Mutational Landscape of Basal Cell Carcinomas by Whole-Exome Sequencing

Inherited Basaloid Neoplasms Associated With SUFU Pathogenic Variants

Importance

Germline SUFU pathogenic variants (PVs) have previously been associated with basal cell nevus syndrome (BCNS) and multiple infundibulocystic basal cell carcinoma syndrome; however, a broader spectrum of cutaneous findings in patients with SUFU PVs has not been well delineated.

Objective

To define the clinical and histopathologic spectrum of cutaneous findings in patients with germline SUFU PVs.

Design, Setting, and Participants

This case series was conducted in multiple US academic dermatology, medical genetics, and medical oncology clinics between July 2014 and July 2022. The study included patients with confirmed germline SUFU PVs who were evaluated by a dermatologist. The analysis took place from March to September 2023.

Main Outcomes and Measures

Histopathologic evaluation of skin biopsies with or without immunohistochemical staining, and targeted next-generation sequencing (NGS) on tumor specimens.

Results

All 5 patients were women. The mean (range) age at presentation was 50.2 (31-68) years, with skin manifestations initially appearing in the fourth to sixth decades of life. None had keratocystic odontogenic tumors. A total of 29 skin pathology specimens from the 5 patients were reviewed; of these, 3 (10.3%) were diagnosed as basaloid follicular hamartomas (BFHs), 10 (34.5%) classified as infundibulocystic basal cell carcinomas (iBCCs), 6 (20.7%) classified as nodular basal cell carcinomas (nBCCs), and 1 (3.4%) as infiltrative basal cell carcinoma (BCC). Targeted NGS studies on tumor specimens suggest that an increased number of UV-signature variants is associated with basal cell carcinomas compared with more indolent basaloid follicular hamartomas.

Conclusions and Relevance

Patients with germline SUFU PVs may present with multiple indolent basaloid neoplasms in addition to conventional basal cell carcinomas, typically appearing in the fourth to sixth decades of life. Although there are overlapping clinical manifestations, these findings help to differentiate the clinical syndrome associated with SUFU PVs from PTCH1 BCNS. Awareness of the clinicopathologic spectrum of SUFU-associated basaloid neoplasms is important for dermatologists and dermatopathologists because many (although not all) of these lesions are indolent and do not require aggressive surgical treatment. Importantly, because SUFU lies downstream of the protein smoothened, vismodegib and other smoothened inhibitors are unlikely to be effective therapies in this subset of patients.

Role of PD-1 in Skin Cancer: Molecular Mechanism, Clinical Applications, and Resistance

Skin cancer is a widespread worldwide health concern, manifesting in many subtypes such as squamous cell carcinoma, basal cell carcinoma, and melanoma. Although all these types occur frequently, they generally lack the possibility of being cured, emphasizing the importance of early discovery and treatment. This comprehensive study explores the role of programmed cell death protein 1 (PD-1) in skin cancer, focusing on its molecular mechanisms in immune regulation and its critical role in tumor immune evasion, while also clarifying the complexities of immune checkpoints in cancer pathogenesis. It critically evaluates the clinical applications of PD-1 inhibitors, spotlighting their therapeutic potential in treating skin cancer, while also addressing the significant challenge of resistance. This work further discusses the evolution of resistance mechanisms against PD-1 inhibitors and suggests potential approaches to mitigate these issues, thereby enhancing the effectiveness of these therapies. The study further highlights the current state of PD-1 targeted therapies and sets the stage for future research aimed at optimizing these treatments for better clinical outcomes in skin cancer.

Squamoid Eccrine Ductal Carcinoma Displays Ultraviolet Mutations and Intermediate Gene Expression Relative to Squamous Cell Carcinoma, Microcystic Adnexal Carcinoma, and Porocarcinoma

Squamoid eccrine ductal carcinoma is a rare infiltrative tumor with morphologic features intermediate between squamous cell carcinoma (SCC) and sweat gland carcinomas such as microcystic adnexal carcinoma. Although currently classified as a sweat gland carcinoma, it has been debated whether squamoid eccrine ductal carcinoma is better classified as a variant of SCC. Furthermore, therapeutic options for patients with advanced disease are lacking. Here, we describe clinicopathologic features of a cohort of 15 squamoid eccrine ductal carcinomas from 14 unique patients, with next-generation sequencing DNA profiling for 12 cases. UV signature mutations were the dominant signature in the majority of cases. TP53 mutations were the most highly recurrent specific gene alteration, followed by mutations in NOTCH genes. Recurrent mutations in driver oncogenes were not identified. By unsupervised comparison of global transcriptome profiles in squamoid eccrine ductal carcinoma (n = 7) to SCC (n = 10), porocarcinoma (n = 4), and microcystic adnexal carcinoma (n = 4), squamoid eccrine ductal carcinomas displayed an intermediate phenotype between SCC and sweat gland tumors. Squamoid eccrine ductal carcinoma displayed significantly higher expression of 364 genes (including certain eccrine markers) and significantly lower expression of 525 genes compared with other groups. Our findings support the classification of squamoid eccrine ductal carcinoma as a carcinoma with intermediate features between SCC and sweat gland carcinoma.

Contribution of Keratinocytes in Skin Cancer Initiation and Progression

Keratinocytes are major cellular components of the skin and are strongly involved in its homeostasis. Oncogenic events, starting mainly from excessive sun exposure, lead to the dysregulation of their proliferation and differentiation programs and promote the initiation and progression of non-melanoma skin cancers (NMSCs). Primary melanomas, which originate from melanocytes, initiate and develop in close interaction with keratinocytes, whose role in melanoma initiation, progression, and immune escape is currently being explored. Recent studies highlighted, in particular, unexpected modes of communication between melanocytic cells and keratinocytes, which may be of interest as sources of new biomarkers in melanomagenesis or potential therapeutic targets. This review aims at reporting the various contributions of keratinocytes in skin basal cell carcinoma (BCC), cutaneous squamous cell carcinoma (cSCC), and melanoma, with a greater focus on the latter in order to highlight some recent breakthrough findings. The readers are referred to recent reviews when contextual information is needed.

Biomarkers in Cutaneous Keratinocyte Carcinomas

Skin cancer is the most common cancer type in the USA, with over five million annually treated cases and one in five Americans predicted to develop the disease by the age of 70. Skin cancer can be classified as melanoma or non-melanoma (NMSC), the latter including basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (SCC). Development of BCC and SCC is impacted by environmental, behavioral, and genetic risk factors and the incidence is on the rise, with the associated number of deaths surpassing those caused by melanoma, according to recent reports. Substantial morbidity is related to both BCC and SCC, including disfigurement, loss of function, and chronic pain, driving high treatment costs, and representing a heavy financial burden to patients and healthcare systems worldwide. Clinical presentations of BCC and SCC can be diverse, sometimes carrying considerable phenotypic similarities to benign lesions, and underscoring the need for the development of disease-specific biomarkers. Skin biomarker profiling plays an important role in deeper disease understanding, as well as in guiding clinical diagnosis and patient management, prompting the use of both invasive and non-invasive tools to evaluate specific biomarkers. In this work, we review the known and emerging biomarkers of BCC and SCC, with a focus on molecular and histologic biomarkers relevant for aspects of patient management, including prevention/risk assessments, tumor diagnosis, and therapy selection.

