CPT2 downregulation adapts HCC to lipid-rich environment and promotes carcinogenesis via acylcarnitine accumulation in obesity

OBJECTIVE

Metabolic reprogramming of tumour cells that allows for adaptation to their local environment is a hallmark of cancer. Interestingly, obesity-driven and non-alcoholic steatohepatitis (NASH)-driven hepatocellular carcinoma (HCC) mouse models commonly exhibit strong steatosis in tumour cells as seen in human steatohepatitic HCC (SH-HCC), which may reflect a characteristic metabolic alteration.

DESIGN

Non-tumour and HCC tissues obtained from diethylnitrosamine-injected mice fed either a normal or a high-fat diet (HFD) were subjected to comprehensive metabolome analysis, and the significance of obesity-mediated metabolic alteration in hepatocarcinogenesis was evaluated.

RESULTS

The extensive accumulation of acylcarnitine species was seen in HCC tissues and in the serum of HFD-fed mice. A similar increase was found in the serum of patients with NASH-HCC. The accumulation of acylcarnitine could be attributed to the downregulation of carnitine palmitoyltransferase 2 (CPT2), which was also seen in human SH-HCC. CPT2 downregulation induced the suppression of fatty acid β-oxidation, which would account for the steatotic changes in HCC. CPT2 knockdown in HCC cells resulted in their resistance to lipotoxicity by inhibiting the Src-mediated JNK activation. Additionally, oleoylcarnitine enhanced sphere formation by HCC cells via STAT3 activation, suggesting that acylcarnitine accumulation was a surrogate marker of CPT2 downregulation and directly contributed to hepatocarcinogenesis. HFD feeding and carnitine supplementation synergistically enhanced HCC development accompanied by acylcarnitine accumulation in vivo.

CONCLUSION

In obesity-driven and NASH-driven HCC, metabolic reprogramming mediated by the downregulation of CPT2 enables HCC cells to escape lipotoxicity and promotes hepatocarcinogenesis.

Stromal remodeling by the BET bromodomain inhibitor JQ1 suppresses the progression of human pancreatic cancer

Inhibitors of bromodomain and extraterminal domain (BET) proteins, a family of chromatin reader proteins, have therapeutic efficacy against various malignancies. However, the detailed mechanisms underlying the anti-tumor effects in distinct tumor types remain elusive. Here, we show a novel antitumor mechanism of BET inhibition in pancreatic ductal adenocarcinoma (PDAC). We found that JQ1, a BET inhibitor, decreased desmoplastic stroma, a hallmark of PDAC, and suppressed the growth of patient-derived tumor xenografts (PDX) of PDACs. In vivo antitumor effects of JQ1 were not always associated with the JQ1 sensitivity of respective PDAC cells, and were rather dependent on the suppression of tumor-promoting activity in cancer-associated fibroblasts (CAFs). JQ1 inhibited Hedgehog and TGF-β pathways as potent regulators of CAF activation and suppressed the expression of α-SMA, extracellular matrix, cytokines, and growth factors in human primary CAFs. Consistently, conditioned media (CM) from CAFs promoted the proliferation of PDAC cells along with the activation of ERK, AKT, and STAT3 pathways, though these effects were suppressed when CM from JQ1-treated CAFs was used. Mechanistically, chromatin immunoprecipitation experiments revealed that JQ1 reduced TGF-β–dependent gene expression by disrupting the recruitment of the transcriptional machinery containing BET proteins. Finally, combination therapy with gemcitabine plus JQ1 showed greater efficacy than gemcitabine monotherapy against PDAC in vivo. Thus, our results reveal BET proteins as the critical regulators of CAF-activation and also provide evidence that stromal remodeling by epigenetic modulators can be a novel therapeutic option for PDAC.

Improvement of luminescence properties of rubidium vanadate, RbVO3, phosphors by erbium doping in the crystal lattice

The thermal quenching effect of RbVO₃ phosphor was effectively improved by Er³⁺ doping into the lattice, as a result, the emission intensity of the phosphor was successfully enhanced.

Abstract B66: BET inhibition remodels tumor stroma and suppresses progression of human pancreatic cancer

Background and Aims: Pancreatic ductal adenocarcinoma (PDAC) is well characterized by dense fibrotic stroma with abundant cancer-associated fibroblasts (CAFs). As CAFs are activated during tumorigenesis and acquire tumor-promoting properties, activated CAFs have been implicated in PDAC progression; however, the precise mechanisms of their activation remain largely unknown. The bromodomain and extraterminal (BET) domain proteins are epigenetic reader proteins that recognize acetylated amino acid residues on histone tails and facilitate gene transcription. Recent studies have demonstrated therapeutic efficacy of BET inhibitors on various cancers including PDAC, mainly through suppression of c-myc transcription; however, how BET inhibitors suppress PDAC growth and their effects on CAFs remains largely unknown. Using patient-derived tumor xenografts (PDX) and primary CAFs, we investigated the therapeutic efficacy and dissected the underlying mechanisms of a BET inhibitor, JQ1, on human PDAC and CAFs.

