The Immunology of Melanoma

Targeting anticancer immunity in melanoma tumour microenvironment: unleashing the potential of adjuvants, drugs, and phytochemicals

Melanoma poses a challenge in oncology because of its aggressive nature and limited treatment modalities. The tumour microenvironment (TME) in melanoma contains unique properties such as an immunosuppressive and high-density environment, unusual vasculature, and a high number of stromal and immunosuppressive cells. In recent years, numerous experiments have focused on boosting the immune system to effectively remove malignant cells. Adjuvants, consisting of phytochemicals, toll-like receptor (TLR) agonists, and cytokines, have shown encouraging results in triggering antitumor immunity and augmenting the therapeutic effectiveness of anticancer therapy. These adjuvants can stimulate the maturation of dendritic cells (DCs) and infiltration of cytotoxic CD8+ T lymphocytes (CTLs). Furthermore, nanocarriers can help to deliver immunomodulators and antigens directly to the tumour stroma, thereby improving their efficacy against malignant cells. The remodelling of melanoma TME utilising phytochemicals, agonists, and other adjuvants can be combined with current modalities for improving therapy outcomes. This review article explores the potential of adjuvants, drugs, and their nanoformulations in enhancing the anticancer potency of macrophages, CTLs, and natural killer (NK) cells. Additionally, the capacity of these agents to repress the function of immunosuppressive components of melanoma TME, such as immunosuppressive subsets of macrophages, stromal and myeloid cells will be discussed.

Tumor-Infiltrating T Cells in Skin Basal Cell Carcinomas and Squamous Cell Carcinomas: Global Th1 Preponderance with Th17 Enrichment-A Cross-Sectional Study

Basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) are high-incidence, non-melanoma skin cancers (NMSCs). The success of immune-targeted therapies in advanced NMSCs led us to anticipate that NMSCs harbored significant populations of tumor-infiltrating lymphocytes with potential anti-tumor activity. The main aim of this study was to characterize T cells infiltrating NMSCs. Flow cytometry and immunohistochemistry were used to assess, respectively, the proportions and densities of T cell subpopulations in BCCs (n = 118), SCCs (n = 33), and normal skin (NS, n = 30). CD8+ T cells, CD4+ T cell subsets, namely, Th1, Th2, Th17, Th9, and regulatory T cells (Tregs), CD8+ and CD4+ memory T cells, and γδ T cells were compared between NMSCs and NS samples. Remarkably, both BCCs and SCCs featured a significantly higher Th1/Th2 ratio (~four-fold) and an enrichment for Th17 cells. NMSCs also showed a significant enrichment for IFN-γ-producing CD8+T cells, and a depletion of γδ T cells. Using immunohistochemistry, NMSCs featured denser T cell infiltrates (CD4+, CD8+, and Tregs) than NS. Overall, these data favor a Th1-predominant response in BCCs and SCCs, providing support for immune-based treatments in NMSCs. Th17-mediated inflammation may play a role in the progression of NMSCs and thus become a potential therapeutic target in NMSCs.

Neurological autoimmunity in melanoma patients: a comparison between those exposed and non-exposed to immune checkpoint inhibitors

BACKGROUND

The clinical spectrum of melanoma-associated neurological autoimmunity, whether melanoma-associated paraneoplastic neurological syndromes (PNS) or induced by immune checkpoint inhibitors (ICI), is not well characterized. We aim to describe the clinical spectrum of melanoma-associated neurological autoimmunity.

METHODS

A systematic review of the literature combined with patients from French databases of paraneoplastic neurological syndromes was conducted. All melanoma patients with a possible immune-mediated neurologic syndrome were included and classified according to whether they had previously been exposed to ICI (ICI-neurotoxicity) or not (ICI-naïve) at first neurological symptoms.

RESULTS

Seventy ICI-naïve (literature: n = 61) and 241 ICI-neurotoxicity patients (literature: n = 180) were identified. Neuromuscular manifestations predominated in both groups, but peripheral neuropathies were more frequent in ICI-neurotoxicity patients (39.4% vs 21.4%, p = 0.005) whereas myositis was more frequent in ICI-naïve patients (42.9% vs 18.7%, p < 0.001). ICI-naïve patients had also more frequent central nervous system (CNS) involvement (35.7% vs 23.7%, p = 0.045), classical paraneoplastic syndrome (25.7% vs 5.8%, p < 0.001), and more frequently positive for anti-neuron antibodies (24/32, 75.0% vs 38/90, 42.2%, p = 0.001). Although more ICI-neurotoxicity patients died during the acute phase (22/202, 10.9% vs 1/51, 2.0%, p = 0.047), mostly myositis patients (14/22, 63.6%), mortality during follow-up was higher in ICI-naïve patients (58.5% vs 29.8%, p < 0.001). There was no significant difference in the frequency of life independence (mRS ≤ 2) in the surviving patients in both groups (95.5% vs 91.0%, p = 0.437).

CONCLUSIONS

Melanoma-associated PNS appear remarkably rare. The clinical similarities observed in neurological autoimmunity between ICI-treated and ICI-naïve patients, characterized predominantly by demyelinating polyradiculoneuropathy and myositis, suggest a potential prior immunization against melanoma antigens contributing to ICI-related neurotoxicity.

