Wnt/β-catenin signaling regulates amino acid metabolism through the suppression of CEBPA and FOXA1 in liver cancer cells

Deregulation of the Wnt/β-catenin pathway is associated with the development of human cancer including colorectal and liver cancer. Although we previously showed that histidine ammonia lyase (HAL) was transcriptionally reduced by the β-catenin/TCF complex in liver cancer cells, the mechanism(s) of its down-regulation by the complex remain to be clarified. In this study, we search for the transcription factor(s) regulating HAL, and identify CEBPA and FOXA1, two factors whose expression is suppressed by the knockdown of β-catenin or TCF7L2. In addition, RNA-seq analysis coupled with genome-wide mapping of CEBPA- and FOXA1-binding regions reveals that these two factors also increase the expression of arginase 1 (ARG1) that catalyzes the hydrolysis of arginine. Metabolome analysis discloses that activated Wnt signaling augments intracellular concentrations of histidine and arginine, and that the signal also increases the level of lactic acid suggesting the induction of the Warburg effect in liver cancer cells. Further analysis reveals that the levels of metabolites of the urea cycle and genes coding its related enzymes are also modulated by the Wnt signaling. These findings shed light on the altered cellular metabolism in the liver by the Wnt/β-catenin pathway through the suppression of liver-enriched transcription factors including CEBPA and FOXA1.

Genome-wide analysis of DNA methylation in pseudomyxoma peritonei originated from appendiceal neoplasms

INTRODUCTION

Pseudomyxoma peritonei (PMP) is a disease characterized by progressive accumulation of intraperitoneal mucinous ascites produced by neoplasms in the abdominal cavity. Since the prognosis of patients with PMP remain unsatisfactory, the development of effective therapeutic drug(s) is a matter of pressing concern. Genetic analyses of PMP have clarified the frequent activation of GNAS and/or KRAS. However, the involvement of global epigenetic alterations in PMPs has not been reported.

METHODS

To clarify the genetic background of the 15 PMP tumors, we performed genetic analysis using AmpliSeq Cancer HotSpot Panel v2. We further investigated global DNA methylation in the 15 tumors and eight non-cancerous colonic epithelial cells using Methylation EPIC array BeadChip (Infinium 850k) containing a total of 865,918 probes.

RESULTS

This is the first report of comprehensive DNA methylation profiles of PMPs in the world. We clarified that the 15 PMPs could be classified into at least two epigenotypes, unique methylation epigenotype (UME) and normal-like methylation epigenotype (NLME), and that genes associated with neuronal development and synaptic signaling may be involved in the development of PMPs. In addition, we identified a set of hypermethylation marker genes such as HOXD1 and TSPYL5 in the 15 PMPs.

CONCLUSIONS

These findings may help the understanding of the molecular mechanism(s) of PMP and contribute to the development of therapeutic strategies for this life-threatening disease.

Expression of PVRL4, a molecular target for cancer treatment, is transcriptionally regulated by FOS

PVRL4 (or nectin‑4) is a promising therapeutic target since its upregulated expression is found in a wide range of human cancer types. Enfortumab vedotin, an antibody‑drug conjugate targeting PVRL4, is clinically used for the treatment of urothelial bladder cancer. In addition, rMV‑SLAMblind, a genetically engineered oncolytic measles virus, can infect cancer cells and induce apoptosis through interaction with PVRL4. Although PVRL4 transcript levels are elevated in breast, lung and ovarian cancer, the mechanisms of its upregulation have not yet been uncovered. To clarify the regulatory mechanisms of elevated PVRL4 expression in breast cancer cells, Assay for Transposase‑Accessible Chromatin‑sequencing and chromatin immunoprecipitation‑sequencing (ChIP‑seq) data were used to search for its regulatory regions. Using breast cancer cells, an enhancer region was ultimately identified. Additional analyses, including ChIP and reporter assays, demonstrated that FOS interacted with the PVRL4 enhancer region, and that alterations of the FOS‑binding motifs in the enhancer region decreased reporter activity. Consistent with these data, exogenous expression of FOS enhanced the reporter activity and PVRL4 expression in breast cancer cells. Furthermore, RNA‑seq analysis using breast cancer cells treated with PVRL4 small interfering RNA revealed its possible involvement in the cytokine response and immune system. These data suggested that FOS was involved, at least partly, in the regulation of PVRL4 expression in breast cancer cells, and that elevated PVRL4 expression may regulate the response of cancer cells to cytokines and the immune system.

Visinin-like 1, a novel target gene of the Wnt/β-catenin signaling pathway, is involved in apoptosis resistance in colorectal cancer

BACKGROUND

Abnormal activation of Wnt/β-catenin signaling is associated with various aspects of cancer development. This study explored the roles of novel target genes of the Wnt/β-catenin signaling pathway in cancer cells.

METHODS

Using the haploid chronic myelogenous leukemia cell line HAP1, RNA sequencing (RNA-seq) was performed to identify genes whose expression was increased by APC disruption and reversed by β-catenin knockdown (KD). The regulatory mechanism and function of one of the candidate genes was investigated in colorectal cancer (CRC) cells.

RESULTS

In total, 64 candidate genes whose expression was regulated by Wnt/β-catenin signaling were identified. Of these candidate genes, the expression levels of six were reduced by β-catenin KD in HCT116 CRC cells in our previous microarray. One of these genes was Visinin-like 1 ( VSNL1 ), which belongs to the neuronal calcium-sensor gene family. The expression of VSNL1 was regulated by the β-catenin/TCF7L2 complex via two TCF7L2-binding elements in intron 1. VSNL1 KDinduced apoptosis in VSNL1-positive CRC cells. Additionally, forced expression of wild-type VSNL1, but not a myristoylation, Ca²⁺ -binding, or dimerization-defective mutant, suppressed the apoptosis induced by camptothecin and doxorubicin in VSNL1-negative CRC cells.

CONCLUSION

Our findings suggest that VSNL1 , a novel target gene of the Wnt/β-catenin signaling pathway, is associated with apoptosis resistance in CRC cells.

Bromodomain protein BRD8 regulates cell cycle progression in colorectal cancer cells through a TIP60-independent regulation of the pre-RC complex

Bromodomain-containing protein 8 (BRD8) is a subunit of the NuA4/TIP60-histone acetyltransferase complex. Although BRD8 has been considered to act as a co-activator of the complex, its biological role remains to be elucidated. Here, we uncovered that BRD8 accumulates in colorectal cancer cells through the inhibition of ubiquitin-dependent protein degradation by the interaction with MRG domain binding protein. Transcriptome analysis coupled with genome-wide mapping of BRD8-binding sites disclosed that BRD8 transactivates a set of genes independently of TIP60, and that BRD8 regulates the expression of multiple subunits of the pre-replicative complex in concert with the activator protein-1. Depletion of BRD8 induced cell-cycle arrest at the G1 phase and suppressed cell proliferation. We have also shown that the bromodomain of BRD8 is indispensable for not only the interaction with histone H4 or transcriptional regulation but also its own protein stability. These findings highlight the importance of bromodomain as a therapeutic target.

Identification of odontogenic ameloblast associated as a novel target gene of the Wnt/β-catenin signaling pathway

The Wnt/β-catenin signaling pathway plays a key role in development and carcinogenesis. Although some target genes of this signaling have been identified in various tissues and neoplasms, the comprehensive understanding of the target genes and their roles in the development of human cancer, including hepatoma and colorectal cancer remain to be fully elucidated. In this study, we searched for genes regulated by the Wnt signaling in liver cancer using HuH-7 hepatoma cells. A comparison of the expression profiles between cells expressing an active form of mutant β-catenin and cells expressing enhanced green fluorescent protein (EGFP) identified seven genes upregulated by the mutant β-catenin gene (CTNNB1). Among the seven genes, we focused in this study on ODAM, odontogenic, ameloblast associated, as a novel target gene. Interestingly, its expression was frequently upregulated in hepatocellular carcinoma, colorectal adenocarcinoma, and hepatoblastoma. We additionally identified a distant enhancer region that was associated with the β-catenin/TCF7L2 complex. Further analyses revealed that ODAM plays an important role in the regulation of the cell cycle, DNA synthesis, and cell proliferation. These data may be useful for clarification of the main molecular mechanism(s) underlying these cancers.

Inhibiting SCAP/SREBP exacerbates liver injury and carcinogenesis in murine nonalcoholic steatohepatitis

Enhanced de novo lipogenesis mediated by sterol regulatory element-binding proteins (SREBPs) is thought to be involved in nonalcoholic steatohepatitis (NASH) pathogenesis. In this study, we assessed the impact of SREBP inhibition on NASH and liver cancer development in murine models. Unexpectedly, SREBP inhibition via deletion of the SREBP cleavage-activating protein (SCAP) in the liver exacerbated liver injury, fibrosis, and carcinogenesis, despite markedly reduced hepatic steatosis. These phenotypes were ameliorated by restoring SREBP function. Transcriptome and lipidome analyses revealed that SCAP-SREBP pathway inhibition altered the fatty acid (FA) composition of phosphatidylcholines due to both impaired FA synthesis and disorganized FA incorporation into phosphatidylcholine via lysophosphatidylcholine acyltransferase 3 (LPCAT3) downregulation, which led to endoplasmic reticulum (ER) stress and hepatocyte injury. Supplementation of phosphatidylcholines significantly improved liver injury and ER stress induced by SCAP deletion. The activity of SCAP-SREBP-LPCAT3 axis was found inversely associated with liver fibrosis severity in human NASH. SREBP inhibition also cooperated with impaired autophagy to trigger liver injury. Thus, excessively strong and broad lipogenesis inhibition was counterproductive for NASH therapy, which will have important clinical implications in NASH treatment.

