Epigenetic and metabolic interplay in cutaneous squamous cell carcinoma

The role of immune metabolism in skin cancers: implications for pathogenesis and therapy

The skin is a complex organ that serves as a critical barrier against external pathogens and environmental impact. Recent advances in immunometabolism have highlighted the intricate link between cellular metabolism and immune function, particularly in the context of skin cancers. This review aims to provide a comprehensive overview of the key metabolic pathways and adaptations that occur in immune cells during homeostasis and activation, and explore how metabolic reprogramming contributes to the pathogenesis of specific skin cancers. We discuss the complex interplay between tumor cells and infiltrating immune cells, which shapes the tumor microenvironment and influences disease outcomes. The review delves into the role of various metabolic pathways, such as glycolysis, oxidative phosphorylation, and lipid metabolism, in the regulation of immune cell function and their impact on the development and progression of skin cancers. Furthermore, we examine the potential of targeting metabolic pathways as a therapeutic strategy in skin cancers and discuss the challenges and future perspectives in this rapidly evolving field. By understanding the metabolic basis of skin immune responses, we can develop novel, personalized therapies for the treatment of skin cancers, ultimately improving patient outcomes and quality of life. The insights gained from this review will contribute to the growing body of knowledge in immunometabolism and its application in the management of skin cancers, paving the way for more effective and targeted interventions in the future.

Methylation status, mRNA and protein expression of the SMAD4 gene in patients with non-melanocytic skin cancers

BACKGROUND

SMAD4 is a potent tumor suppressor. SMAD4 loss increases genomic instability and plays a critical role in the DNA damage response that leads to skin cancer development. We aimed to investigate SMAD4 methylation effects on mRNA and protein expression of SMAD4 in cancer and healthy tissues from patients with basal cell carcinoma (BCC), cutaneous squamous cell carcinoma (cSCC), and basosquamous skin cancer (BSC).

METHODS AND RESULTS

The study included 17 BCC, 24 cSCC and nine BSC patients. DNA and RNA were isolated from cancerous and healthy tissues following punch biopsy. Methylation-specific polymerase chain reaction (PCR) and real-time quantitative PCR methods were used to examine SMAD4 promoter methylation and SMAD4 mRNA levels, respectively. The percentage and intensity of staining of the SMAD4 protein were determined by immunohistochemistry. The percentage of SMAD4 methylation was increased in the patients with BCC (p = 0.007), cSCC (p = 0.004), and BSC (p = 0.018) compared to the healthy tissue. SMAD4 mRNA expression was decreased in the patients with BCC (p˂0.001), cSCC (p˂0.001), and BSC (p = 0.008). The staining characteristic of SMAD4 protein was negative in the cancer tissues of the patients with cSCC (p = 0.00). Lower SMAD4 mRNA levels were observed in the poorly differentiated cSCC patients (p = 0.001). The staining characteristics of the SMAD4 protein were related to age and chronic sun exposure.

CONCLUSIONS

Hypermethylation of SMAD4 and reduced SMAD4 mRNA expression were found to play a role in the pathogenesis of BCC, cSCC, and BSC. A decrease in SMAD4 protein expression level was observed only in cSCC patients. This suggests that epigenetic alterations to the SMAD4 gene are associated with cSCC.

TRIAL REGISTRATION

The name of the trial register: SMAD4 Methylation and Expression Levels in Non-melanocytic Skin Cancers; SMAD4 Protein Positivity. The registration number: NCT04759261 ( https://clinicaltrials.gov/ct2/results?term=NCT04759261 ).

Advances in cutaneous squamous cell carcinoma

Human malignancies arise predominantly in tissues of epithelial origin, where the stepwise transformation from healthy epithelium to premalignant dysplasia to invasive neoplasia involves sequential dysregulation of biological networks that govern essential functions of epithelial homeostasis. Cutaneous squamous cell carcinoma (cSCC) is a prototype epithelial malignancy, often with a high tumour mutational burden. A plethora of risk genes, dominated by UV-induced sun damage, drive disease progression in conjunction with stromal interactions and local immunomodulation, enabling continuous tumour growth. Recent studies have identified subpopulations of SCC cells that specifically interact with the tumour microenvironment. These advances, along with increased knowledge of the impact of germline genetics and somatic mutations on cSCC development, have led to a greater appreciation of the complexity of skin cancer pathogenesis and have enabled progress in neoadjuvant immunotherapy, which has improved pathological complete response rates. Although measures for the prevention and therapeutic management of cSCC are associated with clinical benefit, the prognosis remains poor for advanced disease. Elucidating how the genetic mechanisms that drive cSCC interact with the tumour microenvironment is a current focus in efforts to understand, prevent and treat cSCC.

Update on the Molecular Pathology of Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer, originating from keratinocytes of the spinous layer. Numerous risk factors have been discovered for the initiation and growth of this type of cancer, such as exposure to UV and ionizing radiation, chemical carcinogens, the presence of immunosuppression states, chronic inflammation, infections with high-risk viral strains, and, last but not least, the presence of diseases associated with genetic alterations. The important socio-economic impact, as well as the difficulty associated with therapy for advanced forms, has made the molecular mechanisms underlying this neoplasia more and more intensively studied, with the intention of achieving a better understanding and advancing the treatment of this pathology. This review aims to provide a brief foray into the molecular, genetic, and epigenetic aspects of this cancer, as well as the treatment methods, ranging from the first used to the latest targeted therapies.

The mitochondrial RNA polymerase POLRMT promotes skin squamous cell carcinoma cell growth

RNA polymerase mitochondrial (POLRMT) expression and the potential biological functions in skin squamous cell carcinoma (SCC) were explored. We showed that POLRMT is significantly elevated in skin SCC. Genetic depletion of POLRMT, using shRNA-induced knockdown or CRISPR/Cas9-mediated knockout (KO), resulted in profound anti-skin SCC cell activity. In patient-derived primary skin SCC cells or immortalized lines (A431 and SCC-9), POLRMT shRNA or KO potently suppressed mitochondrial DNA (mtDNA) transcription and suppressed cell viability, proliferation and migration. POLRMT shRNA or KO impaired mitochondrial functions in different skin SCC cells, leading to production of ROS (reactive oxygen species), depolarization of mitochondria and depletion of ATP. Moreover, mitochondrial apoptosis cascade was induced in POLRMT-depleted skin SCC cells. IMT1, a POLRMT inhibitor, largely inhibited proliferation and migration, while inducing depolarization of mitochondria and apoptosis in primary skin SCC cells. Contrarily, ectopic overexpression of POLRMT increased mtDNA transcription and augmented skin SCC cell growth. Importantly, POLRMT shRNA adeno-associated virus injection robustly hindered growth of the subcutaneous A431 xenografts in mice. In the POLRMT shRNA virus-treated A431 xenograft tissues, POLRMT depletion, mtDNA transcription inhibition, cell apoptosis, lipid peroxidation and ATP depletion were detected. Together, overexpressed POLRMT increases mtDNA transcription and promotes skin SCC growth.