RESUMO
The maintenance cytosine DNA methyltransferase DNMT1 and de novo methyltransferase DNMT3b cooperate to establish aberrant DNA methylation and chromatin complexes to repress gene transcription during cancer development. The expression of DNMT3b was constitutively increased 5-20-fold in hTERT/CDK4-immortalized human bronchial epithelial cells (HBECs) before treatment with low doses of tobacco carcinogens. Overexpression of DNMT3b increased and accelerated carcinogen-induced transformation. Genome-wide profiling of transformed HBECs identified 143 DNMT3b-target genes, many of which were transcriptionally regulated by the polycomb repressive complex 2 (PRC2) complex and silenced through aberrant methylation in non-small-cell lung cancer cell lines. Two genes studied in detail, MAL and OLIG2, were silenced during transformation, initially through enrichment for H3K27me3 and H3K9me2, commonly methylated in lung cancer, and exert tumor suppressor effects in vivo through modulating cancer-related pathways. Re-expression of MAL and OLIG2 to physiological levels dramatically reduced the growth of lung tumor xenografts. Our results identify a key role for DNMT3b in the earliest stages of initiation and provide a comprehensive catalog of genes targeted for silencing by this methyltransferase in non-small-cell lung cancer.
Assuntos
DNA (Citosina-5-)-Metiltransferases/genética , Epigênese Genética/genética , Neoplasias Pulmonares/genética , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/biossíntese , Carcinógenos/toxicidade , Cromatina/genética , DNA (Citosina-5-)-Metiltransferase 1 , DNA (Citosina-5-)-Metiltransferases/metabolismo , Metilação de DNA/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Neoplasias Pulmonares/patologia , Glicoproteínas de Membrana/biossíntese , Camundongos , Proteínas do Tecido Nervoso/biossíntese , Fator de Transcrição 2 de Oligodendrócitos , Complexo Repressor Polycomb 2/genética , Complexo Repressor Polycomb 2/metabolismo , Transporte Proteico , Receptores de Interleucina-1/biossíntese , Telomerase/metabolismo , Nicotiana/toxicidade , Ensaios Antitumorais Modelo de Xenoenxerto , DNA Metiltransferase 3BRESUMO
Aerobic glycolysis or the Warburg effect contributes to cancer cell proliferation; however, how this glucose metabolism pathway is precisely regulated remains elusive. Here we show that receptor-interacting protein 1 (RIP1), a cell death and survival signaling factor, regulates mitochondrial oxidative phosphorylation and aerobic glycolysis. Loss of RIP1 in lung cancer cells suppressed peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) expression, impairing mitochondrial oxidative phosphorylation and accelerating glycolysis, resulting in spontaneous DNA damage and p53-mediated cell proliferation inhibition. Thus, although aerobic glycolysis within a certain range favors cancer cell proliferation, excessive glycolysis causes cytostasis. Our data suggest that maintenance of glycolysis by RIP1 is pivotal to cancer cell energy homeostasis and DNA integrity and may be exploited for use in anticancer therapy.
Assuntos
Proliferação de Células , Mitocôndrias/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/fisiologia , Proteínas de Ligação a RNA/fisiologia , Animais , Linhagem Celular Tumoral , Dano ao DNA , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Glicólise , Humanos , Camundongos Nus , Transplante de Neoplasias , Fosforilação Oxidativa , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fatores de Transcrição , Proteína Supressora de Tumor p53/fisiologiaRESUMO
BACKGROUND: Epigenetic silencing by promoter methylation and chromatin remodelling affects hundreds of genes and is a causal event for lung cancer. Treatment of patients with low doses of the demethylating agent 5-azacytidine in combination with the histone deacetylase inhibitor entinostat has yielded clinical responses. The subcutaneous dosing route for consecutive days and reduced bioavailability of 5-azacytidine because of inactivation by cytidine deaminase may limit the expansion of epigenetic therapy into Phase III trials. To mitigate these barriers, an aerosol of 5-azacytidine was generated and characterised. METHODS: The effect of aerosol vs systemic delivery of 5-azacytidine on tumour burden and molecular response of engrafted lung tumours in the nude rat was compared. RESULTS: Pharmacokinetics revealed major improvement in the half-life of 5-azacytidine in lung tissue with aerosol delivery. Aerosolised 5-azacytidine significantly reduced lung tumour burden and induced global demethylation of the epigenome at one-third of the comparable effective systemic dose. High commonality for demethylation of genes was seen in tumours sampled throughout lung lobes and across treated animals receiving the aerosolised drug. CONCLUSION: Collectively, these findings show that aerosolised 5-azacytidine targets the lung, effectively reprogrammes the epigenome of tumours, and is a promising approach to combine with other drugs for treating lung cancer.