Cancer-associated IDH mutations induce Glut1 expression and glucose metabolic disorders through a PI3K/Akt/mTORC1-Hif1α axis

Isocitrate dehydrogenase 1 and 2 (IDH1/2) mutations and their key effector 2-hydroxyglutarate (2-HG) have been reported to promote oncogenesis in various human cancers. To elucidate molecular mechanism(s) associated with IDH1/2 mutations, we established mouse embryonic fibroblasts (MEF) cells and human colorectal cancer cells stably expressing cancer-associated IDH1R132C or IDH2R172S, and analyzed the change in metabolic characteristics of the these cells. We found that IDH1/2 mutants induced intracellular 2-HG accumulation and inhibited cell proliferation. Expression profile analysis by RNA-seq unveiled that glucose transporter 1 (Glut1) was induced by the IDH1/2 mutants or treatment with 2-HG in the MEF cells. Consistently, glucose uptake and lactate production were increased by the mutants, suggesting the deregulation of glucose metabolism. Furthermore, PI3K/Akt/mTOR pathway and Hif1α expression were involved in the up-regulation of Glut1. Together, these results suggest that Glut1 is a potential target regulated by cancer-associated IDH1/2 mutations.

Abstract 2316: Analysis of APC-1B promoter region responsible for familial adenomatous polyposis

APC (APC regulator of WNT signaling pathway) is not only a gene responsible for familial adenomatous polyposis (FAP), a hereditary disease characterized by hundreds or thousands adenomatous polyps in the colon, but also plays a crucial role in sporadic human cancers. Although most of FAP cases are caused by germline mutations in the coding region of APC, deletions or point mutations in the promoter regions are involved in a limited number of cases. Previously, we reported an FAP case with a large deletion of approximately 10 kb encompassing APC promoter 1B and exon1B of the APC gene. Since precise regulatory mechanism(s) of the transcription of APC remains to be clarified, we searched in this study the regulatory domain(s) in the deleted region. First, we performed cap analysis of gene expression (CAGE) analysis, and compared the amount of APC-1A and APC-1B transcripts in the peripheral blood cells of the patient with that of healthy volunteers. As a result, we found that the deletion decreased the amount of APC-1B to 39% - 45% in the patient compared to the healthy controls, and that it did not change the amount of APC-1A in the patient. In addition, an allele-specific expression analysis by deep cDNA sequencing revealed that the amount of APC transcripts from the mutated APC allele is reduced to 11.2% by the deletion in the patient, suggesting that the deletion resulted in the marked decrease of the transcription of the affected allele and that the remaining expression of deleted allele may be driven by other regulatory region(s) such as promoter 1A. Consistently, CAGE analysis demonstrated that APC-1B transcripts are more abundantly expressed than APC-1A transcripts in all tissues tested except for the brain, suggesting that promoter 1B plays a crucial role in the expression of APC transcription. Analysis of promoter 1B by reporter assay identified a critical region for the transcriptional activation between -117 bp and -49 bp of promoter 1B. These data will contribute to the better understanding of regulatory mechanisms of APC transcription and the evaluation of genetic variants located in promoter 1B.

Citation Format: Saya Nakagawa, Kiyoshi Yamaguchi, Kimiko Saito, Kiyoko Takane, Tsuneo Ikenoue, Yoichi Furukawa. Analysis of APC-1B promoter region responsible for familial adenomatous polyposis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2316.

Axin2+ Peribiliary Glands in the Periampullary Region Generate Biliary Epithelial Stem Cells That Give Rise to Ampullary Carcinoma

BACKGROUND & AIMS

Peribiliary glands (PBGs), clusters of epithelial cells residing in the submucosal compartment of extrahepatic bile ducts, have been suggested as biliary epithelial stem/progenitor cell niche; however, evidence to support this claim is limited because of a lack of PBG-specific markers. We therefore sought to identify PBG-specific markers to investigate the potential role of PBGs as stem/progenitor cell niches, as well as an origin of cancer.

METHODS

We examined the expression pattern of the Wnt target gene Axin2 in extrahepatic bile ducts. We then applied lineage tracing to investigate whether Axin2-expressing cells from PBGs contribute to biliary regeneration and carcinogenesis using Axin2-Cre^ERT mice.

RESULTS

Wnt signaling activation, marked by Axin2, was limited to PBGs located in the periampullary region. Lineage tracing showed that Axin2-expressing periampullary PBG cells are capable of self-renewal and supplying new biliary epithelial cells (BECs) to the luminal surface. Additionally, the expression pattern of Axin2 and the mature ductal cell marker CK19 were mutually exclusive in periampullary region, and fate tracing of CK19⁺ luminal surface BECs showed gradual replacement by CK19^- cells, further supporting the continuous replenishment of new BECs from PBGs to the luminal surface. We also found that Wnt signal enhancer R-spondin3 secreted from Myh11-expressing stromal cells, corresponding to human sphincter of Oddi, maintained the periampullary Wnt signal-activating niche. Notably, introduction of PTEN deletion into Axin2⁺ PBG cells, but not CK19⁺ luminal surface BECs, induced ampullary carcinoma whose development was suppressed by Wnt inhibitor.

CONCLUSION

A specific cell population receiving Wnt-activating signal in periampullary PBGs functions as biliary epithelial stem/progenitor cells and also the cellular origin of ampullary carcinoma.

NAFLD exacerbates cholangitis and promotes cholangiocellular carcinoma in mice

Nonalcoholic fatty liver disease (NAFLD) is an increasingly common condition, affecting up to 25% of the population worldwide. NAFLD has been linked to several conditions, including hepatic inflammation, fibrosis, and hepatocellular carcinoma (HCC), however the role of NAFLD in cholangitis and the development of cholangiocellular carcinoma (CCC) remains poorly understood. This study investigated whether a high-fat diet (HFD) promotes cholangitis and the development of CCC in mice. We used liver-specific E-cadherin gene (CDH1) knockout mice, CDH1^∆Liv , which develop spontaneous inflammation in the portal areas along with periductal onion skin-like fibrosis, similar to that of primary sclerosing cholangitis (PSC). An HFD or normal diet (ND) was fed to CDH1^∆Liv mice for 7 mo. In addition, CDH1^∆Liv mice were crossed with LSL-Kras^G12D mice, fed an HFD, and assessed in terms of liver tumor development. The extent of cholangitis and number of bile ductules significantly increased in mice fed an HFD compared with ND-administered CDH1^∆Liv mice. The numbers of Sox9 and CD44-positive stem cell-like cells were significantly increased in HFD mice. LSL-Kras^G12D /CDH1^∆Liv HFD mice exhibited increased aggressiveness along with the development of numerous HCC and CCC, whereas LSL-Kras^G12D /CDH1^∆Liv ND mice showed several macroscopic tumors with both HCC and CCC components. In conclusion, NAFLD exacerbates cholangitis and promotes the development of both HCC and CCC in mice.

Inhibition of histone methyltransferase G9a attenuates liver cancer initiation by sensitizing DNA-damaged hepatocytes to p53-induced apoptosis

While the significance of acquired genetic abnormalities in the initiation of hepatocellular carcinoma (HCC) has been established, the role of epigenetic modification remains unknown. Here we identified the pivotal role of histone methyltransferase G9a in the DNA damage-triggered initiation of HCC. Using liver-specific G9a-deficient (G9a^ΔHep) mice, we revealed that loss of G9a significantly attenuated liver tumor initiation caused by diethylnitrosamine (DEN). In addition, pharmacological inhibition of G9a attenuated the DEN-induced initiation of HCC. After treatment with DEN, while the induction of γH2AX and p53 were comparable in the G9a^ΔHep and wild-type livers, more apoptotic hepatocytes were detected in the G9a^ΔHep liver. Transcriptome analysis identified Bcl-G, a pro-apoptotic Bcl-2 family member, to be markedly upregulated in the G9a^ΔHep liver. In human cultured hepatoma cells, a G9a inhibitor, UNC0638, upregulated BCL-G expression and enhanced the apoptotic response after treatment with hydrogen peroxide or irradiation, suggesting an essential role of the G9a-Bcl-G axis in DNA damage response in hepatocytes. The proposed mechanism was that DNA damage stimuli recruited G9a to the p53-responsive element of the Bcl-G gene, resulting in the impaired enrichment of p53 to the region and the attenuation of Bcl-G expression. G9a deletion allowed the recruitment of p53 and upregulated Bcl-G expression. These results demonstrate that G9a allows DNA-damaged hepatocytes to escape p53-induced apoptosis by silencing Bcl-G, which may contribute to the tumor initiation. Therefore, G9a inhibition can be a novel preventive strategy for HCC.

