The PI3K/mTOR Pathway Is Targeted by Rare Germline Variants in Patients with Both Melanoma and Renal Cell Carcinoma.

Background: Malignant melanoma and RCC have different embryonic origins, no common lifestyle risk factors but intriguingly share biological properties such as immune regulation and radioresistance. An excess risk of malignant melanoma is observed in RCC patients and vice versa. This bidirectional association is poorly understood, and hypothetic genetic co-susceptibility remains largely unexplored. Results: We hereby provide a clinical and genetic description of a series of 125 cases affected by both malignant melanoma and RCC. Clinical germline mutation testing identified a pathogenic variant in a melanoma and/or RCC predisposing gene in 17/125 cases (13.6%). This included mutually exclusive variants in MITF (p.E318K locus, N = 9 cases), BAP1 (N = 3), CDKN2A (N = 2), FLCN (N = 2), and PTEN (N = 1). A subset of 46 early-onset cases, without underlying germline variation, was whole-exome sequenced. In this series, thirteen genes were significantly enriched in mostly exclusive rare variants predicted to be deleterious, compared to 19,751 controls of similar ancestry. The observed variation mainly consisted of novel or low-frequency variants (<0.01%) within genes displaying strong evolutionary mutational constraints along the PI3K/mTOR pathway, including PIK3CD, NFRKB, EP300, MTOR, and related epigenetic modifier SETD2. The screening of independently processed germline exomes from The Cancer Genome Atlas confirmed an association with melanoma and RCC but not with cancers of established differing etiology such as lung cancers. Conclusions: Our study highlights that an exome-wide case-control enrichment approach may better characterize the rare variant-based missing heritability of multiple primary cancers. In our series, the co-occurrence of malignant melanoma and RCC was associated with germline variation in the PI3K/mTOR signaling cascade, with potential relevance for early diagnostic and clinical management.

BRAF inhibitor resistance of melanoma cells triggers increased susceptibility to natural killer cell-mediated lysis.

BACKGROUND: Targeted therapies and immunotherapies are first-line treatments for patients with advanced melanoma. Serine-threonine protein kinase B-RAF (BRAF) and mitogen-activated protein kinase (MEK) inhibition leads to a 70% response rate in patients with advanced melanoma with a BRAFV600E/K mutation. However, acquired resistance occurs in the majority of patients, leading to relapse. Immunotherapies that activate immune cytotoxic effectors induce long-lasting responses in 30% of patients. In that context, combination of targeted therapies with immunotherapy (IT) is a promising approach. We considered boosting natural killer (NK) cell tumor immunosurveillance, as melanoma cells express stress-induced molecules and activate NK cell lysis. METHODS: Here we have generated vemurafenib (a BRAF inihibitor)-resistant (R) cells from BRAFV600E SK28 and M14-sensitive (S) melanoma cell lines and investigated how resistance interferes with immunogenicity to NK cells. We determined the levels of several soluble molecules including NK ligands in 61 melanoma patients at baseline and 6 months M post-treatment with targeted therapies or immunotherapies. RESULTS: Vemurafenib resistance involved activation of p-AKT in SK28R and of p-MEK/p-ERK in M14R cells and was accompanied by modulation of NK ligands. Compared with S cells, SK28R displayed an increased expression of natural killer group 2 D (NKG2D) receptor ligands (major histocompatibility complex class (MHC) I chain-related protein A (MICA) and UL16-binding protein 2 (ULBP2)) whereas M14R exhibited decreased ULBP2 . SK28R and M14R cells induced higher NK degranulation and interferon gamma secretion and were more efficiently lysed by donor and patient NK cells. SK28R showed increased tumor necrosis factor-related apoptosis-inducing ligand receptor II (TRAIL-RII) expression and TRAIL-induced apoptosis, and TRAIL-induced apoptosis of M14R was decreased. Combined BRAF/MEK inhibitors abrogated the growth of SK28S, M14S, and M14R cells, while growth of SK28R was maintained. BRAF/MEK inhibition attenuated NK activity but R cell lines activated polyfunctional NK cells and were lysed with high efficiency. We investigated the relationship of soluble NK ligands and response to treatment in a series of melanoma patients. Soluble NKG2D ligands known to regulate the receptor function have been associated to cancer progression. Serum analysis of patients treated with target therapies or IT indicates that soluble forms of NK ligands (MICA, B7H6, programmed cell death ligand 1, and carcinoembryonic antigen cell adhesion molecule 1) may correlate with clinical response. CONCLUSION: These results support strategies combining targeted therapies and NK-based immunotherapies.

