Identification of a gene signature of a pre-transformation process by senescence evasion in normal human epidermal keratinocytes

Abstract

BackgroundEpidemiological data show that the incidence of carcinomas in humans is highly dependent on age. However, the initial steps of the age-related molecular oncogenic processes by which the switch towards the neoplastic state occurs remain poorly understood, mostly due to the absence of powerful models. In a previous study, we showed that normal human epidermal keratinocytes (NHEKs) spontaneously and systematically escape from senescence to give rise to pre-neoplastic emerging cells.MethodsHere, this model was used to analyze the gene expression profile associated with the early steps of age-related cell transformation. We compared the gene expression profiles of growing or senescent NHEKs to post-senescent emerging cells. Data analyses were performed by using the linear modeling features of the limma package, resulting in a two-sided t test or F-test based on moderated statistics. The p-values were adjusted for multiple testing by controlling the false discovery rate according to Benjamini Hochberg method.The common gene set resulting of differential gene expression profiles from these two comparisons revealed a post-senescence neoplastic emergence (PSNE) gene signature of 286 genes.ResultsAbout half of these genes were already reported as involved in cancer or premalignant skin diseases. However, bioinformatics analyses did not highlight inside this signature canonical cancer pathways but metabolic pathways, including in first line the metabolism of xenobiotics by cytochrome P450. In order to validate the relevance of this signature as a signature of pretransformation by senescence evasion, we invalidated two components of the metabolism of xenobiotics by cytochrome P450, AKR1C2 and AKR1C3. When performed at the beginning of the senescence plateau, this invalidation did not alter the senescent state itself but significantly decreased the frequency of PSNE. Conversely, overexpression of AKR1C2 but not AKR1C3 increased the frequency of PSNE.ConclusionsTo our knowledge, this study is the first to identify reprogrammation of metabolic pathways in normal keratinocytes as a potential determinant of the switch from senescence to pre-transformation.

Defective DNA single-strand break repair is responsible for senescence and neoplastic escape of epithelial cells

“…Filiation-tracing assays and videomicroscopies have proven that these cells do come from the division of fully senescent mother cells 24 . A transcriptomic analysis revealed that these cells display a gene signature of pre-transformation 31 . Moreover, they exhibit a partial epithelial-mesenchymal transition (EMT) with an increase in expression of TWIST and SLUG ( Fig.…”

Level of macroautophagy drives senescent keratinocytes into cell death or neoplastic evasion

“…PSNE cells were shown by a transcriptomics analysis to display transformed characteristics and were evidenced to be able to generate some small skin hyperplasias and non-melanoma carcinomas in nude mice assays. 22 , 24 …”

“…Several data from our group suggest that the oxidative DNA damages encountered by senescent NHEKs could be the mutagenic motor of this postsenescence neoplastic emergence (PSNE). 22 , 24 …”

A novel role for DNA single-strand breaks in senescence and neoplastic escape of epithelial cells

“…4 It is commonly recognized that the raison d'être for the irreversibility of senescence is to prevent proliferation of cells with unrepaired DNA damage that are at risk of neoplastic transformation. However, we and others have shown that in the case of epithelial cells a few senescent cells always spontaneously escape from the cell cycle arrest and develop clones of mutated, transformed, and tumorigenic cells, [5][6][7][8] suggesting that the senescent cell cycle arrest is not fully irreversible in this cell type. In our latest study, we compared the DNA damage occurring at senescence in a classic model of human fibroblasts undergoing replicative senescence and in keratinocytes, in which senescence is followed by neoplastic escape.…”