Nontransformed Colonic Epithelial Cells Research Articles

Abstract LB-184: A lncRNA-histone acetyltransferase complex induces colorectal oncogenesis through regulation of a metabolic kinase network

Abstract Long non-coding RNAs (LncRNAs) through interactions with other cellular macromolecules drive cell processes contributing to important cancer phenotypes. Here we show that HOTAIR, a highly up-regulated lncRNA in human colon cancers, induces transformation of human non-transformed colon epithelial cells. An exon 6 HOTAIR region directly binds the histone acetyltransferase PCAF (KAT2B). The HOTAIR/PCAF complex regulates H3K27 acetylation and transcriptional activation preferentially of genes encoding components of the PI3K/AKT/MEK pathways and induces cell metabolic reprogramming. The transcriptional signature of this HOTAIR/PCAF metabolic circuit is active in colon cancer and correlates with overall patient survival. Topological and mechanistic analyses were employed to characterize the HOTAIR/PCAF interface and design a reversible specific inhibitor (CPDI-1). Selective blocking of the HOTAIR-PCAF interaction, suppresses AKT activation and tumor growth. In conclusion, we demonstrate that disruption of a lncRNA-histone modifier complex interferes with the cancer epigenome and represents a novel approach for cancer therapeutics. Citation Format: Christos Polytarchou, Maria Hatziapostolou, Marina Koutsioumpa, Niki Christodoulou, Tung On Yau, Eleni Birli, Odette Pomenya, Cristina Montiel-Duarte, Swapna Mahurkar Joshi, Daniel W. Hommes, Hein W. Verspaget, Jun Yu, Dimitrios Iliopoulos. A lncRNA-histone acetyltransferase complex induces colorectal oncogenesis through regulation of a metabolic kinase network [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-184.

Inorganic arsenic causes intestinal barrier disruption.

Inorganic arsenic (As) is the most toxic form of As found in food and water. Gastrointestinal disorders have been reported in populations chronically exposed to this arsenical form or to one of its metabolites; however, studies to determine the mechanisms of inorganic As toxicity at the intestinal level are scarce. The aim of this study is to determine the mechanisms of toxicity of inorganic As [As(iii) and As(v)] on intestinal epithelial cells. For this purpose, two human intestinal cell models were used: non-transformed colon epithelial cells (NCM460) and epithelial cells from a colorectal adenocarcinoma (Caco-2). Exposure to As(iii) and As(v) generates an increase in the release of the pro-inflammatory cytokine IL-8 (57-1135%) and an increase in the generation of reactive oxygen and/or nitrogen species (130-340%) in both cell lines. This pro-inflammatory and pro-oxidant response may be responsible for the structural and functional modifications demonstrated in the monolayers formed by both cell types. Treatments with As(iii) and As(v) produce a redistribution of zonula occludens 1 and a reduction in the expression of claudin 1, tight junction proteins that participate in maintaining the structure of the epithelium. All these toxic effects are finally translated into a loss of the barrier function of intestinal monolayers.

Activation of the p53 Transcriptional Program Sensitizes Cancer Cells to Cdk7 Inhibitors

Cdk7, the CDK-activating kinase and transcription factor IIH component, is a target of inhibitors that kill cancer cells by exploiting tumor-specific transcriptional dependencies. However, whereas selective inhibition of analog-sensitive (AS) Cdk7 in colon cancer-derived cells arrests division and disrupts transcription, it does not by itself trigger apoptosis efficiently. Here, we show that p53 activation by 5-fluorouracil or nutlin-3 synergizes with a reversible Cdk7as inhibitor to induce cell death. Synthetic lethality was recapitulated with covalent inhibitors of wild-type Cdk7, THZ1, or the more selective YKL-1-116. The effects were allele specific; a CDK7as mutation conferred both sensitivity to bulky adenine analogs and resistance to covalent inhibitors. Non-transformed colon epithelial cells were resistant tothese combinations, as were cancer-derived cellswith p53-inactivating mutations. Apoptosis was dependent on death receptor DR5, a p53 transcriptional target whose expression was refractory to Cdk7 inhibition. Therefore, p53 activation induces transcriptional dependency to sensitize cancer cells to Cdk7 inhibition.

A functional pseudogene, NMRAL2P, is regulated by Nrf2 and serves as a coactivator of NQO1 in sulforaphane-treated colon cancer cells.