Genome-wide association meta-analyses combining multiple risk phenotypes provide insights into the genetic architecture of cutaneous melanoma susceptibility.

Most genetic susceptibility to cutaneous melanoma remains to be discovered. Meta-analysis genome-wide association study (GWAS) of 36,760 cases of melanoma (67% newly genotyped) and 375,188 controls identified 54 significant (P < 5 × 10-8) loci with 68 independent single nucleotide polymorphisms. Analysis of risk estimates across geographical regions and host factors suggests the acral melanoma subtype is uniquely unrelated to pigmentation. Combining this meta-analysis with GWAS of nevus count and hair color, and transcriptome association approaches, uncovered 31 potential secondary loci for a total of 85 cutaneous melanoma susceptibility loci. These findings provide insights into cutaneous melanoma genetic architecture, reinforcing the importance of nevogenesis, pigmentation and telomere maintenance, together with identifying potential new pathways for cutaneous melanoma pathogenesis.

NK Cell and Fibroblast-Mediated Regulation of Skin Squamous Cell Carcinoma Invasion by CLEC2A Is Compromised in Xeroderma Pigmentosum.

The ability of cancer cells to invade and disseminate can be affected by components of the surrounding microenvironment. To identify dermal components that regulate the growth of epidermal carcinomas, we studied the genetic disease called xeroderma pigmentosum that bears mutations in genes involved in the nucleotide excision repair of DNA. Patients with xeroderma pigmentosum are more prone to develop cutaneous tumors than the general population and their dermal fibroblasts display the features of dermal cancer-associated fibroblasts, which promote the invasion of keratinocytes. Here, we report that 3-dimensional dermal cultures of fibroblasts from healthy donors but not from patients with xeroderma pigmentosum complementation group C express CLEC2A, which is the ligand of the activating NK cell receptor NKp65. A similar loss of CLEC2A was observed in sporadic dermal cancer-associated fibroblasts and upon the culture of fibroblasts with cutaneous squamous cell carcinoma-conditioned medium. Using an innovative 3-dimensional organotypic skin culture model that contain NK cells in addition to fibroblasts and squamous cell carcinoma cells, we unveiled a key role of CLEC2A that orchestrates a crosstalk between fibroblasts and NK cells, thereby leading to the control of squamous cell carcinoma invasion. These findings indicate that CLEC2A-expressing dermal fibroblasts play a major role in immune surveillance of the skin.

NKG2D/NKG2-Ligand Pathway Offers New Opportunities in Cancer Treatment.

The antitumor functions of NK cells are regulated by the integration of positive and negative signals triggered by numerous membrane receptors present on the NK cells themselves. Among the main activating receptors, NKG2D binds several stress-induced molecules on tumor targets. Engagement of NKG2D by its ligands (NKG2D-Ls) induces NK cell activation leading to production of cytokines and target cell lysis. These effects have therapeutic potential as NKG2D-Ls are widely expressed by solid tumors, whereas their expression in healthy cells is limited. Here, we describe the genetic and environmental factors regulating the NKG2D/NKG2D-L pathway in tumors. NKG2D-L expression is linked to cellular stress and cell proliferation, and has been associated with oncogenic mutations. Tumors have been found to alter their to NKG2D-L expression as they progress, which interferes with the antitumor function of the pathway. Nevertheless, this pathway could be advantageously exploited for cancer therapy. Various cancer treatments, including chemotherapy and targeted therapies, indirectly interfere with the cellular and soluble forms of NKG2D-Ls. In addition, NKG2D introduced into chimeric antigen receptors in T- and NK cells is a promising tumor immunotherapy approach.

