Intestine-specific Homeobox Research Articles

Maternal genetics and diet modulate vitamin A homeostasis of the offspring and affect the susceptibility to obesity in adulthood in mice.

Perinatal nutrition exerts a profound influence on adult metabolic health. This study aimed to investigate whether increased maternal vitamin A (VA) supply can lead to beneficial metabolic phenotypes in the offspring. The researchers utilized mice deficient in the intestine-specific homeobox (ISX) transcription factor, which exhibits increased intestinal VA retinoid production from dietary β-carotene (BC). ISX-deficient dams were fed a VA-sufficient or a BC-enriched diet during the last week of gestation and the whole lactation period. Total retinol levels in milk and weanling livers were 2- to 2.5-fold higher in the offspring of BC-fed dams (BC offspring), indicating increased VA supplies during late gestation and lactation. The corresponding VA-sufficient and BC offspring (males and females) were compared at weaning and adulthood after being fed either a standard or high-fat diet (HFD) with regular VA content for 13 weeks from weaning. HFD-induced increases in adiposity metrics, such as fat depot mass and adipocyte diameter, were more pronounced in males than females and were attenuated or suppressed in the BC offspring. Notably, the BC offspring were protected from HFD-induced increases in circulating triacylglycerol levels and hepatic steatosis. These protective effects were associated with reduced food efficiency, enhanced capacity for thermogenesis and mitochondrial oxidative metabolism in adipose tissues, and increased adipocyte hyperplasia rather than hypertrophy in the BC offspring. In conclusion, maternal VA nutrition influenced by genetics may confer metabolic benefits to the offspring, with mild increases in late gestation and lactation protecting against obesity and metabolic dysregulation in adulthood.NEW & NOTEWORTHY A genetic mouse model, deficient in intestine-specific homeobox (ISX) transcription factor, is used to show that a mildly increased maternal vitamin A supply from β-carotene feeding during late gestation and lactation programs energy and lipid metabolism in tissues and protects the offspring from diet-induced hypertrophic obesity and hepatic steatosis. This knowledge may have implications for human populations where polymorphisms in ISX and ISX target genes involved in vitamin A homeostasis are prevalent.

Abstract 5330: Intestine-specific homeobox edits macrophage polarization in the disease microenvironment by activating inflammasome activity

Abstract Inflammasome activity has a pivotal role in the innate immune system, highlighting its importance in the development of various inflammatory diseases, including cancers. However, the specific impact of inflammasome-produced cytokines from tumor cells on disease progression remains uncertain. In this study, we show that the expression levels of inflammasome-related genes (NLRP1 and NLRP3), combined with levels of the intestine-specific homeobox (ISX), significantly correlate with factors like lesion count, disease stage, and lymph vascular invasion. Tumor cells enhance the secretion of key cytokines such as IL-1β and IL-18, exacerbating disease progression via the ISX-TWIST1 complex. In terms of mechanism, transcriptomic analysis and molecular evidence reveal that ISX interacts with the basic helix-loop-helix (bHLH) domain of TWIST1 through its homeobox domain. This interaction forms a transcriptional complex that activates inflammasomes by directly binding to the conserved sequence "-GGDWYR-" in promoter regions of several NF-κB and inflammasome-related genes (NFKBs, RELs, NLRP1, NLRP3, NEK7, AIM2, and ASC). Elevated levels of IL-18, induced by active inflammasomes, lead to the shift of M0 macrophages into the M2-like phenotype within the hepatic microenvironment. In mice with liver-specific ISX mutations, inflammasome-related genes and activities were eliminated, stopping disease progression in an acute hepatic disease model. These findings underscore the critical role of the ISX-TWIST1 complex in liver disease and tumor progression on both mechanistic and clinical levels. They also offer new insights for potential preventive and therapeutic targets in liver disease. Citation Format: Li-Ting Wang, Shih-Hsien Hsu. Intestine-specific homeobox edits macrophage polarization in the disease microenvironment by activating inflammasome activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5330.