The anticancer agent sulforaphane (SFN) acts via multiple mechanisms to modulate gene expression, including the induction of nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-dependent signaling and the inhibition of histone deacetylase activity. Transcriptomics studies were performed in SFN-treated human colon cancer cells and in nontransformed colonic epithelial cells in order to pursue new mechanistic leads. RNA-sequencing corroborated the expected changes in cancer-related pathways after SFN treatment. In addition to NAD(P)H quinone dehydrogenase 1 (NQO1) and other well-known Nrf2-dependent targets, SFN strongly induced the expression of Loc344887. This noncoding RNA was confirmed as a novel functional pseudogene for NmrA-like redox sensor 1, and was given the name NmrA-like redox sensor 2 pseudogene (NMRAL2P). Chromatin immunoprecipitation experiments corroborated the presence of Nrf2 interactions on the NMRAL2P genomic region, and interestingly, NMRAL2P also served as a coregulator of NQO1 in human colon cancer cells. Silencing of NMRAL2P via CRISPR/Cas9 genome-editing protected against SFN-mediated inhibition of cancer cell growth, colony formation, and migration. NMRAL2P is the first functional pseudogene to be identified both as a direct transcriptional target of Nrf2, and as a downstream regulator of Nrf2-dependent NQO1 induction. Further studies are warranted on NMRAL2P-Nrf2 crosstalk and the associated mechanisms of gene regulation.

MKK7 mediates miR‐493‐dependent suppression of liver metastasis of colon cancer cells

The prognosis of advanced colon cancer patients is profoundly affected by the presence or absence of liver metastasis. miR-493 functions as a potent suppressor of liver metastasis, and low-level miR-493 expression in human primary colon cancer is associated with an elevated incidence of liver metastasis. We previously showed that IGF1R is a target gene of miR-493, and that the inhibition of IGF1R partly explains how miR-493 suppresses liver metastasis. However, major functional targets that mediate the antimetastatic activity of miR-493 remain elusive. Here, we extended our search for target genes and identified MKK7, a mitogen-activated protein kinase kinase, as a novel target of miR-493. miR-493 inhibits MKK7 expression by targeting the binding site at the 3′-UTR of the mkk7 gene. MKK7 was expressed in six out of seven colon cancer cell lines examined but not in non-transformed colon epithelial cells, and its expression was required for the activating phosphorylation of JNK. RNA interference-mediated inhibition of MKK7 resulted in marked suppression of liver metastasis of colon cancer cells. A significant decrease of metastasized cells by the MKK7 knockdown was observed, even at early stages of the metastatic settlement, in accordance with a time course of the miR-493-mediated inhibition of the metastasis. Immunohistochemical examination in human primary colon tumors revealed that the occurrence of liver metastasis is associated with elevated levels of MKK7. Thus, MKK7 is a major functional target of miR-493, and its suppression thwarts liver metastasis of colon cancer cells.

An HTS-Compatible 3D Colony Formation Assay to Identify Tumor-Specific Chemotherapeutics

There has been increasing interest in the development of cellular behavior models that take advantage of three-dimensional (3D) cell culture. To enable assessment of differential perturbagen impacts on cell growth in 2D and 3D, we have miniaturized and adapted for high-throughput screening (HTS) the soft agar colony formation assay, employing a laser-scanning cytometer to image and quantify multiple cell types simultaneously. The assay is HTS compatible, providing high-quality, image-based, replicable data for multiple, co-cultured cell types. As proof of concept, we subjected colorectal carcinoma colonies in 3D soft agar to a mini screen of 1528 natural product compounds. Hit compounds from the primary screen were rescreened in an HTS 3D co-culture matrix containing colon stromal cells and cancer cells. By combining tumor cells and normal, nontransformed colon epithelial cells in one primary screening assay, we were able to obtain differential IC50 data, thereby distinguishing tumor-specific compounds from general cytotoxic compounds. Moreover, we were able to identify compounds that antagonized tumor colony formation in 3D only, highlighting the importance of this assay in identifying agents that interfere with 3D tumor structural growth. This screening platform provides a fast, simple, and robust method for identification of tumor-specific agents in a biologically relevant microenvironment.

Abstract 1521: Role of the guanylate-binding-protein 1 (GBP-1) in immunoediting of colorectal carcinoma.

