Divergent phenotypic patterns and commitment to apoptosis of Caco-2 cells during spontaneous and butyrate-induced differentiation

Altered Capacity for H2S Production during the Spontaneous Differentiation of Caco-2 Cells to Colonocytes Due to Reciprocal Regulation of CBS and SELENBP1

Hydrogen sulfide (H₂S) has been proposed to promote tumor growth. Elevated H₂S levels have been detected in human colorectal cancer (CRC) biopsies, resulting from the selective upregulation of cystathionine β-synthase (CBS). In contrast, the recently identified novel H₂S-generating enzyme, selenium-binding protein 1 (SELENBP1), is largely suppressed in tumors. Here, we provide the first comparative analysis of the four human H₂S-producing enzymes and the key H₂S-catabolizing enzyme, sulfide:quinone oxidoreductase (SQOR), in Caco-2 human colorectal adenocarcinoma cells. The gene expression pattern of proliferating Caco-2 cells parallels that of CRC, while confluent cells undergo spontaneous differentiation to a colonocyte-like phenotype. SELENBP1 and SQOR were strongly upregulated during spontaneous differentiation, whereas CBS was downregulated. Cystathionine γ-lyase and 3-mercaptopyruvate sulfurtransferase remained unaffected. Terminally differentiated cells showed an enhanced capacity to produce H₂S from methanethiol and homocysteine. Differentiation induced by exposure to butyrate also resulted in the upregulation of SELENBP1, accompanied by increased SELENBP1 promoter activity. In contrast to spontaneous differentiation, however, butyrate did not cause downregulation of CBS. In summary, SELENBP1 and CBS are reciprocally regulated during the spontaneous differentiation of Caco-2 cells, thus paralleling their opposing regulation in CRC. Butyrate exposure, while imitating some aspects of spontaneous differentiation, does not elicit the same expression patterns of genes encoding H₂S-modulating enzymes.

An inverted in vitro triple culture model of the healthy and inflamed intestine: Adverse effects of polyethylene particles

As environmental pollution with plastic waste is increasing, numerous reports show the contamination of natural habitats, food and drinking water with plastic particles in the micro- and nanometer range. Since oral exposure to these particles is virtually unavoidable, health concerns towards the general population have been expressed and risk assessment regarding ingested plastic particles is of great interest. To study the intestinal effects of polymeric particles with a density of <1 g/cm³ in vitro, we spatially inverted a triple culture transwell model of the healthy and inflamed intestine (Caco-2/HT29-MTX-E12/THP-1), which allows contact between buoyant particles and cells. We validated the inverted model against the original model using the enterotoxic, non-steroidal anti-inflammatory drug diclofenac and subsequently assessed the cytotoxic and pro-inflammatory effects of polyethylene (PE) microparticles. The results show that the inverted model exhibits the same distinct features as the original model in terms of barrier development and inflammatory parameters. Treatment with 2 mM diclofenac causes severe cytotoxicity, DNA damage and complete barrier disruption in both models. PE particles induced cytotoxicity and pro-inflammatory effects in the inverted model, which would have remained undetected in conventional in vitro approaches, as no effect was observed in non-inverted control cultures.

The Potential Use of Sialic Acid From Edible Bird's Nest to Attenuate Mitochondrial Dysfunction by In Vitro Study

Edible bird's nest (EBN) is one of the expensive functional foods in herbal medicine. One of the major glyconutrients in EBN is sialic acid, which has a beneficial effect on neurological and intellectual capability in mammals. The aims of this research were to study the effects of sialic acid from EBN on cell viability and to determine its effect on mitochondria membrane potential (MtMP) in Caco-2, SK-N-MC, SH-SY5Y, and PC-12 cell lines. Fourteen samples of raw EBN were collected from four different states in Malaysia. The confluency of the epithelial monolayers measurement of the tight junction for all the cell lines was determined using transepithelial electrical resistance (TEER), and the sialic acid uptake study in cell lines was determined by using ultra-high performance liquid chromatography (UHPLC). The MTT assay was conducted for cell viability study. The MtMP in cell lines was determined using the Mito Probe JC-1 Assay by flow cytometer analysis. We have recorded a statistically significant difference between the uptake of sialic acid from EBN and the standard solution. A higher amount of sialic acid was absorbed by the cells from extract of EBN compared to the standard solution. The amounts of sialic acid uptake in Caco-2, SK-N-MC, SH-SY5Y, and PC-12 cell lines were (0.019 ± 0.001), (0.034 ± 0.006), (0.021 ± 0.002), and (0.025 ± 0.000) µmol/L, respectively. The MTT results indicated that the concentration of sialic acid increased the cell viability and showed no cytotoxicity effects on cell lines when they were exposed to the sialic acid extract and sialic acid standard at all the tested concentrations. The number of active mitochondria was found to be significantly higher in SH-SY5Y cell lines with a 195% increase when treated with sialic acid from EBN. Although many researchers around the globe use SH-SY5Y and SK-N-MC for Alzheimer's disease (AD) study, based on our finding, SH-SY5Y was found to be the most suitable cell line for AD study by in vitro works where it has a known relationship with mitochondrial dysfunction.

HT-29 and Caco2 Cell Lines Are Suitable Models for Studying the Role of Arachidonic Acid-Metabolizing Enzymes in Intestinal Cell Differentiation

INTRODUCTION

Cytochrome (CYP) epoxygenases (CYP2C and CYP2J) and soluble epoxide hydrolase (sEH) participate in the metabolism of arachidonic acid and may also have a potential role in enterocyte differentiation. The first critical step in the study of intestinal cell differentiation is the determination of a suitable in vitro model, which must be as similar as possible to the conditions of a living organism. It is known that HT-29 and Caco2 cell lines derived from human colorectal carcinomas can differentiate into enterocyte-like cells in appropriate culture conditions.

MATERIAL AND METHODS

We tested 4 different approaches of enterocyte-like differentiation and determined the most appropriate culture conditions for each model. Subsequently, the changes in the expression of CYP epoxygenases and sEH in undifferentiated and differentiated cells were measured by In-Cell ELISA. These results were compared with immunohistochemical profiles of expression of CYP epoxygenases and sEH in samples of human embryonic and fetal intestines as well as adult duodenum and colon.

RESULTS

Our results show that sodium butyrate (NaBt)-differentiated HT-29 cells and spontaneously differentiated Caco2 cells resemble CYP epoxygenases and sEH profiles, corresponding with different types of intestines.

CONCLUSION

Our study revealed that the most suitable models for the study of the role of CYP epoxygenases and sEH expression in differentiation of intestinal epithelium are NaBt-differentiated HT-29 cells and spontaneously differentiated Caco2 cells.