Therapeutic Approaches for Non-Melanoma Skin Cancer: Standard of Care and Emerging Modalities

Skin cancer encompasses a range of cutaneous malignancies, with non-melanoma skin cancers (NMSCs) being the most common neoplasm worldwide. Skin exposure is the leading risk factor for initiating NMSC. Ultraviolet (UV) light induces various genomic aberrations in both tumor-promoting and tumor-suppressing genes in epidermal cells. In conjunction with interactions with a changed stromal microenvironment and local immune suppression, these aberrations contribute to the occurrence and expansion of cancerous lesions. Surgical excision is still the most common treatment for these lesions; however, locally advanced or metastatic disease significantly increases the chances of morbidity or death. In recent years, numerous pharmacological targets were found through extensive research on the pathogenic mechanisms of NMSCs, leading to the development of novel treatments including Hedgehog pathway inhibitors for advanced and metastatic basal cell carcinoma (BCC) and PD-1/PD-L1 inhibitors for locally advanced cutaneous squamous cell carcinoma (cSCC) and Merkel cell carcinoma (MCC). Despite the efficacy of these new drugs, drug resistance and tolerability issues often arise with long-term treatment. Ongoing studies aim to identify alternative strategies with reduced adverse effects and increased tolerability. This review summarizes the current and emerging therapies used to treat NMSC.

Molecular Profiling and the Interaction of Somatic Mutations with Transcriptomic Profiles in Non-Melanoma Skin Cancer (NMSC) in a Population Exposed to Arsenic

Exposure to inorganic arsenic (As) is recognized as a risk factor for non-melanoma skin cancer (NMSC). We followed up with 7000 adults for 6 years who were exposed to As. During follow-up, 2.2% of the males and 1.3% of the females developed basal cell carcinoma (BCC), while 0.4% of the male and 0.2% of the female participants developed squamous cell carcinoma (SCC). Using a panel of more than 400 cancer-related genes, we detected somatic mutations (SMs) in the first 32 NMSC samples (BCC = 26 and SCC = 6) by comparing paired (tissue-blood) samples from the same individual and then comparing them to the SM in healthy skin tissue from 16 participants. We identified (a) a list of NMSC-associated SMs, (b) SMs present in both NMSC and healthy skin, and (c) SMs found only in healthy skin. We also demonstrate that the presence of non-synonymous SMs in the top mutated genes (like PTCH1, NOTCH1, SYNE1, PKHD1 in BCC and TP53 in SCC) significantly affects the magnitude of differential expressions of major genes and gene pathways (basal cell carcinoma pathways, NOTCH signaling, IL-17 signaling, p53 signaling, Wnt signaling pathway). These findings may help select groups of patients for targeted therapy, like hedgehog signaling inhibitors, IL17 inhibitors, etc., in the future.

Treatments on the horizon for locally advanced basal cell carcinoma

Basal cell carcinoma (BCC) is one of the most common human cancers. Most cases of BCC are amenable to surgical and topical treatments with excellent prognosis if diagnosed timely and managed appropriately. However, in a small percentage of cases, it could be locally advanced BBC (laBCC) and not amenable to surgery or radiation, including recurrent, large tumors or tumors that invade deeper tissue. Hedgehog inhibitors (vismodegib and sonidegib) are approved as the first-line treatment of laBCC. PD-1 inhibitor immunotherapy (cemiplimab) is indicated for cases that progressed on or could not tolerate hedgehog inhibitors or when hedgehog inhibitors are contraindicated. Given the modest response and bothersome side effects of some of the agents above, there are reports of novel treatments, and clinical trials are currently evaluating multiple agents.

Skin Cancer Risk Is Increased by Somatic Mutations Detected Noninvasively in Healthy-Appearing Sun-Exposed Skin

Skin cancer risk is increased by exposure to ultraviolet radiation (UVR). Because UVR exposure accumulates over time and lighter skin is more susceptible to UVR, age and skin tone are risk factors for skin cancer. However, measurements of somatic mutations in healthy-appearing skin have not been used to calculate skin cancer risk. In this study, we developed a noninvasive test that quantifies somatic mutations in healthy-appearing sun-exposed skin and applied it to a 1038-subject cohort. Somatic mutations were combined with other known skin cancer risk factors to train a model to calculate risk. The final model (DNA-Skin Cancer Assessment of Risk) was trained to predict personal history of skin cancer from age, family history, skin tone, and mutation count. The addition of mutation count significantly improved model performance (OR = 1.3, 95% confidence interval = 1.14-1.48; P = 5.3 × 10-6) and made a more significant contribution than skin tone. Calculations of skin cancer risk matched the known United States population prevalence, indicating that DNA-Skin Cancer Assessment of Risk was well-calibrated. In conclusion, somatic mutations in healthy-appearing sun-exposed skin increase skin cancer risk, and mutations capture risk information that is not accounted for by other risk factors. Clinical utility is supported by the noninvasive nature of skin sample collection through adhesive patches.

Ultraviolet Radiation Biological and Medical Implications

Ultraviolet (UV) radiation plays a crucial role in the development of melanoma and non-melanoma skin cancers. The types of UV radiation are differentiated by wavelength: UVA (315 to 400 nm), UVB (280 to 320 nm), and UVC (100 to 280 nm). UV radiation can cause direct DNA damage in the forms of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs). In addition, UV radiation can also cause DNA damage indirectly through photosensitization reactions caused by reactive oxygen species (ROS), which manifest as 8-hydroxy-2'-deoxyguanine (8-OHdG). Both direct and indirect DNA damage can lead to mutations in genes that promote the development of skin cancers. The development of melanoma is largely influenced by the signaling of the melanocortin one receptor (MC1R), which plays an essential role in the synthesis of melanin in the skin. UV-induced mutations in the BRAF and NRAS genes are also significant risk factors in melanoma development. UV radiation plays a significant role in basal cell carcinoma (BCC) development by causing mutations in the Hedgehog (Hh) pathway, which dysregulates cell proliferation and survival. UV radiation can also induce the development of squamous cell carcinoma via mutations in the TP53 gene and upregulation of MMPs in the stroma layer of the skin.

Basosquamous Carcinoma: Comprehensive Clinical and Histopathological Aspects, Novel Imaging Tools, and Therapeutic Approaches

Basosquamous carcinoma (BSC), an uncommon and aggressive nonmelanoma skin cancer exhibiting characteristics ranging from basal cell carcinoma (BCC) to squamous cell carcinoma (SCC), is a subject of controversy in terms of its classification, pathogenesis, histologic morphology, biologic behavior, prognosis, and management. This narrative review is based on an electronic search of English-language articles in PubMed that included the terms "basosquamous carcinoma" and/or "metatypical carcinoma of the skin" in their titles. The review aims to succinctly present and assess current data on the epidemiology, clinical presentation, dermoscopic, LC-OCT, and histopathologic characteristics, as well as the genetics and management of BSC, providing insight into this intriguing entity. As a conclusion, dermoscopy, deep incisional biopsies, and immunohistologic techniques should be applied in clinically suspicious lesions to achieve an early diagnosis and better prognosis of this tumor. Surgical treatments, including wide excision and Mohs' micrographic surgery, remain the treatment of choice. Finally, Hedgehog pathway inhibitors and checkpoint inhibitors, must be thoroughly investigated with large controlled trials, since they may offer an alternative solution to irresectable or difficult-to-treat locally advanced cases of basosquamous carcinoma.