Abstract The human guanylate-binding protein 1 (GBP-1) is among the proteins the most highly induced by IFN-γ in every cell type investigated as yet. In vivo, GBP-1 expression is associated with the presence of inflammation and has been observed in autoimmune diseases, inflammatory bowel diseases (IBD) and cancer. In colorectal carcinoma (CRC), we previously reported that the expression of GBP-1 in the cells of the desmoplastic stroma correlates with the presence of an IFN-γ-dominated Th1 microenvironment and with an increased cancer-related 5-year survival. Moreover, GBP-1 expression in the blood vessels of CRC tissue was associated with a reduced angiogenesis. However, the expression and the role of GBP-1 in the tumor cells of CRC remained unknown. In the present study, the analysis of GBP-1 expression in a series of 185 CRCs by immunohistochemistry confirmed that GBP-1 is expressed in stroma cells of CRCs and revealed a significantly less frequent expression in tumor cells, which was contradictory with the broad inducibility of GBP-1. Furthermore, three of six CRC cell lines treated with IFN-γ were unable to express GBP-1 indicating a reduced inducibility in colorectal tumor cells. On the contrary, non-transformed colon epithelial cells strongly expressed GBP-1 in vitro in presence of IFN-γ and in vivo in IBD. Reconstitution of GBP-1 expression in a negative CRC cell line inhibited cell proliferation, migration, invasion and anchorage-independent growth. Using RNA interference, we showed that GBP-1 mediates the anti-proliferative, anti-migratory, anti-invasive and anti-clonogenic effects of IFN-γ in CRC cells. In addition, GBP-1 was able to inhibit tumor growth in vivo. Altogether these results suggested that GBP-1 acts directly as a tumor suppressor in CRC by mediating the effects of IFN-γ. In addition, the loss of GBP-1 expression in tumor cells indicated that tumor evasion from the IFN-γ-dominated Th1 immune response might have occured. This was confirmed by showing, first, that the absence of GBP-1 inducibility in CRC cell lines correlates with resistance to the anti-proliferative and pro-apoptotic effects of IFN-γ and, second, that the resistant cell lines exhibit defects in the IFN-γ signaling pathway. Citation Format: Nathalie Britzen-Laurent, Karoline Lipnik, Matthias Ocker, Elisabeth Naschberger, Vera Schellerer, Roland Croner, Michael Vieth, Maximilian Waldner, Pablo Steinberg, Christine Hohenadl, Michael Stürzl. Role of the guanylate-binding-protein 1 (GBP-1) in immunoediting of colorectal carcinoma. [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 1521. doi:10.1158/1538-7445.AM2013-1521

GBP-1 acts as a tumor suppressor in colorectal cancer cells

The human guanylate-binding protein 1 (GBP-1) is among the proteins the most highly induced by interferon-γ (IFN-γ) in every cell type investigated as yet. In vivo, GBP-1 expression is associated with the presence of inflammation and has been observed in autoimmune diseases, inflammatory bowel diseases (IBD) and cancer. In colorectal carcinoma (CRC), the expression of GBP-1 in the desmoplastic stroma has been previously reported to correlate with the presence of an IFN-γ-dominated T helper type 1 (Th1) micromilieu and with an increased cancer-related 5-year survival. In the present study, the analysis of GBP-1 expression in a series of 185 CRCs by immunohistochemistry confirmed that GBP-1 is expressed in stroma cells of CRCs and revealed a significantly less frequent expression in tumor cells, which was contradictory with the broad inducibility of GBP-1. Furthermore, three of six CRC cell lines treated with IFN-γ were unable to express GBP-1 indicating that colorectal tumor cells tend to downregulate GBP-1. On the contrary, non-transformed colon epithelial cells strongly expressed GBP-1 in vitro in presence of IFN-γ and in vivo in inflammatory bowel diseases. Reconstitution of GBP-1 expression in a negative CRC cell line inhibited cell proliferation, migration and invasion. Using RNA interference, we showed that GBP-1 mediates the antitumorigenic effects of IFN-γ in CRC cells. In addition, GBP-1 was able to inhibit tumor growth in vivo. Altogether, these results suggested that GBP-1 acts directly as a tumor suppressor in CRC and the loss of GBP-1 expression might indicate tumor evasion from the IFN-γ-dominated Th1 immune response.