MC1R variants in childhood and adolescent melanoma: a retrospective pooled analysis of a multicentre cohort.

BACKGROUND: Germline variants in the melanocortin 1 receptor gene (MC1R) might increase the risk of childhood and adolescent melanoma, but a clear conclusion is challenging because of the low number of studies and cases. We assessed the association of MC1R variants with childhood and adolescent melanoma in a large study comparing the prevalence of MC1R variants in child or adolescent patients with melanoma to that in adult patients with melanoma and in healthy adult controls. METHODS: In this retrospective pooled analysis, we used the M-SKIP Project, the Italian Melanoma Intergroup, and other European groups (with participants from Australia, Canada, France, Greece, Italy, the Netherlands, Serbia, Spain, Sweden, Turkey, and the USA) to assemble an international multicentre cohort. We gathered phenotypic and genetic data from children or adolescents diagnosed with sporadic single-primary cutaneous melanoma at age 20 years or younger, adult patients with sporadic single-primary cutaneous melanoma diagnosed at age 35 years or older, and healthy adult individuals as controls. We calculated odds ratios (ORs) for childhood and adolescent melanoma associated with MC1R variants by multivariable logistic regression. Subgroup analysis was done for children aged 18 or younger and 14 years or younger. FINDINGS: We analysed data from 233 young patients, 932 adult patients, and 932 healthy adult controls. Children and adolescents had higher odds of carrying MC1R r variants than did adult patients (OR 1·54, 95% CI 1·02-2·33), including when analysis was restricted to patients aged 18 years or younger (1·80, 1·06-3·07). All investigated variants, except Arg160Trp, tended, to varying degrees, to have higher frequencies in young patients than in adult patients, with significantly higher frequencies found for Val60Leu (OR 1·60, 95% CI 1·05-2·44; p=0·04) and Asp294His (2·15, 1·05-4·40; p=0·04). Compared with those of healthy controls, young patients with melanoma had significantly higher frequencies of any MC1R variants. INTERPRETATION: Our pooled analysis of MC1R genetic data of young patients with melanoma showed that MC1R r variants were more prevalent in childhood and adolescent melanoma than in adult melanoma, especially in patients aged 18 years or younger. Our findings support the role of MC1R in childhood and adolescent melanoma susceptibility, with a potential clinical relevance for developing early melanoma detection and preventive strategies. FUNDING: SPD-Pilot/Project-Award-2015; AIRC-MFAG-11831.

Pembrolizumab for Unresectable or Metastatic Melanoma in Patients Older than 85 Years of Age.

BACKGROUND: Programmed cell death protein-1 (PD-1) inhibitors (pembrolizumab and nivolumab) have been approved for the treatment of advanced melanoma. Over the past decades, patients older than 85 years represent an expanding group of patients in developed countries. In France, 25% of melanomas are diagnosed in patients older than 75 years. OBJECTIVE: To perform a monocentric retrospective study of patients older than 85 years and treated with pembrolizu-mab for unresectable or metastatic melanoma in order to evaluate tolerance and potential benefits of this immunotherapy. METHODS: Medical records of patients treated with the PD-1 inhibitor pembrolizumab between January 2015 and January 2018 were reviewed. RESULTS: Nine patients (6 women and 3 men) older than 85 years were included in the study. The mean age was 89.6 (85-97) years at inclusion. All patients were PS 0 or 1. The mean number of infusions was 4 (1-12). However, most patients were not able to tolerate the 4-infusion schedule. One patient refused the second infusion for personal reasons. Seven patients had grade 3 or 4 treatment-related adverse events. CONCLUSION: These results indicate that pembrolizumab treatment in patients older than 85 years may induce responses but is associated with a high risk of toxicity and impaired autonomy.

