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With an increasing incidence of malignant melanoma, new prognostic biomarkers for clinical decision making have become more important. In this study, we evaluated the role of ecto-NOX disulfide-thiol exchanger 2 (ENOX2/tNOX), a cancer- and growth-associated protein, in the prognosis and therapy of primary malignant melanoma. We conducted a tissue microarray analysis of immunohistochemical ENOX2 protein expression and The Cancer Genome Atlas (TCGA) ENOX2 RNA expression analysis, as well as viability assays and Western blots of melanoma cell lines treated with the ENOX2 inhibitor phenoxodiol (PXD) and BRAF inhibitor (BRAFi) vemurafenib. We discovered that high ENOX2 expression is associated with decreased overall (OS), disease-specific (DSS) and metastasis-free survival (MFS) in primary melanoma (PM) and a reduction in electronic tumor-infiltrating lymphocytes (eTILs). A gradual rise in ENOX2 expression was found with an increase in malignant potential from benign nevi (BNs) via PMs to melanoma metastases (MMs), as well as with an increasing tumor thickness and stage. These results highlight the important role of ENOX2 in cancer growth, progression and metastasis. The ENOX2 expression was not limited to malignant cell lines but could also be found in keratinocytes, fibroblasts and melanocytes. The viability of melanoma cell lines could be inhibited by PXD. A reduced induction of phospho-AKT under PXD could prevent the development of acquired BRAFi resistance. In conclusion, ENOX2 may serve as a potential prognostic marker and therapeutic target in malignant melanoma.

Phototoxicity and skin cancer are severe adverse effects of the anti-fungal drug voriconazole (VOR). These adverse effects resemble those seen in xeroderma pigmentosum, caused by defective DNA nucleotide excision repair (NER), and we show that VOR decreases NER capacity. We show that VOR treatment does not perturb the expression of NER, or other DNA damage-related genes, but that VOR localizes to heterochromatin, in complexes containing histone acetyltransferase general control of amino-acid synthesis 5-like 2. Impairment of general control of amino-acid synthesis 5-like 2 binding to histone H3 reduced acetylation of H3, restricting damage-dependent chromatin unfolding, thereby reducing NER initiation. Restoration of H3 histone acetylation using histone deacetylase inhibitors, rescued VOR-induced NER repression, thus offering a preventive therapeutic option. These findings underline the importance of DNA damage-dependent chromatin remodeling as an important prerequisite of functional DNA repair., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Rationale: Immune checkpoint inhibitor (ICI)-related pneumonitis is a serious autoimmune event affecting as many as 20% of patients with non-small-cell lung cancer (NSCLC), yet the factors underpinning its development in some patients and not others are poorly understood. Objectives: To investigate the role of autoantibodies and autoreactive T cells against surfactant-related proteins in the development of pneumonitis. Methods: The study cohort consisted of patients with NSCLC who provided blood samples before and during ICI treatment. Serum was used for proteomics analyses and to detect autoantibodies present during pneumonitis. T-cell stimulation assays and single-cell RNA sequencing were performed to investigate the specificity and functionality of peripheral autoreactive T cells. The findings were confirmed in a validation cohort comprising patients with NSCLC and patients with melanoma. Measurements and Main Results: Across both cohorts, patients in whom pneumonitis developed had higher pretreatment levels of immunoglobulin G autoantibodies targeting surfactant protein (SP)-B. At the onset of pneumonitis, these patients also exhibited higher frequencies of CD4 + IFN-γ-positive SP-B-specific T cells and expanding T-cell clonotypes recognizing this protein, accompanied by a proinflammatory serum proteomic profile. Conclusions: Our data suggest that the cooccurrence of SP-B-specific immunoglobulin G autoantibodies and CD4 + T cells is associated with the development of pneumonitis during ICI therapy. Pretreatment levels of these antibodies may represent a potential biomarker for an increased risk of developing pneumonitis, and on-treatment levels may provide a diagnostic aid.