Methods: We established PDX lines and primary CAFs from surgically resected human PDAC specimen. For in vivo analyses, mice bearing subcutaneous tumor were treated with vehicle or JQ1. For in vitro analyses, patient-derived PDAC cells and CAFs were treated with vehicle or JQ1 and analyzed separately. To explore the pro-tumorigenic role of secretion from CAFs, PDAC cells were cultured with conditioned medium (CM) that was collected from DMSO- or JQ1- treated CAFs. Chromatin immunoprecipitation (ChIP) assay was performed to assess the binding of transcription factors and histone modifications which are associated with altered gene expression in CAFs by JQ1 treatment.

Results: In vivo experiments revealed that volumes and weights of subcutaneous PDX tumors were significantly smaller in JQ1-treated mice than vehicle-treated mice. Unexpectedly, however, JQ1 exerted only minimal effects to the proliferation of PDAC cells that were isolated from PDX tumors and cultured in vitro, suggesting the involvement of cell-extrinsic mechanisms in the JQ1-mediated suppression of tumor growth in vivo. Of note, histopathological analysis of PDX tumors revealed that JQ1 treatment dramatically ameliorated desmoplastic change, with reduction in extracellular matrix (ECM) deposition and α-SMA expressing CAFs. As α-SMA expression and ECM production is a hallmark of activated CAFs, we hypothesized that JQ1 might inactivate CAFs, thereby reducing their tumor-promoting properties. To test this hypothesis, qPCR was performed to analyze gene expression in primary CAFs cultured in vitro and also in stromal cells in PDX tumors in vivo. As expectedly, JQ1 suppressed the expression of genes implicated in the properties of activated CAF, including ECM, cytokines and growth factors both in vitro and in vivo. Furthermore, when PDAC cells were cultured with CM from DMSO–treated CAFs, proliferation of PDAC cells were promoted along with activation of MAPK, AKT, and STAT3 pathways, which was abrogated when cultured with CM from JQ1-treated CAFs. Consistently, immunoblotting and immunohistochemistry of PDX tumors demonstrated that JQ1 reduced phosphorylation of ERK, AKT, and STAT3 in PDAC cells in vivo. Mechanistically, we found that JQ1 suppressed hedgehog and TGF-β/SMAD3 pathways, both of which play central roles in CAF activation, through disruption of BRD4 recruitment to the promoter regions of their target genes.

Conclusions: BET proteins are critical regulators of CAF-activation in PDAC. Inactivation of CAFs by BET inhibition offers a novel therapeutic approach for PDAC.

Citation Format: Keisuke Yamamoto, Keisuke Tateishi, Yotaro Kudo, Mayumi Hoshikawa, Mariko Tanaka, Takuma Nakatsuka, Hiroaki Fujiwara, Koji Miyabayashi, Ryota Takahashi, Yasuo Tanaka, Hideaki Ijichi, Yousuke Nakai, Hiroyuki Isayama, Yasuyuki Morishita, Taku Aoki, Yoshihiro Sakamoto, Kiyoshi Hasegawa, Norihiro Kokudo, Masashi Fukayama, Kazuhiko Koike.{Authors}. BET inhibition remodels tumor stroma and suppresses progression of human pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B66.

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.

Analysis of individual differences in radiosensitivity using genome editing

Current standards for radiological protection of the public have been uniformly established. However, individual differences in radiosensitivity are suggested to exist in human populations, which could be caused by nucleotide variants of DNA repair genes. In order to verify if such genetic variants are responsible for individual differences in radiosensitivity, they could be introduced into cultured human cells for evaluation. This strategy would make it possible to analyse the effect of candidate nucleotide variants on individual radiosensitivity, independent of the diverse genetic background. However, efficient gene targeting in cultured human cells is difficult due to the low frequency of homologous recombination (HR) repair. The development of artificial nucleases has enabled efficient HR-mediated genome editing to be performed in cultured human cells. A novel genome editing strategy, 'transcription activator-like effector nuclease (TALEN)-mediated two-step single base pair editing', has been developed, and this was used to introduce a nucleotide variant associated with a chromosomal instability syndrome bi-allelically into cultured human cells to demonstrate that it is the causative mutation. It is proposed that this editing technique will be useful to investigate individual radiosensitivity.