Estimating CDKN2A mutation carrier probability among global familial melanoma cases using GenoMELPREDICT.

BACKGROUND: Although rare in the general population, highly penetrant germline mutations in CDKN2A are responsible for 5%-40% of melanoma cases reported in melanoma-prone families. We sought to determine whether MELPREDICT was generalizable to a global series of families with melanoma and whether performance improvements can be achieved. METHODS: In total, 2116 familial melanoma cases were ascertained by the international GenoMEL Consortium. We recapitulated the MELPREDICT model within our data (GenoMELPREDICT) to assess performance improvements by adding phenotypic risk factors and history of pancreatic cancer. We report areas under the curve (AUC) with 95% confidence intervals (CIs) along with net reclassification indices (NRIs) as performance metrics. RESULTS: MELPREDICT performed well (AUC 0.752, 95% CI 0.730-0.775), and GenoMELPREDICT performance was similar (AUC 0.748, 95% CI 0.726-0.771). Adding a reported history of pancreatic cancer yielded discriminatory improvement (P < .0001) in GenoMELPREDICT (AUC 0.772, 95% CI 0.750-0.793, NRI 0.40). Including phenotypic risk factors did not improve performance. CONCLUSION: The MELPREDICT model functioned well in a global data set of familial melanoma cases. Adding pancreatic cancer history improved model prediction. GenoMELPREDICT is a simple tool for predicting CDKN2A mutational status among melanoma patients from melanoma-prone families and can aid in directing these patients to receive genetic testing or cancer risk counseling.

Emerging Role of IL-4-Induced Gene 1 as a Prognostic Biomarker Affecting the Local T-Cell Response in Human Cutaneous Melanoma.

Several studies have emphasized the importance of immune composition of the melanoma microenvironment for clinical outcome. The contribution of IL4I1, a phenylalanine oxidase with immunoregulatory functions, has not been yet explored. Here we studied a primary cutaneous melanoma series from stage I-III patients to investigate the association between in situ IL4I1 expression and clinical parameters or tumor-infiltrating T-cell subsets. IL4I1 was detected in 87% of tumors and was mainly expressed by tumor-associated macrophages and very rare FoxP3+ regulatory T cells. The proportion of IL4I1+ cells was higher in patients with an ulcerated melanoma or with a positive sentinel lymph node and tended to correlate with a rapid relapse and shorter overall survival. This proportion also correlated positively with the presence of regulatory T cells and negatively with the presence of cytotoxic CD8+ T cells. The location of IL4I1+ cells may also be relevant to predict prognosis, because their presence near tumor cells was associated with sentinel lymph node invasion and higher melanoma stage. Collectively, our data show that IL4I1+ cells shape the T-cell compartment and are associated with a higher risk of poor outcome in melanoma, supporting a key role for IL4I1 in immune evasion.

Efficacy of Immunotherapy in Patients with Metastatic Mucosal or Uveal Melanoma.