Elevated levels of peripheral blood and tumor tissue neutrophils are associated with poorer clinical response and therapy resistance in melanoma. The underlying mechanism and the role of neutrophils in targeted therapy is still not fully understood. Serum samples of patients with advanced melanoma were collected and neutrophil-associated serum markers were measured and correlated with response to targeted therapy. Blood neutrophils from healthy donors and patients with advanced melanoma were isolated, and their phenotypes, as well as their in vitro functions, were compared. In vitro functional tests were conducted through nonadherent cocultures with melanoma cells. Protection of melanoma cell lines by neutrophils was assessed under MAPK inhibition. Blood neutrophils from advanced melanoma patients exhibited lower CD16 expression compared to healthy donors. In vitro, both healthy-donor- and patient-derived neutrophils prevented melanoma cell apoptosis upon dual MAPK inhibition. The effect depended on cell-cell contact and melanoma cell susceptibility to treatment. Interference with protease activity of neutrophils prevented melanoma cell protection during treatment in cocultures. The negative correlation between neutrophils and melanoma outcomes seems to be linked to a protumoral function of neutrophils. In vitro, neutrophils exert a direct protective effect on melanoma cells during dual MAPK inhibition. This study further hints at a crucial role of neutrophil-related protease activity in protection.

Recent advances in melanoma therapy have significantly improved the prognosis of metastasized melanoma. However, large therapeutic gaps remain that need to be closed by new strategies. Antiapoptotic Bcl-2 proteins critically contribute to apoptosis deficiency and therapy resistance. They can be targeted by BH3 mimetics, small molecule antagonists that mimic the Bcl-2 homology domain 3 (BH3) of proapoptotic BH3-only proteins. By applying in vitro experiments, we aimed to obtain an overview of the possible suitability of BH3 mimetics for future melanoma therapy. Thus, we investigated the effects of ABT-737 and ABT-263, which target Bcl-2, Bcl-x L and Bcl-w as well as the Bcl-2-selective ABT-199 and the Mcl-1-selective S63845, in a panel of four BRAF -mutated and BRAF -WT melanoma cell lines. None of the inhibitors showed significant effectiveness when used alone; however, combination of S63845 with each one of the three ABTs almost completely abolished melanoma cell survival and induced apoptosis in up to 50-90% of the cells. Special emphasis was placed here on the understanding of the downstream pathways involved, which may allow improved applications of these strategies. Thus, cell death induction was correlated with caspase activation, loss of mitochondrial membrane potential, phosphorylation of histone H2AX, and ROS production. Caspase dependency was demonstrated by a caspase inhibitor, which blocked all effects. Upregulation of Mcl-1, induced by S63845 itself, as reported previously, was blocked by the combinations. Indeed, Mcl-1, as well as XIAP (X-linked inhibitor of apoptosis), were strongly downregulated by combination treatments. These findings demonstrate that melanoma cells can be efficiently targeted by BH3 mimetics, but the right combinations have to be selected. The observed pronounced activation of apoptosis pathways demonstrates the decisive role of apoptosis in the loss of cell viability by BH3 mimetics.

Background: MEK inhibitors (MEKi) were shown to be clinically insufficiently effective in patients suffering from BRAF wild-type (BRAF WT) melanoma, even if the MAPK pathway was constitutively activated due to mutations in NRAS or NF-1. Thus, novel combinations are needed to increase the efficacy and duration of response to MEKi in BRAF WT melanoma. Disulfiram and its metabolite diethyldithiocarbamate are known to have antitumor effects related to cellular stress, and induction of endoplasmic reticulum (ER) stress was found to synergize with MEK inhibitors in NRAS-mutated melanoma cells. Therefore, we investigated the combination of both therapeutics to test their effects on BRAF-WT melanoma cells and compared them with monotherapy using the MEKi trametinib., Methods: The effects of combined therapy with disulfiram or its metabolite diethyldithiocarbamate and the MEKi trametinib were evaluated in a series of BRAF-WT melanoma cell lines by measuring cell viability and apoptosis induction. Cytotoxicity was additionally assessed in 3D spheroids, ex vivo melanoma slice cultures, and in vivo xenograft mouse models. The response of melanoma cells to treatment was studied at the RNA and protein levels to decipher the mode of action. Intracellular and intratumoral copper measurements were performed to investigate the role of copper ions in the antitumor cytotoxicity of disulfiram and its combination with the MEKi., Results: Diethyldithiocarbamate enhanced trametinib-induced cytotoxicity and apoptosis induction in 2D and 3D melanoma culture models. Mechanistically, copper-dependent induction of oxidative stress and ER stress led to Janus kinase (JNK)-mediated apoptosis in melanoma cells. This mechanism was also detectable in patient-derived xenograft melanoma models and resulted in a significantly improved therapeutic effect compared to monotherapy with the MEKi trametinib., Conclusions: Disulfiram and its metabolite represent an attractive pharmaceutical approach to induce ER stress in melanoma cells that potentiates the antitumor effect of MEK inhibition and may be an interesting candidate for combination therapy of BRAF WT melanoma., (© 2024. The Author(s).)