Maltol has anti-cancer effects via modulating PD-L1 signaling pathway in B16F10 cells

Introduction: Among skin cancers, melanoma has a high mortality rate. Recent advances in immunotherapy, particularly through immune checkpoint modulation, have improved the clinical treatment of melanoma. Maltol has various bioactivities, including anti-oxidant and anti-inflammatory properties, but the anti-melanoma property of maltol remains underexplored. The aim of this work is to explore the anti-melanoma potential of maltol through regulating immune checkpoints. Methods: The immune checkpoint PD-L1 was analyzed using qPCR, immunoblots, and immunofluorescence. Melanoma sensitivity towards T cells was investigated via cytotoxicity, cell viability, and IL-2 assays employing CTLL-2 cells. Results: Maltol was found to reduce melanin contents, tyrosinase activity, and expression levels of tyrosinase and tyrosinase-related protein 1. Additionally, maltol suppressed the proliferative capacity of B16F10 and induced cell cycle arrest. Maltol increased apoptotic rates by elevating cleaved caspase-3 and PARP. The co-treatment with maltol and cisplatin revealed a synergistic effect on inhibiting growth and promoting apoptosis. Maltol suppressed IFN-γ-induced PD-L1 and cisplatin-upregulated PD-L1 by attenuating STAT1 phosphorylation, thereby enhancing cisplatin's cytotoxicity against B16F10. Maltol augmented sensitivity to CTLL-2 cell-regulated melanoma destruction, leading to an increase in IL-2 production. Discussion: These findings demonstrate that maltol restricts melanoma growth through the downregulation of PD-L1 and elicits T cell-mediated anti-cancer responses, overcoming PD-L1-mediated immunotherapy resistance of cisplatin. Therefore, maltol can be considered as an effective therapeutic agent against melanoma.

Dual Role of DUOX1-Derived Reactive Oxygen Species in Melanoma

Melanoma is the most serious type of skin cancer. Inflammation and oxidative stress play an essential role in the development of several types of cancer, including melanoma. Although oxidative stress promotes tumor growth, once cells escape from the primary tumor, they are subjected to a more hostile environment, with higher levels of oxidative stress typically killing most cancer cells. As Dual Oxidase 1 (DUOX1) is a major producer of reactive oxygen species (ROS) in epithelia, we used allotransplantation and autochthonous melanoma models in zebrafish together with in silico analysis of the occurrence and relevance of DUOX1 expression of the skin cutaneous melanoma (SKCM) cohort of The Cancer Genome Atlas (TCGA) to address the role of this enzyme in the aggressiveness of melanoma cells in vivo. It was found that high transcript levels of the gene encoding DUOX1 were associated with the poor prognosis of patients in the early-stage melanoma of TCGA cohort. However, DUOX1 transcript levels were not found to be associated to the prognosis of late-stage SKCM patients. In addition, the transcript level of DUOX1 in metastatic SKCM was lower than in primary SKCM. Using zebrafish primary melanoma and allotransplantation models, we interrogated the role of DUOX1 in vivo. Our results confirmed a dual role of DUOX1, which restrains melanoma proliferation but promotes metastasis. As this effect is only observed in immunocompromised individuals, the immune system appears to be able to counteract this elevated metastatic potential of DUOX1-deficient melanomas.

Zebrafish Models to Study the Crosstalk between Inflammation and NADPH Oxidase-Derived Oxidative Stress in Melanoma

Melanoma is the deadliest form of skin cancer, and its incidence continues to increase. In the early stages of melanoma, when the malignant cells have not spread to lymph nodes, they can be removed by simple surgery and there is usually low recurrence. Melanoma has a high mortality rate due to its ability to metastasize; once melanoma has spread, it becomes a major health complication. For these reasons, it is important to study how healthy melanocytes transform into melanoma cells, how they interact with the immune system, which mechanisms they use to escape immunosurveillance, and, finally, how they spread and colonize other tissues, metastasizing. Inflammation and oxidative stress play important roles in the development of several types of cancer, including melanoma, but it is not yet clear under which conditions they are beneficial or detrimental. Models capable of studying the relevance of inflammation and oxidative stress in the early steps of melanocyte transformation are urgently needed, as they are expected to help recognize premetastatic lesions in patients by improving both early detection and the development of new therapies.

Emerging Management Approach for the Adverse Events of Immunotherapy of Cancer

Immunotherapy, which stimulates the body’s immune system, has received a considerable amount of press in recent years because of its powerful benefits. Cancer immunotherapy has shown long-term results in patients with advanced disease that are not seen with traditional chemotherapy. Immune checkpoint inhibitors, cytokines like interleukin 2 (IL-2) and interferon-alpha (IFN), and the cancer vaccine sipuleucel-T have all been licensed and approved by the FDA for the treatment of various cancers. These immunotherapy treatments boost anticancer responses by stimulating the immune system. As a result, they have the potential to cause serious, even fatal, inflammatory and immune-related side effects in one or more organs. Immune checkpoint inhibitors (ICPIs) and chimeric antigen receptor (CAR) T-cell therapy are two immunotherapy treatments that are increasingly being used to treat cancer. Following their widespread usage in the clinic, a wave of immune-related adverse events (irAEs) impacting virtually every system has raised concerns about their unpredictability and randomness. Despite the fact that the majority of adverse effects are minimal and should be addressed with prudence, the risk of life-threatening complications exists. Although most adverse events are small and should be treated with caution, the risk of life-threatening toxicities should not be underestimated, especially given the subtle and unusual indications that make early detection even more difficult. Treatment for these issues is difficult and necessitates a multidisciplinary approach involving not only oncologists but also other internal medicine doctors to guarantee quick diagnosis and treatment. This study’s purpose is to give a fundamental overview of immunotherapy and cancer-related side effect management strategies.

