Project description:Accumulating evidences propose the importance of epigenetic regulation in pancreatic carcinogenesis, but the mechanistic insights of a variety of histone modification process still remains to be elucidated. G9a functions as a transcriptional repressor via the methylating activity specific for histone H3 lysine9. We identified G9a as a critical factor in the development of murine pancreatic oncogenesis.
Project description:Epigenetic gene regulation in various oncogenic pathways is currently an important focus of cancer research. Histone modification plays a pivotal role in human carcinogenesis, but the significance of histone modification in hepatocarcinogenesis remains unknown. We used microarrays to investigate the oncogenic gene regulation by histone methylase G9a in chemically-induced murine hepatocellular carcinioma model.
Project description:Background/aimThe entire mechanisms by which epigenetic modifiers contribute to the development of pancreatic cancer remain unknown. Although the histone methyltransferase G9a is a promising target in human cancers, its role in pancreatic carcinogenesis has been under-studied. The aim of the study was to examine the role of G9a in pancreatic carcinogenesis by a gene-targeting mouse model.Materials and methodsWe established pancreas-specific G9aflox/flox mice and crossed them with Ptf1aCre/; KrasG12D/+ (KC) mice, which spontaneously develop pancreatic cancer. The phenotypes of the resulting KC mice with G9a deletion were examined. We analyzed transcriptomic data by microarray and genome-wide chromatin accessibility by transposase-accessible chromatin using sequencing. We established pancreatic organoids from KC mice.ResultsG9a deficiency impaired the progression of pancreatic intraepithelial neoplasia (PanIN) and prolonged the survival of KC mice. The number of phosphorylated Erk-positive cells and Dclk1-positive cells, which are reported to be essential for the progression of PanIN, were decreased by G9a deletion. UNC0638, an inhibitor of G9a, suppressed the growth of organoids and increased global chromatin accessibility, especially around the regions including the protein phosphatase 2A genes.ConclusionThus, our study suggested the functional interaction of G9a, Dclk1 and Mapk pathway in the Kras-driven pancreatic carcinogenesis. The inhibition of G9a may suppress the initiation of oncogenic Kras-driven pancreatic carcinogenesis.
Project description:Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related mortality among adults in developed countries. The discovery of the most common genetic alterations as well as the development of organoids models of pancreatic cancer have provided insight into the fundamental pathways driving the progression from normal cell, to non-invasive precursor lesion, to widely metastatic disease, offering new opportunities for the discovery of key activated pathways along cancer progression. Obesity is one of the most serious public health challenges of the 21st century. Several epidemiological studies have shown the positive association between obesity and cancer-related morbidity/mortality, as well as poor prognosis and poorer treatment outcome. Despite strong evidence indicates a link between obesity and cancer incidence, the molecular basis of the initiating events remains largely elusive. This is mainly due to the lack of an accurate and reliable model of pancreatic carcinogenesis that mimics human obesity-associated PDAC, making data interpretation difficult and often confusing. Here we propose, to our knowledge, the best suitable and manageable preclinical tool, based on next-generation cell culture models, to study the effects of obesity on pancreatic carcinogenesis. Therefore we tracked the effects of obesity on the natural evolution of PDAC in a genetically-defined transplantable model of syngeneic murine pancreatic preneoplastic lesion (mP) and tumor (mT) derived organoids that recapitulates the progression of human disease from early preinvasive lesions to metastatic disease. Our models indicated that both genetic- and diet-induced obesity promoted incidence engraftment rate and growth of both preneoplastic and neoplastic organoids, favoring pancreatic cancer progression and distant metastases dissemination. Our obesity models of carcinogenesis mimic the evolution of human pancreatic cancer pathology, promoting carcinogenesis and concomitant accumulation of a myeloid infiltrate. These changes in cancer immune infiltrate were also associated to a specific pattern of anti-inflammatory Th2 signature. Moreover, gene expression profile analysis revealed a change in gene expression programs that addresses cells to different pancreatic subtypes and stromal conditions. Our results suggest that organoid-derived transplants in obese mice represent a suitable system to study early step of carcinogenesis and support the hypothesis that inflammation induced by obesity stimulates tumor progression and metastatization during pancreatic carcinogenesis.