Abstract A40: Emergence of CD47- high expression cells confers enhanced tumorigenicity upon KDM6B suppression in pancreatic cancer

The role of genetic mutations in the pathogenesis of pancreatic ductal adenocarcinoma (PDAC) is well established. However, it is still unclear if epigenetic aberrations contribute to PDAC progression.

We previously reported a novel role for the H3K27 demethylase KDM6B/JMJD3 in regulating PDAC progression (Carcinogenesis 2014;35(11):2404-14). KDM6B was downregulated in high grade PDACs and knockdown (KD) of KDM6B in PDAC cells increased the tumorigenicity and enhanced the aggressive phenotypes of these cells in vivo. Furthermore, CCAAT enhancer binding protein alpha gene (CEBPA) was identified as a direct target of KDM6B, and reduced KDM6B- C/EBPα axis was resulted in increased aggressiveness in PDAC cells.

To dissect further the pathological effects caused by loss of KDM6B- C/EBPα function in PDAC cells, we tried to identify a surrogate molecular marker of the cells lacking of KDM6B- function. For the purpose, we used a cDNA microarray to compare the expression profiles of KDM6B- KD and control BxPC3 PDAC cells.

906 genes were upregulated and 639 downregulated in KDM6B- KD BxPC3 cells compared to the control cells. We focused on 58 genes encoding cell-surface molecules that were upregulated in KDM6B- KD BxPC3 cells and validated the expression of 9 surface marker candidates, including 3 that have already been reported to be expressed on PDAC tumor-initiating cells, namely, CD24, CD44, and CD133. Only CD47 was significantly upregulated in the KDM6B- KD BxPC3 cells as confirmed by both quantitative RT-PCR and flow cytometric analysis. CD47 was also upregulated in other PDAC cell lines following KDM6B knockdown.

It has recently been reported that CD47 is upregulated in various malignancies and that an increase in CD47 expression is correlated with a poor prognosis. In line with the previous reports, CD47high cells formed about 4-fold more spheres than non-CD47high cells. The close relationship between CD47 expression and the sphere-forming ability was supported by the finding that CD47low cells formed even fewer spheres. To confirm these results in vivo, the sorted CD47high and non-CD47high cells were subcutaneously xenotransplanted into nude mice. All CD47high cells formed tumors more efficiently than the unfractionated KDM6B- KD cells, while the tumor-forming rate of non-CD47high cells was comparable to that of the Ctrl cells. In addition, when the cells were injected into the spleens of nude mice, CD47high cells demonstrated higher liver metastatic potential than the non-CD47high population.

These data suggested that the increased tumor-initiating potential of KDM6B- KD cells was attributable to this induced CD47high population. Consistently, the expression of KDM6B and C/EBPα inversely correlated with CD47 expression and tumor grade in human PDAC tumors. Collectively, our data provides a link between epigenetic change and PDAC progression, thus offering a novel strategy to target PDAC aggressiveness by intervening in the dynamics of epigenetic process.

Citation Format: Keisuke Yamamoto, Keisuke Tateishi, Yotaro Kudo, Koji Miyabayashi, Ryota Takahashi, Takuma Nakatsuka, Hiroaki Fujiwara, Yousuke Nakai, Yasuo Tanaka, Hideaki Ijichi, Hiroyuki Isayama, Kazuhiko Koike. Emergence of CD47- high expression cells confers enhanced tumorigenicity upon KDM6B suppression in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Chromatin and Epigenetics in Cancer; Sep 24-27, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2016;76(2 Suppl):Abstract nr A40.

Electroencephalogram measurement from the hairy part of the scalp using polymer-based dry microneedle electrodes

This paper reports a successful electroencephalogram (EEG) measurement from the hairy part of the scalp using a polymer-based dry microneedle electrode. The electrode consists of 25 pillars, each of which has a sharp microneedle on the top. Hairs are collected into the gaps of the pillars and the microneedles can reach the scalp surface. Since the microneedles can penetrate through the stratum corneum, no conductive gel is necessary to acquire high quality EEG. We experimentally investigated the pillar diameters in EEG measurement from the occipital region with hairs. The fabricated electrodes successfully measured EEG without any skin preparation or conductive gel.

Sarcopenia, intramuscular fat deposition, and visceral adiposity independently predict the outcomes of hepatocellular carcinoma

BACKGROUND & AIMS

Obesity defined by body mass index (BMI) significantly increases the risk of hepatocellular carcinoma (HCC). In contrast, not only obesity but also underweight is associated with poor prognosis in patients with HCC. Differences in body composition rather than BMI were suggested to be true determinants of prognosis. However, this hypothesis has not been demonstrated conclusively.

