COL10A1 expression distinguishes a subset of cancer-associated fibroblasts present in the stroma of high-risk basal cell carcinoma.

BACKGROUND: Basal cell carcinoma (BCC) is the most frequently diagnosed skin cancer and the most common malignancy in humans. Different morphological subtypes of BCC are associated with low- or high-risk of recurrence and aggressiveness, but the underlying biology of how the individual subtypes arise remains largely unknown. Because the majority of BCCs appear to arise from mutations in the same pathway, we hypothesized that BCC development, growth and invasive potential is also influenced by the tumor microenvironment and in particular by cancer-associated fibroblasts (CAFs) and their secreted factors. OBJECTIVE: We aimed to characterize the stroma of the different BCC subtypes with a focus on CAF populations. METHODS: To investigate the stromal features of the different BCC subtypes, we applied laser-capture microdissection (LCM) followed by RNA sequencing. A cohort of 15 BCC samples from 5 different "pure" subtypes (superficial, nodular, micronodular, sclerosing and basosquamous; n=3 each) were selected and included in the analysis. Healthy skin was used as a control (n=6). We confirmed the results by immunohistochemistry. We validated our findings in two independent, public single-cell RNA sequencing (scRNAseq) datasets and by RNAscope. RESULTS: The stroma of the different BCC subtypes have distinct gene expression signatures. Nodular and micronodular seem to have the most similar signatures, while superficial and sclerosing the most different. By comparing low- and high-risk BCC subtypes, we observed that Collagen 10A1 (COL10A1) is overexpressed in the stroma of sclerosing/infiltrative and basosquamous but not micronodular high-risk subtypes. Those findings were confirmed by immunohistochemistry in a cohort of 89 different BCC and 13 healthy skin samples. Moreover, scRNAseq analysis of BCCs of two independent datasets showed that the COL10A1-expressing population of cells is associated with the stroma adjacent to invasive BCC and shows extracellular matrix remodeling features. CONCLUSION: We identified COL10A1 as a marker of high-risk BCC, in particular of the sclerosing/infiltrative and basosquamous subtypes. We demonstrated at the single cell level that COL10A1 is expressed by a specific CAF population associated with the stroma of invasive BCC. This opens up new tailored treatment options as well as a new prognostic biomarker for BCC progression.

[Management of chronic ulcers: punch grafting]. / Prise en charge des ulcères chroniques : la greffe en pastilles.

Chronic ulcers are a common but important dermatological problem and a major source of expense in the western countries. Skin graft is a surgical procedure in which skin or skin substitute is transplanted in order to close a wound. This article aims to review the different categories of grafts, their indications for the healing of chronic ulcers of the lower limbs, emphasizing the position of punch grafts in the treatment arsenal.

Les ulcères chroniques représentent un problème dermatologique courant et donc une source majeure de dépenses dans les pays occidentaux. La greffe de peau est une intervention chirurgicale au cours de laquelle la peau ou un substitut de peau est transplanté afin de favoriser la cicatrisation d'une plaie. Cet article a pour but de faire le point sur les différentes catégories de greffe, leurs indications dans la prise en charge des ulcères chroniques des membres inférieurs en soulignant la place des greffes en pastilles dans l'arsenal thérapeutique à disposition.

[Dermatofibrosarcoma protuberans†: clinico-pathological aspects and management]. / Dermatofibrosarcoma protuberans†: aspects clinico-pathologiques et prise en charge.

The dermatofibrosarcoma protuberans (DFSP) is the most common form of low-grade cutaneous sarcoma; its infiltrating growth occurs by fingerlike projections, which explain the high rate of recurrence in case of inappropriate surgical procedure. Based on an extensive review of the existing literature, we propose here to discuss the actual criteria for early recognition, diagnosis and optimal take of care of DFSP.

Le dermatofibrosarcoma protuberans (DFSP) est la forme la plus fréquente de sarcome cutané. Son caractère infiltrant du fait de projections tumorales digitiformes caractéristiques expose à un taux de récidive locale très élevé en cas de prise en charge chirurgicale inappropriée. Sur la base d'une revue extensive de la littérature existante, nous proposons ici de revoir les critères diagnostiques du DFSP ainsi que la prise en charge recommandée.