BACKGROUND: The objective was to assess the response rate and survival of patients with metastatic mucosal melanoma (MM) and uveal melanoma (UM) treated with anti-CTLA-4 or anti-PD-1 monoclonal antibodies (mAbs). METHODS: A multicenter retrospective study was performed in 25 dermatology departments in France. All patients with stage III-C to IV MM or UM who were treated with anti-CTLA-4 or anti-PD-1 mAbs between 2008 and 2016 were included and compared after adjustment for main prognostic factors with a second cohort of patients treated with chemotherapy. Tumor response was evaluated according to RECIST v. 1.1 criteria at Week 12. RESULTS: Four-hundred-and-thirty-nine patients were included, 229 MM (151 immunotherapy, 78 chemotherapy) and 210 UM (100 immunotherapy, 110 chemotherapy). Response rates of MM patients treated with immunotherapy were 18/151 (11.9%; 95% CI:7.2%-18.2%), versus 11/78 (14.1%, 95% CI:7.3%-23.8%) in patients treated with chemotherapy (p=0.87). No tumor response was observed in UM patients treated with immunotherapy, versus 4/110 responses (3.6%, 95% CI:1.0-9.0%) in patients treated with chemotherapy (p=0.15). The adjusted overall survival (OS) of MM patients treated with immunotherapy was longer than that of patients treated with chemotherapy HR=0.62 (95% CI: 0.43-0.91), p=0.014, with an unadjusted median OS of 15.97 months [interquartile range (IQR)=6.89-27.11] and 8.82 months [IQR=5.02-14.92], respectively. The adjusted OS of UM patients treated with immunotherapy was not significantly different from that of patients treated with chemotherapy (HR=0.98, 95% CI: 0.66-1.44) p=0.92, with an unadjusted median OS of 13.38 months [IQR=6.03-29.57] and 11.02 months [IQR=6.13-23.93], respectively. CONCLUSION: Immunotherapy significantly improves OS for MM. The prognosis of metastatic UM remains poor.

STAT3 Mediates Nilotinib Response in KIT-Altered Melanoma: A Phase II Multicenter Trial of the French Skin Cancer Network.

Mutated oncogenic KIT is a therapeutic target in melanoma. We conducted a multicenter phase II trial on the KIT inhibitor nilotinib in patients with unresectable melanoma harboring KIT alteration. The primary endpoint was the response rate (complete response or partial response following Response Evaluation Criteria in Solid Tumors criteria) at 6 months. Pharmacodynamic studies using KIT sequencing, qPCR array, and immunostaining of downstream KIT effectors were performed during treatment. Twenty-five patients were included and received 400 mg oral nilotinib twice daily. At 6 months, nilotinib induced tumor response in four patients. The best overall response rate was 20% and the disease control rate was 56%, limited to patients harboring exon 11 or 13 mutations. Four patients exhibited durable response, including three persisting (3.6 and 2.8 years for two patients with stage IIIC and 2.5 years for one with IVM1b melanoma). A reduction in signal transducer and activator of transcription (STAT) 3 phosphorylation and its effectors (BCL-2, MCL-1) in tumors during follow-up was significantly associated with clinical response. In the KIT-mutated melanoma cell line M230, nilotinib reduced STAT3 signaling and STAT inhibitors were as efficient as KIT inhibitors in reducing cell proliferation. Our study evidences a significant association between STAT3 inhibition and response to nilotinib, and provides a rationale for future research assessing STAT inhibitors in KIT-mutated melanoma.

Mutations in ACTRT1 and its enhancer RNA elements lead to aberrant activation of Hedgehog signaling in inherited and sporadic basal cell carcinomas.

Basal cell carcinoma (BCC), the most common human cancer, results from aberrant activation of the Hedgehog signaling pathway. Although most cases of BCC are sporadic, some forms are inherited, such as Bazex-Dupré-Christol syndrome (BDCS)-a cancer-prone genodermatosis with an X-linked, dominant inheritance pattern. We have identified mutations in the ACTRT1 gene, which encodes actin-related protein T1 (ARP-T1), in two of the six families with BDCS that were examined in this study. High-throughput sequencing in the four remaining families identified germline mutations in noncoding sequences surrounding ACTRT1. These mutations were located in transcribed sequences encoding enhancer RNAs (eRNAs) and were shown to impair enhancer activity and ACTRT1 expression. ARP-T1 was found to directly bind to the GLI1 promoter, thus inhibiting GLI1 expression, and loss of ARP-T1 led to activation of the Hedgehog pathway in individuals with BDCS. Moreover, exogenous expression of ACTRT1 reduced the in vitro and in vivo proliferation rates of cell lines with aberrant activation of the Hedgehog signaling pathway. In summary, our study identifies a disease mechanism in BCC involving mutations in regulatory noncoding elements and uncovers the tumor-suppressor properties of ACTRT1.