Real-time cellular impedance monitoring and imaging of biological barriers in a dual-flow membrane bioreactor

The generation of physiologically relevant in-vitro models of biological barriers can play a key role in understanding human diseases and in the development of more predictive methods for assessing toxicity and drug or nutrient absorption. Here, we present an advanced cell culture system able to mimic the dynamic environment of biological barriers while monitoring cell behaviour through real-time impedance measurements and imaging. It consists of a fluidic device with an apical and a basal flow compartment separated by a semi-permeable membrane. The main features of the device are the integration of sensing through transepithelial electrical impedance (TEEI) measurements and transparent windows for optical monitoring within a dual flow system. Caco-2 cells were cultured in the TEEI bioreactor under both flow and static conditions. Although no differences in the expression of peripheral actin and occludin were visible, the cells in dynamic conditions developed higher impedance values at low frequencies, indicative of a higher paracellular electrical impedance with respect to the static cultures. TEEI measurements at high frequency also enabled monitoring monolayer formation, which can be correlated with the observation of an RC behaviour in the impedance spectra. In particular, the cells subject to flow showed accelerated barrier formation and increased vitality with respect to the static controls, again highlighting the importance of dynamic conditions for epithelial cells.

Toll like receptor 3 as an immunotherapeutic target for KRAS mutated colorectal cancer

New therapeutic interventions are essential for improved management of patients with metastatic colorectal cancer (mCRC). This is especially critical for those patients whose tumors harbor a mutation in the KRAS oncogene (40-45% of all patients). This patient cohort is excluded from receiving anti-EGFR monoclonal antibodies that have added a significant therapeutic benefit for KRAS wild type CRC patients. Reovirus, a double stranded (ds) RNA virus is in clinical development for patients with chemotherapy refractory KRAS mutated tumors. Toll Like Receptor (TLR) 3, a member of the toll like receptor family of the host innate immune system is the pattern recognition motif for dsRNA pathogens. Using TLR3 expressing commercial HEK-Blue™-hTLR3 cells we confirm that TLR3 is the host pattern recognition motif responsible for the detection of reovirus. Further, our investigation with KRAS mutated HCT116 cell line showed that effective expression of host TLR3 dampens the infection potential of reovirus by mounting a robust innate immune response. Down regulation of TLR3 expression with siRNA improves the anticancer activity of reovirus. In vivo experiments using human CRC cells derived xenografts in athymic mice further demonstrate the beneficial effects of TLR3 knock down by improving tumor response rates to reovirus. Strategies to mitigate the TLR3 response pathway can be utilized as a tool towards improved reovirus efficacy to specifically target the dissemination of KRAS mutated CRC.

K-Ras mutation and amplification status is predictive of resistance and high basal pAKT is predictive of sensitivity to everolimus in biliary tract cancer cell lines

Advanced biliary tract cancer (BTC) has a poor prognosis and limited treatment options. The PI3K/Akt/mTOR signalling pathway is hyperactivated in a subset of BTCs, and clinical activity of the mTOR inhibitor everolimus has been observed in some patients with BTC. The goal of this study was to identify biomarkers predictive of everolimus response. Twenty BTC cell lines were assessed for everolimus sensitivity with a spectrum of growth inhibitory responses observed. Molecular biomarkers of sensitivity and resistance were identified by interrogation of the activation status of the Ras/MAPK and PI3K/Akt/mTOR pathways. K-Ras mutations and/or amplifications were identified in 45% of cell lines and were associated with resistance to everolimus. Activating mutations in PIK3CA or loss of PTEN was not predictive of everolimus response; however, high basal levels of pAKT were associated with sensitivity, independent of Ras/MAPK pathway activation status. Notably, everolimus inhibited mTOR signalling to a similar extent in sensitive and resistant cell lines, suggesting that relative dependence on the mTOR pathway rather than the magnitude of pathway inhibition determines everolimus response. Consistent with the known limitations of rapalogs, everolimus induced feedback-mediated activation of AKT in BTC cell lines, which could be overcome by cotreatment with an AKT inhibitor or ATP-competitive mTORC1/mTORC2 inhibitors. However, both approaches failed to induce greater apoptosis compared to everolimus, and mTORC1/mTORC2 kinase inhibitors induced compensatory activation of pERK, identifying an inherent limitation of these agents in BTC cell lines. These findings suggest that future trials of everolimus in BTC would benefit from preselecting patients based on their K-Ras and PI3K/mTOR pathway activation status. The study also identifies strategies for enhancing inhibition of the PI3K/mTOR pathway in BTC cell lines.

The effect of polymeric formula on enterocyte differentiation

Exclusive enteral nutrition is established as an initial therapy to induce remission in active Crohn's disease (CD), especially in children, but the mechanisms of action of this therapy are yet to be fully defined. Intestinal alkaline phosphatase (IAP), a recognised marker of enterocyte differentiation, is implicated in the innate gut immune response to enteric pathogens. Using the Caco-2 human adenocarcinoma cell line, this study showed that the incubation of human cells with a polymeric formula (PF) resulted in a dose-dependent increase in the expression of IAP on the cell surface. While further investigation is required to determine the pathway(s) involved, this finding suggests that cell surface-associated IAP may be an aspect of the gut's innate immune response to pathogenic bacteria that is strengthened by PF in the setting of CD.

Impact of micro-environmental changes on respiratory tract infections with intracellular bacteria

Community-acquired pneumonia is caused by intra- and extracellular bacteria, with some of these bacteria also being linked to the pathogenesis of chronic lung diseases, including asthma and chronic obstructive pulmonary disease. Chlamydia pneumoniae is an obligate intracellular pathogen that is highly sensitive to micro-environmental conditions controlling both pathogen growth and host immune responses. The availability of nutrients, as well as changes in oxygen, pH and interferon-γ levels, have been shown to directly influence the chlamydial life cycle and clearance. Although the lung has been traditionally regarded as a sterile environment, sequencing approaches have enabled the identification of a large number of bacteria in healthy and diseased lungs. The influence of the lung microbiota on respiratory infections has not been extensively studied so far and data on chlamydial infections are currently unavailable. In the present study, we speculate on how lung microbiota might interfere with acute and chronic infections by focusing exemplarily on the obligate intracellular C. pneumoniae. Furthermore, we consider changes in the gut microbiota as an additional player in the control of lung infections, especially in view the increasing evidence suggesting the involvement of the gut microbiota in various immunological processes throughout the human body.

Histone deacetylase inhibition impairs normal intestinal cell proliferation and promotes specific gene expression

Mechanisms that maintain proliferation and delay cell differentiation in the intestinal crypt are not yet fully understood. We have previously shown the implication of histone methylation in the regulation of enterocytic differentiation. In this study, we investigated the role of histone deacetylation as an important epigenetic mechanism that controls proliferation and differentiation of intestinal cells using the histone deacetylase inhibitor suberanilohydroxamic acid (SAHA) on the proliferation and differentiation of human and mouse intestinal cells. Treatment of newly confluent Caco‐2/15 cells with SAHA resulted in growth arrest, increased histone acetylation and up‐regulation of the expression of intestine‐specific genes such as those encoding sucrase‐isomaltase, villin and the ion exchanger SLC26A3. Although SAHA has been recently used in clinical trials for cancer treatment, its effect on normal intestinal cells has not been documented. Analyses of small and large intestines of mice treated with SAHA revealed a repression of crypt cell proliferation and a higher expression of sucrase‐isomaltase in both segments compared to control mice. Expression of SLC26A3 was also significantly up‐regulated in the colons of mice after SAHA administration. Finally, SAHA was also found to strongly inhibit normal human intestinal crypt cell proliferation in vitro. These results demonstrate the important implication of epigenetic mechanisms such as histone acetylation/deacetylation in the regulation of normal intestinal cell fate and proliferation. J. Cell. Biochem. 116: 2695–2708, 2015. © 2015 The Authors. Journal of Cellular Biochemistry published by Wiley Periodicals, Inc.