Exploring multisite heterogeneity of human basal cell carcinoma proteome and transcriptome

Basal cell carcinoma (BCC) is the most common type of skin cancer. Due to multiple, potential underlying molecular tumor aberrations, clinical treatment protocols are not well-defined. This study presents multisite molecular heterogeneity profiles of human BCC based on RNA and proteome profiling. Three areas from lesions excised from 9 patients were analyzed. The focus was gene expression profiles based on proteome and RNA measurements of intra-tumor heterogeneity from the same patient and inter-tumor heterogeneity in nodular, infiltrative, and superficial BCC tumor subtypes from different patients. We observed significant overlap in intra- and inter-tumor variability of proteome and RNA expression profiles, showing significant multisite heterogeneity of protein expression in the BCC tumors. Inter-subtype analysis has also identified unique proteins for each BCC subtype. This profiling leads to a deeper understanding of BCC molecular heterogeneity and potentially contributes to developing new sampling tools for personalized diagnostics therapeutic approaches to BCC.

The Immune Microenvironment in Basal Cell Carcinoma

The immune system plays a key role in the suppression and progression of basal cell carcinoma (BCC). The primary aetiological factor for BCC development is exposure to ultraviolet radiation (UVR) which, particularly in lighter Fitzpatrick skin types, leads to the accumulation of DNA damage. UVR has roles in the generation of an immunosuppressive environment, facilitating cancer progression. Rates of BCC are elevated in immunosuppressed patients, and BCC may undergo spontaneous immune-mediated regression. Histologic and immunohistochemical profiling of BCCs consistently demonstrates the presence of an immune infiltrate and associated immune proteins. Early studies of immune checkpoint inhibitors reveal promising results in BCC. Therefore, the host immune system and tumor responses to it are important in BCC pathogenesis. Understanding these interactions will be beneficial for disease prognostication and therapeutic decisions.

Immunotherapy for keratinocyte cancers. Part I: Immune-related epidemiology, risk factors, pathogenesis, and immunotherapy management of keratinocyte cancers

The important role of the immune system in the surveillance and control of keratinocyte cancers (KCs), namely squamous and basal cell carcinomas, is increasingly appreciated, as new immunotherapies have recently become available. As the field of immunotherapy is rapidly evolving, this review synthesizes key concepts and highlights important cellular components within the immune system responsible for attacking KCs. We review the most current data on the epidemiology, risk factors, and immunotherapy management for KCs. Patients will seek advice from dermatologists to help explain why immunotherapies work for KCs and whether they might be appropriate for different clinical scenarios. Collaboration with medical colleagues across different disciplines to evaluate KCs for response to immunotherapy and early recognition of immune-related adverse events will help to optimize patient outcomes.

Cadherins and catenins in cancer: connecting cancer pathways and tumor microenvironment

Cadherin-catenin complexes are integral components of the adherens junctions crucial for cell-cell adhesion and tissue homeostasis. Dysregulation of these complexes is linked to cancer development via alteration of cell-autonomous oncogenic signaling pathways and extrinsic tumor microenvironment. Advances in multiomics have uncovered key signaling events in multiple cancer types, creating a need for a better understanding of the crosstalk between cadherin-catenin complexes and oncogenic pathways. In this review, we focus on the biological functions of classical cadherins and associated catenins, describe how their dysregulation influences major cancer pathways, and discuss feedback regulation mechanisms between cadherin complexes and cellular signaling. We discuss evidence of cross regulation in the following contexts: Hippo-Yap/Taz and receptor tyrosine kinase signaling, key pathways involved in cell proliferation and growth; Wnt, Notch, and hedgehog signaling, key developmental pathways involved in human cancer; as well as TGFβ and the epithelial-to-mesenchymal transition program, an important process for cancer cell plasticity. Moreover, we briefly explore the role of cadherins and catenins in mechanotransduction and the immune tumor microenvironment.

Does the histopathological subtype of primary basal cell carcinoma predict the subtype of secondary tumours? What role do genetic mutations play?

Background

Basal cell carcinoma (BCC) is one of the most common malignancies in the world. The frequency of histopathological subtypes and the distribution on the body of BCC has been well documented. Less has been written on the nature of secondary tumours. The genetics of BCC is starting to be understood, particularly with the advent of newer medical treatments (hedgehog inhibitors).

Objectives

To determine if primary basal cell carcinoma histopathological subtype predicts secondary tumour subtype, as well as their anatomical distribution.

Methods

A retrospective case series of patients over the age of 18 was performed from 2009 to 2014, with at least two separate diagnoses of BCC.

Results

In 394 identified patients, a total of 1355 BCCs arose in the cohort over the 6-year study period. The number of secondary BCCs per patient ranged from 2 to 19 tumours. Nodular BCC was the most likely to reoccur in secondary tumours (53.3%), followed by mixed subtypes (45.7%).

Conclusions

Within our study, we did find a predisposition for secondary BCCs to be of the same histopathological subtype as the primary, particularly with respect to nodular and mixed tumours. Furthermore, we found that secondary tumours were also more likely to occur on the same anatomical site as the primary tumour. We are only just beginning to under the genetic mutations involved in subtype formation.

Genomic Profiling of Metastatic Basal cell Carcinoma Reveals Candidate Drivers of Disease and Therapeutic Targets

Basal cell carcinomas (BCCs) are human beings' most common malignant tumors. Most are easily managed by surgery or topical therapies, and metastasis is rare. Although BCCs can become locally advanced, metastatic BCCs are very uncommon and may be biologically distinct. We assessed the clinicopathologic characteristics of 17 patients with metastatic BCC and pursued whole-exome sequencing of tumor and germline DNA from 8 patients. Genomic profiling revealed aberrant activation of Hedgehog signaling and alterations in GLI transcriptional regulators and Notch and Hippo signaling. Matched local recurrences of primary BCCs and metastases from 3 patients provided evidence of a clonal origin in all cases. Mutations associated with YAP inhibition were found exclusively in 2 hematogenously-spread lung metastases, and metastatic BCCs were enriched for mutations in the YAP/TAZ-binding domain of TEAD genes. Accordingly, YAP/TAZ nuclear localization was associated with metastatic types and Hippo mutations, suggesting an enhanced oncogenic role in hematogenously-spread metastases. Mutations in RET, HGF, and phosphatidylinositol 3‑kinase (PI3K)/protein kinase B (AKT) signaling were enriched compared with a cohort of low clinical-risk BCCs. Our results implicate Hippo and PI3K/AKT dysregulation in metastatic progression of BCCs, making these potential therapeutic targets in metastatic disease. The common clonal origin of matched recurrent and metastatic BCCs suggests that molecular profiling can assist in determining the nature/origin of poorly differentiated metastatic tumors of uncertain type. Genes and pathways enriched for mutations in this cohort are candidate drivers of metastasis and can be used to identify patients at high risk of metastasis who may benefit from aggressive local treatment and careful clinical follow-up.

Comparison of the Basal Cell Carcinoma (BCC) Tumour Microenvironment to Other Solid Malignancies

Basal cell carcinoma (BCC) is the most common form of skin cancer, contributing to nearly a third of new cancer cases in Western countries. Most BCCs are considered low risk "routine" lesions that can either be excised through surgery or treated with chemotherapeutic agents. However, around 1-2% of BCC cases are locally aggressive, present a high risk of metastasis, and often develop chemoresistance, termed advanced BCC. There currently exists no animal model or cell line that can recapitulate advanced BCC, let alone intermediate-risk and high-risk early BCC. We previously found that aggressive BCC tumours presented a Th2 cytokine inflammation profile, mesenchymal stem cell properties, and macrophage-induced tumoral inflammation. In this study, we aimed to identify potential BCC "relatives" among solid-organ malignancies who present similar immune cell proportions in their microenvironment compositions. Using immune cell type deconvolution by CIBERSORTx, and cell type enrichment by xCell, we determined three cancers with the most similar tumour microenvironments as compared to BCC. Specifically, chromophobe renal cell carcinoma, sarcoma, and skin cutaneous melanoma presented significance in multiple cell types, namely in CD4+ T lymphocytes, gammadelta T lymphocytes, and NK cell populations. Consequently, further literature analysis was conducted to understand similarities between BCC and its "relatives", as well as investigating novel treatment targets. By identifying cancers most like BCC, we hope to propose prospective druggable pathways, as well as to gain insight on developing a reliable animal or cell line model to represent advanced BCC.

