Several genetic and epigenetic signatures characterize cancer cells. However, the relationships (causal or consequence link, existence due to a same origin) between these 2 types of signatures were not fully elucidated. In the present work, we reported that the disruption of the DNMT1/PCNA/UHRF1 complex acts as an oncogenic event of the tumor transformation of brain (astrocytes), breast, lung and mesothelial cells. We also show that these tumor transformation processes were associated with the acquisition of cancer hallmark and common genetic and epigenetic signatures. Thus, our data revealed that the global DNA hypomethylation induced by the DNMT1/PCNA/UHRF1 disruption is an oncogenic event of human tumorigenesis, an inducer of epigenetic and genetic signatures frequently observed in several human cancers, and is an initiator of oncogenic events.

Glioblastoma Multiforme (GBM) is the most common brain cancer in adults. Radiotherapy (RT) is the most effective post-operative treatment for the patients even though GBM is one of the most radio-resistant tumors. Dead or dying cells within the tumor are thought to promote resistance to treatment through mechanisms that are very poorly understood. We have evaluated the role of Prostaglandin E2 (PGE2), a versatile bioactive lipid, in GBM radio-resistance. We used an in vitro approach using 3D primary cultures derived from representative GBM patients. We show that irradiated glioma cells produced and released PGE2 in important quantities independently of the induction of cell death. We demonstrate that the addition of PGE2 enhances cell survival and proliferation though its ability to trans-activate the Epithelial Growth Factor receptor (EGFR) and to activate β-catenin. Indeed, PGE2 can substitute for EGF to promote primary cultures survival and growth in vitro and the effect is likely to occur though the Prostaglandin E2 receptor EP2.