[Artificial intelligence and the skin specialist]. / L'intelligence artificielle et le dermatologue.

Artificial intelligence's progress is spread on front pages of both lay and scientific journals. After Chess, after Go, before Dota2 and Starcraft, super-trained softwares have equaled or out-performed dermatologists. But what is the future of these computer programs and how will they change clinical practice for both the general practitioner and the skin specialist? It is time to ask these questions, even though the promises of these new technologies are not yet available.

Les progrès de l'intelligence artificielle s'étalent chaque jour dans les journaux laïques comme scientifiques. Après les échecs, après le jeu de Go, avant Dota2 et Starcraft, des programmes surentraînés ont fait aussi bien, voire mieux qu'un groupe de dermatologues. Mais quel est l'avenir de ces super-programmes et comment vont-ils changer la pratique médicale, pour le médecin de premier recours et pour le spécialiste ? Le temps est venu de se poser ces questions, même si les promesses de ces nouvelles technologies se refusent à nous pour l'instant.

Non-Melanoma Skin Cancers of the Fronto-Temporal Area Preferentially Localize in the Proximity of Arterial Blood Vessels.

BACKGROUND: Squamous cell carcinomas and basal cell carcinomas are both induced by chronic UV exposure. However, their predilection for specific areas of the face remains unexplained. Regional factors such as arterial blood flow may explain specific tumor localization. OBJECTIVE: To determine whether in the fronto-temporal area of the face there is a preferential localization of non-melanoma skin cancer (NMSC) at sites of arterial blood vessels. METHODS: Twenty-two patients with NMSC of the fronto-temporal area were selected for this study. The clinical tumor margins were demarked based on clinical examination. Arterial colocalization was determined using both sonography and histological analysis. RESULTS: Echo-Doppler analysis revealed the colocalization of NMSC with an arterial branch in 59% of the patients. Histologically, colocalization between NMSC and artery was found in 68% of the patients. When combining echo-Doppler and histological results, colocalization of NMSC and arteries were found in 82% of the patients. CONCLUSION: In this study, we found an unexpectedly high colocalization of NMSC with arterial branches in the fronto-temporal area of the face. These results suggest that in addition to UV exposure, pulsatile arterial blood flow may represent an additional factor determining the precise facial localization of NMSC.

[A new vision of skin]. / Une nouvelle vision de la peau.

As of today, the skin will never look the same. Indeed, several technologies allowing the observation of the skin at a microscopic level are now coming of age. This magnifies our visual acuity and thus our capacity to recognize various pathological processes. We herein present three different methods of non-invasive skin imaging we have worked with at the CHUV, which revolutionize the practice of dermatology. In vivo confocal microscopy, ex-vivo confocal microscopy and optical coherence tomography are complementary techniques that are now becoming essential for the modern management of skin cancers, among other uses.

Dès aujourd'hui, vous ne verrez plus la peau de la même manière. En effet, plusieurs technologies de microscopie sur peau intacte arrivent à maturité. Ceci décuple notre acuité visuelle, et donc notre capacité à reconnaître différents processus pathologiques. Nous présentons ici trois techniques d'imagerie cutanée non invasive avec lesquelles nous avons travaillé au CHUV, et qui sont en train de révolutionner la pratique de la dermatologie. Il s'agit de la microscopie confocale par réflectance in vivo ou ex vivo, et de la tomographie par cohérence optique, trois techniques complémentaires qui deviennent indispensables pour la prise en charge des cancers cutanés, mais dont l'utilité va bien au-delà.

Ingenol Mebutate 500 µg for Treatment of the Scalp in Refractory Field Cancerization.