Lycopene Accumulation in Transgenic Mice Lacking One or Both Carotenoid Cleaving Enzymes

Backgroundβ-carotene oxygenase 1 (BCO1) and β-carotene oxygenase 2 (BCO2) are responsible for the cleavage of carotenoids in mammals. Objective: The goals of this study were to (1) establish the relative contribution of each enzyme on lycopene accumulation in mice and (2) examine the role of lycopene on gene expression in the gut of wild type (WT) mice. MethodsWe utilized male and female WT, Bco1-/-, Bco2-/-, and Bco1-/-Bco2-/- double knockout (DKO) mice. We gavaged the mice with either 1 mg of lycopene resuspended in cottonseed oil or vehicle as a control group daily for 2 wk. In a second study, we evaluated the effect of dietary vitamin A on lycopene absorption and intestinal gene expression by RT-PCR. We also quantified lycopene concentration isomer distribution by high performance liquid chromatography. ResultsOf the 11 tissues measured, the liver accounted for 94 to 98% of the lycopene content across genotypes. We did not observe sex differences between genotypes, although hepatic lycopene levels in Bco1-/- mice were approximately half in comparison to the other genotypes; Bco1-/- verses Bco2-/- (P < 0.0001), DKO mice (P < 0.001), WT (ns). Analyses of mitochondrial lycopene content revealed a 3- to 5-fold enrichment compared with total hepatic content (P < 0.05) in all genotypes and sexes. In our second study, WT mice fed a vitamin A-deficient diet (VAD) accumulated greater amounts of lycopene in the liver than those fed a vitamin A-sufficient diet (VAS) (P < 0.01). These changes were accompanied by an upregulation of the vitamin A-responsive transcription factor intestine specific homeobox (ISX) in mice fed VAD + lycopene and VAS + lycopene diets compared with VAD control-fed mice (P < 0.05). ConclusionsOur data suggest that BCO2 is the primary lycopene cleavage enzyme in mice. Lycopene concentration was enriched in the mitochondria of hepatocytes independently of genotype, and lycopene stimulated vitamin A signaling in WT mice.

Phosphorylation of intestine-specific homeobox by ERK1 modulates oncogenic activity and sorafenib resistance.

Nuclear translocation regulated by phosphorylation is a key step in providing activated mitogen-activated protein kinases (MAPKs) access to their nuclear targets; however, the mechanisms linking MAPK-induced nuclear translocation and target gene expression mediating oncologic activity remain obscure. Here, we show that the MAPK extracellular signal-regulated kinase (ERK) 1, but not ERK2, phosphorylated intestine-specific homeobox (ISX), leading to its nuclear translocation and downstream oncogenic signaling. Mechanistically, ERK1 phosphorylated serine 183 of ISX, facilitating its nuclear translocation and downstream target gene expression. In contrast, dominant-negative ERK1 expression in hepatoma cells inhibited the nuclear translocation of ISX and the expression of downstream genes involved in cell proliferation, malignant transformation, and epithelial-mesenchymal transition in vitro and in vivo. An activating mutation in ISX (S183D) exhibited a constitutive nuclear localization and resistance to sorafenib. Additionally, in 576 paired clinical hepatocellular carcinoma (HCC) samples and adjacent normal tissues, ERK1 and ISX were co-expressed in a tumor-specific manner at mRNA and protein levels, while their mRNA levels showed significant correlation with survival duration, tumor size, number, and stage. These results highlight the significance of ERK1/ISX signaling in HCC progression and its potential as a prognostic and therapeutic target in HCC.

