Epithelial damage and tissue γδ T cells promote a unique tumor-protective IgE response.

IgE is an ancient and conserved immunoglobulin isotype with potent immunological function. Nevertheless, the regulation of IgE responses remains an enigma, and evidence of a role for IgE in host defense is limited. Here we report that topical exposure to a common environmental DNA-damaging xenobiotic initiated stress surveillance by γδTCR+ intraepithelial lymphocytes that resulted in class switching to IgE in B cells and the accumulation of autoreactive IgE. High-throughput antibody sequencing revealed that γδ T cells shaped the IgE repertoire by supporting specific variable-diversity-joining (VDJ) rearrangements with unique characteristics of the complementarity-determining region CDRH3. This endogenous IgE response, via the IgE receptor FcεRI, provided protection against epithelial carcinogenesis, and expression of the gene encoding FcεRI in human squamous-cell carcinoma correlated with good disease prognosis. These data indicate a joint role for immunosurveillance by T cells and by B cells in epithelial tissues and suggest that IgE is part of the host defense against epithelial damage and tumor development.

Antibodies to Costimulatory Receptor 4-1BB Enhance Anti-tumor Immunity via T Regulatory Cell Depletion and Promotion of CD8 T Cell Effector Function.

The costimulatory receptor 4-1BB is expressed on activated immune cells, including activated T cells. Antibodies targeting 4-1BB enhance the proliferation and survival of antigen-stimulated T cells in vitro and promote CD8 T cell-dependent anti-tumor immunity in pre-clinical cancer models. We found that T regulatory (Treg) cells infiltrating human or murine tumors expressed high amounts of 4-1BB. Intra-tumoral Treg cells were preferentially depleted by anti-4-1BB mAbs in vivo. Anti-4-1BB mAbs also promoted effector T cell agonism to promote tumor rejection. These distinct mechanisms were competitive and dependent on antibody isotype and FcγR availability. Administration of anti-4-1BB IgG2a, which preferentially depletes Treg cells, followed by either agonistic anti-4-1BB IgG1 or anti-PD-1 mAb augmented anti-tumor responses in multiple solid tumor models. An antibody engineered to optimize both FcγR-dependent Treg cell depleting capacity and FcγR-independent agonism delivered enhanced anti-tumor therapy. These insights into the effector mechanisms of anti-4-1BB mAbs lay the groundwork for translation into the clinic.

Programmed cell death-1 receptor-mediated regulation of Tbet+NK1.1- innate lymphoid cells within the tumor microenvironment.

Innate lymphoid cells (ILCs) play a key role in tissue-mediated immunity and can be controlled by coreceptor signaling. Here, we define a subset of ILCs that are Tbet+NK1.1- and are present within the tumor microenvironment (TME). We show programmed death-1 receptor (PD-1) expression on ILCs within TME is found in Tbet+NK1.1- ILCs. PD-1 significantly controlled the proliferation and function of Tbet+NK1.1- ILCs in multiple murine and human tumors. We found tumor-derived lactate enhanced PD-1 expression on Tbet+NK1.1- ILCs within the TME, which resulted in dampened the mammalian target of rapamycin (mTOR) signaling along with increased fatty acid uptake. In line with these metabolic changes, PD-1-deficient Tbet+NK1.1- ILCs expressed significantly increased IFNγ and granzyme B and K. Furthermore, PD-1-deficient Tbet+NK1.1- ILCs contributed toward diminished tumor growth in an experimental murine model of melanoma. These data demonstrate that PD-1 can regulate antitumor responses of Tbet+NK1.1- ILCs within the TME.

Effect of skin tone on the accuracy of the estimation of arterial oxygen saturation by pulse oximetry: a systematic review.