Patients suffering from chronic lymphocytic leukemia often develop actinic keratosis (AK) and squamous cell carcinoma in sun-exposed areas. In these particular patients, who have a suboptimal immune function, AK treatment can be particularly challenging. We report the case of a patient who failed to respond to most AK treatments, including 5-FU, imiquimod and photodynamic therapy, but responded to ingenol mebutate. We started with 3 applications of 150 µg/g (registered treatment of the scalp) and also 2 applications of 500 µg/g (registered in for trunk and extremities). Both treatments were well tolerated, but only the latter led to significant clinical success. This suggests that 500 µg/g of ingenol mebutate may represent an interesting therapeutic option in patients with mild immunosuppression.

[New light on skin photodynamic therapy]. / Nouvelle lumière sur la thérapie photodynamique cutanée.

Photodynamic therapy (PDT) relies on the cellular toxicity of an exogenous porphyrin that is activated by light rays. Its specificity depends on its cellular uptake, which is typically high in cells with a high metabolism, such as cancer cells and several microbial pathogens. Both the diffusion of the substrate and the penetration of the light in the tissue limit its efficiency to the first few millimeters of the skin. This explains why this technique is used for the treatment of superficial skin cancers (actinic keratosis and basal cell carcinomas), but also for selected skin inflammatory diseases (psoriasis) or infections (leishmaniosis). However, at the bedside, the limitations of PDT are rather the complexity and the pain associated with the treatment. Herein, we present the new developments, in particular concerning the new light sources, which make PDT a better option for our patients.

Human neutrophils drive skin autoinflammation by releasing interleukin (IL)-26.

Autoinflammation is a sterile inflammatory process resulting from increased neutrophil infiltration and overexpression of IL-1 cytokines. The factors that trigger these events are, however, poorly understood. By investigating pustular forms of psoriasis, we show that human neutrophils constitutively express IL-26 and abundantly release it from granular stores upon activation. In pustular psoriasis, neutrophil-derived IL-26 drives the pathogenic autoinflammation process by inducing the expression of IL-1 cytokines and chemokines that further recruit neutrophils. This occurs via activation of IL-26R in keratinocytes and via the formation of complexes between IL-26 and microbiota DNA, which trigger TLR9 activation of neutrophils. Thus our findings identify neutrophils as an important source of IL-26 and point to IL-26 as the key link between neutrophils and a self-sustaining autoinflammation loop in pustular psoriasis.

MHC-I upregulation safeguards neoplastic T cells in the skin against NK cell-mediated eradication in mycosis fungoides.

Cancer-associated immune dysfunction is a major challenge for effective therapies. The emergence of antibodies targeting tumor cell-surface antigens led to advancements in the treatment of hematopoietic malignancies, particularly blood cancers. Yet their impact is constrained against tumors of hematopoietic origin manifesting in the skin. In this study, we employ a clonality-supervised deep learning methodology to dissect key pathological features implicated in mycosis fungoides, the most common cutaneous T-cell lymphoma. Our investigations unveil the prominence of the IL-32ß-major histocompatibility complex (MHC)-I axis as a critical determinant in tumor T-cell immune evasion within the skin microenvironment. In patients' skin, we find MHC-I to detrimentally impact the functionality of natural killer (NK) cells, diminishing antibody-dependent cellular cytotoxicity and promoting resistance of tumor skin T-cells to cell-surface targeting therapies. Through murine experiments in female mice, we demonstrate that disruption of the MHC-I interaction with NK cell inhibitory Ly49 receptors restores NK cell anti-tumor activity and targeted T-cell lymphoma elimination in vivo. These findings underscore the significance of attenuating the MHC-I-dependent immunosuppressive networks within skin tumors. Overall, our study introduces a strategy to reinvigorate NK cell-mediated anti-tumor responses to overcome treatment resistance to existing cell-surface targeted therapies for skin lymphoma.

Activin A-Mediated Polarization of Cancer-Associated Fibroblasts and Macrophages Confers Resistance to Checkpoint Immunotherapy in Skin Cancer.