The Prognostic Relevance of PMCA4 Expression in Melanoma: Gender Specificity and Implications for Immune Checkpoint Inhibition

PMCA4 is a critical regulator of Ca2+ homeostasis in mammalian cells. While its biological and prognostic relevance in several cancer types has already been demonstrated, only preclinical investigations suggested a metastasis suppressor function in melanoma. Therefore, we studied the expression pattern of PMCA4 in human skin, nevus, as well as in primary and metastatic melanoma using immunohistochemistry. Furthermore, we analyzed the prognostic power of PMCA4 mRNA levels in cutaneous melanoma both at the non-metastatic stage as well as after PD-1 blockade in advanced disease. PMCA4 localizes to the plasma membrane in a differentiation dependent manner in human skin and mucosa, while nevus cells showed no plasma membrane staining. In contrast, primary cutaneous, choroidal and conjunctival melanoma cells showed specific plasma membrane localization of PMCA4 with a wide range of intensities. Analyzing the TCGA cohort, PMCA4 mRNA levels showed a gender specific prognostic impact in stage I-III melanoma. Female patients with high transcript levels had a significantly longer progression-free survival. Melanoma cell specific PMCA4 protein expression is associated with anaplasticity in melanoma lung metastasis but had no impact on survival after lung metastasectomy. Importantly, high PMCA4 transcript levels derived from RNA-seq of cutaneous melanoma are associated with significantly longer overall survival after PD-1 blockade. In summary, we demonstrated that human melanoma cells express PMCA4 and PMCA4 transcript levels carry prognostic information in a gender specific manner.

The NOP14 nucleolar protein suppresses the function and stemness of melanoma stem-like cells through Wnt/beta-catenin signaling inactivation

Cancer stem cells (CSCs) are closely related to tumor occurrence, development, metastasis, drug resistance, and recurrence. The role of CSCs in melanoma is poorly understood. Our previous studies suggested that the NOP14 nucleolar protein (NOP14) is involved in melanoma pathogenesis regulation. Importantly, NOP14 overexpression inhibits the Wnt/beta (β)-catenin signaling pathway, an important mechanism regulating CSCs stemness. Therefore, in this study, we aimed to explore the role of NOP14 in the stemness and function of CSCs in melanoma in vitro. CD133, a stem cell marker, was used to identify melanoma stem-like cells (SLCs). NOP14 overexpression subsequently decreased the proportion of CD133⁺ SLCs, impaired the colony-forming capabilities, and downregulated the expression of Nanog, SOX2, and OCT4 stem cell markers in A375 and A875 cells, suggesting that NOP14 suppresses the stemness of melanoma SLCs. NOP14 overexpression suppressed the migration, invasion, and angiogenesis-inducing ability of A375-SLCs and A875-SLCs. NOP14 overexpression also inactivated Wnt/β-catenin signaling in melanoma CD133⁺ SLCs. The Wnt signaling activator BML-284 alleviated the effect of NOP14 overexpression on the stemness and function of melanoma CSCs. In conclusion, NOP14 suppresses the stemness and function of melanoma SLCs by inactivating Wnt/β-catenin signaling. Thus, NOP14 is a novel target for CSC treatment in melanoma.

Abbreviations: CSCs, cancer stem cells; SLCs, stem-like cells; NOP14, NOP14 nucleolar protein; SCID, severe combined immunodeficiency; β-catenin, beta-catenin; lv-NOP14, lentivirals expressing NOP14; PBS, phosphate buffer saline; HUVECs, human umbilical vein endothelial cells.

Correlation of CCL8 expression with immune cell infiltration of skin cutaneous melanoma: potential as a prognostic indicator and therapeutic pathway

BACKGROUND

The tumor microenvironment (TME) is critical in the progression and metastasis of skin cutaneous melanoma (SKCM). Differences in tumor-infiltrating immune cells (TICs) and their gene expression have been linked to cancer prognosis. Given that immunotherapy can be effective against SKCM, we aimed to identify key genes that regulate the immunological state of the TME in SKCM.

METHODS

Data from 471 SKCM patients in the The Cancer Genome Atlas were analyzed using ESTIMATE algorithms to generate an ImmuneScore, StromalScore, and EstimateScore for each patient. Patients were classified into low- or high-score groups based on median values, then compared in order to identify differentially expressed genes (DEGs). Then a protein-protein interaction (PPI) network was developed, and a prognostic model was created using uni- and multivariate Cox regression as well as the least absolute shrinkage and selection operator (LASSO). Key DEGs were identified using the web-based tool GEPIA. Profiles of TIC subpopulations in each patient were analyzed using CIBORSORT, and possible correlations between key DEG expression and TICs were explored. Levels of CCL8 were determined in SKCM and normal skin tissue using immunohistochemistry.