Contribution of mitochondrial GSH transport to matrix GSH status and colonic epithelial cell apoptosis

Previously, we showed that cellular glutathione/glutathione disulfide (GSH/GSSG) play an important role in apoptotic signaling, and early studies linked mitochondrial GSH (mtGSH) loss to enhanced cytotoxicity. The current study focuses on the contribution of mitochondrial GSH transport and mitochondrial GSH/GSSG status to apoptosis initiation in a nontransformed colonic epithelial cell line, NCM460, using menadione (MQ), a quinone with redox cycling bioreactivity, as a model of oxidative challenge. Our results implicate the semiquinone radical in MQ-mediated apoptosis, which was associated with marked oxidation of the mitochondrial soluble GSH and protein-bound thiol pools, mitochondria–to–cytosol translocation of cytochrome c, and activation of caspase-9. MQ-induced apoptosis was potentiated by inhibition of mtGSH uptake in accordance with exacerbated mitochondrial GSSG (mtGSSG) and protein–SSG and compromised mitochondrial respiratory activity. Moreover, cell apoptosis was prevented by N-acetyl- l-cysteine (NAC) pretreatment, which restored cellular redox homeostasis. Importantly, mtGSH transport inhibition effectively blocked NAC-mediated protection in accordance with its failure to attenuate mtGSSG. These results support the importance of mitochondrial GSH transport and the mtGSH status in oxidative cell killing.

Riboflavin uptake by human-derived colonic epithelial NCM460 cells.

Normal microflora of the large intestine synthesize a number of water-soluble vitamins including riboflavin (RF). Recent studies have shown that colonic epithelial cells possess an efficient carrier-mediated mechanism for absorbing some of these micronutrients. The aim of the present study was to determine whether colonic cells also possess a carrier-mediated mechanism for RF uptake and, if so, to characterize this mechanism and study its cellular regulation. Confluent monolayers of the human-derived nontransformed colonic epithelial cells NCM460 and [(3)H]RF were used in the study. Uptake of RF was found to be 1) appreciable and temperature and energy dependent; 2) Na(+) independent; 3) saturable as a function of concentration with an apparent K(m) of 0.14 microM and V(max) of 3.29 pmol x mg protein(-1) x 3 min(-1); 4) inhibited by the structural analogs lumiflavin and lumichrome (K(i) of 1.8 and 14.1 microM, respectively) but not by the unrelated biotin; 5) inhibited in a competitive manner by the membrane transport inhibitor amiloride (K(i) = 0.86 mM) but not by furosemide, DIDS, or probenecid; 6) adaptively regulated by extracellular RF levels with a significant and specific upregulation and downregulation in RF uptake in RF-deficient and oversupplemented conditions, respectively; and 7) modulated by an intracellular Ca(2+)/calmodulin-mediated pathway. These studies demonstrate for the first time the existence of a specialized carrier-mediated mechanism for RF uptake in an in vitro cellular model system of human colonocytes. This mechanism appears to be regulated by extracellular substrate level and by an intracellular Ca(2+)/calmodulin-mediated pathway. It is suggested that the identified transport system may be involved in the absorption of bacterially synthesized RF in the large intestine and that this source of RF may contribute toward RF homeostasis, especially that of colonocytes.

Cultures of Human Colonic Epithelial Cells Isolated from Endoscopical Biopsies from Patients with Inflammatory Bowel Disease. Effect of IFNγ, TNFα and IL-1β on Viability, Butyrate Oxidation and IL-8 Secretion

