Single Base Instability Is Promoted in Vulvar Lichen Sclerosus

Abstract

Single base substitution mutations in codons 248 and 273 of TP53 and codon 12 Kirsten-ras (KRAS) are commonly found in human carcinomas. To determine whether these mutations also occur in normal and inflamed tissues from which carcinomas arise, we utilized the ultra-sensitive polymerase chain reaction/restriction endonuclease/ligase chain reaction mutation assay. Ninety samples of genital skin, including lichen sclerosus (LS) affected skin, adjacent normal and non-adjacent normal, were assayed. Mutations were detected in 103 of 349 assays and consisted of KRAS G34A, G34T, G35A, and TP53 C742T, G818C, C817T, and G818A mutations. Mutant prevalence varied from 1 to 20 per 10(6) wild-type cells. Mutations occurred significantly more frequently in LS (78/224 (35%)) than adjacent normal (20/88 (23%)) and non-adjacent normal genital skin (5/38 (13%)). KRAS G34A mutation was relatively common to all classes of specimen, whereas TP53 gene C742T and G818C mutations were significantly more frequent in LS than normal genital skin. In matched samples, immunohistochemistry evaluation of p53 protein expression revealed the presence of epidermal p53 clones in LS whose presence and number significantly correlated with the presence of TP53 C742T and G818C mutations. Based on these results, it appears oncogenic point mutations occur in normal genital skin, and are selected for in LS.

Human germline and somatic cells have similar TP53 and Kirsten‐RAS gene single base mutation frequencies

“…Restriction endonucleases used for mutation selection in TP53 were Msp I for codon 248, Bsa AI for codon 273; Hph I was used for KRAS codon 12. We have previously reported the PCR primer sequences for these codons [Tapp, et al, 2007].…”

“…The multiplex polymerase chain reaction/restriction endonuclease (PCR/ RE) selection procedures utilized in this work have been previously published [Wilson et al, 2000;Tapp et al, 2007]. Briefly, 6 lg aliquots of spermatozoa DNAs were subjected to three rounds of multiplex PCR amplification and restriction endonuclease digestion specific for codons 248 and 273 of the TP53 gene, and codon 12 of the KRAS gene.…”

“…Understanding the risk of disease associated with mutation in humans requires clarification of the occurrence and frequencies of mutations, and knowledge of the mutation spectra in somatic tissues and gametes. Over the last few decades, a significant amount of information associated with somatic diseases has been published on this subject [Hanahan and Weinberg, 2000;Wilson, 2001;Backvall et al, 2005;Tapp et al, 2007]. Unfortunately, information regarding mutation spectra and frequencies in the germline has not received the same degree of attention.…”

“…However, these studies have, for the most part, been driven by clinical infertility and the search for gross chromosomal abnormalities that may be transmitted through gametes [Rudak et al, 1978;Shelby et al, 1993;Rubes et al, 2002;Schmid et al, 2004]. With the mounting evidence of the impact of single base substitution (SBS) in somatic cells [Wilson, 2001;Tapp et al, 2007] and the potential of SBSs to cause heritable disease in progeny [Cooper and Krawczak, 1990;Crow, 2000Crow, , 2006Goriely et al, 2003], it is important to obtain more information regarding the frequency of single base mutations present in human sperm.…”

Altered global methylation and hydroxymethylation status in vulvar lichen sclerosus: further support for epigenetic mechanisms

“…11,12 However, in our study cohort we could not detect mutations in the KRAS, NRAS or TP53 genes. Similarly to our previously reported data on short-standing VLS, 18 we did not found altered p53 or is likely due to the small sample size investigated.…”