RESULTS

Two scores correlated positively with the prognosis of SKCM patients. Comparison of the low- and high-score groups revealed 1684 up-regulated and 18 down-regulated DEGs, all of which were enriched in immune-related functions. The prognostic model identified CCL8 as a key gene, which CIBERSORT found to correlate with M1 macrophages. Immunohistochemistry revealed strong expression in SKCM tissue, but failed to detect the protein in normal skin tissue.

CONCLUSIONS

CCL8 is a potential prognostic marker for SKCM, and it may become an effective target for melanoma in which M1 macrophages play an important role.

Early melanoma invasivity correlates with gut fungal and bacterial profiles

BACKGROUND

The microbiome is emerging as a crucial player of the immune checkpoint in cancer. Melanoma is a highly immunogenic tumour, and the gut microbiome composition has been correlated to prognosis and evolution of advanced melanoma and proposed as biomarker for immune checkpoint therapy.

OBJECTIVES

We investigated the gut fungal and bacterial composition in early-stage melanoma and correlated microbial profiles with histopathological features.

METHODS

Bacterial 16S rRNA and fungal ITS region sequencing was performed from faecal samples of patients affected by stage I and II melanoma, and healthy controls. A meta-analysis with gut microbiota data from metastatic melanoma patients was also carried out.

RESULTS

We found a combination of gut fungal and bacterial profiles significantly discriminating M patients from controls. In melanoma patients, we observed an abundance of Prevotella copri and yeasts belonging to the Saccharomycetales order. We found bacterial and fungal community correlated to melanoma invasiveness, whereas specific fungal profile correlated to melanoma regression. Bacteroides was identified as general marker of immunogenicity, being shared by regressive and invasive melanoma. In addition, the bacterial community from stage I and II patients were different in structure and richer than those from metastatic melanoma patients.

CONCLUSIONS

Gut microbiota composition in early-stage melanoma changes along the gradient from in situ to invasive (and metastatic) melanoma. Changes in the microbiota and mycobiota are correlated to the histological features of early-stage melanoma, and to the clinical course and response to immune therapies of advanced stage melanoma, through a direct or indirect immunomodulation.

A Retrospective, Observational Analysis of Tumor Infiltrating Lymphocytes and Tumor Regression in Melanoma

BACKGROUND

Tumor infiltrating lymphocytes (TILs) and regression are thought to be distinct markers of the immune response to melanoma.

OBJECTIVE

This study sought to analyze the relationship of TIL grade and presence of regression to each other and to other prognostic histopathologic and clinical values in melanoma.

MATERIALS AND METHODS

A retrospective analysis was conducted using patients diagnosed with melanoma between 2013 and 2019 whose complete histopathologic reports were available.

RESULTS

Regression was seen in 48.9%, 30.1% and 37.9% of patients with brisk, non-brisk, and absent TILs respectively (P=0.019). Melanoma tumors with brisk TILs were found to have a lower Breslow thickness than those with non-brisk or absent (P= 0.001). Tumors with regression were also found to have lower Breslow thickness (P<0.001). Neither TIL grade nor regression were protective of nodal metastasis or associated with improved survival.

CONCLUSION

Brisk TILs have a positive association with thinner tumors and the presence of tumor regression relative to non-brisk or absent TILs. This may suggest a more robust immune response in tumors with brisk TILs. Further exploration of the interplay between TIL grade, lymphocyte cell subtype and lymphocyte density may help explain this finding.

Cutaneous Melanoma Classification: The Importance of High-Throughput Genomic Technologies

Cutaneous melanoma is an aggressive tumor responsible for 90% of mortality related to skin cancer. In the recent years, the discovery of driving mutations in melanoma has led to better treatment approaches. The last decade has seen a genomic revolution in the field of cancer. Such genomic revolution has led to the production of an unprecedented mole of data. High-throughput genomic technologies have facilitated the genomic, transcriptomic and epigenomic profiling of several cancers, including melanoma. Nevertheless, there are a number of newer genomic technologies that have not yet been employed in large studies. In this article we describe the current classification of cutaneous melanoma, we review the current knowledge of the main genetic alterations of cutaneous melanoma and their related impact on targeted therapies, and we describe the most recent high-throughput genomic technologies, highlighting their advantages and disadvantages. We hope that the current review will also help scientists to identify the most suitable technology to address melanoma-related relevant questions. The translation of this knowledge and all actual advancements into the clinical practice will be helpful in better defining the different molecular subsets of melanoma patients and provide new tools to address relevant questions on disease management. Genomic technologies might indeed allow to better predict the biological - and, subsequently, clinical - behavior for each subset of melanoma patients as well as to even identify all molecular changes in tumor cell populations during disease evolution toward a real achievement of a personalized medicine.

Functional T Cell Reactivity to Melanocyte Antigens Is Lost during the Progression of Malignant Melanoma, but Is Restored by Immunization

Simple Summary

Healthy humans develop spontaneous CD8+ T cell responses to melanoma associated antigens (MA) expressed by normal melanocytes. This natural autoimmunity directed against melanocytes might confer protection against the development of malignant melanoma (MM), where MA are overexpressed tumor-associated antigens. We report that functional T cell reactivity to MA is diminished in untreated MM patients. Three lines of evidence suggest that the MA-reactive T cells present in healthy subjects undergo exhaustion once MM establishes itself. First, only the MA-specific T cell reactivity was affected in the MM patients. Second, in these patients, the residual MA-specific T cells were functionally impaired, showing a diminished per cell IFN-γ productivity. Third, immunizations with allogeneic melanoma cells restored natural CD8+ T cell autoimmunity to MA.