Introduction: Patients with NRAS-mutant metastatic melanoma often have an aggressive disease requiring a fast-acting, effective therapy. The MEK inhibitor binimetinib shows an overall response rate of 15% in patients with NRAS-mutant melanoma, providing a backbone for combination strategies. Our previous studies demonstrated that in NRAS-mutant melanoma, the antitumor activity of the MEK inhibitor binimetinib was significantly potentiated by the BRAFV600E/K inhibitor encorafenib through the induction of ER stress, leading to melanoma cell death by apoptotic mechanisms. Encorafenib combined with binimetinib was well tolerated in a phase III trial showing potent antitumor activity in BRAF-mutant melanoma, making a rapid evaluation in NRAS-mutant melanoma imminently feasible. These data provide a mechanistic rationale for the evaluation of binimetinib combined with encorafenib in preclinical and clinical studies on NRAS-mutant metastatic melanoma., Methods: The combination of BRAFi plus MEKi was tested in a monolayer culture of patient-derived cell lines and in corresponding patient-derived tissue slice cultures of NRAS-mutant melanoma. To investigate the treatment in vivo, NSG (NOD. Cg- Prkdc scid Il2rg tm1Wjl /SzJ) mice were subcutaneously injected with three different BRAF wild-type melanoma models harboring oncogenic NRAS mutations and treated orally with encorafenib (6 mg/kg body weight, daily) with or without binimetinib (8 mg/kg body weight, twice daily). In parallel, an individual healing attempt was carried out by treating one patient with an NRAS-mutated tumor., Results: Encorafenib was able to enhance the inhibitory effect on cell growth of binimetinib only in the cell line SKMel147 in vitro. It failed to enhance the apoptotic effect found in two other NRAS-mutated cell lines. Encorafenib led to a hyperactivation of ERK which could be reduced with the combinational treatment. In two of the three patient-derived tissue slice culture models of NRAS-mutant melanomas, a slight tendency of a combinatorial effect was seen which was not significant. Encorafenib showed a slight induction of the ER stress genes ATF4 , CHOP , and NUPR1 . The combinational treatment was able to enhance this effect, but not significantly. In the mouse model, the combination therapy of encorafenib with binimetinib resulted in reduced tumor growth compared to the control and encorafenib groups; however, the best effect in terms of tumor growth inhibition was measured in the binimetinib therapy group. The therapy showed no effect in an individual healing attempt for a patient suffering from metastatic, therapy-refractory NRAS-mutated melanoma., Conclusion: In in vitro and ex vivo settings, the combination therapy was observed to elicit a response; however, it did not amplify the efficacy observed with binimetinib alone, whereas in a patient, the combinational treatment remained ineffective. The preclinical in vivo data showed no increased combinatorial effect. However, the in vivo effect of binimetinib as monotherapy was unexpectedly high in the tested regimen. Nevertheless, binimetinib proved to be advantageous in the treatment of melanoma in vivo and led to high rates of apoptosis in vitro; hence, it still seems to be a good base for combination with other substances in the treatment of patients with NRAS-mutant melanoma.