A pan-cancer-bioinformatic-based literature review of TRPM7 in cancers

TRPM7, a divalent cation-selective channel with kinase domains, has been widely reported to potentially affect cancers. In this study, we conducted multiple bioinformatic analyses based on open databases and reviewed articles that provided evidence for the effects of TRPM7 on cancers. The purposes of this paper are 1) to provide a pan-cancer overview of TRPM7 in cancers; 2) to summarize evidence of TRPM7 effects on cancers; 3) to identify potential future studies of TRPM7 in cancer. Bioinformatics analysis revealed that no cancer-related TRPM7 mutation was found. TRPM7 is aberrantly expressed in most cancer types but the cancer-noncancer expression pattern varies across cancer types. TRPM7 was not associated with survival, TMB, or cancer stemness in most cancer types. TRPM7 affected drug sensitivity and tumor immunity in some cancer types. The in vitro evidence, preclinical in vivo evidence, and clinical evidence for TRPM7 effects on cancers as well as TRPM7 kinase substrate and TRPM7-targeting drugs associated with cancers were summarized to facilitate comparison. We matched the bioinformatics evidence to literature evidence, thereby unveiling potential avenues for future investigation of TRPM7 in cancers. We believe that this paper will help orient research toward important and relevant aspects of the role of TRPM7 in cancers.

Homeostases of epidermis and hair follicle, and development of basal cell carcinoma

Hedgehog signaling (Hh) plays a critical role in embryogenesis. On the other hand, its overactivity may cause basal cell carcinoma (BCC), the most common human cancer. Further, epidermal and hair follicle homeostases may have a key role in the development of BCC. This article describes the importance of different signaling pathways in the different stages of the two processes. The description of the homeostases brought up the importance of the Notch signaling along with the sonic hedgehog (Shh) and the Wnt pathways. Loss of the Notch signaling adversely affects the late stages of hair follicle formation and allows the bulge cells in the hair follicles to take the fate of the keratinocytes in the interfollicular epidermis. Further, the loss of Notch activity upregulates the Shh and Wnt activities, adversely affecting the homeostases. Notably, the Notch signaling is suppressed in BCC, and the peripheral BCC cells, which have low Notch activity, show drug resistance in comparison to the interior suprabasal BCC cells, which have high Notch activity.

Treatment of skin tumors with intratumoral interleukin 12 gene electrotransfer in the head and neck region: a first-in-human clinical trial protocol

BACKGROUND

Immune therapies are currently under intensive investigation providing in many cases excellent responses in different tumors. Other possible approach for immunotherapy is a targeted intratumoral delivery of interleukin 12 (IL-12), a cytokine with anti-tumor effectiveness. Due to its immunomodulatory action, it can be used as an imunostimulating component to in situ vaccinating effect of local ablative therapies. We have developed a phIL12 plasmid devoid of antibiotic resistance marker with a transgene for human IL-12 p70 protein. The plasmid can be delivered intratumorally by gene electrotransfer (GET).

PATIENTS AND METHODS

Here we present a first-in-human clinical trial protocol for phIL12 GET (ISRCTN15479959, ClinicalTrials NCT05077033). The study is aimed at evaluating the safety and tolerability of phIL12 GET in treatment of basal cell carcinomas in patients with operable tumors in the head and neck region. The study is designed as an exploratory, dose escalating study with the aim to determine the safety and tolerability of the treatment and to identify the dose of plasmid phIL12 that is safe and elicits its biological activity.

CONCLUSIONS

The results of this trail protocol will therefore provide the basis for the use of phIL12 GET as an adjuvant treatment to local ablative therapies, to potentially increase their local and elicit a systemic response.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of nonmelanoma skin cancer

Nonmelanoma skin cancers (NMSCs) are some of the most commonly diagnosed malignancies. In general, early-stage NMSCs have favorable outcomes; however, a small subset of patients develop resistant, advanced, or metastatic disease, or aggressive subtypes that are more challenging to treat successfully. Recently, immune checkpoint inhibitors (ICIs) have been approved by the US Food and Drug Administration (FDA) for the treatment of Merkel cell carcinoma (MCC), cutaneous squamous cell carcinoma (CSCC), and basal cell carcinoma (BCC). Although ICIs have demonstrated activity against NMSCs, the routine clinical use of these agents may be more challenging due to a number of factors including the lack of predictive biomarkers, the need to consider special patient populations, the management of toxicity, and the assessment of atypical responses. With the goal of improving patient care by providing expert guidance to the oncology community, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel of experts to develop a clinical practice guideline (CPG). The expert panel drew on the published literature as well as their own clinical experience to develop recommendations for healthcare professionals on important aspects of immunotherapeutic treatment for NMSCs, including staging, biomarker testing, patient selection, therapy selection, post-treatment response evaluation and surveillance, and patient quality of life (QOL) considerations, among others. The evidence- and consensus-based recommendations in this CPG are intended to provide guidance to cancer care professionals treating patients with NMSCs.

Multiple Basal Cell Carcinomas in Immunocompetent Patients

Simple Summary

It is widely known that long-term treatment with immunosuppressive drugs represents a risk factor for the onset of malignancies, including multiple basal cell carcinomas. However, multiple basal carcinomas are ao found in the general population, and even in the absence of specific predisposing genetic mutations. This paper aims, through the retrospective evaluation of all patients diagnosed and surgically treated for basal cell carcinomas during 5 years at our Dermatological Division, to identify the characteristics of these subjects and any possible risk factors, useful for outlining specific surveillance programs. In our experience, multiple carcinomas were identified in over 24% of the subjects analyzed, with several lesions removed, ranging from 2 to 11, confirming the relevance of this phenomenon.

Abstract

Background: The onset of multiple BCCs is a relatively common condition, not only among patients undergoing chronic treatment with immunosuppressant drugs, but also in the general population, although specific risk factors for immunocompetent patients have not been identified. A putative role of somatic mutations in the hedgehog pathway should be considered. Methods: This study is a retrospective observation of all patients diagnosed and surgically treated for BCCs during 5 years at our Dermatological Division. For these patients, we evaluated clinical and histopathological characteristics and data about possible risk factors for BCC. Results: Five-hundred and six patients affected by multiple BCCs, accounting for the 24.2% of the entire sample, have been identified. In these patients, the total number of BCCs was 1516, ranging from 2 to 11. Subjects affected by multiple BCCs were more frequently males, with an older age at diagnosis; multiple BCCs developed mainly on the trunk and were often represented by a nodular histotype. The multivariate analysis highlighted that male gender, older age, nodular BCC, or face involvement at the first diagnosis are risk factors for the development of multiple BCCs. Conclusions: The frequency of multiple BCCs even among the non-immunocompromised population underlines the need to subject patients to a close surveillance program, to allow early diagnosis and treatment of additional cancers.

