Genomic progression of precancerous actinic keratosis to squamous cell carcinoma

Skin Cancer Precursors: From Cancer Genomics to Early Diagnosis

Skin cancers, including melanoma and keratinocyte carcinomas, are responsible for increasing health care burden internationally. Risk stratification and early detection are paramount for prevention and less risky treatment to overall improve patient outcomes and disease morbidity. Here, the authors discuss the key concepts leading to skin cancer initiation and progression. The authors also outline precursor and progression models for melanoma and keratinocyte carcinomas, including discussion of genetic alterations associated with the various stages of progression. Finally, the authors discuss the significance of immunoediting and the drivers behind increased risk of cutaneous malignancy in the state of immune dysregulation.

Genetic evolution of keratinocytes to cutaneous squamous cell carcinoma

We performed multi-omic profiling of epidermal keratinocytes, precancerous actinic keratoses, and squamous cell carcinomas to understand the molecular transitions during skin carcinogenesis. Single-cell mutational analyses showed that most keratinocytes in normal skin had lower mutation burdens than melanocytes and fibroblasts, however keratinocytes with TP53 or NOTCH1 mutations had substantially higher mutation burdens, suggesting that these mutations prime keratinocytes for transformation by increasing their mutation rate. Mutational profiling and spatial transcriptomics on squamous cell carcinomas adjacent to actinic keratoses revealed TERT promoter and CDKN2A mutations emerging in actinic keratoses, whereas additional mutations inactivating ARID2 and activating the MAPK-pathway delineated the transition to squamous cell carcinomas. Spatial variation in gene expression patterns was common in both tumor and immune cells, with high expression of checkpoint molecules at the invasive front of tumors. In conclusion, this study documents key events during the evolution of cutaneous squamous cell carcinoma.

Invasion risk of cutaneous squamous cell carcinoma in situ by histological subtype: a retrospective cohort study

AIMS

Cutaneous squamous cell carcinoma in situ (SCCis) can be classified histopathologically into four subtypes: full-thickness (FT), hypertrophic actinic keratosis (HAK), Bowenoid, and acantholytic types. 3%-5% of SCCis lesions progress to invasive squamous cell carcinoma (iSCC), however progression risk by subtype has not been assessed. Aim one of this study is to quantitatively assess the risk of iSCC associated with each histological subtype of SCCis. Aim two is to evaluate if the histological grade of iSCC differs among subtypes of the associated SCCis.

METHODS

The pathology information system at our institution was queried for cutaneous SCCis cases with and without associated iSCC from 2020 to 2022. The study group consisted of 65 cases of SCCis with associated iSCC and control group 65 randomly selected cases of SCCis without invasion. For each case SCCis subtype was classified as FT, HAK, Bowenoid or acantholytic type. iSCCs were classified as low grade if well to moderately differentiated (LG) and high grade (HG) if moderately to poorly differentiated.

RESULTS

iSCC was most often associated with HAK-type SCCis, followed by acantholytic and FT-type SCCis, with Bowenoid type rarely associated with iSCC. 41% (14/34) of iSCCs associated with HAK-type SCCis were HG compared with 84% (21/25) for FT-type SCCis.

CONCLUSIONS

iSCC is most often associated with HAK-type SCCis, followed by acantholytic and FT-types, and rarely with Bowenoid type. HG invasive SCC is most often associated with FT-type, and LG with HAK-type SCCis. Stratifying SCCis by subtype can inform clinical management.