Background: The role of autoreactive T cells on the course of Coronavirus disease-19 (COVID-19) remains elusive. Type II pneumocytes represent the main target cells of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Autoimmune responses against antigens highly expressed in type II pneumocytes may influence the severity of COVID-19 disease., Objective: The aim of this study was to investigate autoreactive T cell responses against self-antigens highly expressed in type II pneumocytes in the blood of COVID-19 patients with severe and non-severe disease., Methods: We collected blood samples of COVID-19 patients with varying degrees of disease severity and of pre-pandemic controls. T cell stimulation assays with peptide pools of type II pneumocyte antigens were performed in two independent cohorts to analyze the autoimmune T cell responses in patients with non-severe and severe COVID-19 disease. Target cell lysis assays were performed with lung cancer cell lines to determine the extent of cell killing by type II PAA-specific T cells., Results: We identified autoreactive T cell responses against four recently described self-antigens highly expressed in type II pneumocytes, known as surfactant protein A, surfactant protein B, surfactant protein C and napsin A, in the blood of COVID-19 patients. These antigens were termed type II pneumocyte-associated antigens (type II PAAs). We found that patients with non-severe COVID-19 disease showed a significantly higher frequency of type II PAA-specific autoreactive T cells in the blood when compared to severely ill patients. The presence of high frequencies of type II PAA-specific T cells in the blood of non-severe COVID-19 patients was independent of their age. We also found that napsin A-specific T cells from convalescent COVID-19 patients could kill lung cancer cells, demonstrating the functional and cytotoxic role of these T cells., Conclusions: Our data suggest that autoreactive type II PAA-specific T cells have a protective role in SARS-CoV-2 infections and the presence of high frequencies of these autoreactive T cells indicates effective viral control in COVID-19 patients. Type II-PAA-specific T cells may therefore promote the killing of infected type II pneumocytes and viral clearance., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Competing Interests: Conflicts of interest Dr Amaral reports personal honoraria from BMS, CeCaVa, Novartis, and Pierre Fabre, institutional financial support from iFIT, NeraCare, Novartis, Sanofi, and SkylineDx, and institutional research grants from Novartis, outside the submitted work. Drs Sinnberg and Niessner report institutional funding from Novartis and Pierre Fabre outside the submitted work. Dr Ring listed as inventors of the patent entitled “Arenavirus particles to treat solid tumors” (patent number WO2018/185307 A1) describing the application of artLCMV vectors in the treatment of tumors, outside the submitted work. Dr Joerger reports advisory role (institutional): Novartis, AstraZeneca, Basilea Pharmaceutica, Bayer, BMS, Debiopharm, MSD, Roche, and Sanofi, research funding: Swiss Cancer Research, and travel grants: Roche, Sanofi, and Takeda. Dr Schroeder reports institutional grants from Illumina and research grants from BMS Stiftung Immunonkologie outside the submitted work. Dr Cozzio has served as adviser for and/or received speaking fees from AbbVie, Almirall, Amgen, BMS, Eli Lilly, Galderma, LEO Pharma, Janssen-Cilag, Novartis, Pfizer, Pierre Fabre Pharma, Sanofi, and UCB, outside the submitted work. Dr Leiter reports research support from MSD, consulting fees and honoraria from Sun Pharma, Sanofi (personal and institutional), MSD (personal and institutional), Novartis, Roche, and Almirall Hermal, support for attending meeting from Sun Pharma and participation on a Data Safety Monitoring Board or Advisory Board from Sun Pharma, Sanofi, MSD, Novartis, Roche, and Almirall Hermal, outside the submitted work. Dr Thomas reports honoraria for talks or advisory boards from BMS and Pierre Fabre and also reports research funding (institutional) from BMS, Pfizer, MSD, Amgen, argenx, LEO, Novartis, UCB, 4SC, AstraZeneca, BioNtech, Genentech, Roche, Biotech, CureVac, HUYA, Incyte, Idera, Iovance, InflaRx, CerpassRx, Kartos, Nektar, Philogen, Pierre