GBM cells. Furthermore, EZH2 and HP1BP3 co-activate WNT7B expression thereby increasing TMZ resistance and stemness of GBM cells. Importantly, inhibition of WNT7B autocrine via LGK974 effectively reverses the TMZ resistance. Our work clarifies a new oncogenic mechanism of EZH2 by which it interacts with HP1BP3 and epigenetically activates WNT7B thereby promoting TMZ resistance in GSCs. Our results provide a rationale for targeting WNT/β-catenin pathway as a promising strategy to overcome TMZ resistance in GSCs.

The Immunology of DLBCL

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy and is the most common type of malignant lymphoid neoplasm. While some DLBCLs exhibit strong cell-autonomous survival and proliferation activity, others depend on interactions with non-malignant cells for their survival and proliferation. Recent next-generation sequencing studies have linked these interactions with the molecular classification of DLBCL. For example, germinal center B-cell-like DLBCL tends to show strong associations with follicular T cells and epigenetic regulation of immune recognition molecules, whereas activated B-cell-like DLBCL shows frequent genetic aberrations affecting the class I major histocompatibility complex. Single-cell technologies have also provided detailed information about cell-cell interactions and the cell composition of the microenvironment of DLBCL. Aging-related immunological deterioration, i.e., immunosenescence, also plays an important role in DLBCL pathogenesis, especially in Epstein-Barr virus-positive DLBCL. Moreover, DLBCL in "immune-privileged sites"-where multiple immune-modulating mechanisms exist-shows unique biological features, including frequent down-regulation of immune recognition molecules and an immune-tolerogenic tumor microenvironment. These advances in understanding the immunology of DLBCL may contribute to the development of novel therapies targeting immune systems.