The role of Ras in human skin tumorigenesis induction is still ambiguous. Overexpression of oncogenic Ras causes premature senescence in cultured human cells and hyperplasia in transgenic mice. Here, we investigated whether the oncogenic insult outcome might depend on the nature of the founding keratinocyte. We demonstrate that overexpression of the constitutively active Ras-V12 induces senescence in primary human keratinocyte cultures, but that some cells escape senescence and proliferate indefinitely. Ras overexpression in transient-amplifying-or stem-cell-enriched cultures shows that p16 (encoded by CDKN2A) levels are crucial for the final result. Indeed, transient-amplifying keratinocytes expressing high levels of p16 are sensitive to Ras-V12-induced senescence, whereas cells with high proliferative potential, but that do not display p16, are resistant. The subpopulation that sustains the indefinite culture growth exhibits stem cell features. Bypass of senescence correlates with inhibition of the pRb (also known as RB1) pathway and resumption of telomerase reverse transcriptase (TERT) activity. Immortalization is also sustained by activation of the ERK1 and ERK2 (ERK1/2, also known as MAPK3 and MAPK1) and Akt pathways. Moreover, only transduced cultures originating from cultures bearing stem cells induce tumors in nude mice. Our findings demonstrate that the Ras overexpression outcome depends on the clonogenic potential of the recipient keratinocyte and that only the stem cell compartment is competent to initiate tumorigenesis.

Hypercholesterolaemia provokes reactive oxygen species (ROS) increase and is a major risk factor for cardiovascular disease (CVD) development. We previously showed that circulating expression levels were up-regulated in children with familial hypercholesterolaemia (FH). control cholesterol homoeostasis and recently has been demonstrated to directly target the transcription factor zinc finger E-box-binding homeobox 1 (ZEB1). The latter acts in a negative feedback loop with the family. Our previous studies showed that the ROS-dependent up-regulation induces endothelial dysfunction and provokes a ZEB1-dependent apoptosis and senescence. In the present study, we aimed to verify whether circulating was induced in FH children, and whether a correlation existed with Total RNA was extracted from plasma of 28 FH children and 25 age-matched healthy subjects (HS) and levels were measured. We found that was up-regulated in FH compared with HS (4.00 ± 0.48-fold increase, <0.05) and exhibited a positive correlation with did not correlate with plasma lipids, but correlated with C-reactive protein (CRP) plasma levels and glycaemia (GLI). Ordinary least squares (OLS) regression analysis revealed that was significantly affected by GLI and by (<0.01; <0.001 respectively). Moreover, we found that overexpression, in different cell lines, decreased ZEB1 expression and up-regulated both the intracellular and the extracellular expression levels. In conclusion, circulating is up-regulated in FH, probably due to oxidative stress and inflammation and via a-ZEB1-dependent mechanism. The present study could provide the first evidence to point to the use of and, as early biomarkers of CVD, in paediatric FH.

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