Fabre, Regeneron, Replimune, and Sanofi. Dr Garbe reports personal fees from Amgen, MSD, and Philogen and grants and personal fees from Novartis, NeraCare, BMS, Roche, and Sanofi, outside the submitted work. Dr Forchhammer received personal fees from Recordati, Kyowa Kirin, and Takeda Pharmaceuticals (speakers’ honoraria) as well as institutional grants from NeraCare, SkylineDx, and BioNTech outside the submitted work. Dr Levesque has received project-specific research funding outside the scope of this work from Novartis, Roche, Molecular Partners, and Oncobit. Dr Mangana has intermittent projects focused consultancy or advisory relationships with Merck/Pfizer, MSD, Amgen, Novartis, Roche, BMS, and Pierre Fabre and has received travel support from Ultrasun, L’Oreal, MSD, BMS, and Pierre Fabre outside of the submitted work. Dr Dummer reports research funding to their institution for clinical studies from MSD and consulting or advisory roles with MSD, Novartis, Roche, BMS, Amgen, Takeda, Pierre Fabre, Sun Pharma, Sanofi, Catalym, Second Genome, Regeneron, Alligator, T3 Pharma, MaxiVAX, Pfizer, and touchIME outside the submitted work. Dr Schürch is on the Scientific Advisory Board of and has received research funding from Enable Medicine, Inc, both outside the current work. Dr Forschner served as consultant to Roche, Novartis, MSD, BMS, and Pierre Fabre, received travel support from Roche, Novartis, BMS, and Pierre Fabre, received speaker fees from Roche, Novartis, BMS, MSD, and CeGaT and also reports institutional research grants from BMS Stiftung Immunonkologie. Dr Flatz reports grants or contracts from Hookipa Pharma, SAKK/Immunophotonics, DFG grant (Deutsche Forschungsgemeinschaft), Philogen, and Mundipharma, consulting fees from Philogen, Sanofi, Novartis, and BMS, participation on Data Safety Board University of Basel, outside the submitted work. The other authors have no conflicts of interest to declare.

Background: Currently, there remains an incomplete view of cancer stem cells (CSCs) in solid tumours., Methods: We studied a panel of putative CSC surface markers (ALDH1A1, ABCG2, CD44v7/8, CD44v10, CD133, CD271, and Nestin) in 40 established melanoma cell lines and four early-passage melanoma strains by flow cytometry. We additionally examined 40 formalin-fixed paraffin-embedded melanoma tissues using immunofluorescence microscopy. This was compared with their expression in healthy skin, normal differentiated melanocytes and fibroblasts., Results: Most of the putative CSC markers were expressed by both melanoma cell lines and tissues. When present, these proteins were expressed by the majority of cells in the population. However, the expression of these markers by cells in healthy skin sections, normal differentiated melanocytes, and fibroblasts revealed that differentiated non-malignant cells also expressed CSC markers indicating that they lack of specificity for CSCs. Culturing cell lines under conditions more characteristic of the tumour microenvironment upregulated CSC marker expressions in a proportion of cell lines, which correlated with improved cell growth and viability., Conclusions: The testing of melanoma cell lines (n = 40), early-passage cell strains (n = 4), and melanoma tissues (n = 40) showed that several putative CSC markers (ALDH1A1, ABCG2, CD44v7/8, CD44v10, CD133, CD271, and Nestin) are commonly present in a large proportion of melanoma cells in vitro and in situ . Further, we showed that these putative markers lack specificity for CSCs because they are also expressed in differentiated non-malignant cell types (melanocytes, fibroblasts, and skin), which could limit their use as therapeutic targets. These data are consistent with the emerging notion of CSC plasticity and phenotype switching within cancer cell populations., Competing Interests: The authors declare no conflict of interest. Given the role as Editor in Chief, Graham Pawelec had no involvement in the peer-review of this article and has no access to information regarding its peer-review. Full responsibility for the editorial process for this article was delegated to Alfredo Budillon., (© 2023 The Author(s). Published by IMR Press.)