Opposing Tumor-Promoting and -Suppressive Functions of Rictor/mTORC2 Signaling in Adult Glioma and Pediatric SHH Medulloblastoma

Most human cancers arise from stem and progenitor cells by the sequential accumulation of genetic and epigenetic alterations, while cancer modeling typically requires simultaneous multiple oncogenic events. Here, we show that a single p53 mutation, despite causing no defect in the mouse brain, promoted neural stem and progenitor cells to spontaneously accumulate oncogenic alterations, including loss of multiple chromosomal (chr) regions syntenic to human chr10 containing Pten, forming malignant gliomas with PI3K/Akt activation. Rictor/mTORC2 loss inhibited Akt signaling, greatly delaying and reducing glioma formation by suppressing glioma precursors within the subventricular zone stem cell niche. Rictor/mTORC2 loss delayed timely differentiation of granule cell precursors (GCPs) during cerebellar development, promoting sustained GCP proliferation and medulloblastoma formation, which recapitulated critical features of TP53 mutant sonic hedgehog (SHH) medulloblastomas with GLI2 and/or N-MYC amplification. Our study demonstrates that Rictor/mTORC2 has opposing functions in neural stem cells and GCPs in the adult and the developing brain, promoting malignant gliomas and suppressing SHH-medulloblastoma formation, respectively.

Anti-apoptotic effect by the suppression of IRF1 as a downstream of Wnt/β-catenin signaling in colorectal cancer cells

Impaired Wnt signaling pathway plays a crucial role in the development of colorectal cancer through activation of the β-catenin/TCF7L2 complex. Although genes upregulated by Wnt/β-catenin signaling have been intensively studied, the roles of downregulated genes are poorly understood. Previously, we reported that interferon-induced proteins with tetratricopeptide repeats 2 (IFIT2) was downregulated by the Wnt/β-catenin signaling, and that the suppressed expression of IFIT2 conferred antiapoptotic property to colorectal cancer (CRC) cells. However, the mechanisms underlying how Wnt/β-catenin signaling regulates IFIT2 remain to be elucidated. In this study, we have uncovered that the expression of IFIT2 is induced by IRF1, which is negatively regulated by the Wnt/β-catenin signaling. In addition, we found that downregulation of IRF1 is mediated by its degradation through the ubiquitination-proteasome pathway, and that decreased activity of a deubiquitinase complex containing USP1 and UAF1 is involved in the degradation of IRF1 by Wnt/β-catenin signaling. These data should provide better understanding of the Wnt signaling pathway and human carcinogenesis.

Three types of metaplasia model through Kras activation, Pten deletion, or Cdh1 deletion in the gastric epithelium

Chronic inflammation and intestinal metaplasia are strongly associated with gastric carcinogenesis. Kras activation and Pten deletion are observed in intestinal-type gastric cancer, and Cdh1 mutation is associated with diffuse-type gastric cancer. Although various mouse models of gastric carcinogenesis have been reported, few mouse lines enable gene manipulation selectively in the stomach. Here we established a Tff1-Cre bacterial artificial chromosome transgenic mouse line in an attempt to induce gene modification specifically in the gastric pit lineage. In the stomach, Tff1-Cre-mediated recombination was most evident in the pit lineage in the corpus and in entire antral glands; recombination was also observed in a few gastric chief and parietal cells. Outside the stomach, recombination was patchy throughout the intestines, and particularly frequently in the duodenum (Brunner glands), cecum, and proximal colon. In the stomachs of Tff1-Cre;LSL-Kras^G12D mice, proliferating cell clusters expanded throughout the corpus glands, with foveolar cell expansion with ectopic Alcian blue-positive mucins, oxyntic atrophy, and pseudopyloric changes with spasmolytic polypeptide-expressing metaplasia; however, gastric cancer was not observed even at 12 months of age. Corpus-derived organoids from Tff1-Cre;LSL-Kras^G12D mice exhibited accelerated growth and abnormal differentiation with a loss of chief and parietal cell markers. Tff1-Cre;Pten^flox/flox mice displayed similar changes to those seen in Tff1-Cre;LSL-Kras^G12D mice, both with aberrant ERK activation within 3 months. In contrast, Tff1-Cre;Cdh1^flox/flox mice initially showed signet ring-like cells that were rapidly lost with disruption of the mucosal surface, and later developed gastric epithelial shedding with hyperproliferation and loss of normal gastric lineages. Eventually, the glandular epithelium in Tff1-Cre;Cdh1^flox/flox mice was completely replaced by squamous epithelium which expanded from the forestomach. Tff1-Cre mice offer an additional useful tool for studying gastric carcinogenesis both in vivo and in vitro. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Efficacy of liquid-based genetic diagnosis of endometrial cancer

Although liquid-based cytology (LBC) has increased the sensitivity of cytological diagnosis of endometrial cancer (EC) compared with conventional smear cytology, the sensitivity of LBC for the detection of EC is between 70% and 96% and remains unsatisfactory. In the present study, we compared the efficacy of LBC with liquid-based genetic diagnosis (LBGDx) by amplicon sequencing of five genes including PTEN, PIK3CA, CTNNB1, KRAS, and TP53 in 48 LBC subjects who underwent endometrial screening. Consequently, LBC classified 15 samples as "positive or suspicious for malignancy" and the 15 were later confirmed as EC. However, LBC failed to identify five cases who were diagnosed as EC by additional transvaginal ultrasound and endometrial curettage, indicating that the sensitivity of cytology alone was 75% (15/20). LBGDx identified 11 pathogenic PTEN variants in 10 subjects, six PIK3CA variants in nine, three CTNNB1 variants in five, two KRAS variants in four, and three TP53 variants in three. Collectively, at least one pathogenic variant was identified in 19 subjects, which included 17 EC (15 endometrioid carcinoma and 2 endometrial carcinosarcomas), and one cervical adenocarcinoma. However, LBGDx did not identify any pathogenic mutations in three of the 20 EC, indicating that the sensitivity of LBGDx alone was 85% (17/20). Although five EC were negative for malignancy by LBC and three were negative for pathogenic mutations by LBGDx, the combination of LBC and LBGDx would successfully diagnose all 20 EC. These data suggested that LBGDx is a useful strategy to improve the sensitivity of screening of EC by LBC.

Combating herpesvirus encephalitis by potentiating a TLR3-mTORC2 axis

TLR3 is a sensor of double-stranded RNA that is indispensable for defense against infection with herpes simplex virus type 1 (HSV-1) in the brain. We found here that TLR3 was required for innate immune responses to HSV-1 in neurons and astrocytes. During infection with HSV-1, TLR3 recruited the metabolic checkpoint kinase complex mTORC2, which led to the induction of chemokines and trafficking of TLR3 to the cell periphery. Such trafficking enabled the activation of molecules (including mTORC1) required for the induction of type I interferons. Intracranial infection of mice with HSV-1 was exacerbated by impairment of TLR3 responses with an inhibitor of mTOR and was significantly 'rescued' by potentiation of TLR3 responses with an agonistic antibody to TLR3. These results suggest that the TLR3-mTORC2 axis might be a therapeutic target through which to combat herpes simplex encephalitis.

Abstract 3864: Development of high-specific and sensitive reporter assays for the detection of Wnt/β-catenin signaling activity

The Wnt/β-catenin signaling pathway is involved in development, tissue homeostasis, and regeneration. Since aberrant activation of this pathway plays a crucial role in human carcinogenesis, inhibition of this pathway has been shown to be a promising therapeutic strategy for cancers with de-regulated Wnt signaling. Although cell-based assays using synthetic TCF/LEF reporters (also known as TOPFLASH) have contributed to the discovery of small molecules that modulate Wnt signaling pathway, these assays often raise a problem of the specificity in the screening. In this study, we aimed to develop a specific reporter for the detection of Wnt signaling activity. We performed integrated transcriptome analysis and found that expression of histidine ammonia-lyase gene (HAL) is negatively regulated by β-catenin/TCF. In addition to TOPFLASH, we leveraged a promoter region of HAL as another transcriptional readout of Wnt signaling. Subsequently, HepG2 cells stably expressing both optimized HAL promoter reporter and TOPFLASH reporter were established. Since inhibition of the β-catenin/TCF transcriptional activity decreased TOPFLASH activity and simultaneously increased HAL reporter activity, we termed this assay as a bidirectional reporter assay. To verify the effectiveness of this assay, we compared the number of hits in the screening of a test library using the bidirectional assay with that using the conventional TOPFLASH/FOPFLASH assay. Among the 361 compounds in the library, the bidirectional reporter assay identified 9 hits, while the TOPFLASH/FOPFLASH assay did 79 hits. Four compounds were overlapped between these assays, suggesting that the bidirectional assay decreased false positives compared with the conventional assay. The concept of bidirectional assay might be useful for the screening of compounds that regulate other transcriptional factors and/or disease-associated signaling pathways.

Citation Format: Kiyoshi Yamaguchi, Chi Zhu, Tomoyuki Ohsugi, Akari Saku, Tsuneo Ikenoue, Yoichi Furukawa. Development of high-specific and sensitive reporter assays for the detection of Wnt/β-catenin signaling activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3864.

Establishment and analysis of a novel mouse line carrying a conditional knockin allele of a cancer-specific FBXW7 mutation

F-box and WD40 domain protein 7 (FBXW7) is a component of the SKP1-CUL1-F-box protein (SCF) complex that mediates the ubiquitination of diverse oncogenic target proteins. The exploration of FBXW7 mutations in human primary cancer has revealed three mutation hotspots at conserved arginine residues (Arg⁴⁶⁵, Arg⁴⁷⁹, and Arg⁵⁰⁵) in the WD40 domain, which are critical for substrate recognition. To study the function of human FBXW7^R465C, the most frequent mutation in human malignancies, we generated a novel conditional knockin mouse line of murine Fbxw7^R468C corresponding to human FBXW7^R465C. Systemic heterozygous knockin of the Fbxw7^R468C mutation resulted in perinatal lethality due to defects in lung development, and occasionally caused an eyes-open at birth phenotype and cleft palate. Furthermore, mice carrying liver-specific heterozygous and homozygous Fbxw7^R468C alleles cooperated with an oncogenic Kras mutation to exhibit bile duct hyperplasia within 8 months of birth and cholangiocarcinoma-like lesions within 8 weeks of birth, respectively. In addition, the substrates affected by the mutant Fbxw7 differed between the embryos, embryonic fibroblasts, and adult liver. This novel conditional knockin Fbxw7^R468C line should be useful to gain a more profound understanding of carcinogenesis associated with mutation of FBXW7.