Abstract

Healthy human subjects develop spontaneous CD8+ T cell responses to melanoma associated antigens (MA) expressed by normal melanocytes, such as Tyrosinase, MAGE-A3, Melan/Mart-1, gp100, and NY-ESO-1. This natural autoimmunity directed against melanocytes might confer protection against the development of malignant melanoma (MM), where MA are present as overexpressed tumor-associated antigens. Consistent with this notion we report here that functional T cell reactivity to MA was found to be significantly diminished to MAGE-A3, Melan-A/Mart-1, and gp100 in untreated MM patients. Three lines of evidence suggest that the MA-reactive T cells present in healthy subjects undergo exhaustion once MM establishes itself. First, only the MA-specific T cell reactivity was affected in the MM patients; that to third party recall antigens was not. Second, in these patients, the residual MA-specific T cells, unlike third party antigen reactive T cells, were functionally impaired, showing a diminished per cell IFN-γ productivity. Third, we show that immunization with MA restored natural CD8+ T cell autoimmunity to MA in 85% of the MM patients. The role of natural T cell autoimmunity to tumor-associated MA is discussed based on discrete levels of T cell activation thresholds.

Current advancements and future perspectives of immunotherapy in colorectal cancer research

5-Fluorouracil (5-FU) is the first-line chemotherapy drug for colorectal cancer but most of the patients get resistant to the drug on a longer course of treatment. After the successful use of immunotherapy in melanoma treatment, it was explored with enthusiasm in different types of solid cancers including colorectal cancer. Nivolumab and pembrolizumab (Programmed cell death-1 blocking antibodies) have shown efficacy in the mismatch repair deficient high microsatellite instability (dMMR-MSI-H) subtype of metastatic colorectal cancer (CRC) patients. Immunotherapy has shown long time remission in a subset of metastatic CRC patients. The molecular mechanism and emerging roles of immunotherapy in colorectal cancer are explored in this review article and future directions for the proper utilization of the development in immunobiology are suggested.

α-MSH-PE38KDEL Kills Melanoma Cells via Modulating Erk1/2/MITF/TYR Signaling in an MC1R-Dependent Manner

Background/Objective

The immunotoxin α-MSH-PE38KDEL consisting of α-MSH and PE38KDEL showed high cytotoxicity on MSH receptor-positive melanoma cells, suggesting that α-MSH-PE38KDEL might be a potent drug for the treatment of melanoma. Herein, we explored whether the Erk1/2/MITF/TYR signaling, a verified target of α-MSH/MC1R, was involved in α-MSH-PE38KDEL-mediated cytotoxicity.

Methods

Human melanoma cell line A375, mouse melanoma cell line B16-F10, human breast cancer cell line MDA-MB-231 and human primary epidermal melanocytes (HEMa) with different expression levels of MC1R were used in this study. Cell apoptosis and viability were determined by using flow cytometry and MTT assays. Protein expressions were tested by Western blotting.

Results

The expression levels of MC1R in A375 and B16-F10 cells were significantly higher than that of MDA-MB-231 and HEMa. α-MSH-PE38KDEL treatment induced a significant inhibition in cell viability in A375 and B16-F10 cells, while showed no obvious influence in the viability of MDA-MB-231 and HEMa cells. However, knockdown of MC1R abolished α-MSH-PE38KDEL role in promoting cell apoptosis in A375 and B16-F10 cells, and upregulation of MC1R endowed α-MSH-PE38KDEL function to promote cell apoptosis in MDA-MB-231 and HEMa cells. Additionally, α-MSH-PE38KDEL treatment increased the phosphorylation levels of Erk1/2 and MITF (S73), and decreased MITF and TYR expressions in an MC1R-dependent manner. All of the treatments, including inhibition of Erk1/2 with PD98059, MC1R downregulation and MITF overexpression weakened the anti-tumor role of α-MSH-PE38KDEL in melanoma.

Conclusion

Collectively, this study indicates that α-MSH-PE38KDEL promotes melanoma cell apoptosis via modulating Erk1/2/MITF/TYR signaling in an MC1R-dependent manner.

Targeting Tumor-Associated Macrophages to Increase the Efficacy of Immune Checkpoint Inhibitors: A Glimpse into Novel Therapeutic Approaches for Metastatic Melanoma

Immune checkpoint inhibitors (ICIs) represent a promising therapeutic intervention for a variety of advanced/metastatic solid tumors, including melanoma, but in a large number of cases, patients fail to establish a sustained anti-tumor immunity and to achieve a long-lasting clinical benefit. Cells of the tumor micro-environment such as tumor-associated M2 macrophages (M2-TAMs) have been reported to limit the efficacy of immunotherapy, promoting tumor immune evasion and progression. Thus, strategies targeting M2-TAMs have been suggested to synergize with immune checkpoint blockade. This review recapitulates the molecular mechanisms by which M2-TAMs promote cancer immune evasion, with focus on the potential cross-talk between pharmacological interventions targeting M2-TAMs and ICIs for melanoma treatment.

