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BACKGROUND & AIMS - The ARID1A gene encodes a protein that is part of the large adenosine triphosphate (ATP)-dependent chromatin remodeling complex SWI/SNF and is frequently mutated in human pancreatic ductal adenocarcinomas (PDACs). We investigated the functions of ARID1A during formation of PDACs in mice.
METHODS - We performed studies with Ptf1a-Cre;Kras mice, which express activated Kras in the pancreas and develop pancreatic intraepithelial neoplasias (PanINs), as well as those with disruption of Aird1a (Ptf1a-Cre;Kras;Arid1a mice) or disruption of Brg1 (encodes a catalytic ATPase of the SWI/SNF complex) (Ptf1a-Cre;Kras; Brg1mice). Pancreatic ductal cells (PDCs) were isolated from Arid1a mice and from Arid1a;SOX9OE mice, which overexpress human SOX9 upon infection with an adenovirus-expressing Cre recombinase. Pancreatic tissues were collected from all mice and analyzed by histology and immunohistochemistry; cells were isolated and grown in 2-dimensional and 3-dimensional cultures. We performed microarray analyses to compare gene expression patterns in intraductal papillary mucinous neoplasms (IPMNs) from the different strains of mice. We obtained 58 samples of IPMNs and 44 samples of PDACs from patients who underwent pancreatectomy in Japan and analyzed them by immunohistochemistry.
RESULTS - Ptf1a-Cre;Kras mice developed PanINs, whereas Ptf1a-Cre;Kras;Arid1a mice developed IPMNs and PDACs; IPMNs originated from PDCs. ARID1A-deficient IPMNs did not express SOX9. ARID1A-deficient PDCs had reduced expression of SOX9 and dedifferentiated in culture. Overexpression of SOX9 in these cells allowed them to differentiate and prevented dilation of ducts. Among mice with pancreatic expression of activated Kras, those with disruption of Arid1a developed fewer PDACs from IPMNs than mice with disruption of Brg1. ARID1A-deficient IPMNs had reduced activity of the mTOR pathway. Human IPMN and PDAC specimens had reduced levels of ARID1A, SOX9, and phosphorylated S6 (a marker of mTOR pathway activation). Levels of ARID1A correlated with levels of SOX9 and phosphorylated S6.
CONCLUSIONS - ARID1A regulates expression of SOX9, activation of the mTOR pathway, and differentiation of PDCs. ARID1A inhibits formation of PDACs from IPMNs in mice with pancreatic expression of activated KRAS and is down-regulated in IPMN and PDAC tissues from patients.
Copyright © 2018 AGA Institute. Published by Elsevier Inc. All rights reserved.
The survival rate for pancreatic ductal adenocarcinoma (PDAC) remains low. More therapeutic options to treat this disease are needed, for the current standard of care is ineffective. Using an animal model of aggressive PDAC (Kras/p48), we discovered an effect of TGFβ signaling in regulation of G-CSF secretion in pancreatic epithelium. Elevated concentrations of G-CSF in PDAC promoted differentiation of Ly6G cells from progenitors, stimulated IL10 secretion from myeloid cells, and decreased T-cell proliferation via upregulation of Arg, iNOS, VEGF, IL6, and IL1b from CD11b cells. Deletion of in PDAC cells or use of a G-CSF-blocking antibody decreased tumor growth. Anti-G-CSF treatment in combination with the DNA synthesis inhibitor gemcitabine reduced tumor size, increased the number of infiltrating T cells, and decreased the number of Ly6G cells more effectively than gemcitabine alone. Human analysis of human datasets from The Cancer Genome Atlas and tissue microarrays correlated with observations from our mouse model experiments, especially in patients with grade 1, stage II disease. We propose that in aggressive PDAC, elevated G-CSF contributes to tumor progression through promoting increases in infiltration of neutrophil-like cells with high immunosuppressive activity. Such a mechanism provides an avenue for a neoadjuvant therapeutic approach for this devastating disease. .
©2017 American Association for Cancer Research.