BACKGROUND: Pulse oximetry-derived oxygen saturation (SpO2) is an estimate of true arterial oxygen saturation (SaO2). The aim of this review was to evaluate available evidence determining the effect of skin tone on the ability of pulse oximeters to accurately estimate SaO2. METHODS: Published literature was screened to identify clinical and non-clinical studies enrolling adults and children when SpO2 was compared with a paired co-oximetry SaO2 value. We searched literature databases from their inception to March 20, 2023. Risk of bias (RoB) was assessed using the QUADAS-2 tool. Certainty of assessment was evaluated using the GRADE tool. RESULTS: Forty-four studies were selected reporting on at least 222 644 participants (6121 of whom were children) and 733 722 paired SpO2-SaO2 measurements. Methodologies included laboratory studies, prospective clinical, and retrospective clinical studies. A high RoB was detected in 64% of studies and there was considerable heterogeneity in study design, data analysis, and reporting metrics. Only 11 (25%) studies measured skin tone in 2353 (1.1%) participants; the remainder reported participant ethnicity: 68 930 (31.0%) participants were of non-White ethnicity or had non-light skin tones. The majority of studies reported overestimation of SaO2 by pulse oximetry in participants with darker skin tones or from ethnicities assumed to have darker skin tones. Several studies reported no inaccuracy related to skin tone. Meta-analysis of the data was not possible. CONCLUSIONS: Pulse oximetry can overestimate true SaO2 in people with darker skin tones. The clinical relevance of this bias remains unclear, but its magnitude is likely to be greater when SaO2 is lower. SYSTEMATIC REVIEW PROTOCOL: International Prospective Register of Systematic Reviews (PROSPERO): CRD42023390723.

Transcriptomic analysis of cutaneous squamous cell carcinoma reveals a multigene prognostic signature associated with metastasis.

BACKGROUND: Metastasis of cutaneous squamous cell carcinoma (cSCC) is uncommon. Current staging methods are reported to have sub-optimal performances in metastasis prediction. Accurate identification of patients with tumors at high risk of metastasis would have a significant impact on management. OBJECTIVE: To develop a robust and validated gene expression profile signature for predicting primary cSCC metastatic risk using an unbiased whole transcriptome discovery-driven approach. METHODS: Archival formalin-fixed paraffin-embedded primary cSCC with perilesional normal tissue from 237 immunocompetent patients (151 nonmetastasizing and 86 metastasizing) were collected retrospectively from four centers. TempO-seq was used to probe the whole transcriptome and machine learning algorithms were applied to derive predictive signatures, with a 3:1 split for training and testing datasets. RESULTS: A 20-gene prognostic model was developed and validated, with an accuracy of 86.0%, sensitivity of 85.7%, specificity of 86.1%, and positive predictive value of 78.3% in the testing set, providing more stable, accurate prediction than pathological staging systems. A linear predictor was also developed, significantly correlating with metastatic risk. LIMITATIONS: This was a retrospective 4-center study and larger prospective multicenter studies are now required. CONCLUSION: The 20-gene signature prediction is accurate, with the potential to be incorporated into clinical workflows for cSCC.

Coexistence of psoriasis and cutaneous T-cell lymphoma.

It has been reported that individuals with psoriasis are at an increased risk of developing cutaneous T-cell lymphoma (CTCL). However, the increased risk of lymphoma in these patients has been questioned because CTCL in its early stages may be incorrectly labelled as psoriasis, thus introducing potential for misclassification bias. We retrospectively reviewed patients with a confirmed diagnosis of CTCL seen in a tertiary cutaneous lymphoma clinic (n = 115) over a 5-year period and found that 6 (5.2%) patients had clinical evidence of coexisting psoriasis. This demonstrates that there is a small cohort of individuals who develop both psoriasis and CTCL.

How is oral isotretinoin prescribed for the treatment of acne vulgaris? Results from a UK Dermatology Clinical Trials Network (UKDCTN) and British Dermatological Nursing Group (BDNG) survey of health professionals.

We undertook a survey of UK healthcare professionals through the UK Dermatology Clinical Trials Network and British Dermatological Nursing Group to understand clinicians' routine practice of prescribing oral isotretinoin for treatment of acne vulgaris. We also wanted to understand clinicians' experiences and views on prescribing low daily dose regimens. Overall, the survey showed that clinicians adopted a patient-centred approach when deciding isotretinoin dosing. The rationale for using a low-dose regimen varied, but was focused on patient wellbeing during treatment. Some clinicians were concerned that use of a low-dose regimen could be less effective and lead to longer treatment durations. The survey results will be useful to inform a clinical trial investigating the effectiveness and safety of low daily dose isotretinoin for the treatment of acne.

Maternal antenatal vitamin D supplementation and offspring risk of atopic eczema in the first 4 years of life: evidence from a randomized controlled trial.