PURPOSE: Cemiplimab is approved for the treatment of locally advanced basal cell carcinomas (BCC), although with mitigated results. We sought to interrogate the cellular and molecular transcriptional reprogramming underlying BCC resistance to immunotherapy. EXPERIMENTAL DESIGN: Here, we combined spatial and single-cell transcriptomics to deconvolute the spatial heterogeneity of the tumor microenvironment in regard with response to immunotherapy, in a cohort of both naïve and resistant BCCs. RESULTS: We identified subsets of intermingled cancer-associated fibroblasts (CAF) and macrophages contributing the most to CD8 T-cell exclusion and immunosuppression. Within this spatially resolved peritumoral immunosuppressive niche, CAFs and adjacent macrophages were found to display Activin A-mediated transcriptional reprogramming towards extracellular matrix remodeling, suggesting active participation to CD8 T-cell exclusion. In independent datasets of human skin cancers, Activin A-conditioned CAFs and macrophages were associated with resistance to immune checkpoint inhibitors (ICI). CONCLUSIONS: Altogether, our data identify the cellular and molecular plasticity of tumor microenvironment (TME) and the pivotal role of Activin A in polarizing the TME towards immune suppression and ICI resistance.

Differentiation of IL-26+ TH17 intermediates into IL-17A producers via epithelial crosstalk in psoriasis.

Interleukin (IL)-26 is a TH17 cytokine with known antimicrobial and pro-inflammatory functions. However, the precise role of IL-26 in the context of pathogenic TH17 responses is unknown. Here we identify a population of blood TH17 intermediates that produce high levels of IL-26 and differentiate into IL-17A-producing TH17 cells upon TGF-ß1 exposure. By combining single cell RNA sequencing, TCR sequencing and spatial transcriptomics we show that this process occurs in psoriatic skin. In fact, IL-26+ TH17 intermediates infiltrating psoriatic skin induce TGF-ß1 expression in basal keratinocytes and thereby promote their own differentiation into IL-17A-producing cells. Thus, our study identifies IL-26-producing cells as an early differentiation stage of TH17 cells that infiltrates psoriatic skin and controls its own maturation into IL17A-producing TH17 cells, via epithelial crosstalk involving paracrine production of TGF-ß1.

Integrated multi-omics reveals cellular and molecular interactions governing the invasive niche of basal cell carcinoma.

Tumors invade the surrounding tissues to progress, but the heterogeneity of cell types at the tumor-stroma interface and the complexity of their potential interactions hampered mechanistic insight required for efficient therapeutic targeting. Here, combining single-cell and spatial transcriptomics on human basal cell carcinomas, we define the cellular contributors of tumor progression. In the invasive niche, tumor cells exhibit a collective migration phenotype, characterized by the expression of cell-cell junction complexes. In physical proximity, we identify cancer-associated fibroblasts with extracellular matrix-remodeling features. Tumor cells strongly express the cytokine Activin A, and increased Activin A-induced gene signature is found in adjacent cancer-associated fibroblast subpopulations. Altogether, our data identify the cell populations and their transcriptional reprogramming contributing to the spatial organization of the basal cell carcinoma invasive niche. They also demonstrate the power of integrated spatial and single-cell multi-omics to decipher cancer-specific invasive properties and develop targeted therapies.

Connexins orchestrate progression of breast cancer metastasis to the brain by promoting FAK activation.