Germline Variation at CDKN2A and Associations with Nevus Phenotypes among Members of Melanoma Families.

Germline mutations in CDKN2A are frequently identified among melanoma kindreds and are associated with increased atypical nevus counts. However, a clear relationship between pathogenic CDKN2A mutation carriage and other nevus phenotypes including counts of common acquired nevi has not yet been established. Using data from GenoMEL, we investigated the relationships between CDKN2A mutation carriage and 2-mm, 5-mm, and atypical nevus counts among blood-related members of melanoma families. Compared with individuals without a pathogenic mutation, those who carried one had an overall higher prevalence of atypical (odds ratio = 1.64; 95% confidence interval = 1.18-2.28) nevi but not 2-mm nevi (odds ratio = 1.06; 95% confidence interval = 0.92-1.21) or 5-mm nevi (odds ratio = 1.26; 95% confidence interval = 0.94-1.70). Stratification by case status showed more pronounced positive associations among non-case family members, who were nearly three times (odds ratio = 2.91; 95% confidence interval = 1.75-4.82) as likely to exhibit nevus counts at or above the median in all three nevus categories simultaneously when harboring a pathogenic mutation (vs. not harboring one). Our results support the hypothesis that unidentified nevogenic genes are co-inherited with CDKN2A and may influence carcinogenesis.

Shifting the Balance of Activating and Inhibitory Natural Killer Receptor Ligands on BRAFV600E Melanoma Lines with Vemurafenib.

Over 60% of human melanoma tumors bear a mutation in the BRAF gene. The most frequent mutation is a substitution at codon 600 (V600E), leading to a constitutively active BRAF and overactivation of the MAPK pathway. Patients harboring mutated BRAF respond to kinase inhibitors such as vemurafenib. However, these responses are transient, and relapses are frequent. Melanoma cells are efficiently lysed by activated natural killer (NK) cells. Melanoma cells express several stress-induced ligands that are recognized by activating NK-cell receptors. We have investigated the effect of vemurafenib on the immunogenicity of seven BRAF-mutated melanoma cells to NK cells and on their growth and sensitivity to NK-cell-mediated lysis. We showed that vemurafenib treatment modulated expression of ligands for two activating NK receptors, increasing expression of B7-H6, a ligand for NKp30, and decreasing expression of MICA and ULBP2, ligands for NKG2D. Vemurafenib also increased expression of HLA class I and HLA-E molecules, likely leading to higher engagement of inhibitory receptors (KIRs and NKG2A, respectively), and decreased lysis of vemurafenib-treated melanoma cell lines by cytokine-activated NK cells. Finally, we showed that whereas batimastat (a broad-spectrum matrix metalloprotease inhibitor) increased cell surface ULBP2 by reducing its shedding, vemurafenib lowered soluble ULBP2, indicating that BRAF signal inhibition diminished expression of both cell-surface and soluble forms of NKG2D ligands. Vemurafenib, inhibiting BRAF signaling, shifted the balance of activatory and inhibitory NK ligands on melanoma cells and displayed immunoregulatory effects on NK-cell functional activities. Cancer Immunol Res; 5(7); 582-93. ©2017 AACR.

Clinical parameters associated with anti-programmed death-1 (PD-1) inhibitors-induced tumor response in melanoma patients.