Impact of bromodomain‐containing protein 4 (BRD4) and intestine‐specific homeobox (ISX) expression on the prognosis of patients with hepatocellular carcinoma' for better clarity

Epigenetic regulation is important for cancer tumor metastasis and progression, including lung and liver cancer. However, the mechanism of epigenetic regulation in liver cancer leaves much to be discussed. According to a previous study, p300/CBP‐associated factor (PCAF) mediated epithelial–mesenchymal transition (EMT) and promotes cancer metastasis by recruiting intestine‐specific homeobox (ISX) and bromodomain‐containing protein 4 (BRD4) in lung cancer. To figure out whether the three genes are also expressed in patients with hepatocellular carcinoma (HCC) or not, and their correlation with patients’ outcome, BRD4, PCAF, and ISX messenger RNA (mRNA) expression levels in 377 patients with HCC were investigated using quantitative polymerase chain reaction and confocal fluorescence imaging. The correlation of the gene expression (PCAF, ISX, and BRD4) in liver cancer is also being investigated. Here, we show that the mRNA expression of PCAF, BRD4, and ISX in 377 paired specimens from patients with HCC, and the adjacent normal tissues exhibited a tumor‐specific expression pattern, highly correlated with disease pathogenesis, patient survival time, progression stage, and poor prognosis. The results show that ISX and BRD4 can potentially be a target for improving the survival rate.

Genetic and epigenetic regulation of the non-muscle myosin light chain kinase isoform by lung inflammatory factors and mechanical stress.

Rationale: The myosin light chain kinase gene, MYLK, encodes three proteins via unique promoters, including the non-muscle isoform of myosin light chain kinase (nmMLCK), a cytoskeletal protein centrally involved in regulation of vascular integrity. As MYLK coding SNPs are associated with severe inflammatory disorders (asthma, acute respiratory distress syndrome (ARDS)), we explored clinically relevant inflammatory stimuli and promoter SNPs in nmMLCK promoter regulation. Methods: Full-length or serially deleted MYLK luciferase reporter promoter activities were measured in human lung endothelial cells (ECs). SNP-containing non-muscle MYLK (nmMYLK) DNA fragments were generated and nmMYLK promoter binding by transcription factors (TFs) detected by protein–DNA electrophoretic mobility shift assay (EMSA). Promoter demethylation was evaluated by 5-aza-2′-deoxycytidine (5-Aza). A preclinical mouse model of lipopolysaccharide (LPS)-induced acute lung injury (ALI) was utilized for nmMLCK validation. Results: Lung EC levels of nmMLCK were significantly increased in LPS-challenged mice and LPS, tumor necrosis factor-α (TNF-α), 18% cyclic stretch (CS) and 5-Aza each significantly up-regulated EC nmMYLK promoter activities. EC exposure to FG-4592, a prolyl hydroxylase inhibitor that increases hypoxia-inducible factor (HIF) expression, increased nmMYLK promoter activity, confirmed by HIF1α/HIF2α silencing. nmMYLK promoter deletion studies identified distal inhibitory and proximal enhancing promoter regions as well as mechanical stretch-, LPS- and TNFα-inducible regions. Insertion of ARDS-associated SNPs (rs2700408, rs11714297) significantly increased nmMYLK promoter activity via increased transcription binding (glial cells missing homolog 1 (GCM1) and intestine-specific homeobox (ISX), respectively). Finally, the MYLK rs78755744 SNP (−261G/A), residing within a nmMYLK CpG island, significantly attenuated 5-Aza-induced promoter activity. Conclusion: These findings indicate nmMYLK transcriptional regulation by clinically relevant inflammatory factors and ARDS-associated nmMYLK promoter variants are consistent with nmMLCK as a therapeutic target in severe inflammatory disorders.

Overlapping Vitamin A Interventions with Provitamin A Carotenoids and Preformed Vitamin A Cause Excessive Liver Retinol Stores in Male Mongolian Gerbils