Advancements in elucidating the pathogenesis of actinic keratosis: present state and future prospects

Solar keratosis, also known as actinic keratosis (AK), is becoming increasingly prevalent. It is a benign tumor that develops in the epidermis. Individuals with AK typically exhibit irregular, red, scaly bumps or patches as a result of prolonged exposure to UV rays. These growths primarily appear on sun-exposed areas of the skin such as the face, scalp, and hands. Presently, dermatologists are actively studying AK due to its rising incidence rate in the United States. However, the underlying causes of AK remain poorly understood. Previous research has indicated that the onset of AK involves various mechanisms including UV ray-induced inflammation, oxidative stress, complex mutagenesis, resulting immunosuppression, inhibited apoptosis, dysregulated cell cycle, altered cell proliferation, tissue remodeling, and human papillomavirus (HPV) infection. AK can develop in three ways: spontaneous regression, persistence, or progression into invasive cutaneous squamous cell carcinoma (cSCC). Multiple risk factors and diverse signaling pathways collectively contribute to its complex pathogenesis. To mitigate the risk of cancerous changes associated with long-term UV radiation exposure, prompt identification, management, and prevention of AK are crucial. The objective of this review is to elucidate the primary mechanisms underlying AK malignancy and identify potential treatment targets for dermatologists in clinical settings.

PIK Your Poison: The Effects of Combining PI3K and CDK Inhibitors against Metastatic Cutaneous Squamous Cell Carcinoma In Vitro

Cutaneous squamous cell carcinoma (cSCC) is a very common skin malignancy with poor prognosis for patients with locally advanced or metastatic cSCC (mcSCC). PI3K/AKT/mTOR and cell cycle signalling pathways are often dysregulated in mcSCC. A combination drug approach has been theorised to overcome the underwhelming clinical performance of targeted inhibitors as single agents. This study investigates the potential of targeted inhibition of the p110α-subunit of PI3K with PIK-75 or BGT226 (P13Ki), and of CDK1/2/5/9 with dinaciclib (CDKi) as single agents and in combination. The patient-derived mcSCC cell lines, UW-CSCC1 and UW-CSCC2, were used to assess cell viability, migration, cell signalling, cell cycle distribution, and apoptosis. PIK-75, BGT226, and dinaciclib exhibited strong cytotoxic potency as single agents. Notably, the non-malignant HaCaT cell line was unaffected. In 2D cultures, PIK-75 synergistically enhanced the cytotoxic effects of dinaciclib in UW-CSCC2, but not UW-CSCC1. Interestingly, this pattern was reversed in 3D spheroid models. Despite the combination of PIK-75 and dinaciclib resulting in an increase in cell cycle arrest and apoptosis, and reduced cell motility, these differences were largely negligible compared to their single-agent counterpart. The differential responses between the cell lines correlated with driver gene mutation profiles. These findings suggest that personalised medicine approaches targeting PI3K and CDK pathways in combination may yield some benefit for mcSCC, and that more complex 3D models should be considered for drug responsiveness studies in this disease.

Genetic Studies of Actinic Keratosis Development: Where Are We Now?

Actinic keratosis (AK) is a common precancerous skin lesion that can develop into cutaneous squamous cell carcinoma (CSCC). AK is characterized by atypical keratinocytes in the skin's outer layer and is commonly found in sun-exposed areas. Like many precancerous lesions, the development of AK is closely associated with genetic mutations. The molecular biology and transcriptional mechanisms underlying AK development are not well understood. Ultraviolet (UV) light exposure, especially UVA and UVB radiation, is a significant risk factor for AK, causing DNA damage and mutagenic effects. Besides UV exposure, comorbidities like diabetes, rheumatoid arthritis, and psoriasis may also influence AK development. AK patients have shown associations with various internal malignancies, indicating potential vulnerability in cancer-associated genes. Treatment for AK includes cryosurgery, electrodesiccation and curettage, chemotherapeutic creams, photodynamic therapy, or topical immune-modulators. Genomic studies have identified genetic aberrations in AK, with common mutations found in genes like TP53, NOTCH1, and NOTCH2. The progression from AK to CSCC involves chromosomal aberrations and alterations in oncogenes and tumor-suppressor genes. The functional relationships among these genes are not fully understood, but network analysis provides insights into their potential mechanisms. Further research is needed to enhance our understanding of AK's pathogenesis and develop novel therapeutic approaches.

