Real-time PCR analysis of a 3895 bp mitochondrial DNA deletion in nonmelanoma skin cancer and its use as a quantitative marker for sunlight exposure in human skin

Abstract

Previous findings from our own laboratory have shown that the frequency of occurrence (i.e. the simple presence or absence) of the 3895 bp mitochondrial DNA deletion is increased with increasing sun exposure. The present study has significantly extended this work by developing, validating and then using a quantitative real-time PCR assay to investigate for the first time the actual level (as opposed to the frequency of occurrence) of the 3895 bp deletion in human skin from different sun-exposed body sites and tumours from nonmelanoma skin cancer patients. We investigated the 3895 bp deletion in 104 age-matched split human skin samples taken from various sun-exposed sites defined as usually exposed (n ¼ 60) and occasionally exposed (n ¼ 44) when outdoors. The results clearly show an increased level of the 3895 bp deletion with increasing sun exposure. Specifically, there was a significantly higher level of the deletion in the usually sun-exposed compared to the occasionally sun-exposed skin (P ¼ 0.0009 for dermis, P ¼ 0.008 for epidermis; two-tailed t-test). Our study has also extended previous findings by showing that the level of the 3895 bp deletion is significantly higher in the dermis compared with the epidermis both in the occasionally sun-exposed samples (P ¼ 0.0143) and in the usually sun-exposed skin. (P ¼ 0.0007).

Pathobiology of actinic keratosis: Ultraviolet-dependent keratinocyte proliferation

“…52 A separate study demonstrated that the actual levels of a specific 3895ebase pair mitochondrial DNA deletion were significantly higher in dermis samples from skin that was usually exposed to the sun compared with samples from skin that was only occasionally exposed (P \.0009). 25 This damage to the mitochondrial genome may impair the capacity for mitochondrial oxidative phosphorylation, which may increase ROS. 25…”

Human Mitochondrial DNA Polymerase γ Exhibits Potential for Bypass and Mutagenesis at UV-induced Cyclobutane Thymine Dimers

“…Photoaging of the skin has been closely tied to mtDNA mutations and deletions (36,53,54), and there is recent evidence associating mtDNA damage with several types of skin cancer (55)(56)(57)(58)(59). A handful of studies that have tested mtDNA from melanoma and non-melanoma skin cancer patients have revealed a number of A 3 G and T 3 C point mutations (56,57,59), often in the context of pyrimidine:pyrimidine dimers.…”

XPC silencing in normal human keratinocytes triggers metabolic alterations that drive the formation of squamous cell carcinomas

“…To this end, we initially looked for 2 characteristic mtDNA deletions: (a) the 3895-bp deletion, which is known to occur more frequently in sun-exposed skin and is present in nonmelanoma skin cancer (24), and (b) the 4977-bp deletion, which is known to be involved in neurodegenerative diseases and the processes of aging and photoaging (22,23). As shown in Figure 2C, XPC KD cells accumulated both types of mtDNA deletions in a time-dependent manner.…”