Vitamin A (VA) deficiency is a public health problem in some countries. Fortification, supplementation, and increased provitamin A consumption through biofortification are efficacious, but monitoring is needed due to risk of excessive VA intake when interventions overlap. Two studies in 28-36-d-old male Mongolian gerbils simulated exposure to multiple VA interventions to determine the effects of provitamin A carotenoid consumption from biofortified maize and carrots and preformed VA fortificant on status. Study 1 was a 2×2×2 factorial design (n=85) with high-β-carotene maize, orange carrots, and VA fortification at 50% estimated gerbil needs, compared with white maize and white carrot controls. Study 2 was a 2×3 factorial design (n=66) evaluating orange carrot and VA consumption through fortification at 100% and 200% estimated needs. Both studies utilized 2-wk VA depletion, baseline evaluation, 9-wk treatments, and liver VA stores by HPLC. Intestinal scavenger receptor class B member 1 (Scarb1), β-carotene 15,15'-dioxygenase (Bco1), β-carotene 9',10'-oxygenase (Bco2), intestine-specific homeobox (Isx), and cytochrome P450 26A1 isoform α1 (Cyp26a1) expression was analyzed by qRT-PCR in study 2. In study 1, liver VA concentrations were significantly higher in orange carrot (0.69±0.12 μmol/g) and orange maize groups (0.52±0.21 μmol/g) compared with baseline (0.23±0.069 μmol/g) and controls. Liver VA concentrations from VA fortificant alone (0.11±0.053 μmol/g) did not differ from negative control. In study 2, orange carrot significantly enhanced liver VA concentrations (0.85±0.24 μmol/g) relative to baseline (0.43±0.14 μmol/g), but VA fortificant alone (0.42±0.21 μmol/g) did not. Intestinal Scarb1 and Bco1 were negatively correlated with increasing liver VA concentrations (P <0.01, r2=0.25-0.27). Serum retinol concentrations did not differ. Biofortified carrots and maize without fortification prevented VA deficiency in gerbils. During adequate provitamin A dietary intake, preformed VA intake resulted in excessive liver stores in gerbils, despite downregulation of carotenoid absorption and cleavage gene expression.

PCAF‐mediated acetylation of ISX recruits BRD4 to promote epithelial‐mesenchymal transition

Epigenetic regulation is important for cancer progression; however, the underlying mechanisms, particularly those involving protein acetylation, remain to be fully understood. Here, we show that p300/CBP‐associated factor (PCAF)‐dependent acetylation of the transcription factor intestine‐specific homeobox (ISX) regulates epithelial–mesenchymal transition (EMT) and promotes cancer metastasis. Mechanistically, PCAF acetylation of ISX at lysine 69 promotes the interaction with acetylated bromodomain‐containing protein 4 (BRD4) at lysine 332 in tumor cells, and the translocation of the resulting complex into the nucleus. There, it binds to promoters of EMT genes, where acetylation of histone 3 at lysines 9, 14, and 18 initiates chromatin remodeling and subsequent transcriptional activation. Ectopic ISX expression enhances EMT marker expression, including TWIST1, Snail1, and VEGF, induces cancer metastasis, but suppresses E‐cadherin expression. In lung cancer, ectopic expression of PCAF–ISX–BRD4 axis components correlates with clinical metastatic features and poor prognosis. These results suggest that the PCAF–ISX–BRD4 axis mediates EMT signaling and regulates tumor initiation and metastasis.

Abstract 1108: Intestine-specific homeobox recruits p300/CBP-associated factor and bromodomain-containing protein 4 to promote epithelial-mesenchymal transition

Abstract The epithelial-mesenchymal transition is an important process in the cancer progression, but its occurrence and the regulatory mechanism are not fully understood. Intestine specific homeobox acted both as a proto-oncogene and upstream regulator of EMT markers, by which modulates tumorigenic initiation and progression in lung cancer cells. ISX acetylated by PCAF recruits bromodomain-containing protein 4, to initiate chromatin remodeling, and up-regulated EMT downstream regulators in tumors cells. Ectopic expression of ISX was shown to enhance TWIST1, Snail1 expression by recruiting BRD4 to enhance Pol II dependent transcription, lead in to remodeling of the tumor microenvironment. In NSCLC carcinoma, increased ISX expression was noted correlating with distinct clinical metastatic features and poor prognosis. These results suggest that theISX-BRD4 axis mediates EMT signaling and exerts significant regulatory effects on tumor initiation and metastasis. Citation Format: Li-Ting Wang, Shyh-Shin Chiou, Shih-Hsien Hsu. Intestine-specific homeobox recruits p300/CBP-associated factor and bromodomain-containing protein 4 to promote epithelial-mesenchymal transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1108.