Gene editing in dermatology: Harnessing CRISPR for the treatment of cutaneous disease

The discovery of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) system has revolutionized gene editing research. Through the repurposing of programmable RNA-guided CRISPR-associated (Cas) nucleases, CRISPR-based genome editing systems allow for the precise modification of specific sites in the human genome and inspire novel approaches for the study and treatment of inherited and acquired human diseases. Here, we review how CRISPR technologies have stimulated key advances in dermatologic research.  We discuss the role of CRISPR in genome editing for cutaneous disease and highlight studies on the use of CRISPR-Cas technologies for genodermatoses, cutaneous viruses and bacteria, and melanoma. Additionally, we examine key limitations of current CRISPR technologies, including the challenges these limitations pose for the widespread therapeutic application of CRISPR-based therapeutics.

FoxP3, CTLA-4, and IDO in Canine Melanocytic Tumors

Despite promising immunotherapy strategies in human melanoma, there are few studies on the immune environment of canine melanocytic tumors. In humans, the activation of immunosuppressive cell subpopulations, such as regulatory T cells (Tregs) that express forkhead box protein P3 (FoxP3), the engagement of immunosuppressive surface receptors like cytotoxic T lymphocyte antigen (CTLA-4), and the secretion of molecules inhibiting lymphocyte activation, such as indoleamine-pyrrole 2,3-dioxygenase (IDO), are recognized as immunoescape mechanisms that allow tumor growth and progression. The aim of our study was to investigate the expression of these immunosuppression markers in canine melanocytic tumors and to postulate their possible role in melanoma biology and progression. Fifty-five formalin-fixed, paraffin-embedded canine melanocytic tumors (25 oral melanomas; 20 cutaneous melanomas; 10 cutaneous melanocytomas) were selected to investigate the expression of FoxP3, CTLA-4, and IDO by immunohistochemistry and RT-qPCR (real-time quantitative polymerase chain reaction). All of the tested markers showed high gene and protein expression in oral melanomas and were differently expressed in cutaneous melanomas when compared to their benign counterpart. IDO expression was associated with an increased hazard of death both in univariable and multivariable analyses (P < .05). FoxP3 protein expression >6.9 cells/HPF (high-power field) was an independent predictor of death (P < .05). CTLA-4 gene and protein expressions were associated with a worse prognosis, but only in the univariable analysis (P < .05). FoxP3, CTLA-4, and IDO likely play a role in canine melanoma immunoescape. Their expression, if supported by future studies, could represent a prognostic tool in canine melanoma and pave the way to future immunotherapeutic approaches in dogs.

Significance of Tumor Mutation Burden in Immune Infiltration and Prognosis in Cutaneous Melanoma

Background: Melanoma is highly immunogenic and therefore suitable for immunotherapy, but the efficacy is limited by response rate. In several types of tumor, tumor mutation burden (TMB) and immune infiltration have been reported to predict the response to immunotherapy, although each has its limitations. In the current study, we aimed to explore the association of TMB with immune infiltration and prognosis in cutaneous melanoma. Methods: The data of cutaneous melanoma used for analyses was downloaded from The Cancer Genome Atlas (TCGA) database. The mutation data was sorted using "maftools" R package. TMB was estimated and then patients were divided into two groups based on TMB. The association of TMB with prognosis and clinical characteristics was explored. Differential analysis between two TMB groups was performed using "DESeq2" R package to identify differentially expressed genes (DEGs). The function enrichment analyses of DEGs were conducted to screen critical pathways. Besides, DEGs were further filtered to identify two hub genes, based on which a risk score model and nomogram for predicting prognosis were conducted, and the validation was performed using three datasets from Gene Expression Omnibus (GEO) database. Finally, CIBERSORT algorithm and TIMER database were used to assess the effect of TMB and hub genes on immune infiltration. Results: The most common mutation was C > T, and the top three frequently mutated genes were TTN, MUC16, and BRAF. Higher TMB indicated better survival outcomes and lower pathological stages. 735 DEGs were identified and mainly involved in immune-related and adhesion-related pathways. The risk score model and nomogram were validated using receiver operating characteristic (ROC) curves and calibration curves, and exhibited relatively high predictive capability. Decision curve analysis (DCA) was used to assess clinical benefit. As for immune infiltration, the proportion was higher for macrophages M1 and M2 in the high-TMB group, while lower for memory B cells and regulatory T cells. Conclusions: In cutaneous melanoma, TMB was positively correlated with prognosis. The risk score model and nomogram can be conveniently used to predict prognosis. The association of TMB with immune infiltration can help improve the predicting methods for the response to immunotherapy.

Dihydroartemisinin inhibits melanoma by regulating CTL/Treg anti-tumor immunity and STAT3-mediated apoptosis via IL-10 dependent manner

BACKGROUND

It has been shown that dihydroartemisinin (DHA) is effective in the treatment of malaria. Recently studies have demonstrated that DHA also regulates tumor cell growth, angiogenesis, T cell differentiation and generation. However, how DHA affects melanoma development remains poorly defined.

OBJECTIVES

To investigate the effects of DHA on the proliferation and migration of melanoma in vivo and in vitro, and to explore its possible mechanism.

METHODS

B16F10 cells and melanoma-bearing BALB/c mice were used to investigate the effects of DHA on melanoma.