BACKGROUND: Evidence linking prenatal maternal vitamin D supplementation with the offspring's risk of atopic eczema is inconsistent, with most data coming from observational studies. OBJECTIVES: To examine the influence of maternal cholecalciferol supplementation during pregnancy on the risk of atopic eczema in the offspring at ages 12, 24 and 48 months. METHODS: Within the UK Maternal Vitamin D Osteoporosis Study (MAVIDOS) double-blind, randomized placebo-controlled trial, we examined the relationship of maternal vitamin D supplementation during pregnancy with offspring atopic eczema at ages 12, 24 and 48 months. In MAVIDOS, pregnant women were allocated to either cholecalciferol 1000 IU per day or matched placebo, taken from around 14 weeks' gestation until delivery, with the primary outcome of neonatal whole-body bone mineral content. The prevalence of atopic eczema in the offspring was ascertained at ages 12 (n = 635), 24 (n = 610) and 48 (n = 449) months, based on the UK Working Party criteria for the definition of atopic dermatitis. The trial was registered with ISRCTN (82927713) and EudraCT (2007-001716-23). RESULTS: The characteristics of mothers and offspring were similar between the intervention and placebo groups, apart from longer breastfeeding duration in the intervention group. Adjusting for breastfeeding duration, offspring of mothers who received cholecalciferol 1000 IU daily had a lower odds ratio (OR) of atopic eczema at age 12 months [OR 0·55, 95% confidence interval (CI) 0·32-0·97, P = 0·04]; this effect weakened and was not statistically significant at ages 24 months (OR 0·76, 95% CI 0·47-1·23) or 48 months (OR 0·75, 95% CI 0·37-1·52). The statistical interaction of intervention and breastfeeding duration in relation to eczema at age 12 months was not significant (P = 0·41), but stratification showed reduced infantile eczema risk in the intervention group for infants breastfed for ≥ 1 month (OR 0·48, 95% CI 0·24-0·94, P = 0·03) but not in those breastfed for < 1 month (OR 0·80, 95% CI 0·29-2·17, P = 0·66). CONCLUSIONS: Our data provide the first randomized controlled trial evidence of a protective effect of antenatal cholecalciferol supplementation on the risk of infantile atopic eczema, with the effect potentially being via increased breast milk cholecalciferol levels. The findings support a developmental influence on atopic eczema, and point to a potentially modifiable perinatal influence on atopic eczema. What is already known about this topic? There are currently no antenatal interventions proven to reduce the incidence of infantile atopic eczema in the general population. However, observational studies have led to speculation that antenatal vitamin D supplementation may be beneficial.

A systematic review and network meta-analysis of topical pharmacological, oral pharmacological, physical and combined treatments for acne vulgaris.