Characterization of Novel Murine and Human PDAC Cell Models: Identifying the Role of Intestine Specific Homeobox Gene ISX in Hypoxia and Disease Progression

Therapy failure and metastasis-associated mortality are stumbling blocks in the management of PDAC in patients. Failure of therapy is associated to intense hypoxic conditions of tumors. To develop effective therapies, a complete understanding of hypoxia-associated changes in genetic landscape of tumors during disease progression is needed. Because artificially immortalized cell lines do not rightly represent the disease progression, studying genetics of tumors in spontaneous models is warranted. In the current study, we generated a spectrum of spontaneous human (UM-PDC1; UM-PDC2) and murine (HI-PanL, HI-PancI, HI-PanM) models representing localized, invasive, and metastatic PDAC from a patient and transgenic mice (K-rasG12D/Pdxcre/Ink4a/p16-/). These spontaneous models grow vigorously under hypoxia and exhibit activated K-ras signaling, progressive loss of PTEN, and tumorigenicity in vivo. Whereas UM-PDC1 form localized tumors, the UM-PDC2 metastasize to lungs in mice. In an order of progression, these models exhibit genomic instability marked by gross chromosomal rearrangements, centrosome-number variations, Aurora-kinase/H2AX colocalization, loss of primary cilia, and α-tubulin acetylation. The RNA sequencing of hypoxic models followed by qRT-PCR validation and gene-set enrichment identified Intestine-Specific Homeobox factor (ISX)–driven molecular pathway as an indicator PDAC aggressivness. TCGA-PAAD clinical data analysis showed high ISX expression correlation to poor survival of PDAC patients, particularly women. The functional studies showed ISX as a regulator of i) invasiveness and migratory potential and ii) VEGF, MMP2, and NFκB activation in PDAC cells. We suggest that ISX is a potential druggable target and newly developed spontaneous cell models are valuable tools for studying mechanism and testing therapies for PDAC.

PO-318 Intestine-specific homeobox gene ISX integrates IL6 signaling, tryptophan catabolism, and immune suppression

IntroductionThe intestine-specific homeobox transcription factor intestine specific homeobox (ISX) is an IL6-inducible protooncogene implicated in the development of hepatocellular carcinoma, but its mechanistic contributions to this process are undefined.Material and methodsIn this study, we provide evidence that ISX mediates a positive feedback loop integrating inflammation, tryptophan catabolism,and immune suppression.Results and discussionsWe found that ISX-mediated IL6-induced expression of the tryptophan catabolic enzymes Indoleamine2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenasein hepatocellular carcinoma cells, resulting in an ISX dependent increase in the tryptophan catabolite kynurenine and its receptor aryl hydrocarbon receptor (AHR). Activation of this kynurenine/AHR signaling axis acted through a positive feedback mechanism to increase ISX expression and enhance cellular proliferation and tumorigenic potential. RNAi-mediated attenuation of ISX or AHR reversed these effects. In an IDO1-dependent manner, ectopic expression of ISX induced expression of genes encoding the critical immune modulators CD86 (B7-2)and programmed death ligand-1 (PD-L1), through which ISX conferred a significant suppressive effect on the CD8+ T-cell response. In hepatocellular carcinoma specimens, expression of IDO1, kynurenine, AHR, and PD-L1 correlated negatively with survival.ConclusionOverall, our results identified a feed-forward mechanism of immune suppression in hepatocellular carcinoma organized by ISX, which involves kynurenine-AHR signaling and PD-L1, offering insights into immune escape by hepatocellular carcinoma, which may improve its therapeutic management

PO-354 Disrupting the acetylation of ISX-BRD4 by p300/CBP-associated factor (PCAF) suppresses tumour metastasis