Decreased expression of interferon-induced protein 2 (IFIT2) by Wnt/β-catenin signaling confers anti-apoptotic properties to colorectal cancer cells

Impaired Wnt signaling pathway plays a crucial role in the development of colorectal cancer through activation of the β-catenin/TCF7L2 complex. Although genes up-regulated by Wnt/β-catenin signaling have been intensively studied, the roles of down-regulated genes are poorly understood. In this study, we explored a global gene expression of colorectal cancer cells transfected with β-catenin siRNAs or a dominant negative form of TCF7L2 (dnTCF7L2), and identified a set of genes down-regulated by Wnt/β-catenin signaling. Among the genes, we focused here on IFIT2, a gene encoding interferon-induced protein with tetratricopeptide repeats. A reporter assay using plasmids containing a 5’-flanking region of the gene showed that the reporter activity was enhanced by either transduction of β-catenin siRNA or dnTCF7L2, suggesting that the region is involved in the transcriptional regulation as a downstream of the β-catenin/TCF7L2 complex. Consistent with this result, expression of IFIT2 was significantly lower in colorectal cancer tissues than that in normal tissues. Exogenous IFIT2 expression decreased cell proliferation and increased apoptosis of colorectal cancer cells. These data suggested that the down-regulation of IFIT2 by Wnt/β-catenin signaling may play a vital role in human colorectal carcinogenesis through the suppression of apoptosis.

RASAL1 is a potent regulator of hepatic stellate cell activity and liver fibrosis

Liver fibrosis, leading to cirrhosis and liver failure, can occur after chronic liver injury. The transition of hepatic stellate cells (HSCs) from quiescent cells into proliferative and fibrogenic cells is a central event in liver fibrosis. Here, we show that RAS protein activator like-1 (RASAL1), a RAS-GTPase-activating protein, which switches off RAS activity, is significantly decreased during HSC activation, and that HSC activation can be antagonized by forced expression of the RASAL1 protein. We demonstrate that RASAL1 suppresses HSC proliferation by regulating the Ras-MAPK pathway, and that RASAL1 suppresses HSC fibrogenic activity by regulating the PKA-LKB1-AMPK-SRF pathway by interacting with angiotensin II receptor, type 1. We also show that RASAL1-deficient mice are more susceptible to liver fibrosis. These data demonstrate that deregulated RASAL1 expression levels and the affected downstream intracellular signaling are central mediators of perpetuated HSC activation and fibrogenesis in the liver.

Bidirectional reporter assay using HAL promoter and TOPFLASH improves specificity in high-throughput screening of Wnt inhibitors

Constitutive activation of Wnt signaling plays an important role in colorectal and liver tumorigenesis. Cell-based assays using synthetic TCF/LEF (T-cell factor/lymphoid enhancer factor) reporters, as readouts of β-catenin/TCF-dependent transcriptional activity, have contributed greatly to the discovery of small molecules that modulate Wnt signaling. In the present study, we report a novel screening method, called a bidirectional dual reporter assay. Integrated transcriptome analysis identified a histidine ammonia-lyase gene (HAL) that was negatively regulated by β-catenin/TCF-dependent transcriptional activity. We leveraged a promoter region of the HAL gene as another transcriptional readout of Wnt signaling. Cells stably expressing both an optimized HAL reporter and the TCF/LEF reporter enabled bidirectional reporter activities in response to Wnt signaling. Increased HAL reporter activity and decreased TCF/LEF reporter activity were observed simultaneously in the cells when β-catenin/TCF7L2 was inhibited. Notably, this method could decrease the number of false positives observed when screening an inhibitor library compared with the conventional TCF/LEF assay. We found that Brefeldin A, a disruptor of the Golgi apparatus, inhibited the Wnt/β-catenin signaling pathway. The utility of our system could be expanded to examine other disease-associated pathways beyond the Wnt/β-catenin signaling pathway.

Abstract 736: Cell lineage-oriented clinical sequencing unveils distinct clonal ontogeny of acute myeloid leukemia with myelodysplasia-related changes

Acute myeloid leukemia (AML) is characterized by unregulated clonal expansion and maturation arrest of myeloid committed progenitors (MP). AML generally represents de novo onset or evolves from preceding myelodysplastic syndrome (MDS), which is defined by refractory cytopenias, clonal hematopoiesis, and/or multi-lineage dysplasia. The WHO classification 2008 includes this entity as “AML with myelodysplasia-related changes (AML-MRC)”, and currently, diagnosis of AML-MRC is based on either previous history of MDS, multi-lineage dysplasia, or MDS-related cytogenetic abnormality. However, AML-MRC often represents de novo onset without these MDS-compatible clinical features. Considering that AML-MRC exhibits rather poor prognosis with refractoriness to conventional chemotherapy against AML, more accurate and objective diagnostic approach is requisite to unveil hidden “MDS signatures” in patients with apparently de novo AML. A certain set of gene mutations is specific and recurrent in MDS. Given the pre-existing “MDS signatures”, the founder gene mutations might be detected in not only blast cells but also neutrophils and/or T cells in AML-MRC. To test this hypothesis, we performed FACS sorting of neutrophils, T cells, and blasts fractions, respectively, followed by mutation screening using targeted deep sequencing, namely, cell lineage-oriented sequencing (CLS). Genomic DNA both from each cell fraction and buccal swab was subjected to screening mutations in 54 genes which are tightly involved in MDS and AML. Pair-end deep sequencing was performed on an Illumina MiSeq, using library prepared by TruSight Myeloid Panel (Illumina, San Diego, CA). Bioinformatic analysis was performed by in-house pipeline. We performed CLS of clinically diagnosed AML-MRC (n=7), suspected AML-MRC (n=2), de novo AML (AML with t(15;17) or AML with inv16, n=4), MDS (RAEB-1 and RAEB-II, n=3), and familial MDS (n=1). As expected, in a familial MDS case, overlapping germline RUNX1 driver mutation was demonstrated in granulocytes, blast cells and T cells, supporting that it would be originated from a hematopoietic stem cell. Notably, in MDS, AML-MRC, and suspected AML-MRC cases with no germ-line mutations, the founder mutations present in neutrophils were also retained in the AML blast cells, irrespective of a history of MDS, suggesting that these are derived from a myeloid progenitor cell. In marked contrast, there were no overlapping driver mutations between blast cell and neutrophil fractions in de novo AML characterized by recurrent chromosomal abnormalities. In summary, CLS revealed that founder mutations are shared by neutrophils and AML blast cells in AML-MRC, but not in de novo AML. Although our data should be validated in a larger cohort of AML cases, CLS is a promising approach to molecular diagnosis of latent AML-MRC which require distinct therapeutic options from de novo AML.

Citation Format: Kazuaki Yokoyama, Nozomi Yusa, Sousuke Nakamura, Mika Ito, Asako Kobayashi, Masayuki Kobayashi, Rika Kasajima, Hiroaki Yui, Eigo Shimizu, Atushi Niida, Rui Yamaguti, Tsuneo Ikenoue, Seiya Imoto, Yoichi Frukawa, Satoru Miyano, Arinobu Tojo. Cell lineage-oriented clinical sequencing unveils distinct clonal ontogeny of acute myeloid leukemia with myelodysplasia-related changes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 736. doi:10.1158/1538-7445.AM2017-736

Abstract 373: Wnt signaling induces anti-apoptotic effect in colorectal cancer cells through the suppression of IFITs

Impaired Wnt signaling pathway plays a crucial role in the development of colorectal cancer through the activation of β-catenin/TCF complex. Although genes up-regulated by Wnt/β-catenin signaling has been well studied, the down-regulated genes are poorly understood. To clarify the comprehensive changes regulated by the signaling in colorectal cancer cells, we explored a global gene expression of CRC cells transfected with β-catenin siRNAs or dominant negative form of TCF7L2 (dnTCF7L2). Consequently, a set of genes that were negatively regulated by β-catenin/TCF were identified. Among the genes, three members of interferon-induced proteins with tetratricopeptide repeats (IFIT) family (IFIT1, IFIT2, and IFIT3) expression were significantly increased by the inhibition of β-catenin/TCF. Comparison of gene expression data from normal colonic mucosa and the tumor tissues showed that the expression of IFIT1 and IFIT2 in the tumors was significantly lower than that in normal tissues. To elucidate the mechanism of IFITs expression regulated by β-catenin/TCF, we performed a reporter assay using plasmid containing 1.2-kb of 5’-flanking region of the IFIT2 gene. As a result, the reporter activity was significantly enhanced by either transduction of β-catenin or dnTCF7L2, suggesting that blockage of β-catenin/TCF stimulated IFITs through the promoter. In addition, we found that overexpression of IFIT2 increased apoptosis and decreased cell proliferation in SW480 and HCT116 cells. These results imply that Wnt signaling may promote anti-apoptotic effect in cancer cells through the suppression of IFIT2. Our findings suggest that analysis of down-regulated genes in response to activated Wnt/β-catenin signaling provides a better understanding of human colorectal carcinogenesis.