Background The identification of the melanoma patients sensitive to anti-PD-1 inhibitors, nivolumab or pembrolizumab, is a major therapeutic challenge and an urgent need. We hypothesized that the natural history of the disease might partly reflect the immune state of the patients. Methods We analyzed our cohort of melanoma patients treated with anti-PD-1 from August 2014 to January 2016 in our institution. Objective response was defined as a complete or partial response according to v1.1 RECIST criteria. Results Among 63 metastatic melanoma patients, the overall response rate was 43%. Median time from diagnosis to anti-PD-1 initiation was longer among responders than non-responders (64 months vs. 35 months, p = 0.02). The response rate was 10% in patients starting anti-PD-1 within 1 year, 35% after 1 to 5 years and 63% after 5 years. Performance status (PS) 0 was also associated with enhanced tumor response: 70% of responders were PS 0 vs. 36% of non-responders (p = 0.04). PS 0, normal LDH levels and wild-type BRAF status were significant predictors of progression free survival. Conclusion A long time lapse from diagnosis to anti-PD-1 initiation and PS 0 are associated with higher sensitivity to anti-PD-1 in melanoma patients. These two clinical features might reflect a potentially intact immune system of the host.

Germline CDKN2A/P16INK4A mutations contribute to genetic determinism of sarcoma.

BACKGROUND: Sarcomas are rare mesenchymal malignancies whose pathogenesis is poorly understood; both environmental and genetic risk factors could contribute to their aetiology. METHODS AND RESULTS: We performed whole-exome sequencing (WES) in a familial aggregation of three individuals affected with soft-tissue sarcoma (STS) without TP53 mutation (Li-Fraumeni-like, LFL) and found a shared pathogenic mutation in CDKN2A tumour suppressor gene. We searched for individuals with sarcoma among 474 melanoma-prone families with a CDKN2A-/+ genotype and for CDKN2A mutations in 190 TP53-negative LFL families where the index case was a sarcoma. Including the initial family, eight independent sarcoma cases carried a germline mutation in the CDKN2A/p16INK4A gene. In five out of seven formalin-fixed paraffin-embedded sarcomas, heterozygosity was lost at germline CDKN2A mutations sites demonstrating complete loss of function. As sarcomas are rare in CDKN2A/p16INK4A carriers, we searched in constitutional WES of nine carriers for potential modifying rare variants and identified three in platelet-derived growth factor receptor (PDGFRA) gene. Molecular modelling showed that two never-described variants could impact the PDGFRA extracellular domain structure. CONCLUSION: Germline mutations in CDKN2A/P16INK4A, a gene known to predispose to hereditary melanoma, pancreatic cancer and tobacco-related cancers, account also for a subset of hereditary sarcoma. In addition, we identified PDGFRA as a candidate modifier gene.

Deciphering the Role of Oncogenic MITFE318K in Senescence Delay and Melanoma Progression.

Background: MITF encodes an oncogenic lineage-specific transcription factor in which a germline mutation ( MITFE318K ) was identified in human patients predisposed to both nevus formation and, among other tumor types, melanoma. The molecular mechanisms underlying the oncogenic activity of MITF E318K remained uncharacterized. Methods: Here, we compared the SUMOylation status of endogenous MITF by proximity ligation assay in melanocytes isolated from wild-type (n = 3) or E318K (n = 4) MITF donors. We also used a newly generated Mitf E318K knock-in (KI) mouse model to assess the role of Mitf E318K (n = 7 to 13 mice per group) in tumor development in vivo and performed transcriptomic analysis of the tumors to identify the molecular mechanisms. Finally, using immortalized or normal melanocytes (wild-type or E318K MITF, n = 2 per group), we assessed the role of MITF E318K on the induction of senescence mediated by BRAF V600E . All statistical tests were two-sided. Results: We demonstrated a decrease in endogenous MITF SUMOylation in melanocytes from MITF E318K patients (mean of cells with hypoSUMOylated MITF, MITF E318K vs MITF WT , 94% vs 44%, difference = 50%, 95% CI = 21.8% to 67.2%, P = .004). The Mitf E318K mice were slightly hypopigmented (mean melanin content Mitf WT vs Mitf E318K/+ , 0.54 arbitrary units [AU] vs 0.36 AU, difference = -0.18, 95% CI = -0.36 to -0.007, P = .04). We provided genetic evidence that Mitf E318K enhances BRaf V600E -induced nevus formation in vivo (mean nevus number for Mitf E318K , BRaf V600E vs Mitf WT , BRaf V600E , 68 vs 44, difference = 24, 95% CI = 9.1 to 38.9, P = .006). Importantly, although Mitf E318K was not sufficient to cooperate with BRaf V600E alone in promoting metastatic melanoma, it accelerated tumor formation on a BRaf V600E , Pten-deficient background (median survival, Mitf E318K/+ = 42 days, 95% CI = 31 to 46 vs Mitf WT = 51 days, 95% CI = 50 to 55, P < .001). Transcriptome analysis suggested a decrease in senescence in tumors from Mitf E318K mice. We confirmed this hypothesis by in vitro experiments, demonstrating that Mitf E318K impaired the ability of human melanocytes to undergo BRAF V600E -induced senescence. Conclusions: We characterized the functions of melanoma-associated MITF E318K mutations. Our results demonstrate that MITF E318K reduces the program of senescence to potentially favor melanoma progression in vivo.