IntroductionThe epithelial–mesenchymal transition (EMT) is an important process in the progression of cancer, but its occurrence and the regulatory mechanism are not fully understood.Material and methodsIn this study, Intestine specific homeobox (ISX) acted both as an proto-oncogene and upstream regulator of EMT markers, by which modulates tumorigenic initiation and progression in lung cancer cells.Results and discussionsMechanistically, ISX acetylated by p300/CBP- associated factor (PCAF) recruits chromatin reader, bromodomain- containing protein 4 (BRD4), to initiate chromatin remodelling, and upregulated EMT downstream regulators in tumours cells. Ectopic expression of ISX were shown to enhance TWIST1, Snail1, vascular endothelial growth factor (VEGF) expression by recruiting BRD4 to enhance Pol II-dependent transcription, leading to remodelling of the tumour microenvironment. Neutralising VEGF by avastin effectively abrogates metastasis induced by the ISX-BRD4 complex. In NSCLC carcinoma samples, significantly increased ISX expression was noted, correlating with distinct clinical metastatic features and poor prognosis.ConclusionThese results suggest that the ISX-BRD4 axis mediates EMT signalling and exerts significant regulatory effects on tumour initiation and metastasis.

Transcription factor ISX mediates the cross talk between diet and immunity

The intestinal epithelium is a major site for the conversion of dietary β-carotene to retinaldehyde by the enzyme BCO1. The majority of retinaldehyde is further metabolized to retinol (vitamin A), esterified and packaged into triacylglycerol-rich chylomicrons for bodily distribution. Some serve on-site for the synthesis of retinoic acid, a hormone-like compound, which exerts pleiotropic and dominant effects on gastrointestinal immunity. We report here that the intestine-specific homeobox protein ISX is critical to control the metabolic flow of β-carotene through this important branching point of vitamin A metabolism. This transcription factor represses Bco1 gene expression in response to retinoic acid signaling. In ISX-deficient mice, uncontrolled Bco1 gene expression led to increased retinoid production in the intestine. Systemically, this production resulted in highly elevated hepatic retinoid stores. In the intestine, it increased the expression of retinoic acid-inducible target genes such as Aldh1a2, Dhrs3, and Ccr9 The β-carotene-inducible disruption of retinoid homeostasis affected gut-homing and differentiation of lymphocytes and displayed morphologically in large lymphoid follicles along the intestine. Furthermore, it was associated with an infiltration of the pancreas by gut-derived lymphocytes that manifested as a pancreatic insulitis with β-islet cell destruction and systemic glucose intolerance. Thus, our study identifies an important molecular interlink between diet and immunity and indicates that vitamin A homeostasis must be tightly controlled by ISX to maintain immunity and tolerance at the intestinal barrier.

In vitro and in vivo imaging and tracking of intestinal organoids from human induced pluripotent stem cells.

Human intestinal organoids (hIOs) derived from human pluripotent stem cells (hPSCs) have immense potential as a source of intestines. Therefore, an efficient system is needed for visualizing the stage of intestinal differentiation and further identifying hIOs derived from hPSCs. Here, 2 fluorescent biosensors were developed based on human induced pluripotent stem cell (hiPSC) lines that stably expressed fluorescent reporters driven by intestine-specific gene promoters Krüppel-like factor 5 monomeric Cherry (KLF5mCherry) and intestine-specific homeobox enhanced green fluorescence protein (ISXeGFP). Then hIOs were efficiently induced from those transgenic hiPSC lines in which mCherry- or eGFP-expressing cells, which appeared during differentiation, could be identified in intact living cells in real time. Reporter gene expression had no adverse effects on differentiation into hIOs and proliferation. Using our reporter system to screen for hIO differentiation factors, we identified DMH1 as an efficient substitute for Noggin. Transplanted hIOs under the kidney capsule were tracked with fluorescence imaging (FLI) and confirmed histologically. After orthotopic transplantation, the localization of the hIOs in the small intestine could be accurately visualized using FLI. Our study establishes a selective system for monitoring the in vitro differentiation and for tracking the in vivo localization of hIOs and contributes to further improvement of cell-based therapies and preclinical screenings in the intestinal field.-Jung, K. B., Lee, H., Son, Y. S., Lee, J. H., Cho, H.-S., Lee, M.-O., Oh, J.-H., Lee, J., Kim, S., Jung, C.-R., Kim, J., Son, M.-Y. In vitro and in vivo imaging and tracking of intestinal organoids from human induced pluripotent stem cells.

