Metformin shows anti-neoplastic properties by inhibition of oxidative phosphorylation and glycolysis in epidermolysis bullosa-associated aggressive cutaneous squamous cell carcinoma.

BACKGROUND: While most cutaneous squamous cell carcinomas (cSCCs) are treatable, certain high-risk cSCCs, such as those in recessive dystrophic epidermolysis bullosa (RDEB) patients, are particularly aggressive. Owing to repeated wounding, inflammation and unproductive healing, RDEB patients have a 68% cumulative risk of developing life-threatening cSCCs by the age of 35, and a 70% risk of death by the age of 45. Despite aggressive treatment, cSCC represents the leading cause of premature mortality in these patients, highlighting an unmet clinical need. Increasing evidence points to a role of altered metabolism in the initiation and maintenance of cSCC, making metabolism a potential therapeutic target. OBJECTIVES: We sought to determine the feasibility of targeting tumour cell energetics as a strategy to selectively hinder the growth advantage of aggressive cSCC. METHODS: We evaluated the cell energetics profiles of RDEB-SCC cells by analysing available gene expression data against multiple gene signatures and single-gene targets linked to metabolic reprogramming. Additionally, we employed real-time metabolic profiling to measure glycolysis and respiration in these cells. Furthermore, we investigated the anti-neoplastic properties of the metformin against human and murine high-risk cSCCs in vitro and in vivo. RESULTS: Gene expression analyses highlighted a divergence in cell energetics profiles between RDEB-SCC and non-malignant RDEB keratinocytes, with tumour cells demonstrating enhanced respiration and glycolysis scores. Real-time metabolic profiling supported these data and additionally highlighted a metabolic plasticity of RDEB-SCC cells. Against this background, metformin exerted an anti-neoplastic potential by hampering both respiration and glycolysis, and by inhibiting proliferation in vitro. Metformin treatment in an analogous model of fast-growing murine cSCC resulted in delayed tumour onset and slower tumour growth, translating to a 29% increase in median overall survival. CONCLUSIONS: Our data indicate that metformin exerts anti-neoplastic properties in aggressive cSCCs that exhibit high-risk features by interfering with respiration and glycolytic processes.

Construction and validation of an RNA trans-splicing molecule suitable to repair a large number of COL7A1 mutations.

RNA trans-splicing has become a versatile tool in the gene therapy of monogenetic diseases. This technique is especially valuable for the correction of mutations in large genes such as COL7A1, which underlie the dystrophic subtype of the skin blistering disease epidermolysis bullosa. Over 800 mutations spanning the entire length of the COL7A1 gene have been associated with defects in type VII collagen, leading to excessive fragility of epithelial tissues, the hallmark of dystrophic epidermolysis bullosa (DEB). In the present study, we designed an RNA trans-splicing molecule (RTM) that is capable of repairing any given mutation within a 4200 nucleotide region spanning the 3' half of COL7A1. The selected RTM, RTM28, was able to induce accurate trans-splicing into endogenous COL7A1 pre-mRNA transcripts in a type VII collagen-deficient DEB patient-derived cell line. Correct trans-splicing was detected at the RNA level by semiquantitative RT-PCR and correction of full-length type VII collagen was confirmed at the protein level by immunofluorescence and western blot analyses. Our results demonstrate that RTM28, which covers >60% of all mutations reported in DEB and is thus the longest RTM described so far for the repair of COL7A1, represents a promising candidate for therapeutic applications.