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Simple Summary: CD8+ CTCL subtypes manifest with widespread clinical, histologic, and phenotypic features that inform the classification of the disease. Through this review, we highlight the importance of utilizing the synergy of clinical, histologic, and immunohistochemical findings to determine a correct diagnosis and applicable treatment plan. Although the vast majority of CTCL subtypes are of the CD4+ T-helper cell differentiation phenotype, there is a spectrum of CD8+ variants that manifest wide-ranging clinical, histologic, and phenotypic features that inform the classification of the disease. CD8, like CD4, and cytotoxic molecules (including TIA and granzyme) are readily detectable via IHC staining of tissue and, when expressed on the phenotypically abnormal T-cell population, can help distinguish specific CTCL subtypes. Nonetheless, given that the histopathologic differential for CD8+ lymphoproliferative disorders and lymphomas may range from very indolent lymphomatoid papulosis (LyP) to aggressive entities like CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma (AECTCL), CD8 and/or cytotoxic molecule expression alone is insufficient for diagnosis and is not in itself an indicator of prognosis. We present a review of CTCL subtypes that can demonstrate CD8 positivity: CD8+ mycosis fungoides (MF), LyP type D, subcutaneous panniculitis-like T-cell lymphoma (SPTCL), primary cutaneous gamma/delta T-cell lymphoma (PCGDTL), CD8+ AECTCL, and acral CD8+ T-cell lymphoproliferative disorder (acral CD8+ TCLPD). These diseases may have different clinical manifestations and distinctive treatment algorithms. Due to the rare nature of these diseases, it is imperative to integrate clinical, histologic, and immunohistochemical findings to determine an accurate diagnosis and an appropriate treatment plan. [ABSTRACT FROM AUTHOR]

Tumours use various strategies to evade immune surveillance.sup.1,2. Immunotherapies targeting tumour immune evasion such as immune checkpoint blockade have shown considerable efficacy on multiple cancers.sup.3,4 but are ineffective for most patients due to primary or acquired resistance.sup.5-7. Recent studies showed that some epigenetic regulators suppress anti-tumour immunity.sup.2,8-12, suggesting that epigenetic therapies could boost anti-tumour immune responses and overcome resistance to current immunotherapies. Here we show that, in mouse melanoma models, depletion of KDM5B--an H3K4 demethylase that is critical for melanoma maintenance and drug resistance.sup.13-15--induces robust adaptive immune responses and enhances responses to immune checkpoint blockade. Mechanistically, KDM5B recruits the H3K9 methyltransferase SETDB1 to repress endogenous retroelements such as MMVL30 in a demethylase-independent manner. Derepression of these retroelements activates cytosolic RNA-sensing and DNA-sensing pathways and the subsequent type-I interferon response, leading to tumour rejection and induction of immune memory. Our results demonstrate that KDM5B suppresses anti-tumour immunity by epigenetic silencing of retroelements. We therefore reveal roles of KDM5B in heterochromatin regulation and immune evasion in melanoma, opening new paths for the development of KDM5B-targeting and SETDB1-targeting therapies to enhance tumour immunogenicity and overcome immunotherapy resistance. KDM5B recruits SETDB1 to repress endogenous retroelements such as MMVL30, suppressing anti-tumour immunity, and the depletion of KDM5B induces a robust adaptive immune response and enhances the response to immune checkpoint blockade., Author(s): Shang-Min Zhang [sup.1] , Wesley L. Cai [sup.1] [sup.12] , Xiaoni Liu [sup.1] [sup.2] , Durga Thakral [sup.2] , Jiesi Luo [sup.3] [sup.4] , Lok Hei Chan [sup.1] , [...]