Epigenetics in Intestinal Epithelial Cell Renewal

A controlled balance between cell proliferation and differentiation is essential to maintain normal intestinal tissue renewal and physiology. Such regulation is powered by several intracellular pathways that are translated into the establishment of specific transcription programs, which influence intestinal cell fate along the crypt-villus axis. One important check-point in this process occurs in the transit amplifying zone of the intestinal crypts where different signaling pathways and transcription factors cooperate to manage cellular proliferation and differentiation, before secretory or absorptive cell lineage terminal differentiation. However, the importance of epigenetic modifications such as histone methylation and acetylation in the regulation of these processes is still incompletely understood. There have been recent advances in identifying the impact of histone modifications and chromatin remodelers on the proliferation and differentiation of normal intestinal crypt cells. In this review we discuss recent discoveries on the role of the cellular epigenome in intestinal cell fate, development, and tissue renewal. J. Cell. Physiol. 231: 2361-2367, 2016. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

Dual Targeting of Bromodomain and Extraterminal Domain Proteins, and WNT or MAPK Signaling, Inhibits c-MYC Expression and Proliferation of Colorectal Cancer Cells

Inhibitors of the bromodomain and extraterminal domain (BET) protein family attenuate the proliferation of several tumor cell lines. These effects are mediated, at least in part, through repression of c-MYC. In colorectal cancer, overexpression of c-MYC due to hyperactive WNT/β-catenin/TCF signaling is a key driver of tumor progression; however, effective strategies to target this oncogene remain elusive. Here, we investigated the effect of BET inhibitors (BETi) on colorectal cancer cell proliferation and c-MYC expression. Treatment of 20 colorectal cancer cell lines with the BETi JQ1 identified a subset of highly sensitive lines. JQ1 sensitivity was higher in cell lines with microsatellite instability but was not associated with the CpG island methylator phenotype, c-MYC expression or amplification status, BET protein expression, or mutation status of TP53, KRAS/BRAF, or PIK3CA/PTEN Conversely, JQ1 sensitivity correlated significantly with the magnitude of c-MYC mRNA and protein repression. JQ1-mediated c-MYC repression was not due to generalized attenuation of β-catenin/TCF-mediated transcription, as JQ1 had minimal effects on other β-catenin/TCF target genes or β-catenin/TCF reporter activity. BETi preferentially target super-enhancer-regulated genes, and a super-enhancer in c-MYC was recently identified in HCT116 cells to which BRD4 and effector transcription factors of the WNT/β-catenin/TCF and MEK/ERK pathways are recruited. Combined targeting of c-MYC with JQ1 and inhibitors of these pathways additively repressed c-MYC and proliferation of HCT116 cells. These findings demonstrate that BETi downregulate c-MYC expression and inhibit colorectal cancer cell proliferation and identify strategies for enhancing the effects of BETi on c-MYC repression by combinatorial targeting the c-MYC super-enhancer. Mol Cancer Ther; 15(6); 1217-26. ©2016 AACR.

Remodeling of Tight Junctions and Enhancement of Barrier Integrity of the CACO-2 Intestinal Epithelial Cell Layer by Micronutrients

The micronutrients zinc, quercetin, butyrate, indole and berberine were evaluated for their ability to induce remodeling of epithelial tight junctions (TJs) and enhance barrier integrity in the CACO-2 gastrointestinal epithelial cell culture model. All five of these chemically very diverse micronutrients increased transepithelial electrical resistance (R_t) significantly, but only berberine also improved barrier integrity to the non-electrolyte D-mannitol. Increases of R_t as much as 200% of untreated controls were observed. Each of the five micronutrients also induced unique, signature-like changes in TJ protein composition, suggesting multiple pathways (and TJ arrangements) by which TJ barrier function can be enhanced. Decreases in abundance by as much as 90% were observed for claudin-2, and increases of over 300% could be seen for claudins -5 and -7. The exact effects of the micronutrients on barrier integrity and TJ protein composition were found to be highly dependent on the degree of differentiation of the cell layer at the time it was exposed to the micronutrient. The substratum to which the epithelial layer adheres was also found to regulate the response of the cell layer to the micronutrient. The implications of these findings for therapeutically decreasing morbidity in Inflammatory Bowel Disease are discussed.

A novel class I HDAC inhibitor, MPT0G030, induces cell apoptosis and differentiation in human colorectal cancer cells via HDAC1/PKCδ and E-cadherin

Accumulation of genetic and epigenetic changes contributes to cancer development and progression. Compared with gene mutations or deletions, epigenetic changes are reversible, which alter the chromatin structure remodeling instead of changes in DNA sequence, and therefore become a promising strategy for chemotherapy. Histone deacetylases (HDACs) are a class of enzymes that responsible for the epigenetic regulation of gene expression. MPT0G030 is a potent and selective class I HDAC inhibitor which showed broad-spectrum cytotoxicity against various human cancer cell lines. in vitro fluorometric HDAC activity assay showed that MPT0G030 effectively inhibited Class I HDACs (HDAC1~3), which were overexpressed in many malignant neoplasms. Interestingly, MPT0G030 not only induced histone acetylation and tumor suppressor p21 transcription, but also redistributed E-cadherin and activated Protein Kinase C δ (PKCδ), which was linked to cell apoptosis and differentiation. Further, activation of PKCδ was demonstrated to be modulated through HDAC1. The in vivo anticancer activity of MPT0G030 and the importance of PKCδ were confirmed in the HT-29 tumor xenograft models. Taken together, those results indicate that MPT0G030, a class I HDAC inhibitor, has great potential as a new drug candidate for cancer therapy.

Oncolytic reovirus preferentially induces apoptosis in KRAS mutant colorectal cancer cells, and synergizes with irinotecan

Reovirus is a double stranded RNA virus, with an intrinsic preference for replication in KRAS mutant cells. As 45% of human colorectal cancers (CRC) harbor KRAS mutations, we sought to investigate its efficacy in KRAS mutant CRC cells, and examine its impact in combination with the topoisimerase-1 inhibitor, irinotecan. Reovirus efficacy was examined in the KRAS mutant HCT116, and the isogenic KRAS WT Hke3 cell line, and in the non-malignant rat intestinal epithelial cell line. Apoptosis was determined by flow cytometry and TUNEL staining. Combination treatment with reovirus and irintoecan was investigated in 15 CRC cell lines, including the HCT116 p21 isogenic cell lines. Reovirus preferentially induced apoptosis in KRAS mutant HCT116 cells compared to its isogenic KRAS WT derivative, and in KRAS mutant IEC cells. Reovirus showed a greater degree of caspase 3 activation with PARP 1 cleavage, and preferential inhibition of p21 protein expression in KRAS mutant cells. Reovirus synergistically induced growth inhibition when combined with irinotecan. This synergy was lost upon p21 gene knock out. Reovirus preferentially induces apoptosis in KRAS mutant colon cancer cells. Reovirus and irinotecan combination therapy is synergistic, p21 mediated, and represents a novel potential treatment for patients with CRC.