RESULTS

DHA had inhibitory effect on melanoma proliferation in a time-and dose-dependent manner. Treatment of DHA attenuated melanoma severity and histopathological changes in BALB/c mice. DHA also inhibited melanoma invasion, migration, and community formation in a dose-dependent manner. Flow cytometry revealed a significant increase in IFN-γ⁺CD8⁺ T cells in the DHA groups. In tumor microenvironment and spleen, DHA induced expansion of CD8⁺CTL, while, CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cells and IL-10⁺CD4⁺CD25⁺ T cells were normalized by DHA treatment. DHA diminished expression of IL-10 and IL-6, and increased the expression of IFN-γ in the tumor and spleen. Moreover, DHA administration significantly promoted the mitochondrial apoptosis of melanoma by regulating the STAT3 pathway.

CONCLUSION

DHA induces mitochondrial apoptosis and alters cytokines expression by inhibiting the phosphorylation of STAT3. DHA improves anti-tumor immunity in mice through controlling CD8⁺CTL function by counteracting IL-10-dependent Treg cells suppression, which promises to be an alternative drug for melanoma.

Gene editing in dermatology: Harnessing CRISPR for the treatment of cutaneous disease

The discovery of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) system has revolutionized gene editing research. Through the repurposing of programmable RNA-guided CRISPR-associated (Cas) nucleases, CRISPR-based genome editing systems allow for the precise modification of specific sites in the human genome and inspire novel approaches for the study and treatment of inherited and acquired human diseases. Here, we review how CRISPR technologies have stimulated key advances in dermatologic research.  We discuss the role of CRISPR in genome editing for cutaneous disease and highlight studies on the use of CRISPR-Cas technologies for genodermatoses, cutaneous viruses and bacteria, and melanoma. Additionally, we examine key limitations of current CRISPR technologies, including the challenges these limitations pose for the widespread therapeutic application of CRISPR-based therapeutics.

Modern Aspects of Immunotherapy with Checkpoint Inhibitors in Melanoma

Although melanoma is one of the most immunogenic tumors, it has an ability to evade anti-tumor immune responses by exploiting tolerance mechanisms, including negative immune checkpoint molecules. The most extensively studied checkpoints represent cytotoxic T lymphocyte-associated protein-4 (CTLA-4) and programmed cell death protein 1 (PD-1). Immune checkpoint inhibitors (ICI), which were broadly applied for melanoma treatment in the past decade, can unleash anti-tumor immune responses and result in melanoma regression. Patients responding to the ICI treatment showed long-lasting remission or disease control status. However, a large group of patients failed to respond to this therapy, indicating the development of resistance mechanisms. Among them are intrinsic tumor properties, the dysfunction of effector cells, and the generation of immunosuppressive tumor microenvironment (TME). This review discusses achievements of ICI treatment in melanoma, reasons for its failure, and promising approaches for overcoming the resistance. These methods include combinations of different ICI with each other, strategies for neutralizing the immunosuppressive TME and combining ICI with other anti-cancer therapies such as radiation, oncolytic viral, or targeted therapy. New therapeutic approaches targeting other immune checkpoint molecules are also discussed.

Citrus unshiu peel suppress the metastatic potential of murine melanoma B16F10 cells in vitro and in vivo

The peel of Citrus unshiu Marcow. fruits (CU) has long been used as a traditional medicine that has therapeutic effects against pathogenic diseases, including asthma, vomiting, dyspepsia, blood circulation disorders, and various types of cancer. In this study, we investigated the effect of CU peel on metastatic melanoma, a highly aggressive skin cancer, in B16F10 melanoma cells, and in B16F10 cells inoculated‐C57BL/6 mice. Our results show that ethanol extracts of CU (EECU) inhibited cell growth and increased the apoptotic cells in B16F10 cells. EECU also stimulated the induction of mitochondria‐mediated intrinsic pathway, with reduced mitochondrial membrane potential and increased generation of intracellular reactive oxygen species. Furthermore, EECU suppressed the migration, invasion, and colony formation of B16F10 cells. In addition, the oral administration of EECU reduced serum lactate dehydrogenase activity without weight loss, hepatotoxicity, nor nephrotoxicity in B16F10 cell‐inoculated mice. Moreover, EECU markedly suppressed lung hypertrophy, the number and expression of metastatic tumor nodules, and the expression of inflammatory tumor necrosis factor‐alpha in lung tissue. In conclusion, our findings suggest that the inhibitory effect of EECU on the metastasis of melanoma indicates that it may be regarded as a potential therapeutic herbal drug for melanoma.