Intestine-Specific Homeobox Gene ISX Integrates IL6 Signaling, Tryptophan Catabolism, and Immune Suppression.

The intestine-specific homeobox transcription factor intestine-specific homeobox (ISX) is an IL6-inducible proto-oncogene implicated in the development of hepatocellular carcinoma, but its mechanistic contributions to this process are undefined. In this study, we provide evidence that ISX mediates a positive feedback loop integrating inflammation, tryptophan catabolism, and immune suppression. We found that ISX-mediated IL6-induced expression of the tryptophan catabolic enzymes Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase in hepatocellular carcinoma cells, resulting in an ISX-dependent increase in the tryptophan catabolite kynurenine and its receptor aryl hydrocarbon receptor (AHR). Activation of this kynurenine/AHR signaling axis acted through a positive feedback mechanism to increase ISX expression and enhance cellular proliferation and tumorigenic potential. RNAi-mediated attenuation of ISX or AHR reversed these effects. In an IDO1-dependent manner, ectopic expression of ISX induced expression of genes encoding the critical immune modulators CD86 (B7-2) and programmed death ligand-1 (PD-L1), through which ISX conferred a significant suppressive effect on the CD8+ T-cell response. In hepatocellular carcinoma specimens, expression of IDO1, kynurenine, AHR, and PD-L1 correlated negatively with survival. Overall, our results identified a feed-forward mechanism of immune suppression in hepatocellular carcinoma organized by ISX, which involves kynurenine-AHR signaling and PD-L1, offering insights into immune escape by hepatocellular carcinoma, which may improve its therapeutic management. Cancer Res; 77(15); 4065-77. ©2017 AACR.

Aryl hydrocarbon receptor promotes hepatocellular carcinoma tumorigenesis by targeting intestine‐specific homeobox expression

The aryl hydrocarbon receptor (AHR), a major chemical sensor, is thought to play a role in various biological contexts, including cell cycle regulation and tumorigenesis. However, its regulatory mechanisms remain unclear. We propose herein a novel mechanism through which AHR promotes tumorigenesis by targeting expression of the oncogene intestine-specific homeobox (ISX) in hepatocellular carcinoma (HCC). Compared to paired tumor-adjacent tissues and non-HCC tumors, HCCs exhibited an increased and hierarchical pattern of AHR expression. Patients exhibiting high AHR expression had a significantly shorter survival duration, compared to those with low and medium expression. Functionally, AHR was found to target the newly discovered proto-oncogene, ISX, resulting in the increased expression of this gene and its downstream targets, CCND1 and E2F1. Ablation of AHR or ISX in hepatoma cells suppressed cell growth, whereas overexpression promoted cell proliferation and led to enhanced tumorigenic activity in vitro and in vivo. These results provide evidence to support a critical role for the AHR/ISX axis in HCC tumorigenesis and suggest its potential utility as a new therapeutic and prognostic target for HCC.

191 - Intestine-Specific Homeobox (ISX) is an Important Regulator for Gastric Carcinogenesis with Potential for Molecular Target

191 - Intestine-Specific Homeobox (ISX) is an Important Regulator for Gastric Carcinogenesis with Potential for Molecular Target

Common SNP rs6564851 in the BCO1 Gene Affects the Circulating Levels of β-Carotene and the Daily Intake of Carotenoids in Healthy Japanese Women.