METHODS

We measured skeletal muscle index (SMI), mean muscle attenuation (MA), visceral adipose tissue index, subcutaneous adipose tissue index, and visceral to subcutaneous adipose tissue area ratios (VSR) via computed tomography in a large-scale retrospective cohort of 1257 patients with different stages of HCC, and comprehensively analyzed the impact of body composition on the prognoses.

RESULTS

Among five body composition components, low SMI (called sarcopenia), low MA (called intramuscular fat [IMF] deposition), and high VSR (called visceral adiposity) were significantly associated with mortality, independently of cancer stage or Child-Pugh class. A multivariate analysis revealed that sarcopenia (hazard ratio [HR], 1.52; 95% confidence interval [CI], 1.18-1.96; p=0.001), IMF deposition (HR, 1.34; 95% CI, 1.05-1.71; p=0.020), and visceral adiposity (HR, 1.35; 95% CI, 1.09-1.66; p=0.005) but not BMI were significant predictors of survival. The prevalence of poor prognostic body composition components was significantly higher in underweight and obese patients than in normal weight patients.

CONCLUSIONS

Sarcopenia, IMF deposition, and visceral adiposity independently predict mortality in patients with HCC. Body composition rather than BMI is a major determinant of prognosis in patients with HCC.

Electroencephalogram measurement from the hairy part of the scalp using polymer-based dry microneedle electrodes

This paper reports a successful electroencephalogram (EEG) measurement from the hairy part of the scalp using a polymer-based dry microneedle electrode. The electrode consists of 25 pillars, each of which has a sharp microneedle on the top. Hairs are collected into the gaps of the pillars and the microneedles can reach the scalp surface. Since the microneedles can penetrate through the stratum corneum, no conductive gel is necessary to acquire high quality EEG. We experimentally investigated the pillar diameters in EEG measurement from the occipital region with hairs. The fabricated electrodes successfully measured EEG without any skin preparation or conductive gel.

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.

Evaluation of the non-functional tooth contact in patients with temporomandibular disorders by using newly developed electronic system

The aims of this study were to introduce a novel electronic system for reliable evaluation of the non-functional tooth contact in patients with temporomandibular disorders (TMDs) and investigate the possible associations between the non-functional tooth contact and some characteristics of the patients with TMD. We designed and installed a software program to send emails regarding the non-functional tooth contact to the subjects' preregistered cellular phones at intervals of 20 ± 9 min daily for 10 consecutive days. Twelve patients with TMD and 12 gender- and age-matched healthy subjects responded via emails to one of 3 choices: no tooth contact, tooth contact during oral functions or tooth contact not associated with oral functions. The influence of subjective stress, anxiety, depression, personality and daily activities on tooth contact was then assessed. The frequency of the non-functional tooth contact was significantly higher in the patients with TMD than in the healthy subjects (35·0% vs. 9·6%, P < 0·001), while no significant group difference was found for the frequency of functional tooth contact, the stress, anxiety, depression and personality.

High ubiquitous mitochondrial creatine kinase expression in hepatocellular carcinoma denotes a poor prognosis with highly malignant potential

We previously reported the increased serum mitochondrial creatine kinase (MtCK) activity in patients with hepatocellular carcinoma (HCC), mostly due to the increase in ubiquitous MtCK (uMtCK), and high uMtCK mRNA expression in HCC cell lines. We explored the mechanism(s) and the relevance of high uMtCK expression in HCC. In hepatitis C virus core gene transgenic mice, known to lose mitochondrial integrity in liver and subsequently develop HCC, uMtCK mRNA and protein levels were increased in HCC tissues but not in non-tumorous liver tissues. Transient overexpression of ankyrin repeat and suppressor of cytokine signaling box protein 9 (ASB9) reduced uMtCK protein levels in HCC cells, suggesting that increased uMtCK levels in HCC cells may be caused by increased gene expression and decreased protein degradation due to reduced ASB9 expression. The reduction of uMtCK expression by siRNA led to increased cell death, and reduced proliferation, migration and invasion in HCC cell lines. Then, consecutive 105 HCC patients, who underwent radiofrequency ablation with curative intent, were enrolled to analyze their prognosis. The patients with serum MtCK activity >19.4 U/L prior to the treatment had significantly shorter survival time than those with serum MtCK activity ≤ 19.4 U/L, where higher serum MtCK activity was retained as an independent risk for HCC-related death on multivariate analysis. In conclusion, high uMtCK expression in HCC may be caused by hepatocarcinogenesis per se but not by loss of mitochondrial integrity, of which ASB9 could be a negative regulator, and associated with highly malignant potential to suggest a poor prognosis.