The efficacy of targeting the MAPK signaling pathway in patients with melanoma is limited by the rapid development of resistance mechanisms that result in disease relapse. In this article, we focus on targeting the DNA repair pathway as an antimelanoma therapy, especially in MAPK inhibitor resistant melanoma cells using PARP inhibitors. We found that MAPK inhibitor resistant melanoma cells are particularly sensitive to PARP inhibitor treatment due to a lower basal expression of the DNA damage sensor ataxia-telangiectasia mutated (ATM). As a consequence, MAPK inhibitor resistant melanoma cells have decreased homologous recombination repair activity leading to a reduced repair of double-strand breaks caused by the PARP inhibitors. We validated the clinical relevance of our findings by ATM expression analysis in biopsies from patients with melanoma before and after development of resistance to MAPK inhibitors. Furthermore, we show that inhibition of the MAPK pathway induces a homologous recombination repair deficient phenotype in melanoma cells irrespective of their MAPK inhibitor sensitivity status. MAPK inhibition results in a synthetic lethal interaction of a combinatorial treatment with PARP inhibitors, which significantly reduces melanoma cell growth in vitro and in vivo . In conclusion, this study shows that PARP inhibitor treatment is a valuable therapy option for patients with melanoma, either as a single treatment or as a combination with MAPK inhibitors depending on ATM expression., Significance: We show that MAPK inhibitor resistant melanoma cells exhibit low ATM expression increasing their sensitivity toward PARP inhibitors and that a combination of MAPK/PARP inhibitors act synthetically lethal in melanoma cells. Our study shows that PARP inhibitor treatment is a valuable therapy option for patients with melanoma, either as a single treatment or as a combination with MAPK inhibitors depending on ATM expression, which could serve as a novel biomarker for treatment response., (© 2023 The Authors; Published by the American Association for Cancer Research.)

Background: The mitogen-activated protein kinase (MAPK) signaling pathway is frequently hyperactivated in malignant melanoma and its inhibition has proved to be an efficient treatment option for cases harboring BRAF V600 mutations (BRAF Mut ). However, there is still a significant need for effective targeted therapies for patients with other melanoma subgroups characterized by constitutive MAPK activation, such as tumors with NRAS or NF-1 alterations (NRAS Mut , NF-1 LOF ), as well as for patients with MAPK pathway inhibitor-resistant BRAF Mut melanomas, which commonly exhibit a reactivation of this pathway. p90 ribosomal S6 kinases (RSKs) represent central effectors of MAPK signaling, regulating cell cycle progression and survival., Methods: RSK activity and the functional effects of its inhibition by specific small molecule inhibitors were investigated in established melanoma cell lines and patient-derived short-term cultures from different MAPK pathway-hyperactivated genomic subgroups (NRAS Mut , BRAF Mut , NF-1 LOF ). Real-time qPCR, immunoblots and flow cytometric cell surface staining were used to explore the molecular changes following RSK inhibition. The effect on melanoma cell growth was evaluated by various two- and three-dimensional in vitro assays as well as with melanoma xenograft mouse models. Co-cultures with gp100- or Melan-A-specific cytotoxic T cells were used to assess immunogenicity of melanoma cells and associated T-cell responses., Results: In line with elevated activity of the MAPK/RSK signaling axis, growth and survival of not only BRAF Mut but also NRAS Mut and NF-1 LOF melanoma cells were significantly impaired by RSK inhibitors. Intriguingly, RSK inhibition was particularly effective in three-dimensional growth settings with long-term chronic drug exposure and suppressed tumor cell growth of in vivo melanoma models. Additionally, our study revealed that RSK inhibition simultaneously promoted differentiation and immunogenicity of the tumor cells leading to enhanced T-cell activation and melanoma cell killing., Conclusions: Collectively, RSK inhibitors exhibited both multi-layered anti-tumor efficacy and broad applicability across different genomic melanoma subgroups. RSK inhibition may therefore represent a promising novel therapeutic strategy for malignant melanoma with hyperactivated MAPK signaling., (© 2023. The Author(s).)