Citation Format: Tomoyuki Ohsugi, Kiyoshi Yamaguchi, Chi Zhu, Tsuneo Ikenoue, Yoichi Furukawa. Wnt signaling induces anti-apoptotic effect in colorectal cancer cells through the suppression of IFITs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 373. doi:10.1158/1538-7445.AM2017-373

Genetic alterations in Japanese extrahepatic biliary tract cancer

Biliary tract cancer (BTC) is one of the most devastating types of malignant neoplasms worldwide. However, the mechanisms underlying the development and progression of BTC remain unresolved. BTC includes extrahepatic bile duct carcinoma (EBDC), gallbladder carcinoma (GBC) and ampulla of Vater carcinoma (AVC), named according to the location of the tumor. Although genetic alterations of intrahepatic cholangiocarcinoma have been investigated, those of EBDC, GBC and AVC have not yet been fully understood. The present study analyzed somatic mutations of 50 cancer-associated genes in 27 Japanese BTC cells, including: 11 EBDC, 14 GBC and 2 AVC. Next-generation sequencing using an Ion AmpliSeq Cancer Panel identified a total of 44 somatic mutations across 14 cancer-associated genes. Among the 44 mutations, 42 were judged as pathological mutations. Frequent mutations were identified in tumor protein 53 (TP53) (14/27), SMAD family member 4 (SMAD4) (6/27), phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit α (PIK3CA) (6/27), and Kirsten rat sarcoma (KRAS) (6/27); no significant differences were identified between EBDC and GBC tissues. Notably, the frequency of the PIK3CA mutation was higher when compared with previous reports. This result may suggest that the activation of the PIK3CA-protein kinase B signaling pathway, in addition to the abrogation of p53, SMAD4 and RAS mitogen-activated protein kinase may have a crucial role in the carcinogenesis of Japanese BTC. These findings may be useful for the development of personalized therapies for BTC.

Identification of FERM domain-containing protein 5 as a novel target of β-catenin/TCF7L2 complex

Deregulation of the canonical Wnt signaling pathway plays an important role in human tumorigenesis through the accumulation of β‐catenin and subsequent transactivation of TCF7L2. Although some of the consequences associated with the accumulated β‐catenin have been clarified, the comprehensive effect of activated β‐catenin/TCF7L2 transcriptional complex on tumorigenesis remains to be elucidated. To understand the precise molecular mechanisms underlying colorectal cancer, we searched for genes regulated by the complex in colorectal tumors. We performed expression profile analysis of HCT116 and SW480 colon cancer cells treated with β‐catenin siRNAs, and ChIP‐sequencing using anti‐TCF7L2 antibody. Combination of these data with public microarray data of LS174 cells with a dominant‐negative form of TCF7L2 identified a total of 11 candidate genes. In this paper, we focused on FERM domain‐containing protein 5 (FRMD5), and confirmed that it is regulated by both β‐catenin and TCF7L2. An additional reporter assay disclosed that a region in intron1 transcriptionally regulated the expression of FRMD5. ChIP assay also corroborated that TCF7L2 associates with this region. These data suggested that FRMD5 is a novel direct target of the β‐catenin/TCF7L2 complex.

Pseudomyxoma peritonei of a mature ovarian teratoma caused by mismatch repair deficiency in a patient with Lynch syndrome: a case report

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare disease with an estimated incidence of 1-2 cases per million individuals per year. PMP is characterized by the accumulation of abundant mucinous or gelatinous fluid derived from disseminated tumorous cells. Most of the tumorous cells are originated from rupture of appendiceal neoplasms, but some are from the metastasis of cancer of the colon, ovary, fallopian tube, urachus, colorectum, gallbladder, stomach, pancreas, lung and breast. Although frequent mutations in KRAS and/or GNAS genes have been reported, precise molecular mechanism underlying PMP remains to be elucidated. It is of note that mucinous tumour is one of the frequent histological features of colorectal cancer (CRC) in Lynch syndrome (LS), an autosomal dominantly inherited disease caused by a germline mutation of the DNA mismatch repair (MMR) genes including human mutL homolog 1 (MLH1), human mutS homolog 2 (MSH2), human mutS homolog 6 (MSH6), and postmeiotic segregation increased 2 (PMS2). Therefore, typical LS-associated tumours show mismatch repair instability. Although LS patients are most strongly predisposed to CRC, PMPs from mucinous CRC have not been reported in LS patients.

CASE PRESENTATION

In this report, we report a case of PMP originating from an ovarian teratoma in a LS patient. The patient had surgical treatment of PMP arising from an ovarian teratoma at the age of 38 years, and later developed a transverse colon cancer at the age of 40. The patient's family history fulfilled the Amsterdam criteria, and genetic analysis of the peripheral leukocytes identified a germ line mutation in the MLH1 gene (MLH1 c.1546dupC p.Q516PfsX3). Interestingly, immunohistochemical staining showed that the expression of MLH1 was lost in the colon cancer as well as the ovarian teratoma. Consistent with the loss of MLH1 expression, both tumours showed high microsatellite instability (MSI-H).

CONCLUSION

This case suggested that LS patients may develop various types of tumours including ovarian PMP, and that mismatch repair deficiency may play a role in the development of PMP derived from, at least, a part of ovarian teratomas.

Abstract 658: Elucidation of cellular origin of mouse intrahepatic cholangiocarcinoma induced by liver-specific Kras activation and Pten deletion

Regarding the carcinogenesis of intrahepatic cholangiocarcinoma (ICC), growing interest has been focused on its cellular origin, namely cholangiocytes, progenitor cells, or hepatocytes. We have recently established a novel mouse model of ICC by introducing liver-specific Kras activation and Pten deletion using Alb-Cre mice, in which Cre/loxP-mediated gene recombination was achieved in hepatoblasts and mature hepatocytes. To elucidate the cellular origin of ICC in this mouse model, we utilized hepatocyte or cholangiocyte-lineage specific gene engineering using a tamoxifen (TMX) inducible-Cre/loxP system. The mice carrying Kras activation and Pten deletion by Alb-CreERT2 mice with the TMX treatment at eight weeks of age developed hepatocellular carcinoma and hepatocyte dysplasia within three months. Fluorescence microscopy analyses disclosed that the Cre/loxP-mediated gene recombination was specifically observed in hepatocytes in the mice. In contrast, the mice carrying Kras activation and Pten deletion by Alb-CreERT2 mice at ten days of age induced ICC alone within two months. The gene recombination occurred in cholangiocytes as well as hepatocytes. Expectedly, ICCs were developed in the mice carrying cholangiocyte-specific Kras activation and Pten deletion by K19CreERT mice treated with TMX at 8 weeks after birth. TMX-induced, Cre/loxP-mediated recombination was achieved in epithelia of various organs including intrahepatic bile ducts in these mice. These results suggest that the cellular origin of ICC in mice carrying liver-specific Kras activation and Pten deletion was cholangiocytes but not hepatocytes. This mouse model should be useful for better understanding of human ICC of cholangiocyte-origin and the development of new therapeutic strategies for the disease.

Citation Format: Tsuneo Ikenoue, Yumi Terakado, Kiyoshi Yamaguchi, Yoichi Furukawa. Elucidation of cellular origin of mouse intrahepatic cholangiocarcinoma induced by liver-specific Kras activation and Pten deletion. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 658.

A potent therapeutics for gallbladder cancer by combinatorial inhibition of the MAPK and mTOR signaling networks

BACKGROUND

Gallbladder cancer (GBC) is the most common type of cancer with the worst prognosis among the bile duct cancers. There still remains a clear need for effective mechanism-based novel therapeutic approaches. A crosstalk between mitogen-activated protein kinase (MAPK) and the mammalian target of Rapamycin (mTOR) signaling pathways has been reported in several cancers. We hypothesized that targeting both pathways in combination will be a potent therapeutic for GBC.

METHODS

Expression of phospho-ERK and phospho-S6rp protein were evaluated by immunostaining in surgically resected GBC specimens (n = 30). GBC cell lines and a xenograft model were treated with CI-1040, an inhibitor of MEK (mitogen-activated protein kinase kinase) and RAD001, an inhibitor of mTOR, alone or in combination, and then, we examined the cell proliferation and tumor growth, cell cycle status, and apoptosis.

RESULTS

Analysis of human GBC tissues demonstrated that MAPK and mTOR signaling pathways were frequently coordinately dysregulated in one third of them. The combination therapy inhibited both signaling pathways and subsequently inhibited human GBC cell proliferation in vitro and xenograft tumor growth in vivo. Compared to the single treatment, the combination therapy significantly induced cell cycle arrest and apoptosis with decreased cyclin D1 expression.

CONCLUSIONS

The double blockade of MAPK and mTOR signaling pathways inhibits the signal crosstalk and shows anti-tumor activity, which can be a potent therapeutic for GBC, especially for the patients with hyperactivated signaling of both pathways.