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.

Effects of free fatty acids on human salivary gland epithelial cells

Obesity and type 2 diabetes (T2D) are characterized by decreased insulin sensitivity and higher concentrations of free fatty acids (FFAs) in plasma. Among FFAs, saturated fatty acids (SFAs), such as palmitate, have been proposed to promote inflammatory responses. Primary Sjögren's syndrome (SS) is an autoimmune disease characterized by inflammatory mononuclear cell infiltration and destruction of epithelial cells in the salivary and lacrimal glands. IL-6 production and α-fodrin degradation are increased in salivary gland epithelial cells of patients with primary SS. Although previous studies have shown a link between SS and either dyslipidemia or T2D, little is known about the clinical significance of FFAs in primary SS. Here we report that SFAs, but not unsaturated fatty acids, induced IL-6 production via NF-κB and p38 MAPK activation in human salivary gland epithelial cells. Moreover, palmitate induced apoptosis and α-fodrin degradation by caspase-3 activation. Unlike salivary gland epithelial cells, induction of IL-6 production and the degradation of α-fodrin in response to palmitate were undetectable in squamous carcinoma cells and keratinocytes. Taken together, SFAs induced IL-6 production and α-fodrin degradation in salivary gland epithelial cells, implicating a potential link between the pathogenesis of primary SS and SFAs level in plasma.

Abstract 2982: Reduced expression of histone demethylase KDM6B promotes pancreatic cancer progression through downregulation of C/EBPα

It has become increasingly clear that epigenetic aberrations are involved in the pathogenesis of various cancer. In pancreatic cancer, however, the implication of epigenetic alteration remains elusive. In our screening analysis for epigenetic regulators that affect the phenotype of pancreatic cancer, we identified KDM6B/JMJD3, a H3K27me3 demethylase, as a candidate gene. KDM6B/JMJD3 activates INK4a/ARF locus during oncogene-induced senescence, thus it is supposed to suppress tumorigenesis; however, its role in established cancer remains unclear. In this study, our aim is to clarify the role of KDM6B in the progression of pancreatic cancer and to understand the underlying mechanisms.

We generated pancreatic cancer cell lines stably knocked down for KDM6B by shRNAs. Matrigel invasion assay, soft agar colony formation assay, tumor sphere formation assay revealed increased invasiveness, anchorage-independent growth and tumorigenicity of KDM6B-knockdown (KD) cells, respectively. To confirm these phenotypic changes in vivo, these cells were xenotransplanted into nude mice. In intrasplenic injection experiments, mice injected with KDM6B-KD cells showed significantly shorter survival. When tumor cells were orthotopically implanted into the pancreas, mice injected with KDM6B-KD cells developed massive peritoneal dissemination with hemorrhagic ascites, while no mice injected with control cells developed peritoneal dissemination.

To identify genes responsible for the phenotypic change, we performed cDNA microarray analysis. Gene set enrichment analysis (GSEA) revealed significant expression change of C/EBP-target genes upon KDM6B ablation. Among the C/EBP transcription family members, the downregulation of CEBPA, a putative tumor suppressor gene, was confirmed in KDM6B-KD cells. ChIP assay showed specific increase of H3K27me3 levels in the upstream region of CEBPA gene after KDM6B depletion. Notably, enforced expression of CEBPA rescued the increased invasiveness and tumorigenicity of KDM6B-KD cells, indicating that reduction of KDM6B expression in pancreatic cancer enhances its aggressiveness through downregulation of C/EBPα.

Notably, we identified a cell surface protein reflective of KDM6B expression and tumorigenic potential of pancreatic cancer cells; flow cytometry analysis revealed that cells with higher expression of this molecule expressed lower KDM6B and showed increased tumorigenicity. Immunohistochemical analysis of pancreatic cancer specimen showed a positive correlation between this marker expression and tumor grade, while KDM6B and C/EBPα expression was seldom observed in high grade tumor.

Collectively, these data suggest a role for the KDM6B-CEBPA axis in the regulation of tumorigenictiy of pancreatic cancer cells, providing a link between epigenetic change and pancreatic cancer progression.

Citation Format: Keisuke Yamamoto, Keisuke Tateishi, Yotaro Kudo, Miwako Kakiuchi, Shinzo Yamamoto, Koji Miyabayashi, Yoshinari Asaoka, Hideaki Ijichi, Masao Omata, Kazuhiko Koike. Reduced expression of histone demethylase KDM6B promotes pancreatic cancer progression through downregulation of C/EBPα. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2982. doi:10.1158/1538-7445.AM2013-2982

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.