PTEN phosphatase-independent maintenance of glandular morphology in a predictive colorectal cancer model system

Organotypic models may provide mechanistic insight into colorectal cancer (CRC) morphology. Three-dimensional (3D) colorectal gland formation is regulated by phosphatase and tensin homologue deleted on chromosome 10 (PTEN) coupling of cell division cycle 42 (cdc42) to atypical protein kinase C (aPKC). This study investigated PTEN phosphatase-dependent and phosphatase-independent morphogenic functions in 3D models and assessed translational relevance in human studies. Isogenic PTEN-expressing or PTEN-deficient 3D colorectal cultures were used. In translational studies, apical aPKC activity readout was assessed against apical membrane (AM) orientation and gland morphology in 3D models and human CRC. We found that catalytically active or inactive PTEN constructs containing an intact C2 domain enhanced cdc42 activity, whereas mutants of the C2 domain calcium binding region 3 membrane-binding loop (M-CBR3) were ineffective. The isolated PTEN C2 domain (C2) accumulated in membrane fractions, but C2 M-CBR3 remained in cytosol. Transfection of C2 but not C2 M-CBR3 rescued defective AM orientation and 3D morphogenesis of PTEN-deficient Caco-2 cultures. The signal intensity of apical phospho-aPKC correlated with that of Na(+)/H(+) exchanger regulatory factor-1 (NHERF-1) in the 3D model. Apical NHERF-1 intensity thus provided readout of apical aPKC activity and associated with glandular morphology in the model system and human colon. Low apical NHERF-1 intensity in CRC associated with disruption of glandular architecture, high cancer grade, and metastatic dissemination. We conclude that the membrane-binding function of the catalytically inert PTEN C2 domain influences cdc42/aPKC-dependent AM dynamics and gland formation in a highly relevant 3D CRC morphogenesis model system.

The intestinal epithelial cell differentiation marker intestinal alkaline phosphatase (ALPi) is selectively induced by histone deacetylase inhibitors (HDACi) in colon cancer cells in a Kruppel-like factor 5 (KLF5)-dependent manner

The histone deacetylase inhibitor (HDACi) sodium butyrate promotes differentiation of colon cancer cells as evidenced by induced expression and enzyme activity of the differentiation marker intestinal alkaline phosphatase (ALPi). Screening of a panel of 33 colon cancer cell lines identified cell lines sensitive (42%) and resistant (58%) to butyrate induction of ALP activity. This differential sensitivity was similarly evident following treatment with the structurally distinct HDACi, MS-275. Resistant cell lines were significantly enriched for those harboring the CpG island methylator phenotype (p = 0.036, Chi square test), and resistant cell lines harbored methylation of the ALPi promoter, particularly of a CpG site within a critical KLF/Sp regulatory element required for butyrate induction of ALPi promoter activity. However, butyrate induction of an exogenous ALPi promoter-reporter paralleled up-regulation of endogenous ALPi expression across the cell lines, suggesting the presence or absence of a key transcriptional regulator is the major determinant of ALPi induction. Through microarray profiling of sensitive and resistant cell lines, we identified KLF5 to be both basally more highly expressed as well as preferentially induced by butyrate in sensitive cell lines. KLF5 overexpression induced ALPi promoter-reporter activity in resistant cell lines, KLF5 knockdown attenuated butyrate induction of ALPi expression in sensitive lines, and butyrate selectively enhanced KLF5 binding to the ALPi promoter in sensitive cells. These findings demonstrate that butyrate induction of the cell differentiation marker ALPi is mediated through KLF5 and identifies subsets of colon cancer cell lines responsive and refractory to this effect.

Claudin-3 overexpression increases the malignant potential of colorectal cancer cells: roles of ERK1/2 and PI3K-Akt as modulators of EGFR signaling

The altered expressions of claudin proteins have been reported during the tumorigenesis of colorectal cancer. However, the molecular mechanisms that regulate these events in this cancer type are poorly understood. Here, we report that epidermal growth factor (EGF) increases the expression of claudin-3 in human colorectal adenocarcinoma HT-29 cells. This increase was related to increased cell migration and the formation of anchorage-dependent and anchorage-independent colonies. We further showed that the ERK1/2 and PI3K-Akt pathways were involved in the regulation of these effects because specific pharmacological inhibition blocked these events. Genetic manipulation of claudin-1 and claudin-3 in HT-29 cells showed that the overexpression of claudin-1 resulted in decreased cell migration; however, migration was not altered in cells that overexpressed claudin-3. Furthermore, the overexpression of claudin-3, but not that of claudin-1, increased the tight junction-related paracellular flux of macromolecules. Additionally, an increased formation of anchorage-dependent and anchorage-independent colonies were observed in cells that overexpressed claudin-3, while no such changes were observed when claudin-1 was overexpressed. Finally, claudin-3 silencing alone despite induce increase proliferation, and the formation of anchoragedependent and -independent colonies, it was able to prevent the EGF-induced increased malignant potential. In conclusion, our results show a novel role for claudin-3 overexpression in promoting the malignant potential of colorectal cancer cells, which is potentially regulated by the EGF-activated ERK1/2 and PI3K-Akt pathways.

Epigenetic control of HNF-4α in colon carcinoma cells affects MUC4 expression and malignancy

BACKGROUND

We previously found that enhanced expression of hepatocyte nuclear factor 4α (HNF-4α) is associated with hyper-proliferation of colon carcinoma cells. Here, the effect of histone deacetylase (HDAC) inhibitors on proliferation and the expression of HNF-4α and its downstream target genes were assessed in HM7, LS174T, HT29 and Caco-2 colon carcinoma cell lines.

RESULTS

HNF-4α expression was found to vary in the different colon carcinoma cell lines tested, being highest in HM7. Additionally, a direct correlation with proliferation was observed. In HM7 cells, the weak HDAC inhibitor butyrate significantly inhibited the transcription of HNF-4α, its downstream target gene MUC4, and genes associated with proliferation, including the proliferating cell nuclear antigen gene PCNA. siRNA-mediated silencing of HNF-4α exerted an effect similar to butyrate on HM7 cell proliferation. The stronger HDAC inhibitor trichostatin A (TSA) exerted an effect similar to that of siRNA-mediated HNF-4α silencing and, concomitantly, inhibited the expression of the transcription factor gene SP1. Also, siRNA-mediated silencing of HDAC3 and HDAC4 reduced HNF-4α expression. Chromatin immunoprecipitation (ChIP) assays revealed that TSA induces hyperacetylation of histones H3 and H4 and, concomitantly, inhibits SP1 binding to the HNF-4α promoter. Subsequent electromobility shift assays supported these latter findings.

CONCLUSIONS

HNF-4α transcriptional expression and activity are tightly controlled by epigenetic mechanisms. HDAC inhibitor targeting of HNF-4α may serve as an effective treatment for advanced colon carcinomas, since downstream cancer-associated target genes such as MUC4 are significantly down-regulated by this treatment.

Goat milk with and without increased concentrations of lysozyme improves repair of intestinal cell damage induced by enteroaggregative Escherichia coli

BACKGROUND

Enteroaggregative Escherichia coli (EAEC) causes diarrhea, malnutrition and poor growth in children. Human breast milk decreases disease-causing bacteria by supplying nutrients and antimicrobial factors such as lysozyme. Goat milk with and without human lysozyme (HLZ) may improve the repair of intestinal barrier function damage induced by EAEC. This work investigates the effect of the milks on intestinal barrier function repair, bacterial adherence in Caco-2 and HEp-2 cells, intestinal cell proliferation, migration, viability and apoptosis in IEC-6 cells in the absence or presence of EAEC.