Overexpression of microRNA‑21 inhibits the growth and metastasis of melanoma cells by targeting MKK3

Melanoma is an aggressive skin carcinoma with poor prognosis, and is prevalent worldwide. It was demonstrated that microRNA (miR)‑21 and mitogen‑activated protein kinase kinase 3 (MKK3) both participated in the occurrence and development of various tumors; however, their detailed roles in the progression of melanoma remain unclear. Reverse transcription‑quantitative PCR (RT‑qPCR) and western blot analyses were conducted to examine the expression levels of miR‑21 and MKK3 in clinical specimens of patients with melanoma and melanoma cell lines. A dual‑luciferase reporter assay was performed to verify the target interaction between miR‑21 and MKK3. The mRNA and protein expressions of MKK3 were measured using RT‑qPCR and western blot analysis, respectively, following transfection with miR‑21 mimics and inhibitor. Subsequently, Cell Counting Kit‑8 and colony formation assays, and flow cytometry were conducted to assess the effects of miR‑21 and MKK3 on the cell growth of melanoma. Cell migration and invasion experiments were performed to evaluate the effects of miR‑21 and MKK3 on the cell metastasis of melanoma. It was revealed that MKK3 was upregulated, and miR‑21 was downregulated in patients with melanoma and melanoma cell lines. MKK3 was demonstrated to be a direct target of miR‑21. Furthermore, it was demonstrated that upregulated miR‑21 expression and downregulated MKK3 expression suppressed cell proliferation and colony formation, promoted apoptosis, delayed the cell cycle, and inhibited cell migration and invasion. The present findings suggested that miR‑21 could inhibit the cell growth and metastasis of melanoma by negatively regulating MKK3.

Decreased T-Cell Programmed Death Receptor-1 Expression in Pregnancy-Associated Melanoma

INTRODUCTION

Pregnancy depends on tolerance of an immunologically foreign fetus through type 1 T-cell suppression. Worse melanoma outcomes have been described within 1 year of childbirth. We assessed immunopathologic factors that may account for the observed negative impact of pregnancy on outcome.

MATERIALS AND METHODS

Women of child-bearing age with ≥24 months follow-up were identified from our Institutional Melanoma Registry. Women with available primary tumor blocks were compared [history of childbirth within 1 year of diagnosis (CB1Y) (n = 18) vs. nonpregnant age-matched controls (n = 13)]. Immunohistochemical staining with quantification of immune infiltrates: CD68 tumor-associated macrophages, CD3 tumor-infiltrating T cells, and PD-1 activated/exhausted T cells; and hematolymphangiogenesis: CD31/D2-40 blood vessels and D2-40 lymphatics was performed by 2 blinded dermatopathologists.

RESULTS

CB1Y tumors showed decreased CD3 tumor-infiltrating T cells (P < 0.05) with significantly reduced PD1 expression (P ≤ 0.05). The CD3:PD1 ratio was higher in CB1Y (P < 0.05). Other tested parameters did not significantly differ between the 2 groups.

DISCUSSION

As PD1 expression is induced during type 1 T-cell activation, these data suggest that immune ignorance or suppression may predominate in CB1Y. Further studies are required to identify interventions that may promote tumor-associated T-cell inflammation in such patients.

FoxP3 and IDO in Canine Melanocytic Tumors

Human melanoma is one of the deadliest forms of cancer, with poor prognosis and high resistance to chemotherapy and radiotherapy. The discovery of immunosuppressive mechanisms in the human melanoma microenvironment led to the use of new prognostic markers and to the development of immunotherapies targeting immune checkpoint molecules. Immunoescape mechanisms in canine melanoma have not yet been investigated, and no such immunotherapy has been tested. The aim of this study was to provide preliminary data on the expression of transcription factor forkhead box protein P3 (FoxP3) and indoleamine 2,3-dioxygenase (IDO) in primary canine melanocytic tumors and to investigate their prognostic role. Formalin-fixed, paraffin-embedded samples from 74 canine melanocytic tumors (26 oral melanomas, 23 cutaneous melanomas, and 25 cutaneous melanocytomas) were retrospectively evaluated by immunohistochemistry to explore the expression of FoxP3 and IDO. An increased risk of death due to melanoma was associated with a higher number of FoxP3+ cells per high-power field (FoxP3+/HPF), a higher percentage of CD3+ cells that were also FoxP3+ infiltrating and surrounding the tumor (%FoxP3), and a higher number of IDO+ cells/HPF (IDO+/HPF). A prognostic value for FoxP3 and IDO is suggested by our study, with optimal cutoffs of 14.7 FoxP3+ cells/HPF, 6.1 IDO+ cells/HPF, and 12.5% FoxP3+ cells. Both markers were also associated with tumor type. Multivariable analysis identified IDO+/HPF ( P < .001) as an independent prognostic marker. Even though stratification by diagnosis caused a loss of significance, results from the present study suggest a prognostic role for IDO and FoxP3, possibly related to the establishment of an immunosuppressive microenvironment.

A Task Force Against Local Inflammation and Cancer: Lymphocyte Trafficking to and Within the Skin

The skin represents a specialized site for immune surveillance consisting of resident, inflammatory and memory populations of lymphocytes. The entry and retention of T cells, B cells, and ILCs is tightly regulated to facilitate detection of pathogens, inflammation and tumors cells. Loss of individual or multiple populations in the skin may break tolerance or increase susceptibility to tumor growth and spread. Studies have significantly advanced our understanding of the role of skin T cells and ILCs at steady state and in inflammatory settings such as viral challenge, atopy, and autoimmune inflammation. The knowledge raised by these studies can benefit to our understanding of immune cell trafficking in primary melanoma, shedding light on the mechanisms of tumor immune surveillance and to improve immunotherapy. This review will focus on the T cells, B cells, and ILCs of the skin at steady state, in inflammatory context and in melanoma. In particular, we will detail the core chemokine and adhesion molecules that regulate cell trafficking to and within the skin, which may provide therapeutic avenues to promote tumor homing for a team of lymphocytes.