Where Artificial Intelligence Can Take Us in the Management and Understanding of Cancerization Fields

Squamous cell carcinoma and its precursor lesion actinic keratosis are often found together in areas of skin chronically exposed to sun, otherwise called cancerisation fields. The clinical assessment of cancerisation fields and the correct diagnosis of lesions within these fields is usually challenging for dermatologists. The recent adoption of skin cancer diagnostic imaging techniques, particularly LC-OCT, helps clinicians in guiding treatment decisions of cancerization fields in a non-invasive way. The combination of artificial intelligence and non-invasive skin imaging opens up many possibilities as AI can perform tasks impossible for humans in a reasonable amount of time. In this text we review past examples of the application of AI to dermatological images for actinic keratosis/squamous cell carcinoma diagnosis, and we discuss about the prospects of the application of AI for the characterization and management of cancerization fields.

Single-cell RNA-seq reveals actinic keratosis-specific keratinocyte subgroups and their crosstalk with secretory-papillary fibroblasts

BACKGROUND AND AIM

Actinic keratosis (AK) represents an intraepidermal malignant neoplasm with the proliferation of atypical keratinocytes. AK lesions are regarded as early in situ squamous cell carcinomas (SCCs) having the potential to progress into invasive SCC (iSCC) and metastasize, causing death. This study aimed to investigate the heterogeneity of keratinocytes and how this heterogeneity promoted AK development and progression.

METHODS

We employed single-cell RNA sequencing (scRNA-seq) to examine the heterogeneity of keratinocytes and dermal fibroblast clusters in AKs and adjacent normal skins. Cell clustering, pseudotime trajectory construction, gene ontology enrichment analysis, transcription factor network analysis, and cell-cell communication were used to investigate the heterogeneity of keratinocytes in AK. The cellular identity and function were verified by immunohistochemical and immunofluorescence staining.

RESULTS

Using scRNA-seq, we revealed 13 keratinocyte subgroups (clusters 0-12) in AK tissues and characterized 2 AK-specific clusters. Cluster 9 displayed high levels of IL1R2 and WFDC2, and cluster 11 showed high levels of FADS2 and FASN. The percentages of cells in these two clusters significantly increased in AK compared with normal tissues. The existence and spatial localization of AK-specific IL1R2+WFDC2+ cluster were verified by immunohistochemical and immunofluorescence staining. Functional studies indicated that the genes identified in the IL1R2+WFDC2+ cluster were crucial for epithelial cell proliferation, migration, and angiogenesis. Further immunofluorescent staining revealed the interactions between AK-specific keratinocytes and secretory-papillary fibroblasts mainly through ANGPTL4-ITGA5 signalling pathway rarely seen in normal tissues.

CONCLUSION

The findings of this study might help better understand AK pathogenesis.

European consensus-based interdisciplinary guideline for invasive cutaneous squamous cell carcinoma. Part 1: Diagnostics and prevention-Update 2023

Invasive cutaneous squamous cell carcinoma (cSCC) is one of the most common cancers in white populations, accounting for 20% of all cutaneous malignancies. Overall, cSCC mostly has very good prognosis after treatment, with 5-year cure rates greater than 90%. Despite the overall favourable prognosis and the proportionally rare deaths, cSCC is associated with a high total number of deaths due to its high incidence. A collaboration of multidisciplinary experts from the European Association of Dermato-Oncology (EADO), the European Dermatology Forum (EDF), the European Society for Radiotherapy and Oncology (ESTRO), the European Union of Medical Specialists (UEMS), the European Academy of Dermatology and Venereology (EADV) and the European Organization of Research and Treatment of Cancer (EORTC), was formed to update recommendations on cSCC, based on current literature and expert consensus. Part 1 of the guidelines addresses the updates on classification, epidemiology, diagnosis, risk stratification, staging and prevention in immunocompetent as well as immunosuppressed patients.