METHODS

Rat intestinal epithelial cells (IEC-6, ATCC, Rockville, MD) were used for proliferation, migration and viability assays and human colon adenocarcinoma (Caco-2, ATCC, Rockville, MD) and human larynx carcinoma (HEp-2, ATCC, Rockville, MD) cells were used for bacterial adhesion assays. Goats expressing HLZ in their milk were generated and express HLZ in milk at concentration of 270 μg/ml. Cells were incubated with pasteurized milk from either transgenic goats expressing HLZ or non-transgenic control goats in the presence and absence of EAEC strain 042 (O44:H18).

RESULTS

Cellular proliferation was significantly greater in the presence of both HLZ transgenic and control goat milk compared to cells with no milk. Cellular migration was significantly decreased in the presence of EAEC alone but was restored in the presence of milk. Milk from HLZ transgenic goats had significantly more migration compared to control milk. Both milks significantly reduced EAEC adhesion to Caco-2 cells and transgenic milk resulted in less colonization than control milk using a HEp-2 assay. Both milks had significantly increased cellular viability as well as less apoptosis in both the absence and presence of EAEC.

CONCLUSIONS

These data demonstrated that goat milk is able to repair intestinal barrier function damage induced by EAEC and that goat milk with a higher concentration of lysozyme offers additional protection.

STK31 maintains the undifferentiated state of colon cancer cells

The expression of serine/threonine kinase (STK) family is frequently altered in human cancers. However, the functions of these kinases in cancer development remain elusive. Here, we report that STK31 is robustly and heterogeneously expressed in colon cancer tissues and plays a critical role in determining the differentiation state of colon cancer cells. Knockdown or overexpression of STK31 induced or inhibited differentiation of colon cancer cells, respectively. Deletion of the STK domain abolished the inhibiting effect of STK31. Associated with differentiation, knockdown of STK31 resulted in significant suppression of tumorigenicity both in vitro and in vivo. Genome microarray analysis showed that knockdown of STK31 altered the expression profile of genes that are known to be involved in germ cell and cancer differentiation. Taken together, these results suggest that STK31 is able to control the differentiation state of colon cancer cells, which critically depends on its STK domain. The present findings may shed light on the new therapeutic approach against cancer by targeting STK31 and cancer differentiation.

Dual targeting of the epidermal growth factor receptor using the combination of cetuximab and erlotinib: preclinical evaluation and results of the phase II DUX study in chemotherapy-refractory, advanced colorectal cancer

PURPOSE

This preclinical and phase II study evaluated the efficacy and safety of the combination of cetuximab and erlotinib in metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

The activity and mechanism of action of the combination of cetuximab plus erlotinib were investigated in vitro in colorectal cancer cell lines. In the clinical study, patients with chemotherapy-refractory mCRC were treated with cetuximab 400 mg/m(2) as a loading dose and then weekly cetuximab 250 mg/m(2) with erlotinib 100 mg orally daily. The primary end point was response rate (RR), which was evaluated separately in KRAS wild-type (WT) versus KRAS mutant tumors. Secondary end points included toxicity, progression-free survival (PFS), and overall survival. Target accrual was 50 patients, with a one-stage design.

RESULTS

Preclinical studies demonstrated synergistic activity of cetuximab and erlotinib cotreatment on growth inhibition of colon cancer cell lines both as a result of enhanced inhibition of the epidermal growth factor receptor pathway and differential effects on STAT3. In the clinical study, 50 patients were enrolled, with 48 patients evaluable for response. The overall RR was 31% (95% CI, 26% to 57%), with a median PFS of 4.6 months (95% CI, 2.8 to 5.6 months). RR was 41% (95% CI, 26% to 57%) in KRAS WT tumors, with a median PFS of 5.6 months (95% CI, 2.9 to 5.6 months). There was no response in 11 patients with KRAS mutations. Frequent grade 3 and 4 toxicities were rash (48%), hypomagnesaemia (18%), and fatigue (10%).

CONCLUSION

The combination of cetuximab and erlotinib synergistically inhibits growth of colon cancer cell lines, achieves promising efficacy in patients with KRAS WT mCRC, and merits evaluation in further randomized studies.

Modulation of cell cycle regulators by HDACs

Histone deacetylases (HDACs) catalyze the deacetylation of lysine residues on histones and non-histone proteins. HDACs have been shown to control the functions of key cell cycle proteins. Consistent with this, the overexpression of HDACs has been observed in multiple cancers, resulting in deregulation of the cell cycle and uncontrolled proliferation. This review focuses on the impact that HDACs have on cell cycle control through the deacetylation of proteins.

Association between low colonic short-chain fatty acids and high bile acids in high colon cancer risk populations

We propose that the influence of diet on colon cancer risk is mediated by the microbiota. To investigate how dietary fat influences risk, we compared the colonic contents of 12 adult high-risk African Americans (AAs) and 10 Caucasian Americans (CAs) who consumed a high-fat diet (123 ± 11 g/d and 129 ± 17 g/d, respectively) to 13 native Africans (NAs) who subsisted on a low-fat (38 ± 3.0 g/d) diet, all aged 50-60 yr. The colonic bile acids were measured by LC-MS and the short-chain fatty acids (SCFAs) by GC. The chief secondary colonic bile acids, deoxycholic acid and lithocholic acid, were correlated with fat intake and similar between AAs and CAs, but 3-4 times higher than in AAs (p < 0.05). The major SCFAs were lower in AAs (p < 0.001) and CAs (p < 0.001) compared to AAs, but conversely, the branched chain fatty acids (BFCA) were higher. Our results suggest that the higher risk of colon cancer in Americans may be partly explained by their high-fat and high-protein, low complex carbohydrate diet, which produces colonic residues that promote microbes to produce potentially carcinogenic secondary bile acids and less antineoplastic SCFAs. The role of BCFA in colonic carcinogenesis deserves further study.

Association between low colonic short-chain fatty acids and high bile acids in high colon cancer risk populations

We propose that the influence of diet on colon cancer risk is mediated by the microbiota. To investigate how dietary fat influences risk, we compared the colonic contents of 12 adult high-risk African Americans (AAs) and 10 Caucasian Americans (CAs) who consumed a high-fat diet (123 ± 11 g/d and 129 ± 17 g/d, respectively) to 13 native Africans (NAs) who subsisted on a low-fat (38 ± 3.0 g/d) diet, all aged 50-60 yr. The colonic bile acids were measured by LC-MS and the short-chain fatty acids (SCFAs) by GC. The chief secondary colonic bile acids, deoxycholic acid and lithocholic acid, were correlated with fat intake and similar between AAs and CAs, but 3-4 times higher than in AAs (p < 0.05). The major SCFAs were lower in AAs (p < 0.001) and CAs (p < 0.001) compared to AAs, but conversely, the branched chain fatty acids (BFCA) were higher. Our results suggest that the higher risk of colon cancer in Americans may be partly explained by their high-fat and high-protein, low complex carbohydrate diet, which produces colonic residues that promote microbes to produce potentially carcinogenic secondary bile acids and less antineoplastic SCFAs. The role of BCFA in colonic carcinogenesis deserves further study.