Basal cell carcinomas acquire secondary mutations to overcome dormancy and progress from microscopic to macroscopic disease

Basal cell carcinomas (BCCs) frequently possess immense mutational burdens; however, the functional significance of most of these mutations remains unclear. Here, we report that loss of Ptch1, the most common mutation that activates upstream Hedgehog (Hh) signaling, initiates the formation of nascent BCC-like tumors that eventually enter into a dormant state. However, rare tumors that overcome dormancy acquire the ability to hyperactivate downstream Hh signaling through a variety of mechanisms, including amplification of Gli1/2 and upregulation of Mycn. Furthermore, we demonstrate that MYCN overexpression promotes the progression of tumors induced by loss of Ptch1. These findings suggest that canonical mutations that activate upstream Hh signaling are necessary, but not sufficient, for BCC to fully progress. Rather, tumors likely acquire secondary mutations that further hyperactivate downstream Hh signaling in order to escape dormancy and enter a trajectory of uncontrolled expansion.

Trieu et al. generate BCC mouse models in which rare macroscopic tumors form alongside numerous failed microscopic lesions. Successful macroscopic tumors acquire secondary changes that elevate Gli1, Gli2, and/or Mycn levels, causing hyperactivation of downstream Hedgehog (Hh) signaling. Loss of p53 and Notch1 also contributes to tumor progression.

Clinical activity of PD-1 inhibition in the treatment of locally advanced or metastatic basal cell carcinoma

Background

Basal cell carcinoma (BCC) is the most common malignancy worldwide, yet the management of patients with advanced or metastatic disease is challenging, with limited treatment options. Recently, programmed death receptor 1 (PD-1) inhibition has demonstrated activity in BCC after prior Hedgehog inhibitor treatment.

Methods

We conducted a multicenter, retrospective analysis of BCC patients treated with PD-1 inhibitor therapy. We examined the efficacy and safety of PD-1 therapy, as well as clinical and pathological variables in association with outcomes. Progression-free survival (PFS), overall survival (OS) and duration of response (DOR) were calculated using Kaplan-Meier methodology. Toxicity was graded per Common Terminology Criteria for Adverse Events V.5.0.

Results

A total of 29 patients with BCC who were treated with PD-1 inhibition were included for analysis, including 20 (69.0%) with locally advanced and 9 (31.0%) with metastatic disease. The objective response rate was 31.0%, with five partial responses (17.2%), and four complete responses (13.8%). Nine patients had stable disease (31.0%), with a disease control rate of 62.1%. The median DOR was not reached. Median PFS was 12.2 months (95% CI 0.0 to 27.4). Median OS was 32.4 months (95% CI 18.1 to 46.7). Two patients (6.9%) developed grade 3 or higher toxicity, while four patients (13.8%) discontinued PD-1 inhibition because of toxicity. Higher platelets (p=0.022) and any grade toxicity (p=0.024) were significantly associated with disease control rate.

Conclusions

The clinical efficacy of PD-1 inhibition among patients with advanced or metastatic BCC in this real-world cohort were comparable to published trial data. Further investigation of PD-1 inhibition is needed to define its optimal role for patients with this disease.

The Immunogenetics of Non-melanoma Skin Cancer

Non-melanoma skin cancer (NMSC) is the most common malignancy seen in Caucasians and includes basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). The incidence of NMSC is showing an increasing trend which is attributed to the increased use of sunbeds, recreational sun exposure, aging population, and partly to improved screening and reporting. Ultraviolet (UV) radiation plays the most crucial role in the pathogenesis of both BCC and SCC by inducing DNA damage and mutagenic photoproducts. Other risk factors are fair skin, old age, genetic predisposition, immunosuppression, ionizing radiation, organic chemicals, and HPV infection. The role of genomic instability, genetic mutations/aberrations, and host immunity has been fairly illustrated in several studies. This chapter aims to discuss these aspects of NMSC in detail.

Modern understanding of the pathogenesis of basal cell skin cancer

The incidence of basal cell skin cancer is increasing worldwide. The initiation and progression of basal cell skin cancer is due to the interaction of environmental factors and the patient's genetic characteristics. Aberrant activation of the transmission of the Hedgehog signaling pathway is the main pathogenetic pathway of carcinogenesis. Since basal cell skin cancer is manifested by significant variability of morphological structure, aggressiveness and response to treatment, the disclosure of the molecular genetics of pathogenesis will become the basis for developing new approaches and increasing the effectiveness of treatment, as well as overcoming tumor resistance to treatment. To search for the necessary literature, the PubMed, MedLine, Web of Science and RSCI databases were used.

Profile of Basal Cell Carcinoma Mutations and Copy Number Alterations - Focus on Gene-Associated Noncoding Variants

Basal cell carcinoma (BCC) of the skin is the most common cancer in humans, characterized by the highest mutation rate among cancers, and is mostly driven by mutations in genes involved in the hedgehog pathway. To date, almost all BCC genetic studies have focused exclusively on protein-coding sequences; therefore, the impact of noncoding variants on the BCC genome is unrecognized. In this study, with the use of whole-exome sequencing of 27 tumor/normal pairs of BCC samples, we performed an analysis of somatic mutations in both protein-coding sequences and gene-associated noncoding regions, including 5'UTRs, 3'UTRs, and exon-adjacent intron sequences. Separately, in each region, we performed hotspot identification, mutation enrichment analysis, and cancer driver identification with OncodriveFML. Additionally, we performed a whole-genome copy number alteration analysis with GISTIC2. Of the >80,000 identified mutations, ~50% were localized in noncoding regions. The results of the analysis generally corroborated the previous findings regarding genes mutated in coding sequences, including PTCH1, TP53, and MYCN, but more importantly showed that mutations were also clustered in specific noncoding regions, including hotspots. Some of the genes specifically mutated in noncoding regions were identified as highly potent cancer drivers, of which BAD had a mutation hotspot in the 3'UTR, DHODH had a mutation hotspot in the Kozak sequence in the 5'UTR, and CHCHD2 frequently showed mutations in the 5'UTR. All of these genes are functionally implicated in cancer-related processes (e.g., apoptosis, mitochondrial metabolism, and de novo pyrimidine synthesis) or the pathogenesis of UV radiation-induced cancers. We also found that the identified BAD and CHCHD2 mutations frequently occur in melanoma but not in other cancers via The Cancer Genome Atlas analysis. Finally, we identified a frequent deletion of chr9q, encompassing PTCH1, and unreported frequent copy number gain of chr9p, encompassing the genes encoding the immune checkpoint ligands PD-L1 and PD-L2. In conclusion, this study is the first systematic analysis of coding and noncoding mutations in BCC and provides a strong basis for further analyses of the variants in BCC and cancer in general.

Basosquamous Carcinoma: A Commentary

Simple Summary

Basosquamous carcinoma is a rare, aggressive non-melanoma skin cancer with features that lie between those of basal cell carcinoma and squamous cell carcinoma. A lot of controversy has been raised around the classification, pathogenesis, histologic morphology, biologic behavior, prognosis and management of this tumor. This is a narrative review based on articles published on PubMed in English language which had in their title the terms “basosquamous carcinoma” and/or “metatypical carcinoma of the skin”. The aim of this review was to summarize and evaluate the latest data of the English literature regarding epidemiology, clinical presentation, dermoscopic and histopathologic characteristics, as well as the genetics and management of BSC to better characterize basosquamous skin lesions.