BACKGROUND: Various treatments for acne vulgaris exist, but little is known about their comparative effectiveness in relation to acne severity. OBJECTIVES: To identify best treatments for mild-to-moderate and moderate-to-severe acne, as determined by clinician-assessed morphological features. METHODS: We undertook a systematic review and network meta-analysis of randomized controlled trials (RCTs) assessing topical pharmacological, oral pharmacological, physical and combined treatments for mild-to-moderate and moderate-to-severe acne, published up to May 2020. Outcomes included percentage change in total lesion count from baseline, treatment discontinuation for any reason, and discontinuation owing to side-effects. Risk of bias was assessed using the Cochrane risk-of-bias tool and bias adjustment models. Effects for treatments with ≥ 50 observations each compared with placebo are reported below. RESULTS: We included 179 RCTs with approximately 35 000 observations across 49 treatment classes. For mild-to-moderate acne, the most effective options for each treatment type were as follows: topical pharmacological - combined retinoid with benzoyl peroxide (BPO) [mean difference 26·16%, 95% credible interval (CrI) 16·75-35·36%]; physical - chemical peels, e.g. salicylic or mandelic acid (39·70%, 95% CrI 12·54-66·78%) and photochemical therapy (combined blue/red light) (35·36%, 95% CrI 17·75-53·08%). Oral pharmacological treatments (e.g. antibiotics, hormonal contraceptives) did not appear to be effective after bias adjustment. BPO and topical retinoids were less well tolerated than placebo. For moderate-to-severe acne, the most effective options for each treatment type were as follows: topical pharmacological - combined retinoid with lincosamide (clindamycin) (44·43%, 95% CrI 29·20-60·02%); oral pharmacological - isotretinoin of total cumulative dose ≥ 120 mg kg-1 per single course (58·09%, 95% CrI 36·99-79·29%); physical - photodynamic therapy (light therapy enhanced by a photosensitizing chemical) (40·45%, 95% CrI 26·17-54·11%); combined - BPO with topical retinoid and oral tetracycline (43·53%, 95% CrI 29·49-57·70%). Topical retinoids and oral tetracyclines were less well tolerated than placebo. The quality of included RCTs was moderate to very low, with evidence of inconsistency between direct and indirect evidence. Uncertainty in findings was high, in particular for chemical peels, photochemical therapy and photodynamic therapy. However, conclusions were robust to potential bias in the evidence. CONCLUSIONS: Topical pharmacological treatment combinations, chemical peels and photochemical therapy were most effective for mild-to-moderate acne. Topical pharmacological treatment combinations, oral antibiotics combined with topical pharmacological treatments, oral isotretinoin and photodynamic therapy were most effective for moderate-to-severe acne. Further research is warranted for chemical peels, photochemical therapy and photodynamic therapy for which evidence was more limited. What is already known about this topic? Acne vulgaris is the eighth most common disease globally. Several topical, oral, physical and combined treatments for acne vulgaris exist. Network meta-analysis (NMA) synthesizes direct and indirect evidence and allows simultaneous inference for all treatments forming an evidence network. Previous NMAs have assessed a limited range of treatments for acne vulgaris and have not evaluated effectiveness of treatments for moderate-to-severe acne. What does this study add? For mild-to-moderate acne, topical treatment combinations, chemical peels, and photochemical therapy (combined blue/red light; blue light) are most effective. For moderate-to-severe acne, topical treatment combinations, oral antibiotics combined with topical treatments, oral isotretinoin and photodynamic therapy (light therapy enhanced by a photosensitizing chemical) are most effective. Based on these findings, along with further clinical and cost-effectiveness considerations, National Institute for Health and Care Excellence (NICE) guidance recommends, as first-line treatments, fixed topical treatment combinations for mild-to-moderate acne and fixed topical treatment combinations, or oral tetracyclines combined with topical treatments, for moderate-to-severe acne.

Does music reduce anxiety for patients undergoing dermatological surgery? A systematic review.

BACKGROUND: The incidence of skin cancer is increasing globally, leading to a greater need for dermatologists to perform skin surgery. However, skin surgery can be a potentially stressful experience for patients due to the fear of a possible cancer diagnosis coupled with anxiety related to pain and cosmetic outcomes. AIM: To examine whether there is any evidence to support the hypothesis that listening to music during dermatological surgery under local anaesthesia can help reduce patient anxiety. METHODS: This systematic review considered all original research published until May 2020. Four relevant studies were identified, comprising a total of 381 patients (three randomized control trials and one case-control trial). RESULTS: Two of the four studies showed a significant reduction in perioperative anxiety in patients who had listened to music during surgery. Both of the other studies showed no statistically significant difference between music and no music for patients, although one of these noted reduced anxiety in surgeons. CONCLUSION: There is currently limited evidence to support the use of perioperative music in clinical practice to reduce anxiety in skin surgery. However, given the potential benefits and the likely limited costs of this simple intervention, we believe that further research on this topic is warranted.

Cost-effectiveness of topical pharmacological, oral pharmacological, physical and combined treatments for acne vulgaris.

BACKGROUND: Acne vulgaris is a common skin condition that may cause psychosocial distress. There is evidence that topical treatment combinations, chemical peels and photochemical therapy (combined blue/red light) are effective for mild-to-moderate acne, while topical treatment combinations, oral antibiotics combined with topical treatments, oral isotretinoin and photodynamic therapy are most effective for moderate-to-severe acne. Effective treatments have varying costs. The National Institute for Health and Care Excellence (NICE) in England considers cost-effectiveness when producing national clinical, public health and social care guidance. AIM: To assess the cost-effectiveness of treatments for mild-to-moderate and moderate-to-severe acne to inform relevant NICE guidance. METHODS: A decision-analytical model compared costs and quality-adjusted life-years (QALYs) of effective topical pharmacological, oral pharmacological, physical and combined treatments for mild-to-moderate and moderate-to-severe acne, from the perspective of the National Health Service in England. Effectiveness data were derived from a network meta-analysis. Other model input parameters were based on published sources, supplemented by expert opinion. RESULTS: All of the assessed treatments were more cost-effective than treatment with placebo (general practitioner visits without active treatment). For mild-to-moderate acne, topical treatment combinations and photochemical therapy (combined blue/red light) were most cost-effective. For moderate-to-severe acne, topical treatment combinations, oral antibiotics combined with topical treatments, and oral isotretinoin were the most cost-effective. Results showed uncertainty, as reflected in the wide confidence intervals around mean treatment rankings. CONCLUSION: A range of treatments are cost-effective for the management of acne. Well-conducted studies are needed to examine the long-term clinical efficacy and cost-effectiveness of the full range of acne treatments.