Molecular profiles of high-grade and low-grade pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is a rare disease exhibiting a distinct clinical feature caused by cancerous cells that produce mucinous fluid in the abdominal cavity. PMPs originate most frequently from the appendix and less frequently from the ovary. This disease can range from benign to malignant, and histologically, PMP is classified into two types: disseminated peritoneal adenomucinosis (DPAM) representing the milder phenotype, and peritoneal mucinous adenocarcinomas (PMCA) representing the aggressive phenotype. Although histological classification is clinically useful, the pathogenesis of PMP remains largely unknown. To elucidate the molecular mechanisms underlying PMP, we analyzed 18 PMP tumors comprising 10 DPAMs and 8 PMCAs. DNA was extracted from tumor and matched non-tumorous tissues, and was sequenced using Ion AmpliSeq Cancer Panel containing 50 cancer-related genes. Analysis of the data identified a total of 35 somatic mutations in 10 genes, and all mutations were judged as pathological mutations. Mutations were frequently identified in KRAS (14/18) and GNAS (8/18). Interestingly, TP53 mutations were found in three of the eight PMCAs, but not in the DPAMs. PIK3CA and AKT1 mutations were also identified in two PMCAs, but not in the DPAMs. These results suggested that KRAS and/or GNAS mutations are common genetic features of PMP, and that mutations in TP53 and/or genes related to the PI3K-AKT pathway may render malignant properties to PMP. These findings may be useful for the understanding of tumor characteristics, and facilitate the development of therapeutic strategies.

Inhibition of autophagy exerts anti-colon cancer effects via apoptosis induced by p53 activation and ER stress

BACKGROUND

Although some molecularly targeted drugs for colorectal cancer are used clinically and contribute to a better prognosis, the current median survival of advanced colorectal cancer patients is not sufficient. Autophagy, a basic cell survival mechanism mediated by recycling of cellular amino acids, plays an important role in cancer. Recently, autophagy has been highlighted as a promising new molecular target. The unfolded protein response (UPR) reportedly act in complementary fashion with autophagy in intestinal homeostasis. However, the roles of UPR in colon cancer under autophagic inhibition remain to be elucidated. We aim to clarify the inhibitory effect of autophagy on colon cancer.

METHODS

We crossed K19 (CreERT) and Atg5 (flox/flox) mice to generate Atg5 (flox/flox)/K19 (CreERT) mice. Atg5 (flox/flox)/K19 (CreERT) mice were first treated with azoxymethane/dextran sodium sulfate and then injected with tamoxifen to inhibit autophagy in CK19-positive epithelial cells. To examine the anti-cancer mechanisms of autophagic inhibition, we used colon cancer cell lines harboring different p53 gene statuses, as well as small interfering RNAs (siRNAs) targeting Atg5 and immunoglobulin heavy-chain binding protein (BiP), a chaperone to aid folding of unfolded proteins.

RESULTS

Colon tumors in Atg5 (flox/flox)/K19 (CreERT) mice showed loss of autophagic activity and decreased tumor size (the total tumor diameter was 28.1 mm in the control and 20.7 mm in Atg5 (flox/flox)/K19 (CreERT) mice, p = 0.036). We found that p53 and UPR/endoplasmic reticulum (ER) stress-related proteins, such as cleaved caspase 3, and CAAT/enhancer-binding protein homologous protein, are up-regulated in colon tumors of Atg5 (flox/flox)/K19 (CreERT) mice. Although Atg5 and BiP silencing, respectively, increased apoptosis in p53 wild type cells, Atg5 silencing alone did not show the same effect on apoptosis in p53 mutant cells. However, co-transfection of Atg5 and BiP siRNAs led to increased apoptosis in p53 mutant cells.

CONCLUSIONS

Blocking autophagy has potential in the treatment of colon cancer by inducing apoptosis via p53 and ER stress, and suppressing the UPR pathway is a valid strategy to overcome resistance to autophagic inhibition.

Abstract 4825: Association between genetic profiles and histological classifications of 18 Japanese pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is a rare disease occurring in 1-2 / 1000,000 and shows a distinct clinical feature caused by cancerous cells that produce mucin or gelatinous fluid in the abdominal cavity. Tumor cells are the most frequently originated from appendiceal mucinous cancer, and less frequently from mucinous tumors of the ovary. PMP is histologically classified into two types; disseminated peritoneal adenomucinosis (DPAM) showing milder phenotype, and peritoneal mucinous adenocarcinomas (PMCA) exhibiting more aggressive phenotype. Several molecular studies have shown frequent mutations in the KRAS and GNAS genes. However molecular profiles associated with different histological and/or clinical characteristics remain largely unknown. To elucidate molecular mechanisms underlying PMP, we analyzed 18 Japanese PMP tumors comprising of 10 DPAMs and 8 PMCAs. DNA was extracted from tumor tissues and their matched normal samples, and was subjected to amplicon sequencing using Ion AmpliSeq Cancer Panel v2 (Life Technologies) containing 49 cancer-related genes. In the 18 tumors, we identified a total of 42 somatic mutations (34 missense, 1 deletion, 1 insertion, 2 intron, 1 splice site mutations, and 3 synonymous mutations) in 13 genes. Of the 42 mutations, 35 were judged as pathogenic, and the remaining seven as non-pathogenic by the search of public databases and reports, or by in silico analysis. KRAS and GNAS mutations were found in 14 (77.8%) and 8 (44.4%) tumors, respectively. Interestingly, no mutations were detected in APC or CTNNB1. Notably, TP53 mutation was found in 3 of the 8 PMCAs, but not in the 10 DPAMs. Two of the 8 PMCAs carried mutation in either PIK3CA or AKT1. These data suggest that KRAS and/or GNAS mutations play a vital role in the development of both types of PMP, and that inactivation of Wnt signaling pathway may not be involved in the tumorigenesis. Furthermore, mutations in TP53 and/or genes related to PIK3CA-AKT pathway may be associated with malignant properties of PMCA. Further studies will facilitate the elucidation of molecular mechanism underlying PMP, and contribute to the development of effective therapeutic and preventive strategies to this disease.

Citation Format: Rei Noguchi, Hideaki Yano, Yoshimasa Gohda, Ryuichiro Suda, Toru Igari, Yasunori Ohta, Naohide Yamashita, Kiyoshi Yamaguchi, Yumi Terakado, Tsuneo Ikenoue, Yoichi Furukawa. Association between genetic profiles and histological classifications of 18 Japanese pseudomyxoma peritonei. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4825. doi:10.1158/1538-7445.AM2015-4825

Abstract 4921: Next-generation sequencing as a potential tool in the diagnostics of APC mosaicism in FAP patient

Familial adenomatous polyposis (FAP) is a hereditary disease characterized by the development of multiple adenomatous polyps ranging from hundreds to thousands in the large intestine, and extra-colonic tumors. Patients are predisposed to colorectal cancer that accounts for ∼1% of newly diagnosed colorectal cancer cases. Most of FAP cases result from germline mutations in the tumor suppressor gene APC (adenomatous polyposis coli), but some cases are caused by germline mutations in MUTYH, POLD1, or POLE. The rate of mutation detection depends on the methods used for genetic testing and the genes analyzed in the patients. Although sequence analysis of APC by the Sanger method is routinely performed for genetic testing, there remain cases whose mutations are not detected by the analysis. Next-generation sequencing (NGS) has enabled us to analyze the comprehensive human genome, improving the chance of identifying disease causative variants. In this study, we conducted whole-genome sequencing of a sporadic adenomatous polyposis patient in which we did not find any pathogenic APC mutations by the conventional Sanger sequencing. As a result, whole-genome sequencing and subsequent amplicon-based targeted sequencing identified a mosaic mutation of c.3175G>T, p.E1059X in approximately 12% of his peripheral leucocytes. Additional deep sequencing of his buccal mucosa, hair follicles, non-cancerous mucosa of the stomach and colon disclosed that these tissues harbored the APC mutation at different frequencies. Our data suggest that genetic testing by NGS facilitates the identification of genetic mosaicism responsible for hereditary diseases. NGS will improve genetic diagnosis of hereditary diseases whose mutations have been overlooked by conventional direct sequencing.

Citation Format: Kiyoshi Yamaguchi, Mitsuhiro Komura, Rui Yamaguchi, Seiya Imoto, Eigo Shimizu, Shinichi Kasuya, Tetsuo Shibuya, Seira Hatakeyama, Norihiko Takahashi, Tsuneo Ikenoue, Keisuke Hata, Giichiro Tsurita, Masaru Shinozaki, Yutaka Suzuki, Sumio Sugano, Satoru Miyano, Yoichi Furukawa. Next-generation sequencing as a potential tool in the diagnostics of APC mosaicism in FAP patient. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4921. doi:10.1158/1538-7445.AM2015-4921

Abstract 2301: The generation of colorectal cancer mouse model based on microsatellite instability and the identification of transforming growth factor-beta signal target

Background & Aims:

The transforming growth factor-beta (TGF-beta) signal is a tumor-suppressor pathway that is commonly inactivated in about 90% of microsatellite instability (MSI) colorectal cancer (CRC). However, there was little evidence what gene is regulated by TGF-beta signal in the multistep progression sequence of CRC. The first aim of the present study was to generate a mouse model that is null for Tgfbr2 and Apc in the colon epithelium and forms tumors in the colon. The second aim was to analyze the tumors that arose in the mice model for the purpose to identify the gene regulated by TGF-beta signal.