Intrinsic mitochondrial membrane potential and associated tumor phenotype are independent of MUC1 over-expression

We have established previously that minor subpopulations of cells with stable differences in their intrinsic mitochondrial membrane potential (Δψm) exist within populations of mammary and colonic carcinoma cells and that these differences in Δψm are linked to tumorigenic phenotypes consistent with increased probability of participating in tumor progression. However, the mechanism(s) involved in generating and maintaining stable differences in intrinsic Δψm and how they are linked to phenotype are unclear. Because the mucin 1 (MUC1) oncoprotein is over-expressed in many cancers, with the cytoplasmic C-terminal fragment (MUC1 C-ter) and its integration into the outer mitochondrial membrane linked to tumorigenic phenotypes similar to those of cells with elevated intrinsic Δψm, we investigated whether endogenous differences in MUC1 levels were linked to stable differences in intrinsic Δψm and/or to the tumor phenotypes associated with the intrinsic Δψm. We report that levels of MUC1 are significantly higher in subpopulations of cells with elevated intrinsic Δψm derived from both mammary and colonic carcinoma cell lines. However, using siRNA we found that down-regulation of MUC1 failed to significantly affect either the intrinsic Δψm or the tumor phenotypes associated with increased intrinsic Δψm. Moreover, whereas pharmacologically mediated disruption of the Δψm was accompanied by attenuation of tumor phenotype, it had no impact on MUC1 levels. Therefore, while MUC1 over-expression is associated with subpopulations of cells with elevated intrinsic Δψm, it is not directly linked to the generation or maintenance of stable alterations in intrinsic Δψm, or to intrinsic Δψm associated tumor phenotypes. Since the Δψm is the focus of chemotherapeutic strategies, these data have important clinical implications in regard to effectively targeting those cells within a tumor cell population that exhibit stable elevations in intrinsic Δψm and are most likely to contribute to tumor progression.

Fibroblast growth factor receptor-3 (FGFR-3) regulates expression of paneth cell lineage-specific genes in intestinal epithelial cells through both TCF4/beta-catenin-dependent and -independent signaling pathways

Fibroblast growth factor receptor-3 (FGFR-3) expression in the developing intestine is restricted to the undifferentiated epithelial cells within the lower portion of the crypt. We previously showed that mice lacking functional FGFR-3 have a significant decrease in the number of Paneth cells in the small intestine. Here, we used Caco2 cells to investigate whether FGFR-3 signaling can directly modulate expression of Paneth cell differentiation markers through its effects on TCF4/β-catenin or through other signaling pathways downstream of this receptor. Caco2 cells treated with FGFR-3 ligands or expressing FGFR-3(K650E), a constitutively active mutant, resulted in a significantly increased expression of genes characteristic of mature Paneth cells, including human α-defensins 5 and 6 (HD5 and HD6) and Paneth cell lysozyme, whereas enterocytic differentiation markers were reduced. Activation of FGFR-3 signaling sustained high levels of β-catenin mRNA expression, leading to increased TCF4/β-catenin-regulated transcriptional activity in Caco2 cells. Sustained activity of the TCF4/β-catenin pathway was required for the induction of Paneth cell markers. Activation of the MAPK pathway by FGFR-3 is also required for the induction of Paneth cell markers in addition to and independent of the effect of FGFR-3 on TCF4/β-catenin activity. These studies suggest that coordinate activation of multiple independent signaling pathways downstream of FGFR-3 is involved in regulation of Paneth cell differentiation.

Dietary modulation of gut functional ecology studied by fecal metabonomics

A major source of intestinal metabolites results from both host and microbial processing of dietary nutrients. (1)H NMR-based metabolic profiling of mouse feces was carried out over time in different microbiome mouse models, including conventional (n = 9), conventionalized (n = 10), and "humanized" gnotobiotic mice inoculated with a model of human baby microbiota (HBM, n = 17). HBM mice were supplemented with Lactobacillus paracasei with (n = 10) and without (n = 7) prebiotics. Animals not supplemented with prebiotics received a diet enriched in glucose and lactose as placebo. In conventionalized animals, microbial populations and activities converged in term of multivariate mapping toward conventional mice. Both groups decreased bacterial processing of dietary proteins when switching to a diet enriched in glucose and lactose, as described with low levels of 5-aminovalerate, acetate, and propionate and high levels of lysine and arginine. The HBM model differs from conventional and conventionalized microbiota in terms of type, proportion, and metabolic activity of gut bacteria (lower short chain fatty acids (SCFAs), lactate, 5-aminovalerate, and oligosaccharides, higher bile acids and choline). The probiotics supplementation of HBM mice was associated with a specific amino acid pattern that can be linked to L. paracasei proteolytic activities. The combination of L. paracasei with the galactosyl-oligosaccharide prebiotics was related to the enhanced growth of bifidobacteria and lactobacilli, and a specific metabolism of carbohydrates, proteins, and SCFAs. The present study describes how the assessment of metabolic changes in feces may provide information for studying nutrient-microbiota relationships in different microbiome mouse models.

Transcriptional attenuation in colon carcinoma cells in response to butyrate

The short-chain fatty acid sodium butyrate (NaB), produced in the colonic lumen, induces cell cycle arrest, differentiation, and/or apoptosis in colorectal carcinoma cells in vitro, establishing a potential role for NaB in colon cancer prevention. We have previously shown that butyrate decreases cyclin D1 and c-myc expression, each essential for intestinal tumor development, by transcriptional attenuation. Here, we determined that butyrate-induced transcriptional attenuation of the cyclin D1 and c-myc genes in SW837 human colorectal adenocarcinoma cells occurs at ∼100 nucleotides downstream of the transcription start site, with a similar positioning in Caco-2 cells. A concomitant decrease in RNA polymerase II occupancy at the 5' end of each gene was observed. Because transcriptional regulation is associated with chromatin remodeling, we investigated by chromatin immunoprecipitation whether the histone deacetylase inhibitory activity of butyrate altered chromatin structure at the attenuated loci. Although the distributions of histone H3 trimethylated on K4 and K36 along the cyclin D1 and c-myc genes were consistent with current models, butyrate induced only modest decreases in these modifications, with a similar effect on acetylated H3 and a modest increase in histone H3 trimethylated on K27. Finally, transcriptome analysis using novel microarrays showed that butyrate-induced attenuation is widespread throughout the genome, likely independent of transcriptional initiation. We identified 42 loci potentially paused by butyrate and showed that the transcription patterns are gene specific. The biological functions of these loci encompass a number of effects of butyrate on the physiology of intestinal epithelial cells.