Brain metastasis is a complication of increasing incidence in patients with breast cancer at advanced disease stage. It is a severe condition characterized by a rapid decline in quality of life and poor prognosis. There is a critical clinical need to develop effective therapies to prevent and treat brain metastases. Here, we describe a unique and robust spontaneous preclinical model of breast cancer metastasis to the brain (4T1-BM2) in mice that has been instrumental in uncovering molecular mechanisms guiding metastatic dissemination and colonization of the brain. Key experimental findings were validated in the additional murine D2A1-BM2 model and in human MDA231-BrM2 model. Gene expression analyses and functional studies, coupled with clinical transcriptomic and histopathological investigations, identified connexins (Cxs) and focal adhesion kinase (FAK) as master molecules orchestrating breast cancer colonization of the brain. Cx31 promoted homotypic tumor cell adhesion, heterotypic tumor-astrocyte interaction, and FAK phosphorylation. FAK signaling prompted NF-κB activation inducing Lamc2 expression and laminin 332 (laminin 5) deposition, α6 integrin-mediated adhesion, and sustained survival and growth within brain parenchyma. In the MDA231-BrM2 model, the human homologous molecules CX43, LAMA4, and α3 integrin were involved. Systemic treatment with FAK inhibitors reduced brain metastasis progression. In conclusion, we report a spontaneous model of breast cancer metastasis to the brain and identified Cx-mediated FAK-NF-κB signaling as a mechanism promoting cell-autonomous and microenvironmentally controlled cell survival for brain colonization. Considering the limited therapeutic options for brain metastatic disease in cancer patients, we propose FAK as a therapeutic candidate to further pursue in the clinic.

Sphingolipids control dermal fibroblast heterogeneity.

Human cells produce thousands of lipids that change during cell differentiation and can vary across individual cells of the same type. However, we are only starting to characterize the function of these cell-to-cell differences in lipid composition. Here, we measured the lipidomes and transcriptomes of individual human dermal fibroblasts by coupling high-resolution mass spectrometry imaging with single-cell transcriptomics. We found that the cell-to-cell variations of specific lipid metabolic pathways contribute to the establishment of cell states involved in the organization of skin architecture. Sphingolipid composition is shown to define fibroblast subpopulations, with sphingolipid metabolic rewiring driving cell-state transitions. Therefore, cell-to-cell lipid heterogeneity affects the determination of cell states, adding a new regulatory component to the self-organization of multicellular systems.

The HHIP-AS1 lncRNA promotes tumorigenicity through stabilization of dynein complex 1 in human SHH-driven tumors.

Most lncRNAs display species-specific expression patterns suggesting that animal models of cancer may only incompletely recapitulate the regulatory crosstalk between lncRNAs and oncogenic pathways in humans. Among these pathways, Sonic Hedgehog (SHH) signaling is aberrantly activated in several human cancer entities. We unravel that aberrant expression of the primate-specific lncRNA HedgeHog Interacting Protein-AntiSense 1 (HHIP-AS1) is a hallmark of SHH-driven tumors including medulloblastoma and atypical teratoid/rhabdoid tumors. HHIP-AS1 is actively transcribed from a bidirectional promoter shared with SHH regulator HHIP. Knockdown of HHIP-AS1 induces mitotic spindle deregulation impairing tumorigenicity in vitro and in vivo. Mechanistically, HHIP-AS1 binds directly to the mRNA of cytoplasmic dynein 1 intermediate chain 2 (DYNC1I2) and attenuates its degradation by hsa-miR-425-5p. We uncover that neither HHIP-AS1 nor the corresponding regulatory element in DYNC1I2 are evolutionary conserved in mice. Taken together, we discover an lncRNA-mediated mechanism that enables the pro-mitotic effects of SHH pathway activation in human tumors.

c-FOS drives reversible basal to squamous cell carcinoma transition.

While squamous transdifferentiation within subpopulations of adenocarcinomas represents an important drug resistance problem, its underlying mechanism remains poorly understood. Here, using surface markers of resistant basal cell carcinomas (BCCs) and patient single-cell and bulk transcriptomic data, we uncover the dynamic roadmap of basal to squamous cell carcinoma transition (BST). Experimentally induced BST identifies activator protein 1 (AP-1) family members in regulating tumor plasticity, and we show that c-FOS plays a central role in BST by regulating the accessibility of distinct AP-1 regulatory elements. Remarkably, despite prominent changes in cell morphology and BST marker expression, we show using inducible model systems that c-FOS-mediated BST demonstrates reversibility. Blocking EGFR pathway activation after c-FOS induction partially reverts BST in vitro and prevents BST features in both mouse models and human tumors. Thus, by identifying the molecular basis of BST, our work reveals a therapeutic opportunity targeting plasticity as a mechanism of tumor resistance.