Inherited duplications of PPP2R3B predispose to nevi and melanoma via a C21orf91-driven proliferative phenotype.

PURPOSE: Much of the heredity of melanoma remains unexplained. We sought predisposing germline copy-number variants using a rare disease approach. METHODS: Whole-genome copy-number findings in patients with melanoma predisposition syndrome congenital melanocytic nevus were extrapolated to a sporadic melanoma cohort. Functional effects of duplications in PPP2R3B were investigated using immunohistochemistry, transcriptomics, and stable inducible cellular models, themselves characterized using RNAseq, quantitative real-time polymerase chain reaction (qRT-PCR), reverse phase protein arrays, immunoblotting, RNA interference, immunocytochemistry, proliferation, and migration assays. RESULTS: We identify here a previously unreported genetic susceptibility to melanoma and melanocytic nevi, familial duplications of gene PPP2R3B. This encodes PR70, a regulatory unit of critical phosphatase PP2A. Duplications increase expression of PR70 in human nevus, and increased expression in melanoma tissue correlates with survival via a nonimmunological mechanism. PPP2R3B overexpression induces pigment cell switching toward proliferation and away from migration. Importantly, this is independent of the known microphthalmia-associated transcription factor (MITF)-controlled switch, instead driven by C21orf91. Finally, C21orf91 is demonstrated to be downstream of MITF as well as PR70. CONCLUSION: This work confirms the power of a rare disease approach, identifying a previously unreported copy-number change predisposing to melanocytic neoplasia, and discovers C21orf91 as a potentially targetable hub in the control of phenotype switching.

Proteomic Profiling of Archived Tissue of Primary Melanoma Identifies Proteins Associated with Metastasis.

Formalin-fixed paraffin embedded (FFPE) clinical tissues represent an abundant and unique resource for translational proteomic studies. In the US, melanoma is the 5th and 6th most common cancer in men and women, respectively, affecting over 230,000 people annually and metastasising in 5-15% of cases. Median survival time for distant metastatic melanoma is 6-9 months with a 5-year-survival of < 15%. In this study, 24 primary FFPE tumours which have metastasised (P-M) and 24 primary FFPE tumours which did not metastasise (P-NM) were subjected to proteomic profiling. In total, 2750 proteins were identified, of which 16 were significantly differentially expressed. Analysis of TCGA data demonstrated that expression of the genes encoding for 6 of these 16 proteins had a significant effect on survival in cutaneous melanoma. Pathway analysis of the proteomics data revealed mechanisms likely involved in the process of melanoma metastasis, including cytoskeleton rearrangement, extracellular changes and immune system alterations. A machine learning prediction model scoring an AUC of 0.922, based on these 16 differentially expressed proteins was able to accurately classify samples into P-M and P-NM. This study has identified potential biomarkers and key processes relating to melanoma metastasis using archived clinical samples, providing a basis for future studies in larger cohorts.

Persistent kallikrein 5 activation induces atopic dermatitis-like skin architecture independent of PAR2 activity.