Cytokjne-mediated impairment of viability and metabolic function of epithelial cells has been suggested as a possible early pathogenic event in the development of inflammatory bowel disease (IBD). It is currently unknown whether pro-inflammatory cytokines have a direct effect on human nontransformed colonic epithelial cells. We investigated the effects of TNFα, IFNγ and IL-1β on viability, short chain fatty acid (butyrate) oxidation and IL-8 secretion in human colonic epithelial cell cultures in vitro obtained from macroscopically normal mucosa from IBD patients and controls. Colonic crypts were isolated from endoscopical biopsies by ultra-short (10 min) EDTA/EGTA treatment, and exposed to TNFα, IFNγ and IL-1β for 24 hours. The combination of TNFoc+IFNγ induced a significant decrease in cell viability as judged by methyltetrazoleum (MTT) metabolism which decreased to median 68 % of unexposed cultures (P<0.01). This effect was more pronounced than that observed after addition of TNFα (median 88 %) (P<0.05), but not IFNγ alone (median 78 %), whereas IL-1(3 had no significant effect. Cells from IBD patients were significantly less sensitive to TNFα + IFNγ exposure (median 74 %) compared to cells from controls (median 58 %) (P < 0.05). Butyrate oxidation, as measured by entrapment of CO2, was not inhibited in cells exposed to TNFα + IFNγ, neither from controls (median 112%) nor from IBD patients (median 108%), suggesting a relative increase of this specific metabolic function in living cells in response to immunoinflammatory stress. IL-8 levels in cell supernatants were increased by TNFα + IFNγ, supporting the role of the epithelium in signalling between luminal factors and mucosal immune cells. In conclusion, we report that TNFα and IFNγ damage and influence human colonic epithelial cell function in vitro and that such mechanisms, if operative in vivo, also may be involved in the pathogenesis of IBD

Biotin uptake by human colonic epithelial NCM460 cells: a carrier-mediated process shared with pantothenic acid.

Previous studies showed that the normal microflora of the large intestine synthesizes biotin and that the colon is capable of absorbing intraluminally introduced free biotin. Nothing, however, is known about the mechanism of biotin absorption in the large intestine and its regulation. To address these issues, we used the human-derived, nontransformed colonic epithelial cell line NCM460. The initial rate of biotin uptake was found to be 1) temperature and energy dependent, 2) Na+ dependent (coupling ratio of 1:1), 3) saturable as a function of concentration [apparent Michaelis constant (Km) of 19.7 microM], 4) inhibited by structural analogs with a free carboxyl group at the valeric acid moiety, and 5) competitively inhibited by the vitamin pantothenic acid (inhibition constant of 14.4 microM). Pretreatment with the protein kinase C (PKC) activators phorbol 12-myristate 13-acetate (PMA) and 1, 2-dioctanoyl-sn-glycerol significantly inhibited biotin uptake. In contrast, pretreatment with the PKC inhibitors staurosporine and chelerythrine led to a slight, but significant, increase in biotin uptake. The effect of PMA was mediated via a marked decrease in maximal uptake velocity and a slight increase in apparent Km. Pretreatment of cells with modulators of the protein kinase A-mediated pathway, on the other hand, showed no significant effect on biotin uptake. These results demonstrate, for the first time, the functional existence of a Na+-dependent, specialized carrier-mediated system for biotin uptake in colonic epithelial cells. This system is shared with pantothenic acid and appears to be under the regulation of an intracellular PKC-mediated pathway.

Establishment of Human Colonic Epithelial Cells in Long-Term Culture

Study of normal colonic function is important in understanding the cellular mechanisms of carcinogenesis and other diseases of the colon. However, colonic pathophysiological studies have been limited due to the lack of long-term cultures of normal human colonic epithelial cells. The purpose of the present study was to develop methods of isolating viable human colonic epithelial cells for the establishment of nontransformed colonic epithelial cell lines. Human colonic epithelial cells were isolated from surgically resected normal human colons. We found that the use of a short enzymatic digestion gave a consistently higher number (>90%) of viable human colonic epithelial cells. These isolated colonocytes were grown on plastic, collagen-coated filters, or feeder layers using different media formulations. Those colonocytes from the initial primary cultures that were most “epithelial” in appearance were cloned and passaged to establish long-term cultures of nontransformed human colonic epithelial cells. The epithelial nature and secretory function of these established cell lines were confirmed by morphological criteria (light microscopy, phase contrast microscopy, and electron microscopy). We found that the long-term cultures remained immunopositive to anti-cytokeratin antibodies and immunonegative to anti-vimentin antibodies. Using a soft agar assay we found that the colonocytes did not form colonies, suggesting that the long-term culturing did not cause these cells to become transformed. Under serum-free conditions, we found that epidermal growth factor and transforming growth factor-α were equally potent in their mitogenic effects for these colonocytes. Some of the subcultured cells could be maintained for at least 8 months and still retain their epithelial characteristics. We believe that this methodology will serve as a valuable tool for the isolation and culturing of human colonic epithelial cells for studies of normal and malignant colonic disease processes.