Project description:Regulatory T cells (Treg) are common in the tumor microenvironment in both human pancreatic cancer and in genetically engineered mouse models of the disease. Previous studies in orthotopic syngeneic models of pancreatic cancer -recapitulated in our own data- indicated that Treg depletion results CD8+ T cell-mediated tumor regression. In human patients and in mouse models, regulatory T cells accumulate during the onset of Pancreatic Intraepithelial Neoplasia (PanIN), the earliest steps of carcinogenesis. We thus generated a genetic model to investigate the role of regulatory T cells during the onset of pancreatic carcinogenesis. Unexpectedly, depletion of Tregs during early stages of carcinogenesis led to accelerated tumor progression.
Project description:G9a (EHMT2) and the G9a-like protein GLP (EHMT1) form a stable G9a/GLP heterodimer in embryonic stem cells and function cooperatively to establish and maintain the abundant repressive H3K9me2 modification, in addition to modifying several non-histone proteins. The G9a-dependent H3K9me2 is implicated in lineage-specific gene silencing and covers large chromosomal domains. While the mechanism of H3K9me2maintenance by G9a/GLP is known, how new patterns of this modification are established is not well understood. With this in mind, we used FLAG affinity purification of G9a under two different stringency conditions (150 and 300 mM NaCl) coupled with mass spectrometry to identify proteins stably associated with G9a/GLP, which could serve as potential recruiters of the complex to unmodified chromatin.
Project description:We report a novel translation-regulatory function of G9a, a histone methyltransferase and well-understood transcriptional repressor, in promoting hyperinflammation and lymphopenia; two hallmarks of endotoxin tolerance (ET)-associated chronic inflammatory complications. Using multiple approaches, we demonstrate that G9a interacts with multiple translation regulators during ET, particularly the N6-methyladenosine (m6A) RNA methyltransferase METTL3, to co-upregulate expression of certain m6A-modified mRNAs that encode immune-checkpoint and anti-inflammatory proteins. Mechanistically, G9a promotes m6A methyltransferase activity of METTL3 at translational/post-translational level by regulating its expression, its methylation, and its cytosolic localization during ET. Additionally, from a broader view extended from the G9a-METTL3-m6A translation regulatory axis, our translatome proteomics approach identified numerous “G9a-translated” proteins that unite the networks associated with inflammation dysregulation, T cell dysfunction, and systemic cytokine response. In sum, we identified a previously unrecognized function of G9a in protein-specific translation that can be leveraged to treat ET-related chronic inflammatory diseases.
Project description:<p>Metabolic reprogramming is a hallmark of cancer and is crucial for cancer progression, making it an attractive therapeutic target. Understanding the role of metabolic reprogramming in cancer initiation could help identify prevention strategies. To address this, we investigated metabolism during acinar-to-ductal metaplasia (ADM), the first step of pancreatic carcinogenesis. Glycolytic markers were elevated in ADM lesions compared to normal tissue from human samples. Comprehensive metabolic assessment in three mouse models with pancreas-specific activation of KRAS, PI3K or MEK1 using Seahorse measurements, NMR metabolome analysis, mass spectrometry, isotope tracing and RNA-seq analysis revealed a switch from oxidative phosphorylation to glycolysis in ADM. Blocking the metabolic switch attenuated ADM formation. Furthermore, mitochondrial metabolism was required for de novo synthesis of serine and glutathione but not for ATP production. MYC mediated the increase in GSH intermediates in ADM, and inhibition of GSH synthesis suppressed ADM development. This study thus identifies metabolic changes and vulnerabilities in the early stages of pancreatic carcinogenesis.</p>
Project description:The host antitumor immunity changes drastically during carcinogenesis. Intraductal papillary-mucinous neoplasm (IPMN) of the pancreas is a precursor lesion of pancreatic cancer and progresses according to adenoma-carcinoma sequence. We found that the host antitumor immune reaction changes from an immune response to immune tolerance between intraductal papillary-mucinous adenoma (IPMA) and intraductal papillary-mucinous carcinoma (IPMC). In order to determine molecules affecting intraepithelial DC infiltration in IPMNs during multistep carcinogenesis, we examined the gene-expression profiles of entire transcripts of neoplastic cells at different stages. We collected normal and neoplastic epithelial cells from frozen tissue sections (normal main pancreatic duct, IPMA, IPMC, and invasive carcinoma originating in IPMN) by laser microdissection, extracted total RNA from them, and analyzed their gene expression profiles using Affymetrix microarrays.