BACKGROUND: Upregulation of kallikreins (KLKs) including KLK5 has been reported in atopic dermatitis (AD). KLK5 has biological functions that include degrading desmosomal proteins and inducing proinflammatory cytokine secretion through protease-activated receptor 2 (PAR2). However, due to the complex interactions between various cells in AD inflamed skin, it is difficult to dissect the precise and multiple roles of upregulated KLK5 in AD skin. OBJECTIVE: We investigated the effect of upregulated KLK5 on the expression of epidermal-related proteins and cytokines in keratinocytes and on skin architecture. METHODS: Lesional and nonlesional AD skin biopsies were collected for analysis of morphology and protein expression. The relationship between KLK5 and barrier-related molecules was investigated using an ex vivo dermatitis skin model with transient KLK5 expression and a cell model with persistent KLK5 expression. The influence of upregulated KLK5 on epidermal morphology was investigated using an in vivo skin graft model. RESULTS: Upregulation of KLK5 and abnormal expression of desmoglein 1 (DSG1) and filaggrin, but not PAR2 were identified in AD skin. PAR2 was increased in response to transient upregulation of KLK5, whereas persistently upregulated KLK5 did not show this effect. Persistently upregulated KLK5 degraded DSG1 and stimulated secretion of IL-8, IL-10, and thymic stromal lymphopoietin independent of PAR2 activity. With control of higher KLK5 activity by the inhibitor sunflower trypsin inhibitor G, restoration of DSG1 expression and a reduction in AD-related cytokine IL-8, thymic stromal lymphopoietin, and IL-10 secretion were observed. Furthermore, persistently elevated KLK5 could induce AD-like skin architecture in an in vivo skin graft model. CONCLUSIONS: Persistently upregulated KLK5 resulted in AD-like skin architecture and secretion of AD-related cytokines from keratinocytes in a PAR2 independent manner. Inhibition of KLK5-mediated effects may offer potential as a therapeutic approach in AD.

First-in-human studies of seletalisib, an orally bioavailable small-molecule PI3Kδ inhibitor for the treatment of immune and inflammatory diseases.

PURPOSE: PI3Ks are potential therapeutic targets in immune-inflammatory diseases. These studies aimed to investigate the safety, tolerability and PK profile of seletalisib, a selective inhibitor of PI3Kδ in humans. METHODS: These phase I, randomised, double-blind, placebo-controlled, single-centre studies (NCT02303509, NCT02207595) evaluated single and multiple oral doses of seletalisib (5-90 mg QD and 30 mg BID) in healthy adults and subjects with mild-to-moderate psoriasis (Study-1). Pharmacodynamic effects on markers of inflammation were assessed via changes in ex vivo basophil degranulation and histological assessment of psoriatic skin biopsies. RESULTS: Seletalisib was well tolerated at doses ≤15 mg (Study-1) and ≤45 mg QD (Study-2) for 14 days. No safety concerns or dose-limiting toxicities were identified (Study-1). Incidence of gastrointestinal-related AEs was not dose related but higher incidences of rash AEs were associated with higher-dose seletalisib (Study-2 rash AEs: 18 in 12 seletalisib-treated subjects versus 1 in 1 placebo-treated subject). Mean seletalisib plasma concentration-time profiles increased with increasing doses after single and multiple dosing, with no major deviations from dose-proportionality. There was no unexpected accumulation or loss of exposure after multiple dosing (time-independent pharmacokinetic profile). Apparent t 1/2 values were supportive of once-daily dosing (geometric mean t1/2: Study-1, 17.7-21.1 h; Study-2, 18.1-22.4 h). No clinically significant food effect was observed (Study-1). Pharmacodynamic findings demonstrated ex vivo inhibition of basophil degranulation, improvements in histological assessment of skin biopsies and other markers of psoriatic biology and preliminary evidence of target engagement in psoriatic skin tissue. CONCLUSIONS: Seletalisib safety, tolerability and pharmacokinetic/pharmacodynamic profiles support its continued clinical development in immune-inflammatory diseases.

Characteristics of immunosuppressive regulatory T cells in cutaneous squamous cell carcinomas and role in metastasis.