Abstract

Basosquamous carcinoma is a rare, aggressive non-melanoma skin cancer with features that lie between those of basal cell carcinoma and squamous cell carcinoma. A lot of controversy has been raised around the classification, pathogenesis, histologic morphology, biologic behavior, prognosis and management of this tumor. This is a narrative review based on an electronic search of articles published in PubMed in English language which had in their title the terms “basosquamous carcinoma” and/or “metatypical carcinoma of the skin”. The aim of this review was to summarize and evaluate current data regarding epidemiology, clinical presentation, dermoscopic and histopathologic characteristics, as well as the genetics and management of BSC, in order to shed some more light onto this intriguing entity. As a conclusion, dermoscopy, deep incisional biopsies and immunohistologic techniques (Ber-EP4) should be applied in clinically suspicious lesions in order to achieve an early diagnosis and better prognosis of this tumor. Surgical treatments, including wide excision and Mohs’ micrographic surgery, remain the treatment of choice. Finally, vismodegib, a Hedgehog pathway inhibitor, must be thoroughly investigated, with large controlled trials, since it may offer an alternative solution to irresectable or difficult-to-treat, locally advanced cases of basosquamous carcinoma.

Novel PTCH1 and concurrent TP53 mutations in four patients with numerous non-syndromic basal cell carcinomas: The paradigm of oncogenic synergy

There has been a significant increase in basal cell carcinoma (BCC) incidence, the most common cancer in humans and the age of presentation with the first diagnosis of BCC has decreased in past decades. In this study, we investigated the possibility of genetic markers that can lead to earlier and closer observation of patients at high risk for development of multiple BCCs. The overall goal is to decrease the morbidity and the economic burden of diagnosis and treatment of recurring and/or advanced BCCs. Four patients with numerous BCCs, some of them exceptionally large, were included in this study. A sample of representative BCCs, normal non-sun-exposed skin and blood samples were obtained from each patient. Whole-exome sequencing of DNA was conducted on all samples, and a series of bioinformatics filtering was performed to identify potentially pathogenic sequence variants. The analysis of the data resulted in detection of oncogenic mutations in PTCH1, two of which being novel, and concurrent mutations in TP53 in BCC tumours of all four patients. Such mutations may explain the numerous and postexcision recurring nature of the BCCs of exceptionally large size observed in all these patients, and they can be suggested to serve as a genetic marker for high-risk patients for early detection, prognostication and close follow-up.

Hedgehog Pathway Inhibitors against Tumor Microenvironment

Targeting the hedgehog (HH) pathway to treat aggressive cancers of the brain, breast, pancreas, and prostate has been ongoing for decades. Gli gene amplifications have been long discovered within malignant glioma patients, and since then, inhibitors against HH pathway-associated molecules have successfully reached the clinical stage where several of them have been approved by the FDA. Albeit this success rate implies suitable progress, clinically used HH pathway inhibitors fail to treat patients with metastatic or recurrent disease. This is mainly due to heterogeneous tumor cells that have acquired resistance to the inhibitors along with the obstacle of effectively targeting the tumor microenvironment (TME). Severe side effects such as hyponatremia, diarrhea, fatigue, amenorrhea, nausea, hair loss, abnormal taste, and weight loss have also been reported. Furthermore, HH signaling is known to be involved in the regulation of immune cell maturation, angiogenesis, inflammation, and polarization of macrophages and myeloid-derived suppressor cells. It is critical to determine key mechanisms that can be targeted at different levels of tumor development and progression to address various clinical issues. Hence current research focus encompasses understanding how HH controls TME to develop TME altering and combinatorial targeting strategies. In this review, we aim to discuss the pros and cons of targeting HH signaling molecules, understand the mechanism involved in treatment resistance, reveal the role of the HH pathway in anti-tumor immune response, and explore the development of potential combination treatment of immune checkpoint inhibitors with HH pathway inhibitors to target HH-driven cancers.

Subtype-Specific Analyses Reveal Infiltrative Basal Cell Carcinomas Are Highly Interactive with their Environment

Little is known regarding the molecular differences between basal cell carcinoma (BCC) subtypes, despite clearly distinct phenotypes and clinical outcomes. In particular, infiltrative BCCs have poorer clinical outcomes in terms of response to therapy and propensity for dissemination. In this project, we aimed to use exome sequencing and RNA sequencing to identify somatic mutations and molecular pathways leading to infiltrative BCCs. Using whole-exome sequencing of 36 BCC samples (eight infiltrative) combined with previously reported exome data (58 samples), we determine that infiltrative BCCs do not contain a distinct somatic variant profile and carry classical UV-induced mutational signatures. RNA sequencing on both datasets revealed key differentially expressed genes, such as POSTN and WISP1, suggesting increased integrin and Wnt signaling. Immunostaining for periostin and WISP1 clearly distinguished infiltrative BCCs, and nuclear β-catenin staining patterns further validated the resulting increase in Wnt signaling in infiltrative BCCs. Of significant interest, in BCCs with mixed morphology, infiltrative areas expressed WISP1, whereas nodular areas did not, supporting a continuum between subtypes. In conclusion, infiltrative BCCs do not differ in their genomic alteration in terms of initiating mutations. They display a specific type of interaction with the extracellular matrix environment regulating Wnt signaling.

Immune checkpoint inhibitors for advanced or metastatic basal cell carcinoma: how much evidence do we need?

Basal cell carcinoma (BCC) is one of the most frequent and most curable tumors at its early stages. BCC rarely metastasizes and its treatment in this setting is still challenging. Hedgehog inhibitors showed an activity in advanced or metastatic disease. However, there is an unmet need for new agents. Immune checkpoint inhibitors have been assessed in melanoma and other cutaneous tumors, and very recently an anti-PD1 was approved for advanced BCC. In this paper, available data are reviewed on experimental and preclinical studies evaluating immunotherapy in BCC, as well as on the clinical evidence supporting the efficacy and safety of immune checkpoint inhibitors for advanced or metastatic BCC based on case reports, case series and clinical trials.

Known and new facts on basal cell carcinoma

Basal cell carcinoma (BCC) is the most common malignant tumor in light‐skinned people and amounts to about 75 % of all cases of skin cancer. Increasing incidence rates have been reported for decades all over the world. The main risk factors include UV radiation, male sex, light skin type, advanced age, long‐term immunosuppression, a positive individual or family history, and certain genodermatoses. BCC metastasizes only rarely, and its mortality is low, but it is associated with significant morbidity. Genetic mutations especially in the hedgehog pathway play an important role in BCC pathogenesis. Non‐invasive procedures such as optical coherence tomography or confocal laser scan microscopy are increasingly utilized for diagnostics in addition to visual inspection and dermatoscopy, but only in exceptional cases can histological confirmation of the diagnosis be dispensed with. Various clinical and histological subtypes have been defined. Differentiating between BCC with high and low risk of recurrence has a significant influence on the choice of treatment. Most BCC can be treated effectively and safely with standard surgery, or in selected cases with topical treatment. Locally advanced and metastasized BCC must be treated with radiation or systemic therapy. Radiation is also an option for older patients with contraindications for surgery. The hedgehog inhibitors vismodegib and sonidegib are currently approved for systemic therapy of BCC in Europe. Approval for the PD1 inhibitor cemiplimab as second‐line therapy is expected in the near future.

Application of epigenetics in dermatological research and skin management

BACKGROUND

Epigenetics has recently evolved from a collection of diverse phenomena to a defined and far-reaching field of study. Epigenetic modifications of the genome, such as DNA methylation and histone modifications, have been reported to play a role in some skin diseases or cancer.

AIMS

The purpose of this article was to review the development of epigenetic in recent decades and their applications in dermatological research.

METHODS

An extensive literature search was conducted on epigenetic modifications since the first research on epigenetic.