Structure-activity relationship of butyrate analogues on apoptosis, proliferation and histone deacetylase activity in HCT-116 human colorectal cancer cells

1. Butyrate, a bacteria fermentative product in the colonic lumen, has been shown to produce a wide variety of biological effects in human cancer cells in vitro. However, there are pharmacological drawbacks associated with the use of butyrate therapy and there are limited published data on the structure-activity relationship of butyrate analogues in colorectal cancer cells. Previously, we determined structure-activity relationship using HT-29 human colorectal cancer cells. However, it was viewed as important to explore similar relationships in another colorectal cancer cell line. 2. Therefore, in the present study, the in vitro structure-activity relationship of butyrate analogues was examined by investigating their effects on apoptosis, cell proliferation, histone deacetylase (HDAC) activity and lactate dehydrogenase (LDH) leakage as a measure of cell toxicity in HCT-116 human colorectal cancer cells. 3. Of the 32 analogues tested, only 4-benzoylbutyrate, 3-benzo-ylpropionate, 4-(4-nitrophenyl)butyrate and 3-(4-fluorobenzoyl)propionate exhibited comparable biological effects to butyrate. The common structural properties of the compounds of interest were to lack amino or hydroxyl substitutions at the 2-, 3- and/or 4-position of the aliphatic moiety of butyrate. 4. The present study reveals a dissociation between the induction of apoptosis, inhibition of cell proliferation, HDAC activity and LDH leakage. The results indicate differential responses of butyrate analogues in HT-29 and HCT-116 colorectal cancer cells.

Intestinal epithelial cells in vitro

Recent advances in the biology of stem cells has resulted in significant interest in the development of normal epithelial cell lines from the intestinal mucosa, both to exploit the therapeutic potential of stem cells in tissue regeneration and to develop treatment models of degenerative disorders of the digestive tract. However, the difficulty of propagating cell lines of normal intestinal epithelium has impeded research into the molecular mechanisms underlying differentiation of stem/progenitor cells into the various intestinal lineages. Several short-term organ/organoid and epithelial cell culture models have been described. There is a dearth of long-term epithelial and/or stem cell cultures of intestine. With an expanding role of stem cells in the treatment of degenerative disorders, there is a critical need for additional efforts to develop in vitro models of stem/progenitor epithelial cells of intestine. The objective of this review is to recapitulate the current status of technologies and knowledge for in vitro propagation of intestinal epithelial cells, markers of the intestinal stem cells, and gene and protein expression profiles of the intestinal cellular differentiation.

Efficacy of butyrate analogues in HT-29 cancer cells

1. Butyrate is a well known product of starch fermentation by colonic bacteria and is of interest owing to its ability to induce in vitro apoptosis and cell differentiation, as well as to inhibit cell growth in colorectal and other cancer cells. Synthetic analogues of butyrate may also possess cellular activities in a variety of cultured cells. The aim of the present study was to evaluate the effects of butyrate analogues on apoptosis, proliferation and histone deacetylase (HDAC) activity in HT-29 colorectal cancer cells. In addition, the effects of these analogues on lactate dehydrogenase leakage, as a measure of non-specific cytotoxicity, were evaluated in HT-29 cells. 2. Of the 26 analogues examined, four (propionate, 4-benzoylbutyrate, 4-(4-aminophenyl)butyrate and benzyloxyacetate) exhibited comparable effects to butyrate. Interestingly, no activity was noted for compounds carrying amino, hydroxyl or methyl substitutions at the 2-, 3- or 4-position of the aliphatic moiety of butyrate. 3. In conclusion, chemical changes to the structure of butyrate can significantly modify the biological activity assayed in HT-29 colorectal cancer cells in vitro.

Human colon fibroblasts induce differentiation and proliferation of intestinal epithelial cells through the direct paracrine action of keratinocyte growth factor

The effects exerted by the keratinocyte growth factor (KGF) on intestinal epithelial cells cultured in vitro are influenced by cell confluence and differentiation through the modulation of keratinocyte growth factor receptor (KGFR) expression. In order to better define the contribution of KGF on the intestinal epithelial cell differentiation and proliferation, here we developed a coculture model, able to mimick in vitro the epithelial-mesenchymal interactions of the bowel. In consequence of its ability to produce KGF, demonstrated by real-time PCR and Western blot analysis, the human colon fibroblast cell line CCD-18 has been selected as coculture partner for the intestinal epithelial Caco-2 cell line. Analysis of the expression of the differentiation and proliferation markers CEA and Ki67, through double immunofluorescence assays, showed that either the coculture with CCD-18 cells or the incubation with primary colon fibroblast-derived conditioned media (CM-F and CM-F2) induced an increase in differentiation and proliferation of confluent intestinal epithelial Caco-2 or HT29 cells, parallel to that obtained by KGF treatment. Use of anti-KGF blocking antibodies and of a tyrosine kinase KGFR inhibitor demonstrated the contribution of KGF and the direct role of its receptor in the regulation of epithelial growth and differentiation, indicating that KGF is a crucial paracrine factor involved in promoting these effects.

Valproic acid enhances bosutinib cytotoxicity in colon cancer cells

Unbalanced histone deacetylase (HDAC) hyperactivity is a common feature of tumor cells. Inhibition of HDAC activity is often associated with cancer cell growth impairment and death. Valproic acid (VPA) is a HDAC inhibitor used for the treatment of epilepsy. It has recently been recognized as a promising anticancer drug. We investigated the effects of VPA on growth and survival of colon cancer cells. VPA caused growth inhibition and programmed cell death that correlated with histone hyperacetylation. VPA modulated the expression of various factors involved in cell cycle control and apoptosis and induced caspase activation. Interestingly, VPA induced downregulation of c-Src and potentiated the cytotoxic effects of the c-Src inhibitor bosutinib, both in vitro and in vivo. The combination of sublethal doses of VPA and bosutinib led to massive apoptosis of colon cancer cells, irrespective of their genetic background. These results suggest that VPA may be employed as a positive modulator of bosutinib antitumor activity in colorectal cancer.

Expression of selenium-binding protein 1 characterizes intestinal cell maturation and predicts survival for patients with colorectal cancer

To identify candidate genes involved in the development of colorectal cancer, we used cDNA microarrays to analyze gene expression differences between human colorectal tumors and paired adjacent normal mucosa. We identified approximately 3.5-fold significant downregulation of selenium-binding protein 1 (SBP1) in colorectal tumors compared to normal mucosa (p = 0.003). Importantly, stage III colorectal cancer patients with low tumor-SBP1 expression had significantly shorter disease-free and overall survival as compared with those patients with high tumor-SBP1 expression (p = 0.04 and 0.03, respectively). We further characterized the role of SBP1 in colorectal cancer in vivo and in vitro. In normal tissue, SBP1 was maximally expressed in terminally differentiated epithelial cells on the luminal surface of crypts in the large intestine. Consistent with this in vivo localization, SBP1 was upregulated during in vitro colonic cell differentiation along the absorptive (Caco-2) and secretory (HT29 Clones 16E and 19A) cell lineages. Downregulation (approximately 50%) of SBP1 expression by small interfering RNA in colonic cancer cells was associated with reduced expression of another epithelial differentiation marker, carcinoembryonic antigen (CEA), although PCNA and p21(WAF1/cip1 )expression were not altered. These data demonstrate that higher expression of SBP1 is associated with differentiation of the normal colonic epithelia and may be a positive prognostic factor for survival in stage III colorectal carcinoma.