BACKGROUND: Non-melanoma skin cancer is the most common cancer worldwide, and cutaneous squamous cell carcinomas (SCCs) account for substantial morbidity and mortality because of their potential for metastasis. SCCs are surrounded by an immune cell infiltrate containing regulatory T cells (Tregs). The aim of this study was to characterise Tregs in SCCs and investigate whether increased Treg numbers in primary skin SCCs are associated with subsequent metastasis. METHODS: Lymphocytes were extracted from freshly excised skin SCC tumours and corresponding peripheral blood and normal skin. Flow cytometry was used for T-cell analysis and cell sorting. Tritiated thymidine based lymphocyte proliferation assays and interferon γ (IFNγ) ELISPOT assays were used to assess peritumoral lymphocyte function in vitro. Immunohistochemistry was performed on primary cutaneous SCC sections from tumours that subsequently metastasised and from those that did not after 5-year follow-up. FINDINGS: Increased frequencies of CD3+CD4+CD25hiCD127loFOXP3+ Tregs were found in SCCs (21·5% of CD4+ immune infiltrate, n=60 tumours) compared with corresponding peripheral blood (5·4%) and normal skin (7·6%). SCC Tregs expressed significantly higher levels of the co-stimulatory molecules OX40 (37·2% of FOXP3+ cell population, n=10 tumours) and 4-1BB (12·6%, n=9) than peritumoral non-regulatory T cells and Tregs from peripheral blood and normal skin (p=0·0005). The inhibitory receptor CTLA4 and the transcription factor Helios were expressed at high levels in peritumoral Tregs. SCC Tregs significantly suppressed phytohaemagglutinin-stimulated peritumoral CD4+ T-cell proliferation (p=0·005, n=10), peritumoral CD8+ T-cell proliferation (p=0·015, n=9), and IFNγ secretion by CD4+ effector T cells (p=0·026, n=10). Increased in-vitro proliferation of phytohaemagglutinin-stimulated peritumoral CD4+ T cells was shown after the addition of anti-OX40 antibodies (p=0·0078, n=9 tumours) and anti-4-1BB antibodies (p=0·0039, n=9). Immunohistochemistry showed fewer CD8+ T cells in SCCs that metastasised (n=29) than in non-metastatic SCCs (n=26) (28·5% of immune infiltrate vs 44·6%%, p<0·0001) and more FOX3+ Tregs (28·5% of immune infiltrate vs 49·3%, p<0·0001). INTERPRETATION: Our study shows that immunosuppressive Tregs are present in the immune infiltrate of cutaneous SCCs, and contribute to ineffective anti-tumour immune responses, thereby permitting SCC development and promoting metastasis. FUNDING: Wellcome Trust, National Institute for Health Research.

Variants of the melanocortin-1 receptor: do they matter clinically?

The melanocortin 1 receptor (MC1R) gene encodes for a seven-pass transmembrane receptor primarily expressed on melanocytes and melanoma cells. Single nucleotide polymorphisms (SNPs, also termed variants) in MC1R frequently cause red hair, fair skin and are associated with melanoma and keratinocyte-derived skin cancer development. Activation of wild-type (WT) MC1R in skin assists cutaneous photoprotection whereas reduced MC1R signalling, seen with MC1R variants, impairs ultraviolet radiation (UVR)-protective responses. As ancestral humans migrated out of Africa, the evolutionary advantage of MC1R variants may have related to improved cutaneous vitamin D synthesis and higher birthweight reported with certain MC1R variants. Reduced photoprotection secondary to MC1R dysfunction involves pigmentary and non-pigmentary mechanisms (reduced DNA repair, effects on cell proliferation and possibly immunological parameters), leading to clonal expansion of mutated cells within skin and subsequent carcinogenesis. Recent investigations suggest an association between MC1R genotype and vitiligo, with preliminary evidence that a MC1R agonist, [Nle4-D-Phe7]-alpha-MSH, in combination with UVB, assists repigmentation. Future development of compounds to correct defective MC1R responses secondary to MC1R variants could result in photoprotective benefits for fair-skinned individuals and reduce their skin cancer risk.

Impaired expression of metallothioneins contributes to allergen-induced inflammation in patients with atopic dermatitis.

Regulation of cutaneous immunity is severely compromised in inflammatory skin disease. To investigate the molecular crosstalk underpinning tolerance versus inflammation in atopic dermatitis, we utilise a human in vivo allergen challenge study, exposing atopic dermatitis patients to house dust mite. Here we analyse transcriptional programmes at the population and single cell levels in parallel with immunophenotyping of cutaneous immunocytes revealed a distinct dichotomy in atopic dermatitis patient responsiveness to house dust mite challenge. Our study shows that reactivity to house dust mite was associated with high basal levels of TNF-expressing cutaneous Th17 T cells, and documents the presence of hub structures where Langerhans cells and T cells co-localised. Mechanistically, we identify expression of metallothioneins and transcriptional programmes encoding antioxidant defences across all skin cell types, that appear to protect against allergen-induced inflammation. Furthermore, single nucleotide polymorphisms in the MTIX gene are associated with patients who did not react to house dust mite, opening up possibilities for therapeutic interventions modulating metallothionein expression in atopic dermatitis.