RESULTS

This article summarizes the concept and development of epigenetics, as well as the process and principle of epigenetic modifications such as DNA methylation, histone modification, and non-coding RNA. Their application in some skin diseases and cosmetic research and development is also summarized.

CONCLUSIONS

This information will help to understand the mechanisms of epigenetics and some non-coding RNA, the discovery of the related drugs, and provide new insights for skin health management and cosmetic research and development.

Review of the Molecular Genetics of Basal Cell Carcinoma; Inherited Susceptibility, Somatic Mutations, and Targeted Therapeutics

Simple Summary

Basal cell carcinoma is the most common human cancer worldwide. The molecular basis of BCC involves an interplay of inherited genetic susceptibility and somatic mutations, commonly induced by exposure to UV radiation. In this review, we outline the currently known germline and somatic mutations implicated in the pathogenesis of BCC with particular attention paid toward affected molecular pathways. We also discuss polymorphisms and associated phenotypic traits in addition to active areas of BCC research. We finally provide a brief overview of existing non-surgical treatments and emerging targeted therapeutics for BCC such as Hedgehog pathway inhibitors, immune modulators, and histone deacetylase inhibitors.

Abstract

Basal cell carcinoma (BCC) is a significant public health concern, with more than 3 million cases occurring each year in the United States, and with an increasing incidence. The molecular basis of BCC is complex, involving an interplay of inherited genetic susceptibility, including single nucleotide polymorphisms and genetic syndromes, and sporadic somatic mutations, often induced by carcinogenic exposure to UV radiation. This review outlines the currently known germline and somatic mutations implicated in the pathogenesis of BCC, including the key molecular pathways affected by these mutations, which drive oncogenesis. With advances in next generation sequencing and our understanding of the molecular genetics of BCC, established and emerging targeted therapeutics are offering new avenues for the non-surgical treatment of BCC. These agents, including Hedgehog pathway inhibitors, immune modulators, and histone deacetylase inhibitors, will also be discussed.

Molecular profiling of basal cell carcinomas in young patients

BACKGROUND

Basal cell carcinoma (BCC) represents by far the most common non-melanoma skin cancer (NMSC) in the world with an increasing incidence of 3% to 10% per year, especially in patients under the age of 40. While variants in the sonic Hedgehog and cell cycle regulation pathways account for the majority of BCC cases in adults, the molecular etiology of BCC in young patients is unelucidated yet. This study aims to investigate the molecular profile of BCC in the young population.

METHODS

28 tumors belonging to 25 Lebanese patients under the age of 40, presenting different stages of BCC and diagnosed at Hôtel Dieu de France-Saint Joseph University Medical Center were included in this study. A selected panel of 150 genes involved in cancer was analyzed by Next Generation Sequencing (NGS) in the 28 included tumors.

RESULTS

Genetic variants detected in more than 5% of the reads, with a sequencing depth ≥ 50x, were selected. Two hundred and two genetic variants in 48 different genes were detected, with an overall average sequencing depth of 1069x. Among the 28 studied tumors, 18 (64.3%) show variations in the PTCH1 gene, 6 (21.4%) in TP53 and 3 (10.7%) in SMO.

CONCLUSIONS

This is the first study reporting NGS-based analysis of BCC in a cohort of young patients. Our results highlight the involvement of the hedgehog and cell cycle regulation pathways in the genesis of BCC in the general population. The inclusion of a larger cohort of young patients is needed to confirm our findings.

Molecular alterations in basal cell carcinoma subtypes

A number of genes have been implicated in the pathogenesis of BCC in addition to the Hedgehog pathway, which is known to drive the initiation of this tumour. We performed in-depth analysis of 13 BCC-related genes (CSMD1, CSMD2, DPH3 promoter, PTCH1, SMO, GLI1, NOTCH1, NOTCH2, TP53, ITIH2, DPP10, STEAP4, TERT promoter) in 57 BCC lesions (26 superficial and 31 nodular) from 55 patients and their corresponding blood samples. PTCH1 and TP53 mutations were found in 71.9% and 45.6% of BCCs, respectively. A high mutation rate was also detected in CSMD1 (63.2%), NOTCH1 (43.8%) and DPP10 (35.1%), and frequent non-coding mutations were identified in TERT (57.9%) and DPH3 promoter (49.1%). CSMD1 mutations significantly co-occurred with TP53 changes (p = 0.002). A significant association was observed between the superficial type of BCC and PTCH1 (p = 0.018) and NOTCH1 (p = 0.020) mutations. In addition, PTCH1 mutations were significantly associated with intermittent sun exposure (p = 0.046) and the occurrence of single lesions (p = 0.021), while NOTCH1 mutations were more frequent in BCCs located on the trunk compared to the head/neck and extremities (p = 0.001). In conclusion, we provide further insights into the molecular alterations underlying the tumorigenic mechanism of superficial and nodular BCCs with a view towards novel rationale-based therapeutic strategies.

The transcriptional landscape analysis of basal cell carcinomas reveals novel signalling pathways and actionable targets

Basal cell carcinoma (BCC) is the most common skin cancer and human malignancy. By analyzing BCC RNA sequencing data according to clinically important features, we identified novel differentially regulated genes and new targetable pathways. Several biomarkers were validated in patient-derived BCC samples.

Basal cell carcinoma (BCC) is the most common skin cancer and human malignancy. Although most BCCs are easily managed, some are aggressive locally, require Mohs micrographic surgery, or can even metastasize. In the latter, resistance to Sonic Hedgehog inhibitors may occur. Despite their frequent occurrence in clinical practice, their transcriptional landscape remains poorly understood. By analyzing BCC RNA sequencing data according to clinically important features (all BCCs versus normal skin, high-risk versus low-risk BCCs based solely on histopathological subtypes with aggressive features, advanced versus non-advanced BCCs, and vismodegib-resistant versus vismodegib-sensitive tumors), we have identified novel differentially regulated genes and new targetable pathways implicated in BCC tumorigenesis. Pathways as diverse as IL-17, TLR, Akt/PI3K, cadherins, integrins, PDGF, and Wnt/β-catenin are promising therapeutic avenues for local and systemic agents in managing this common malignancy, including through drug re-purposing of existing medications. We experimentally validated several of these targets as biomarkers in our patient-derived cohort of primary BCC tumors.

Photoprotection according to skin phototype and dermatoses: practical recommendations from an expert panel

Increasing evidence on the impact of the different wavelengths of sunlight on the skin demonstrates the need for tailored recommendations of sunscreen according to skin phototype and dermatoses, which is now possible due to advances in the filters and formulations of sunscreens. A selective literature search was performed by an international expert panel, focusing on the type of sunscreen to recommend for photoaging, skin cancers, photodermatoses, pigmentary disorders and skin inflammatory disorders. Protection against ultraviolet (UV)B is especially important for light skin as there is a high risk of sunburn, DNA damage and skin cancers. Darker skin may be naturally better protected against UVB but is more prone to hyperpigmentation induced by visible light (VL) and UVA. Protection against UVA, VL and infrared A can be helpful for all skin phototypes as they penetrate deeply and cause photoaging. Long‐wave UVA1 plays a critical role in pigmentation, photoaging, skin cancer, DNA damage and photodermatoses. Adapting the formulation and texture of the sunscreen to the type of skin and dermatoses is also essential. Practical recommendations on the type of sunscreen to prescribe are provided to support the clinician in daily practice.