The circulating levels of β-carotene are modulated not only by sex, but also by autosomal gene variations and fruit intake. The aim of this study was to investigate the interactions between β-carotene metabolism-related gene single nucleotide polymorphisms (SNPs; genetic factors) and nutrient intake (environmental factors) relating to their effects on circulating β-carotene. The serum concentrations of β-carotene and the habitual food intake of 92 healthy Japanese adults were examined. All subjects were genotyped for three common SNPs: rs6564851 in the β-carotene 15,15′-oxygenase 1 (BCO1) gene, rs2278986 in the scavenger receptor class B member 1 (SCARB1) gene and rs362090 in the intestine-specific homeobox (ISX) gene. Univariate analysis revealed that the circulating β-carotene levels were significantly higher in rs6564851 GG homozygotes (p = 0.003). Additionally, the daily intake of β-cryptoxanthin was positively associated with the circulating β-carotene levels in female GG homozygotes of rs6564851 (p = 0.023), and the daily intake of α- and β-carotenes, and β-cryptoxanthin was significantly lower in female rs6564851 T allele carries than in female GG homozygotes (p = 0.009, 0.008, 0.009, respectively). The present study apparently indicates that higher circulating β-carotene levels in female rs6564851 GG homozygotes depend on carotenoid intake.

Abstract 2275: Intestine-specific homeobox (ISX) upregulates E2F1 expression and related oncogenic activities in HCC

Abstract Intestine-specific homeobox (ISX), a newly identified proto-oncogene, is known to regulate cell proliferation and drive hepatocellular carcinoma (HCC) formation; however, the underlying mechanisms linking gene expression and tumor formation remain obscure. In this study, we showed that ISX transcriptionally activates E2F1 expression and related oncogenic activity by directly binding to its promoter region. Mechanistically, forced ISX expression upregulated the expression and nucleus translocation of the E2F1-DP1 complex phosphorylated by the cyclin D1-CDKs complex, which promoted oncogenic activities of ISX-E2F1 axis in hepatoma cells. In addition, co-expression of both ISX and E2F1 significantly promoted cell proliferation and anti-apoptotic signals instead of apoptosis and autophagy induced by the tumor suppressors p53 and RB1. In contrast, short hairpin RNA-mediated attenuation of ISX and E2F1, respectively, in hepatoma cells decreased cell proliferation and malignant transformation in vitro and in vivo. The mRNA expression was compared in 238 paired specimens of HCC and adjacent normal tissues, and E2F1, as an expression of ISX, pathologically exhibited a tumor-specific expression pattern and was highly correlated with ISX expression, patient survival time, progression stage, and poor prognosis. Taken together, our results highlight that E2F1 is an important downstream gene of ISX in hepatoma progression. Citation Format: Shen-Nien Wang, Li-Ting Wang, Shih-Hsien Hsu. Intestine-specific homeobox (ISX) upregulates E2F1 expression and related oncogenic activities in HCC. [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 2275.

Intestine-specific homeobox (ISX) upregulates E2F1 expression and related oncogenic activities in HCC.

Intestine-specific homeobox (ISX), a newly identified proto-oncogene, is involved in cell proliferation and progression of hepatocellular carcinoma (HCC). However, the underlying mechanisms linking gene expression and tumor formation remain unclear. In this study, we found that ISX transcriptionally activated E2F transcription factor 1 (E2F1) and associated oncogenic activity by directly binding to the E2 site of its promoter. Forced expression of ISX increased the expression of and phosphorylated the serine residue at position 332 of E2F1, which may be translocated into the nucleus to form the E2F1–DP-1 complex, suggesting that the promotion of oncogenic activities of the ISX–E2F1 axis plays a critical role in hepatoma cells. Coexpression of ISX and E2F1 significantly promoted p53 and RB-mediated cell proliferation and anti-apoptosis, and repressed apoptosis and autophagy. In contrast, short hairpin RNAi-mediated attenuation of ISX and E2F1 decreased cell proliferation and malignant transformation, respectively, in hepatoma cells in vitro and in vivo. The mRNA expression of E2F1 and ISX in 238 paired specimens from human HCC patients, and the adjacent, normal tissues exhibited a tumor-specific expression pattern which was highly correlated with disease pathogenesis, patient survival time, progression stage, and poor prognosis. Therefore, our results indicate that E2F1 is an important downstream gene of ISX in hepatoma progression.