Method & Result:

Previously we have described the generation of the ‘CDX2P-G19Cre;Apcflox/flox mice’ (called Apc KO mice) which is randomly null for Apc in the colonic epithelium. By mating Tgfbr2flox/flox mice with Apcflox/flox and CDX2P9.5-G19Cre mice, we have finally generated a mouse model ‘CDX2P-G19Cre;Apcflox/flox;Tgfbr2flox/flox mice’ (called Apc+Tgfbr2 KO mice) which is null for Apc and Tgfbr2. In these model, the tumors with well differentiated adenocarcinoma arose mainly in proximal colon and most of mice died at 4 weeks age due to tumor bleeding. Therefore the mice were harvested at 3 weeks age to evaluate the development of colon tumors. Total RNAs of only cancerous tissue areas were extracted from frozen samples by the laser capture microdissection method. We compared gene expression profiles of these mice's tumors (n = 3, respectively) with Mouse Exon 1.0 ST Array (Affymetrix). Gene X expression of Apc+Tgfbr2 KO mice tumors was most highly upregurated by 9.25-fold compared with Apc KO mice (p = 0.045). The array data was validated by quantitative PCR. For human CRC samples, mutations of repetitive mononucleotide tracts in the coding regions of TGFBR2 were identified by direct sequencing. By immunohistochemical analysis, the expression of X was classified according to the percentage of stained cancer cells. The expression was considered to be ‘positive’ if ≥30% of cancer cells were stained. An analysis demonstrated that 11 (100%) of 11 mutated TGFBR2 cases were positive for X, whereas 10 (66.7%) of 15 wild type TGFBR2 cases were positive (P = 0.033), indicating that high expression of X was correlated with TGFBR2 mutation in human CRCs samples. Additionally, the cell proliferation assay revealed that silencing of X led to a significant reduction in CRC cell proliferation. Conversely, forced expression of X enhanced CRC cell proliferation in vitro.

Conclusion:

We have generated an in vivo model system that Apc and Tgfbr2 were inactivated only in the colonic epithelium and tumors with well differentiated adenocarcinoma arose mainly in proximal colon. The analysis of this model revealed that Gene X is regulated by a TGF-beta signal and likely promotes cell proliferation in CRC.

Citation Format: Masashi Miguchi, Takao Hinoi, Manabu Shimomura, Tomohiro Adachi, Yasufumi Saito, Hiroaki Niitsu, Masatoshi Kochi, Yusuke Sotomaru, Hideaki Ijichi, Tsuneo Ikenoue, Kunitoshi Shigeyasu, Kohji Tanakaya, Kazuhiro Sentani, Naohide Oue, Wataru Yasui, Hideki Ohdan. The generation of colorectal cancer mouse model based on microsatellite instability and the identification of transforming growth factor-beta signal target. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2301. doi:10.1158/1538-7445.AM2015-2301

Attenuated familial adenomatous polyposis with desmoids caused by an APC mutation

We present here a case of attenuated familial adenomatous polyposis (AFAP) with a family history of desmoids and thyroid tumors. This patient had no colonic polyps but did have multiple desmoids. Genetic analysis identified a 4-bp deletion in codon 2644 (c.7932_7935delTTAT: p.Tyr2645LysfsX14) of the adenomatous polyposis coli (APC) gene. In cases with limited numbers of colonic polyps and desmoids, AFAP may be caused by a mutation in the 3′ region of APC.

Detection of APC mosaicism by next-generation sequencing in an FAP patient

Familial adenomatous polyposis (FAP) of the colon is characterized by multiple polyps in the intestine and extra-colonic manifestations. Most FAP cases are caused by a germline mutation in the tumor-suppressor gene APC, but some cases of adenomatous polyposis result from germline mutations in MUTYH, POLD1 or POLE. Although sequence analysis of APC by the Sanger method is routinely performed for genetic testing, there remain cases whose mutations are not detected by the analysis. Next-generation sequencing has enabled us to analyze the comprehensive human genome, improving the chance of identifying disease causative variants. In this study, we conducted whole-genome sequencing of a sporadic FAP patient in which we did not find any pathogenic APC mutations by the conventional Sanger sequencing. Whole-genome sequencing and subsequent deep sequencing identified a mosaic mutation of c.3175G>T, p.E1059X in ~12% of his peripheral leukocytes. Additional deep sequencing of his buccal mucosa, hair follicles, non-cancerous mucosa of the stomach and colon disclosed that these tissues harbored the APC mutation at different frequencies. Our data implied that genetic analysis by next-generation sequencing is an effective strategy to identify genetic mosaicism in hereditary diseases.

Characterization of a new small bowel adenocarcinoma cell line and screening of anti-cancer drug against small bowel adenocarcinoma

Small bowel adenocarcinoma (SBA) is a rare, aggressive malignancy with a poor prognosis, and the mechanisms of carcinogenesis in SBA remain unclear. Our aims were to investigate the molecular mechanisms underlying SBA and to identify treatments by establishing and characterizing an SBA cell line and performing anti-cancer drug screening. SIAC1 cells, established from jejunal SBA, showed epithelial characteristics and formed organoids in 3D culture. SIAC1 cells had a heterozygous β-catenin deletion mutation, resulting in a stable β-catenin protein with enhanced Wnt/β-catenin activity. SIAC1 cells lacked MLH1 and MSH6 expression, and target genes such as TGFBR2 and ACVR2 showed frameshift mutations. Among 10 clinical SBA samples, 2 (20%) had interstitial deletions in β-catenin, expression of mismatch repair protein was aberrant in 4 (40%), and heterozygous frameshift mutations of three target genes were found in all 10 samples. On screening assay using 140 compounds, eribulin significantly inhibited SIAC1 cell growth both in vitro and in vivo by inhibition of the Wnt/β-catenin pathway via enhanced degradation of β-catenin. In conclusion, we established an SBA cell line with molecular characteristics similar to those of clinical SBA samples, including β-catenin deletion and mismatch repair protein deficiency, that will be useful for SBA research. Eribulin might be a candidate for SBA treatment due to its inhibitory effect on Wnt/β-catenin signaling.

Abstract B10: Epidermal growth factor receptor inhibitor prolongs survival in pancreatic cancer by blocking gemcitabine-induced mitogen-activated protein kinase signal

Pancreatic ductal adenocarcinoma (PDAC) is the most deadly cancer worldwide. Although many regimens have been tried against PDAC, an epidermal growth factor receptor (EGFR) inhibitor erlotinib in combination with gemcitabine is the only molecular target drug superior to gemcitabine alone. However, the mechanism by which PDAC with extremely frequent KRAS-mutation benefits from EGFR inhibition remains largely unknown. In this study, we evaluated the efficacy of erlotinib in combination with gemcitabine using a murine PDAC model with transforming growth factor-beta receptor II knockout plus Kras activation and investigated the mode of action.

The mice were treated using the following drug doses and treatment schedules; erlotinib was administered from 3 weeks of age and gemcitabine was administered from 4 weeks of age. We isolated PDAC cells from the murine PDAC tissues. Effects of erlotinib on the proliferation and intracellular signaling of the murine PDAC cells or human PDAC cell lines were examined in vitro. We sacrificed the mice at 7 weeks of age, and excised the pancreatic tissues and processed for western blot analysis and immunohistochemistry. We evaluated the expression of EGFR ligands by real-time PCR and the heterodimer formation of EGFR with ErbB2 by immunoprecipitaiton after incubation with gemcitabine in vitro. We assessed whether the effect of gemcitabine on EGFR/ErbB2 activation is secondary to mitogen activated protein kinase (MAPK) signal activation after incubation with or without MEK inhibitor and gemcitabine by western blot analysis and real-time PCR.

Gemcitabine + erlotinib inhibited PDAC progression and significantly prolonged the survival of the PDAC mice compared to gemcitabine alone. Gemcitabine or erlotinib also inhibited in vitro PDAC cell proliferation. Interestingly, Gemcitabine induced MAPK signaling, which was dramatically inhibited by adding erlotinib, even in the Kras-mutant PDAC cells. The suggested mechanisms were that gemcitabine induced EGFR ligand expression and also ErbB2 activation by increasing heterodimer formation with EGFR and maintaining high ErbB2 protein level in PDAC cells. We observed that the gemcitabine-induced MAPK signaling activation was in part due to induction of Egfr ligands(Egf, Tgf-a, Amphiregulin) expression by real-time PCR and ELISA. Using a phospho-RTK antibody array, we also observed that Gem induced Erbb2 activation in PDAC cells, and validated by western blot analysis, real-time PCR, and immunohistochemistry. Erlotinib inhibited the ErbB2 activation, partly by inhibiting heterodimer formation with EGFR and also decreasing ErbB2 protein expression in PDAC cells.

We observed that gemcitabine-induced EGFR ligands up-regulation and EGFR/ErbB2 activation require intact MAPK signaling and these are secondary effects of MAPK signal activation and that gemcitabine induced the activation irrespective of KRAS status and gemcitabine sensitivity.

This model helps us to evaluate an efficacy of new drugs and to investigate mechanisms of the mode of action and chemoresistance. This study provides clinical insights into potent therapeutic strategies for this difficult cancer.