Insulin-like growth factor binding protein 3 (IGFBP3) modulates cell growth through IGF-dependent and -independent mechanisms. Reports suggest that the serum levels of IGFBP3 are associated with various cancers and that IGFBP3 expression is significantly decreased in cisplatin (CDDP)-resistant lung cancer cells. Based on these findings, we investigated whether deficiency accelerates mouse lung tumorigenesis and if expression of IGFBP3 enhances CDDP response by focusing on the IGF1 signaling cascade. To this end, an -null mouse model was generated in combination with to compare the tumor burden. Then, IGF-dependent signaling was assessed after expressing wild-type or a mutant IGFBP3 without IGF binding capacity in non-small cell lung cancer (NSCLC) cells. Finally, the treatment response to CDDP chemotherapy was evaluated under conditions of IGFBP3 overexpression. -null mice had increased lung tumor burden (>2-fold) and only half of human lung cancer cells survived after expression of IGFBP3, which corresponded to increased cleaved caspase-3 (10-fold), inactivation of IGF1 and MAPK signaling. In addition, overexpression of IGFBP3 increased susceptibility to CDDP treatment in lung cancer cells. These results, for the first time, demonstrate that IGFBP3 mediates lung cancer progression in a mouse model. Furthermore, overexpression of IGFBP3 induced apoptosis and enhanced cisplatin response and confirmed that the suppression is in part by blocking IGF1 signaling. These findings reveal that IGFBP3 is effective in lung cancer cells with high IGF1 signaling activity and imply that relevant biomarkers are essential in selecting lung cancer patients for IGF1-targeted therapy. .
©2017 American Association for Cancer Research.
Wilms tumor (WT) is the most common renal neoplasm of childhood and affects 1 in 10 000 children aged less than 15 years. These embryonal tumors are thought to arise from primitive nephrogenic rests that derive from the metanephric mesenchyme during kidney development and are characterized partly by increased Wnt/β-catenin signaling. We previously showed that coordinate activation of Ras and β-catenin accelerates the growth and metastatic progression of a murine WT model. Here, we show that activating KRAS mutations can be found in human WT. In addition, high levels of phosphorylated AKT are present in the majority of WT. We further show in a mouse model and in renal epithelial cells that Ras cooperates with β-catenin to drive metastatic disease progression and promotes in vitro tumor cell growth, migration, and colony formation in soft agar. Cellular transformation and metastatic disease progression of WT cells are in part dependent on PI3K/AKT activation and are inhibited via pharmacological inhibition of this pathway. Our studies suggest both KRAS mutations and AKT activation are present in WT and may represent novel therapeutic targets for this disease.
© 2017 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.
Recent studies have shown that circular RNAs (circRNAs) are abundant, widely expressed in mammals, and can display cell-type specific expression. However, how production of circRNAs is regulated and their precise biological function remains largely unknown. To study how circRNAs might be regulated during colorectal cancer progression, we used three isogenic colon cancer cell lines that differ only in KRAS mutation status. Cellular RNAs from the parental DLD-1 cells that contain both wild-type and G13D mutant KRAS alleles and isogenically-matched derivative cell lines, DKO-1 (mutant KRAS allele only) and DKs-8 (wild-type KRAS allele only) were analyzed using RNA-Seq. We developed a bioinformatics pipeline to identify and evaluate circRNA candidates from RNA-Seq data. Hundreds of high-quality circRNA candidates were identified in each cell line. Remarkably, circRNAs were significantly down-regulated at a global level in DLD-1 and DKO-1 cells compared to DKs-8 cells, indicating a widespread effect of mutant KRAS on circRNA abundance. This finding was confirmed in two independent colon cancer cell lines HCT116 (KRAS mutant) and HKe3 (KRAS WT). In all three cell lines, circRNAs were also found in secreted extracellular-vesicles, and circRNAs were more abundant in exosomes than cells. Our results suggest that circRNAs may serve as promising cancer biomarkers.
Secretion of RNAs in extracellular vesicles is a newly recognized form of intercellular communication. A potential regulatory protein for microRNA (miRNA) secretion is the critical RNA-induced silencing complex (RISC) component Argonaute 2 (Ago2). Here, we use isogenic colon cancer cell lines to show that overactivity of KRAS due to mutation inhibits localization of Ago2 to multivesicular endosomes (MVEs) and decreases Ago2 secretion in exosomes. Mechanistically, inhibition of mitogen-activated protein kinase kinases (MEKs) I and II, but not Akt, reverses the effect of the activating KRAS mutation and leads to increased Ago2-MVE association and increased exosomal secretion of Ago2. Analysis of cells expressing mutant Ago2 constructs revealed that phosphorylation of Ago2 on serine 387 prevents Ago2-MVE interactions and reduces Ago2 secretion into exosomes. Furthermore, regulation of Ago2 exosomal sorting controls the levels of three candidate miRNAs in exosomes. These data identify a key regulatory signaling event that controls Ago2 secretion in exosomes.
Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.
Fibrosis compromises pancreatic ductal carcinoma (PDAC) treatment and contributes to patient mortality, yet antistromal therapies are controversial. We found that human PDACs with impaired epithelial transforming growth factor-β (TGF-β) signaling have high epithelial STAT3 activity and develop stiff, matricellular-enriched fibrosis associated with high epithelial tension and shorter patient survival. In several KRAS-driven mouse models, both the loss of TGF-β signaling and elevated β1-integrin mechanosignaling engaged a positive feedback loop whereby STAT3 signaling promotes tumor progression by increasing matricellular fibrosis and tissue tension. In contrast, epithelial STAT3 ablation attenuated tumor progression by reducing the stromal stiffening and epithelial contractility induced by loss of TGF-β signaling. In PDAC patient biopsies, higher matricellular protein and activated STAT3 were associated with SMAD4 mutation and shorter survival. The findings implicate epithelial tension and matricellular fibrosis in the aggressiveness of SMAD4 mutant pancreatic tumors and highlight STAT3 and mechanics as key drivers of this phenotype.
The current paradigm of pancreatic neoplastic transformation proposes an initial step whereby acinar cells convert into acinar-to-ductal metaplasias, followed by progression of these lesions into neoplasias under sustained oncogenic activity and inflammation. Understanding the molecular mechanisms driving these processes is crucial to the early diagnostic and prevention of pancreatic cancer. Emerging evidence indicates that transcription factors that control exocrine pancreatic development could have either, protective or facilitating roles in the formation of preneoplasias and neoplasias in the pancreas. We previously identified that the homeodomain transcription factor Prox1 is a novel regulator of mouse exocrine pancreas development. Here we investigated whether Prox1 function participates in early neoplastic transformation using in vivo, in vitro and in silico approaches. We found that Prox1 expression is transiently re-activated in acinar cells undergoing dedifferentiation and acinar-to-ductal metaplastic conversion. In contrast, Prox1 expression is largely absent in neoplasias and tumors in the pancreas of mice and humans. We also uncovered that Prox1-heterozygosis markedly increases the formation of acinar-to-ductal-metaplasias and early neoplasias, and enhances features associated with inflammation, in mouse pancreatic tissues expressing oncogenic Kras. Furthermore, we discovered that Prox1-heterozygosis increases tissue damage and delays recovery from inflammation in pancreata of mice injected with caerulein. These results are the first demonstration that Prox1 activity protects pancreatic cells from acute tissue damage and early neoplastic transformation. Additional data in our study indicate that this novel role of Prox1 involves suppression of pathways associated with inflammatory responses and cell invasiveness.
Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.
OBJECTIVES - KRAS mutations are the most commonly found mutations in patients with non-small cell lung cancer (NSCLC) adenocarcinoma histology. The clinical implications of KRAS mutations in patients with advanced NSCLC are not well defined. We sought to determine if there is a correlation between KRAS mutation status, response to cytotoxic chemotherapy, and survival in patients with metastatic or recurrent NSCLC.
MATERIALS AND METHODS - Patients with metastatic or recurrent NSCLC and tumor mutation analyses were analyzed for response to conventional chemotherapy. The presence or absence of tumor mutations was assessed with the SNaPshot assay, which detects >40 somatic mutations in eight genes, including KRAS. ALK fluorescence in-situ hybridization analysis was done separately. Associations between KRAS mutation status and response to chemotherapy and survival were assessed.
RESULTS - We identified 80 patients with metastatic or recurrent NSCLC and a KRAS activating mutation, and we compared these patients to 70 patients who were pan negative (no detectable mutation by the SNaPshot assay and ALK negative). Patients with KRAS-mutant advanced NSCLC demonstrated a significantly shorter progression-free survival in response to first line chemotherapy (4.5 months versus 5.7 months, p=0.008) compared to pan-mutation negative patients. Overall survival was also significantly shorter in patients with KRAS-mutant advanced NSCLC compared to patients without KRAS activating mutations (8.8 months versus 13.5 months, p=0.038).
CONCLUSIONS - Within this single institution retrospective analysis, patients with advanced NSCLC and a KRAS activating mutation exhibited inferior responses to cytotoxic chemotherapy and decreased survival compared to patients with advanced NSCLC and no KRAS mutation.
Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.