PIK3CA mutations in cutaneous squamous cell carcinoma

Oncogenic PIK3CA mutation activates phosphoinositide 3-kinase (PI3K) enzyme, and PI3K-AKT signaling activation induces several growth-regulatory transcription factors. PIK3CA mutations have attracted attention as biomarker in clinical trials of various inhibitors including PI3K inhibitors. About 80% of PIK3CA mutations in human cancers are observed in 'hot spot' regions: exon 9 (E542K and E545K) and exon 20 (H1047R). There were few reports about clinical significance of PIK3CA mutations in cutaneous cell carcinoma (cSCC). Thus, we investigate the prevalence of three PIK3CA hot spot mutations in 143 cases with cSCC and evaluate the correlation between the presence of these mutations and clinical characteristics by using ddPCR. The frequency of each E542K, E545K and H1047R PIK3CA mutations was 1.4% (2/143), 2.8% (4/143), and 0.7% (1/143) respectively. No significant correlation was found between PIK3CA mutations and clinical characteristics. Although additional basic researches and clinical trials are necessary, various inhibitors may be effective therapeutics for PIK3CA mutation-positive cSCC. Our study revealed the prevalence of PIK3CA mutations in cSCC.

Mutational Landscape of Normal Human Skin: Clues to Understanding Early-Stage Carcinogenesis in Keratinocyte Neoplasia

Normal skin contains numerous clones carrying cancer driver mutations. However, the mutational landscape of normal skin and its clonal relationship with skin cancer requires further elucidation. The aim of our study was to investigate the mutational landscape of normal human skin. We performed whole-exome sequencing using physiologically normal skin tissues and the matched peripheral blood (n = 39) and adjacent-matched skin cancers from a subset of patients (n = 10). Exposed skin harbored a median of 530 mutations (10.4/mb, range = 51-2,947), whereas nonexposed skin majorly exhibited significantly fewer mutations (median = 13, 0.25/mb, range = 1-166). Patient age was significantly correlated with the mutational burden. Mutations in six driver genes (NOTCH1, FAT1, TP53, PPM1D, KMT2D, and ASXL1) were identified. De novo mutational signature analysis identified a single signature with components of UV- and aging-related signatures. Normal skin harbored only three instances of copy-neutral loss of heterozygosity in 9q (n = 2) and 6q (n = 1). The mutational burden of normal skin was not correlated with that of matched skin cancers, and no protein-coding mutations were shared. In conclusion, we revealed the mutational landscape of normal skin, highlighting the role of driver genes in the malignant progression of normal skin.

Immunohistochemical Analysis of Single-Stranded DNA Binding Protein 2 in Non-Melanoma Skin Cancers

Single-stranded DNA binding protein 2 (SSBP2) is a tumor suppressor candidate. In this study, the expression level and clinicopathological significance of SSBP2 in squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) were evaluated. We also identified biological pathways associated with a set of genes potentially related to SSBP2. Immunohistochemistry (IHC) was performed on 70 SCC and 146 BCC cases to assess SSBP2 expression semi-quantitatively. In addition, the associations between SSBP2 expression and clinicopathological characteristics were analyzed. Gene ontology (GO) enrichment analysis was performed using publicly available data and web-based bioinformatics tools. Compared with BCC, SCC had a significantly low SSBP2 expression (p < 0.001). In total, 12 (17.1%) of the 70 SCC cases and 30 (20.5%) of the 146 BCC cases showed low SSBP2 expression. Among SCC cases, ulceration (p = 0.005) and a deep level of invasion (p = 0.012) showed an association with low SSBP2 expression. Local recurrence was slightly more common in the SCC subgroup with low SSBP2 expression, although the difference was not significant (p = 0.058). Using GO enrichment analysis, we identified several biological functions performed by a set of 36 genes in SCC. SSBP2 evaluation using IHC can be helpful in the differential diagnosis of SCC and BCC. SSBP2 expression was associated with tumor invasiveness in SCC.