Sarcopenic overweight is associated with early acute limiting toxicity of anti-PD1 checkpoint inhibitors in melanoma patients.

Little is known on factors predicting toxicity of anti-PD1 checkpoint inhibitors. Sarcopenic obesity is associated with increased acute toxicity of cytotoxic agents and targeted therapies. We explored whether body composition also influenced the occurrence of early acute limiting toxicity (ALT) of anti-PD1 in melanoma patients. This is a monocentric, retrospective study analyzing toxicity outcome in consecutive melanoma patients treated with nivolumab or pembrolizumab. Various parameters linked to the patient or the disease status have been analysed. Body mass index (BMI; kg/m2) and muscle mass using CT were measured prior to treatment initiation. Chi-squared test and Mann-Whitney's tests were used for the comparison of categorical and continuous variables respectively. Among 68 melanoma patients treated with anti-PD1 (47 pembrolizumab, 21 nivolumab), 38 (56%) patients had a BMI ≥ 25 kg/m2 and 11 (16%) a BMI ≥ 30, while 13 (19%) had both sarcopenia and a BMI ≥ 25 kg/m2. For the 11 (16%) patients who experienced early ALT, the mean BMI was higher (27.9 versus 24.7 kg/m2; p = 0.04). Among the 32 female patients, sarcopenic overweight patients had a 6.5-fold increased risk of ALT (50 versus 7.7%; p = 0.01). Sarcopenic overweight is associated with more early ALT of anti-PD1 in melanoma patients.

IL4-induced gene 1 promotes tumor growth by shaping the immune microenvironment in melanoma.

Amino acid catabolizing enzymes emerged as a crucial mechanism used by tumors to dampen immune responses. The L-phenylalanine oxidase IL-4 induced gene 1 (IL4I1) is expressed by tumor-associated myeloid cells of most solid tumors, including melanoma. We previously provided the only evidence that IL4I1 accelerates tumor growth by limiting the CD8+ T cell mediated immune response, in a mouse model of melanoma cell transplantation. Here, we explored the role of IL4I1 in Ret mice, a spontaneous model of melanoma. We found that IL4I1 was expressed by CD11b+ myeloid cells and that its activity correlated with disease aggressiveness. IL4I1 did not enhance tumor cell proliferation or angiogenesis, but orchestrated the remodeling of the immune compartment within the primary tumor. Indeed, the inactivation of IL4I1 limited the recruitment of polymorphonuclear myeloid-derived suppressor cells and enhanced the infiltration by Th1 and cytotoxic T cells, thus delaying tumor development and metastatic dissemination. Accordingly, human primary melanomas that were poorly infiltrated by IL4I1+ cells exhibited a higher density of CD8+ T cells. Collectively, our findings strengthen the rationale for therapeutic targeting of IL4I1 as one of the key immune regulators.