The article discusses the recent approval of a cell therapy called lifileucel for the treatment of melanoma. Lifileucel uses a patient's own tumor-infiltrating T lymphocytes (TILs) to target and treat melanoma. This approval marks a significant advancement in cancer treatment, as it is the first cell therapy to be approved for a solid tumor. Clinical trials have shown that lifileucel has a response rate between 30% and 50%, making it a valuable addition to the treatment options for melanoma patients who do not respond to other therapies. However, there are still challenges to overcome, such as the need for a surgical procedure to isolate TILs and the exclusion of patients with certain conditions. Ongoing research is focused on improving the effectiveness and specificity of T-cell therapies for melanoma. [Extracted from the article]

Recurrence of advanced melanoma after therapy is a major risk factor for reduced survival, and treatment options are limited. Antitumor immune memory plays a critical role in preventing melanoma recurrence and memory T cells could be a potent cell-based therapy, but the identity, and functional properties of the required immune cells are incompletely understood. Here, we show that an IL-7Rhi tumor-specific CD8+ population is critical for antitumor memory and can be epigenetically augmented to drive powerful antitumor immune responses. Using a model of functional antimelanoma memory, we found that high IL-7R expression selectively marks a CD8+ population in lymphoid organs that plays critical roles in maintaining tumor remission after immunotherapy or surgical resection. This population has intrinsic cytotoxic activity, lacks markers of exhaustion and has superior antitumor efficacy. IL-7Rhi cells have a functionally poised epigenetic landscape regulated by DNA methylation, which can be augmented by hypomethylating agents to confer improved survival and complete melanoma clearance in naive mice. Importantly, greater than 95% of tumor-specific T cells in draining lymph nodes after therapy express high levels of IL-7R. This overlap between IL-7Rhi and antigen-specific T cells allows for enrichment of a potent functional CD8+ population without determining antigen-specificity, which we demonstrate in a melanoma model without a known antigen. We identify that IL-7R expression in human melanoma is an independent prognostic factor of improved survival. These findings advance our basic understanding of antitumor memory and suggest a cell-based therapy using high IL-7R expression to enrich for a lymph node population with superior antitumor activity that can be augmented by hypomethylating agents. [ABSTRACT FROM AUTHOR]

Multiple ligand-receptor interactions between antigen-specific T cells and macrophages in the dermis could help explain how PD-1 controls the location of self-antigen-specific T cells and compartmentalizes T cells away from self-antigens. For example, anti-PD-1 antibody leads to activation of CD8 SP + sp T cells recognizing hair follicle autoantigens on keratinocytes in checkpoint-associa--ted alopecia areata.[13] However, the origin of these autoantigen recognizing T cells and whether they derive from previously tolerant T cells or arise I de novo i is unclear. (Right) PD-1 blockade leads to loss of T-cell tolerance to self-antigen, localization of self-antigen-specific T cells to the epidermis, increased cytokine release, keratinocyte death and skin inflammation. [Extracted from the article]

The aim of this study is to determine the significance of programmed death ligand 1 (PD‐L1 or CD274) methylation in relation to PD‐L1 expression and survival in melanoma. Despite the clinical importance of therapies targeting the PD‐1/PD‐L1 immune checkpoint in melanoma, factors regulating PD‐L1 expression, including epigenetic mechanisms, are not completely understood. In this study, we examined PD‐L1 promoter methylation in relation to PD‐L1 expression and overall survival in melanoma patients. Our results suggest that DNA methylation regulates PD‐L1 expression in melanoma, and we identify the key methylated CpG loci in the PD‐L1 promoter, establish PD‐L1 methylation as an independent survival prognostic factor, provide proof of concept for altering PD‐L1 expression by hypomethylating agents, and uncover that PD‐L1 methylation is associated with an interferon signaling transcriptional phenotype. Based on our findings, measuring and altering PD‐L1 promoter DNA methylation may have potential prognostic and therapeutic applications in melanoma. [ABSTRACT FROM AUTHOR]

This study evaluates the use of HMG‐CoA reductase inhibitors, or statins, as an adjunctive to BRAF and MEK inhibition as a treatment in melanomas and other tumors with driver mutations in the MAPK pathway. Experiments used simvastatin in conjunction with vemurafenib and selumetinib in vitro and simvastatin with vemurafenib in vivo to demonstrate additional growth abrogation beyond MAPK blockade alone. Additional studies demonstrated that statin anti‐tumor effects appeared to depend on inhibition of isoprenoid synthesis given rescue with add‐back of downstream metabolites. Ultimately, we concluded that statins represent a possible useful adjunctive therapy in MAPK‐driven tumors when given with current approved targeted therapy. [ABSTRACT FROM AUTHOR]