Citation Format: Koji Miyabayashi, Hideaki Ijichi, Ryota Takahashi, Dai Mohri, Keisuke Yamamoto, Yoshinari Asaoka, Tsuneo Ikenoue, Keisuke Tateishi, Harold L. Moses, Kazuhiko Koike. Epidermal growth factor receptor inhibitor prolongs survival in pancreatic cancer by blocking gemcitabine-induced mitogen-activated protein kinase signal. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B10. doi: 10.1158/1557-3125.RASONC14-B10

Loss of histone demethylase KDM6B enhances aggressiveness of pancreatic cancer through downregulation of C/EBPα

Genetic mutations in pancreatic ductal adenocarcinoma (PDAC) with critical roles have been well examined. The recent discovery of alterations in genes encoding histone modifiers suggests their possible roles in the complexity of cancer development. We previously reported loss of heterozygosity of the KDM6B gene, which encodes a histone demethylase for trimethylated histone H3 lysine 27, a repressive chromatin mark, in PDAC cells. In this study, we demonstrated that loss of KDM6B enhanced aggressiveness of PDAC cells. KDM6B has been regarded as a tumor suppressor that mediates oncogenic KRAS-induced senescence. Consistently, KDM6B was highly expressed in pancreatic precancerous lesions (pancreatic intraepithelial neoplasms); then, the expression decreased as the malignant grade progressed. We found that knockdown of KDM6B in PDAC cells promoted tumor sphere formation and increased peritoneal dissemination and liver metastasis in vivo. Microarray and chromatin immunoprecipitation analysis implicated CEBPA for aggressiveness induced by KDM6B knockdown. CEBPA knockdown recapitulated the phenotypic change of PDAC cells after KDM6B knockdown, which was reversed by forced expression of C/EBPα. Moreover, similar protein expression patterns of KDM6B and C/EBPα in human PDAC emphasized their functional correlation. Notably, pharmacological inhibition of the H3K27 methylase EZH2 in PDAC cells inhibited tumor sphere formation along with the upregulation of CEBPA expression, and this effect was impaired in KDM6B knockdown cells, highlighting the role for KDM6B in the activation of CEBPA. Together, our results propose a significant role for the KDM6B-C/EBPα axis in the PDAC phenotype.

Identification of two Wnt-responsive elements in the intron of RING finger protein 43 (RNF43) gene

RING finger protein 43 (RNF43), an E3-type ubiquitin ligase, is frequently up-regulated in human colorectal cancer. It has been shown that expression of RNF43 is regulated by the Wnt-signaling pathway. However the regulatory region(s) for its transcriptional activation has not been clarified. In this study, we have shown for the first time that RNF43 is a direct target of TCF4/β-catenin complex, and that its expression is regulated by a regulatory region containing two Wnt-responsive elements (WREs) in intron2. A reporter gene assay revealed that nucleotide substitutions in the WREs decreased the reporter activity in colon cancer cells, suggesting that both WREs are involved in the transcriptional activation. Knockdown of β-catenin by siRNA suppressed the reporter activity. In addition, ChIP assay showed that both elements associate with TCF4/β-catenin complex in colon cancer cells. These data indicate that expression of RNF43 is regulated by the canonical Wnt/β-catenin pathway through binding of the WREs with TCF4/β-catenin complex. These findings should be useful for the understanding of the regulatory mechanism of RNF43 and may contribute to the clarification of signaling pathways regulated by RNF43.

Overexpression of cohesion establishment factor DSCC1 through E2F in colorectal cancer

Ctf18-replication factor C complex including Dscc1 (DNA replication and sister chromatid cohesion 1) is implicated in sister chromatid cohesion, DNA replication, and genome stability in S. cerevisiae and C. elegans. We previously performed gene expression profiling in primary colorectal cancer cells in order to identify novel molecular targets for the treatment of colorectal cancer. A feature of the cancer-associated transcriptional signature revealed from this effort is the elevated expression of the proto-oncogene DSCC1. Here, we have interrogated the molecular basis for deviant expression of human DSCC1 in colorectal cancer and its ability to promote survival of cancer cells. Quantitative PCR and immunohistochemical analyses corroborated that the expression level of DSCC1 is elevated in 60-70% of colorectal tumors compared to their matched noncancerous colonic mucosa. An in silico evaluation of the presumptive DSCC1 promoter region for consensus DNA transcriptional regulatory elements revealed a potential role for the E2F family of DNA-binding proteins in controlling DSCC1 expression. RNAi-mediated reduction of E2F1 reduced expression of DSCC1 in colorectal cancer cells. Gain- and loss-of-function experiments demonstrated that DSCC1 is involved in the viability of cancer cells in response to genotoxic stimuli. We reveal that E2F-dependent expression of DSCC1 confers anti-apoptotic properties in colorectal cancer cells, and that its suppression may be a useful option for the treatment of colorectal cancer.

Associations of intrauterine growth restriction with placental pathological factors, maternal factors and fetal factors; clinicopathological findings of 257 Japanese cases

Intrauterine growth restriction (IUGR) is the leading cause of fetal mortality and morbidity. As an etiology, each of placental findings, maternal factors and fetal factors has been reported to be associated with IUGR, although a comprehensive approach to examine all of these parameters as a cause of IUGR has not been reported. In the present study, therefore, we comprehensively examined the placental findings and maternal and fetal factors in the cases of IUGR (n=257, mean maternal age, 30 years; gestational weeks, 34 weeks) and normal growth pregnancies (n=258, mean maternal age, 30 years; gestational weeks, 33 weeks), and determined risk factors for IUGR. The prevalence of pregnancy hypertension (PHT) (19% vs. 8%, P<0.01), smoking habit (3% vs. 0.7%, P<0.05) and fetal anomaly (3.5% vs. 0.8%, P<0.05) were higher in IUGR cases than normal growth pregnancies. Pathologically, the prevalence of infarction (33% vs. 14%, P<0.05), fetal vessel thrombosis (22% vs. 6%, P<0.001) and chronic villitis (11% vs. 3%, P<0.001) were higher in IUGR cases than those in normal growth pregnancies. A multivariable regression analysis revealed that maternal factors (PHT), fetal factors (anomaly), and placental findings (infarction, fetal vessel thrombosis, and chronic villitis) are independently associated with increased risk of IUGR (all P<0.01).

Temporal changes in PTEN and mTORC2 regulation of hematopoietic stem cell self-renewal and leukemia suppression

Pten deletion from adult mouse hematopoietic cells activates the PI3-kinase pathway, inducing hematopoietic stem cell (HSC) proliferation, HSC depletion, and leukemogenesis. Pten is also mutated in human leukemias, but rarely in early childhood leukemias. We hypothesized that this reflects developmental changes in PI3-kinase pathway regulation. Here we show that Rictor deletion prevents leukemogenesis and HSC depletion after Pten deletion in adult mice, implicating mTORC2 activation in these processes. However, Rictor deletion had little effect on the function of normal HSCs. Moreover, Pten deletion from neonatal HSCs did not activate the PI3-kinase pathway or promote HSC proliferation, HSC depletion, or leukemogenesis. Pten is therefore required in adult, but not neonatal, HSCs to negatively regulate mTORC2 signaling. This demonstrates that some critical tumor suppressor mechanisms in adult cells are not required by neonatal cells. Developmental changes in key signaling pathways therefore confer temporal changes upon stem cell self-renewal and tumor suppressor mechanisms.

Histone demethylase KDM4C regulates sphere formation by mediating the cross talk between Wnt and Notch pathways in colonic cancer cells

Alterations in genes coding for histone modifiers are found in human cancers, suggesting that histone modification is involved in malignant features of neoplastic cells. This study showed that a histone demethylase KDM4C is significant for colonosphere formation by mediating the cross talk between oncogenic pathways through a feed-forward mechanism. The expression of KDM4C gene was increased in spheres from colorectal cancer (CRC) cells and the knockdown (KD) of KDM4C eliminated colonosphere formation. We found that the KD of β-catenin, an important oncogenic factor in CRC, resulted in not only decreased sphere formation but also impaired upregulation of KDM4C gene in spheres. β-Catenin bound to the KDM4C promoter, suggesting that KDM4C is involved in the sphere-forming ability downstream of β-catenin in CRC cells. Microarray analysis identified the JAG1 gene that codes for a notch ligand Jagged1 responsible for sphere formation as a target of KDM4C. KDM4C KD decreased the expression of JAG1 gene, and the downregulation of JAG1 gene recapitulated the impaired colonosphere formation. JAG1 is also a target of β-catenin, and chromatin immunoprecipitation analysis showed the binding of β-catenin and KDM4C onto the JAG1 promoter during colonosphere formation. Importantly, KDM4C KD ruined the recruitment of β-catenin onto the JAG1 promoter independently of the H3-K9 methylation status and blunted JAG1 expression during sphere formation. These data indicate that KDM4C maintains the sphere-forming capacity in CRCs by mediating the β-catenin-dependent transcription of JAG1 in a feed-forward manner.

Erlotinib prolongs survival in pancreatic cancer by blocking gemcitabine-induced MAPK signals

Pancreatic ductal adenocarcinoma (PDAC) is one of the most deadly cancers worldwide. Although many regimens have been used for PDAC treatment, the combination of the EGF receptor (EGFR) inhibitor erlotinib with gemcitabine has been the only molecular-targeted drug tested so far that has been superior to gemcitabine alone. The mechanism underlying this effective combinational regimen remains unknown. Here, we show that the combination is superior to gemcitabine alone in blocking progression and prolonging survival in a murine model of PDAC (Kras activation with Tgfbr2 knockout). We found that gemcitabine induced mitogen-activated protein kinase signaling, which was dramatically inhibited by erlotinib even in the Kras-activated PDAC cells in the mouse model. Mechanistic investigations suggested that gemcitabine induces EGFR ligand expression and ERBB2 activation by increasing heterodimer formation with EGFR, thereby maintaining high levels of ERBB2 protein in PDAC cells. Overall, our findings suggest a significant role of ERBB in PDAC treatment.