Background: Recent advances in digital pathology have enabled accurate and standardised enumeration of tumour-infiltrating lymphocytes (TILs). Here, we aim to evaluate TILs as a percentage electronic TIL score (eTILs) and investigate its prognostic and predictive relevance in cutaneous melanoma., Methods: We included stage I to IV cutaneous melanoma patients and used hematoxylin-eosin-stained slides for TIL analysis. We assessed eTILs as a continuous and categorical variable using the published cut-off of 16.6% and applied Cox regression models to evaluate associations of eTILs with relapse-free, distant metastasis-free, and overall survival. We compared eTILs of the primaries with matched metastasis. Moreover, we assessed the predictive relevance of eTILs in therapy-naïve metastases according to the first-line therapy., Findings: We analysed 321 primary cutaneous melanomas and 191 metastatic samples. In simple Cox regression, tumour thickness (p < 0.0001), presence of ulceration (p = 0.0001) and eTILs ≤16.6% (p = 0.0012) were found to be significant unfavourable prognostic factors for RFS. In multiple Cox regression, eTILs ≤16.6% (p = 0.0161) remained significant and downgraded the current staging. Lower eTILs in the primary tissue was associated with unfavourable relapse-free (p = 0.0014) and distant metastasis-free survival (p = 0.0056). In multiple Cox regression adjusted for tumour thickness and ulceration, eTILs as continuous remained significant (p = 0.019). When comparing TILs in primary tissue and corresponding metastasis of the same patient, eTILs in metastases was lower than in primary melanomas (p < 0.0001). In therapy-naïve metastases, an eTILs >12.2% was associated with longer progression-free survival (p = 0.037) and melanoma-specific survival (p = 0.0038) in patients treated with anti-PD-1-based immunotherapy. In multiple Cox regression, lactate dehydrogenase (p < 0.0001) and eTILs ≤12.2% (p = 0.0130) were significantly associated with unfavourable melanoma-specific survival., Interpretation: Assessment of TILs is prognostic in primary melanoma samples, and the eTILs complements staging. In therapy-naïve metastases, eTILs ≤12.2% is predictive of unfavourable survival outcomes in patients receiving anti-PD-1-based therapy., Funding: See a detailed list of funding bodies in the Acknowledgements section at the end of the manuscript., Competing Interests: Declaration of interests SF received personal fees from Kyowa Kirin and Takeda Pharmaceuticals, institutional grants from NeraCare, SkylineDx, and BioNTech, all outside the submitted work. TA reports institutional grants and personal fees from Novartis, institutional grants from NeraCare, Sanofi, SkylineDx, personal fees from CeCaVa, Pierre Fabre, BMS all outside the submitted work, participate on a data safety monitoring board for Unicancer. DLR reports grants and personal fees from Amgen, Astra Zeneca, Cepheid, Konica—Minolta, Lilly, NextCure personal fees from Cell Signaling Technology, Danaher, Fluidigm, GSK, Merck, Monopteros, NanoString, Odonate, Paige. AI, Regeneron, Roche, Sanofi, Ventana and Verily, royalties from Rarecyte, all outside the submitted work. CG reports grants and personal fees from NeraCare, Novartis, Roche, Sanofi, personal fees from Amgen, BMS, MSD, and Philogen, all outside the submitted work. TE reports personal fees from Novartis, BMS, Almirall Hermal, CureVac, Sanofi, MSD, Pierre Fabre and institutional grants from MSD, Sanofi, BMS, Pfizer, GenenTech, Seagan, Regeneron all outside the submitted work. IB reports having received speaker fees from Bayer, Pfizer, Takeda and AstraZeneca. MR reports grants from AB Science, Abbott, AbbVie, Alcedis, Almirall Hermal, Amgen, Anaptys Bio, Argenx, AstraZeneca, Bayer, Biogen Idec, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, CureVac, DelArrivo, Deutsche Forschungsgemeinschaft, Deutsche Krebshilfe, Dynavax Tech, Eli Lilly, Galderma, Genentech, GSK, Hoffmann La Roche, Hokusai, Idera Pharmaceuticals, Ilkos Therapeutic, Immatics biotechnologies, Incyte, Iovance Biotherapeutics, Janssen Cilag, Johnson & Johnson, LEO Pharma, Merck, MSD Sharp &Dohme, Novartis Pharmaceuticals, PellePharm, Pfizer, Philogen, Regeneron Pharmaceuticals, Sanofi Aventis, Schering Plough, Sun Pharma, Technische Universitat Dresden, Topaz Therapeutics, UCB, Universitatsklinik Essen, Universitatklinik Koln, Wilhelm Sander-Stiftung, 4SC. The other authors report no potential conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)