Cellular heterogeneity and microenvironmental control of skin cancer

Healthy tissues harbour a surprisingly high number of cells that carry well-known cancer-causing mutations without impacting their physiological function. In recent years, strong evidence accumulated that the immediate environment of mutant cells profoundly impact their prospect of malignant progression. In this review, focusing on the skin, we investigate potential key mechanisms that ensure tissue homeostasis despite the presence of mutant cells, as well as critical factors that may nudge the balance from homeostasis to tumour formation. Functional in vivo studies and single-cell transcriptome analyses have revealed a tremendous cellular heterogeneity and plasticity within epidermal (stem) cells and their respective niches, revealing for example wild-type epithelial cells, fibroblasts or immune-cell subsets as critical in preventing cancer formation and malignant progression. It's the same cells, however, that can drive carcinogenesis. Therefore, understanding the abundance and molecular variation of cell types in health and disease, and how they interact and modulate the local signalling environment will thus be key for new therapeutic avenues in our battle against cancer.

Tumor Clearance and Immune Cell Recruitment in UV-Induced Murine Squamous Cell Carcinoma Exposed to Ablative Fractional Laser and Imiquimod Treatment

BACKGROUND AND OBJECTIVES

Keratinocyte carcinoma (KC) is the most common cancer worldwide, and squamous cell carcinoma (SCC) is the second most frequent subtype. Ablative fractional laser (AFL)-assisted drug delivery significantly enhances the uptake of topically applied drugs. The objective of this study was to assess tumor response and perform a descriptive characterization of the local recruitment of immune cells and systemic immune mediator levels in an ultraviolet radiation (UVR)-induced murine SCC model after AFL treatment alone and combined with topical imiquimod.

STUDY DESIGN/MATERIALS AND METHODS

Immunocompetent hairless mice (C3·Cg/TifBomTac, n = 74) were irradiated with solar-simulated UVR until 3-mm SCCs developed. The mice were divided into four interventional groups: AFL alone, AFL + imiquimod, imiquimod alone, and untreated SCC controls. AFL was given as a single treatment, whereas imiquimod was applied daily until the mice were euthanized on Days 0, 2, 7, or 14. SCCs were photographed and measured (mm) to assess the therapeutic response. Skin samples were processed for histopathological and immunohistochemical analyses, as well as for flow cytometry. Cytokine expression changes in sera were analyzed using ELISpot cytokine arrays.

RESULTS

Treatment of mouse SCCs with AFL + imiquimod induced the most robust immune cell infiltration and the greatest proportion of tumor clearance compared to other interventions. Early innate immune cell infiltration was induced by AFL + imiquimod treatment as the number of neutrophils and macrophages had increased fourfold within 2 days of treatment initiation compared with untreated SCC control mice (P < 0.05). AFL treatment alone had a more limited effect, with a fourfold increase in neutrophils (P < 0.05) but no significant increase in the number of macrophages. Correspondingly, treatment with AFL + imiquimod had the greatest effects on the adaptive immune cell recruitment: CD4⁺ T-helper cells increased threefold at Day 7 compared with untreated SCCs (P = 0.0001) and, notably, cytotoxic CD8⁺ T cells increased 14-fold at Day 14 (P = 0.0112). In addition, FOXP3⁺ regulatory T cells (Tregs) increased 14-fold at Day 7 (P = 0.0026), suggesting the resolution of the inflammatory infiltration. AFL treatment alone induced a moderate immune cell infiltration (a twofold increase in CD4⁺ T-helper cells, P = 0.0200; a threefold increase in CD8⁺ T cells, P = 0.0100; and a 14-fold increase in FOXP3⁺ Tregs at Day 14, P = 0.0021), whereas imiquimod alone did not significantly increase cell counts. AFL + imiquimod treatment increased CXCL12 serum levels threefold at Day 14 (P = 0.0200).

CONCLUSION

AFL treatment alone and in combination with imiquimod induces substantial tumor clearance associated with local recruitment of innate and adaptive immune cells in UVR-induced murine SCCs. These results may provide a basis for new immunotherapeutic approaches to KC treatment.

Management of Advanced Basal Cell Carcinoma of the Head and Neck

Basal cell carcinoma is the most common human malignancy, with an incidence exceeding all other cancers combined. Advanced basal cell cancer requires a multidisciplinary approach to management. The mainstay of treatment remains surgical excision with appropriate reconstruction. Some advanced tumors may require radical resections; however, extensive, high-risk surgery may be justified by the indolent biology of the disease and the likelihood of cure. Other options, such as radiation or systemic targeted therapy, may be considered in selected patients who either refuse or are not candidates for surgery. The focus of this article is primarily on management of these high-risk cases.

Basal cell carcinomas of the scalp after radiotherapy for tinea capitis in childhood: A genetic and epigenetic study with comparison with basal cell carcinomas evolving in chronically sun-exposed areas

BACKGROUND

Basal cell carcinoma (BCC) has been mostly associated with sun exposure, but ionizing radiation is also a known risk factor. It is not clear if the pathogenesis of BCC, namely at a genomic and epigenetic level, differs according to the underlying triggering factors.

OBJECTIVE

The present study aims to compare genetic and epigenetic changes in BCCs related to ionizing radiation and chronic sun exposure.

METHODS

Tumor samples from BCCs of the scalp in patients submitted to radiotherapy to treat tinea capitis in childhood and BCCs from sun-exposed areas were analysed through array comparative genomic hybridization (array-CGH) and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) to detect copy number alterations and methylation status of specific genes.

RESULTS

Genomic characterization of tumor samples revealed several copy number gains and losses in all chromosomes, with the most frequent gains observed at 2p, 6p, 12p, 14q, 15q, 18q, Xp and Yp, and the most frequent losses observed at 3q, 14q, 16p, 17q, 22q, Xp, Yp and Yq. We developed a statistical model, encompassing gains in 3p and 16p and losses in 14q and 20p, with potential to discriminate BCC samples with sporadic aetiology from BCC samples that evolve after radiotherapy in childhood for the treatment of tinea capitis, which presented statistical significance (P = 0.003). Few methylated genes were detected through MS-MLPA, most frequently RARB and CD44.

CONCLUSIONS

Our study represents a step forward in the understanding of the genetic mechanisms underlying the pathogenesis of BCC and suggests potential differences according to the underlying ris k factors.

Distinct transcriptomic landscapes of cutaneous basal cell carcinomas and squamous cell carcinomas

The majority of non-melanoma skin cancer (NMSC) is cutaneous basal cell carcinoma (BCC) or squamous cell carcinoma (SCC), which are also called keratinocyte carcinomas, as both of them originate from keratinocytes. The incidence of keratinocyte carcinomas is over 5 million per year in the US, three-fold higher than the total incidence of all other types of cancer combined. While there are several reports on gene expression profiling of BCC and SCC, there are significant variations in the reported gene expression changes in different studies. One reason is that tumor-adjacent normal skin specimens were not included in many studies as matched controls. Furthermore, while numerous studies of skin stem cells in mouse models have been reported, their relevance to human skin cancer remains unknown. In this report, we analyzed gene expression profiles of paired specimens of keratinocyte carcinomas with their matched normal skin tissues as the control. Among several novel findings, we discovered a significant number of zinc finger encoding genes up-regulated in human BCC. In BCC, a novel link was found between hedgehog signaling, Wnt signaling, and the cilium. While the SCC cancer-stem-cell gene signature is shared between human and mouse SCCs, the hair follicle stem-cell signature of mice was not highly represented in human SCC. Differential gene expression (DEG) in human BCC shares gene signature with both bulge and epidermal stem cells. We have also determined that human BCCs and SCCs have distinct gene expression patterns, and some of them are not fully reflected in current mouse models.