Methylation-mediated silencing of protein kinase C zeta induces apoptosis avoidance through ATM/CHK2 inactivation in dedifferentiated chondrosarcoma
Menée à l'aide d'une analyse in silico de la méthylation de l'ADN de chondrosarcomes dédifférenciés et de chondrosarcomes conventionnels puis menée à l'aide d'échantillons tumoraux et de lignées cellulaires, cette étude met en évidence un mécanisme par lequel la réduction du niveau d'expression de la protéine kinase C zêta, induite par la méthylation de l'ADN, prévient l'apoptose des cellules des chondrosarcomes dédifférenciés via l'inactivation de la voie de signalisation ATM/CHK2
Background : Dedifferentiated chondrosarcoma (DDCS) is an aggressive bone tumour with a poor prognosis and no effective treatment. Because changes in DNA methylation play critical roles in DDCS, we explored the roles that DNA methylation plays in oncogenesis to potentially identify an effective epigenetic treatment. Methods : We identified genes downregulated in DDCS vs. conventional chondrosarcoma (CCS) due to DNA methylation using in silico analysis. The results were validated in DDCS clinical samples, and the molecular functions of the genes of interest were investigated in multiple chondrosarcoma cell lines (NDCS-1, SW1353, and OUMS-27). The therapeutic effect of decitabine, a DNA methyltransferase inhibitor, was evaluated in vitro and in vivo. Results : PRKCZ was specifically downregulated by DNA methylation in DDCS. Overexpression of PRKCZ decreased the proliferation of NDCS-1 and SW1353 cells. PRKCZ directly bound to and activated ATM, which was followed by phosphorylation of CHK2 and subsequent apoptosis. Decitabine increased PRKCZ expression through de-methylating the promoter region of PRKCZ, which activated the ATM/CHK2 pathway and inhibited cell proliferation by inducing apoptosis. Conclusions : Increased DNA methylation and reduced expression of PRKCZ prevents apoptosis via inactivation of the ATM/CHK2 pathway in DDCS. Decitabine-induced expression of PRKCZ represents a promising therapy for DDCS.