Genomic landscape of multiple Bowen's disease using whole-exome sequencing

The genomic landscape of Bowen's disease (BD), with multiple manifestations, has not yet been determined. This study aimed to investigate the genomic alterations in multiple BD. We performed whole-exome sequencing of BD lesions (n = 9) and matched germlines collected from three patients with multiple (≥3) BD to detect somatic and germline mutations. We found a median of 64 somatic mutations in each sample (range 20-267). UV-signature mutations accounted for 64.9% (median, range 26.0%-82.1%) of point mutations. Putative driver mutations were found in five BDs (RB1 p.R445*, ARID2 p.R274*, TP53 p.Y163D/p.Y205D/p.R342*, KMT2C p.R4549C) but not in the other four lesions. Somatic mutations were not shared between multiple BD lesions collected from the same patient, indicating a different clonal origin. We also found no known pathogenic germline mutations in cancer-related genes. The mutational signature analysis revealed that UV signatures (SBS7a/7b) and age-related signatures (SBS1/5) were the main active signatures. Copy number alterations (CNAs) were found in two BDs: one with extensive CNA regions (21.7% of the genome), including driver genes (PIK3CA/SOX2/TP63 and MYC gain, and CDKN2A loss), and the other with 1q gain. Our study revealed that multiple BD lesions harbor distinct genomic landscapes, suggesting that they have different risks of malignant progression.

Skin Cancer Pathobiology at a Glance: A Focus on Imaging Techniques and Their Potential for Improved Diagnosis and Surveillance in Clinical Cohorts

Early diagnosis is essential for completely eradicating skin cancer and maximizing patients' clinical benefits. Emerging optical imaging modalities such as reflectance confocal microscopy (RCM), optical coherence tomography (OCT), magnetic resonance imaging (MRI), near-infrared (NIR) bioimaging, positron emission tomography (PET), and their combinations provide non-invasive imaging data that may help in the early detection of cutaneous tumors and surgical planning. Hence, they seem appropriate for observing dynamic processes such as blood flow, immune cell activation, and tumor energy metabolism, which may be relevant for disease evolution. This review discusses the latest technological and methodological advances in imaging techniques that may be applied for skin cancer detection and monitoring. In the first instance, we will describe the principle and prospective clinical applications of the most commonly used imaging techniques, highlighting the challenges and opportunities of their implementation in the clinical setting. We will also highlight how imaging techniques may complement the molecular and histological approaches in sharpening the non-invasive skin characterization, laying the ground for more personalized approaches in skin cancer patients.

Genomic comparison between an in vitro three-dimensional culture model of melanoma and the original primary tumor

Three-dimensional (3D) melanoma culture is a personalized in vitro model that can be used for high-fidelity pre-clinical testing and validation of novel therapies. However, whether the genomic landscape of 3D cultures faithfully reflects the original primary tumor which remains unknown. The purpose of our study was to compare the genomic landscapes of 3D culture models with those of the original tumors. Patient-derived xenograft (PDX) tumors were established by engrafting fresh melanoma tissue from each patient. Then, a 3D culture model was generated using cryopreserved PDX tumors embedded in pre-gelled porcine skin decellularized extracellular matrix with normal human dermal fibroblasts. Using whole-exome sequencing, the genomic landscapes of 3D cultures, PDX tumors, and the original tumor were compared. We found that 91.4% of single-nucleotide variants in the original tumor were detected in the 3D culture and PDX samples. Putative melanoma driver mutations (BRAF p.V600E, CDKN2A p.R7*, ADAMTS1 p.Q572*) were consistently identified in both the original tumor and 3D culture samples. Genome-wide copy number alteration profiles were almost identical between the original tumor and 3D culture samples, including the driver events of ARID1B loss, BRAF gain, and CCND1 gain. In conclusion, our study revealed that the genomic profiles of the original tumor and our 3D culture model showed high concordance, indicating the reliability of our 3D culture model in reflecting the original characteristics of the tumor.