Histone deacetylases are required for androgen receptor function in hormone-sensitive and castrate-resistant prostate cancer

Transcriptional activity of the androgen receptor (AR) is crucial for growth and survival of prostate cancer even upon development of resistance to androgen ablation and antiandrogen therapies. Therefore, novel therapies that can suppress AR transcriptional activity when conventional hormone therapies fail are needed. Here, we show that histone deacetylase (HDAC) inhibitors, including SAHA (vorinostat) and LBH589, which are currently being tested in clinic, could be such a therapy. HDAC inhibitors block the AR-mediated transcriptional activation of many genes, including the TMPRSS2 gene involved in fusion with ETS family members in a majority of prostate cancers. Genetic knockdown of either HDAC1 or HDAC3 can also suppress expression of AR-regulated genes, recapitulating the effect of HDAC inhibitor treatment. Whereas HDAC inhibitor treatment can lower androgen receptor protein levels in prostate cancer cells, we show that independent of AR protein levels, HDAC inhibitors block AR activity through inhibiting the assembly of coactivator/RNA polymerase II complex after AR binds to the enhancers of target genes. Failed complex assembly is associated with a phase shift in the cyclical wave of AR recruitment that typically occurs in response to ligand treatment. HDAC inhibitors retain the ability to block AR activity in castration-resistant prostate cancer models and, therefore, merit clinical investigation in this setting. The HDAC-regulated AR target genes defined here can serve as biomarkers to ensure sufficient levels of HDAC inhibition.

KLF4 regulation in intestinal epithelial cell maturation

The Krüppel-like factor 4 (KLF4) transcription factor suppresses tumorigenesis in gastrointestinal epithelium. Thus, its expression is decreased in gastric and colon cancers. Moreover, KLF4 regulates both differentiation and growth that is likely fundamental to its tumor suppressor activity. We dissected the expression of Klf4 in the normal mouse intestinal epithelium along the crypt-villus and cephalo-caudal axes. Klf4 reached its highest level in differentiated cells of the villus, with levels in the duodenum>jejunum>ileum, in inverse relation to the representation of goblet cells in these regions, the lineage previously linked to KLF4. In parallel, in vitro studies using HT29cl.16E and Caco2 colon cancer cell lines clarified that KLF4 increased coincident with differentiation along both the goblet and absorptive cell lineages, respectively, and that KLF4 levels also increased during differentiation induced by the short chain fatty acid butyrate, independently of cell fate. Moreover, we determined that lower levels of KLF4 expression in the proliferative compartment of the intestinal epithelium are regulated by the transcription factors TCF4 and SOX9, an effector and a target, respectively, of beta-catenin/Tcf signaling, and independently of CDX2. Thus, reduced levels of KLF4 tumor suppressor activity in colon tumors may be driven by elevated beta-catenin/Tcf signaling.

Expression profile of histone deacetylases 1, 2 and 3 in ovarian cancer tissues

OBJECTIVE

To investigate the expression levels of histone deacetylase (HDAC) 1, 2, and 3 in ovarian cancer tissues and normal ovarian tissues.

METHODS

Randomly assigned each of six patients with serous, mucinous and endometrioid ovarian cancer were included. Another six patients with normal ovarian tissue were included for comparison. RT-PCR was performed to quantify the levels of HDACs1-3 mRNA in the cancer and normal tissues. Western blot analysis was performed to measure the expression levels of HDACs1-3 protein. The HDACs1-3 expression pattern was also topologically examined by immunohistochemistry.

RESULTS

Increased mRNA expressions of HDCA1, HDAC 2 and HDAC 3 were detected in 83%, 67% and 83% of 18 cancer tissue samples, compared to normal tissue samples. The relative densities of HDAC1 mRNA and HDAC3 mRNA in the serous, mucinous and endometrioid cancer tissues, and HDAC2 mRNA in serous cancer tissues were significantly higher than those of the normal tissues, respectively (p<0.05). Overexpression of HDAC1, HDAC2 and HDAC3 proteins were detected in 94%, 72% and 83% of 18 cancer samples, respectively. The relative densities of HDAC1 protein and HDAC3 protein in serous, mucinous and endometrioid cancer, and HDAC2 protein in serous and mucinous cancer tissues were significantly higher than those of normal tissues, respectively (p<0.05). Most cancer tissues expressed moderate to strong staining of HDACs1, 2 and 3 in immunohistochemistry. Staining of HDAC2 was weak in only one endometrioid cancer tissue.

CONCLUSION

HDACs1-3 are over expressed in ovarian cancer tissues and probably play a significant role in ovarian carcinogenesis.

Proteomic changes during intestinal cell maturation in vivo

Intestinal epithelial cells undergo progressive cell maturation as they migrate along the crypt-villus axis. To determine molecular signatures that define this process, proteins differentially expressed between the crypt and villus were identified by 2D-DIGE and MALDI-MS. Forty-six differentially expressed proteins were identified, several of which were validated by immunohistochemistry. Proteins upregulated in the villus were enriched for those involved in brush border assembly and lipid uptake, established features of differentiated intestinal epithelial cells. Multiple proteins involved in glycolysis were also upregulated in the villus, suggesting increased glycolysis is a feature of intestinal cell differentiation. Conversely, proteins involved in nucleotide metabolism, and protein processing and folding were increased in the crypt, consistent with functions associated with cell proliferation. Three novel paneth cell markers, AGR2, HSPA5 and RRBP1 were also identified. Notably, significant correlation was observed between overall proteomic changes and corresponding gene expression changes along the crypt-villus axis, indicating intestinal cell maturation is primarily regulated at the transcriptional level. This proteomic profiling analysis identified several novel proteins and functional processes differentially induced during intestinal cell maturation in vivo. Integration of proteomic, immunohistochemical, and parallel gene expression datasets demonstrate the coordinated manner in which intestinal cell maturation is regulated.

HDAC4 promotes growth of colon cancer cells via repression of p21

The class II Histone deacetylase (HDAC), HDAC4, is expressed in a tissue-specific manner, and it represses differentiation of specific cell types. We demonstrate here that HDAC4 is expressed in the proliferative zone in small intestine and colon and that its expression is down-regulated during intestinal differentiation in vivo and in vitro. Subcellular localization studies demonstrated HDAC4 expression was predominantly nuclear in proliferating HCT116 cells and relocalized to the cytoplasm after cell cycle arrest. Down-regulating HDAC4 expression by small interfering RNA (siRNA) in HCT116 cells induced growth inhibition and apoptosis in vitro, reduced xenograft tumor growth, and increased p21 transcription. Conversely, overexpression of HDAC4 repressed p21 promoter activity. p21 was likely a direct target of HDAC4, because HDAC4 down-regulation increased p21 mRNA when protein synthesis was inhibited by cycloheximide. The importance of p21 repression in HDAC4-mediated growth promotion was demonstrated by the failure of HDAC4 down-regulation to induce growth arrest in HCT116 p21-null cells. HDAC4 down-regulation failed to induce p21 when Sp1 was functionally inhibited by mithramycin or siRNA-mediated down-regulation. HDAC4 expression overlapped with that of Sp1, and a physical interaction was demonstrated by coimmunoprecipitation. Chromatin immunoprecipitation (ChIP) and sequential ChIP analyses demonstrated Sp1-dependent binding of HDAC4 to the proximal p21 promoter, likely directed through the HDAC4-HDAC3-N-CoR/SMRT corepressor complex. Consistent with increased transcription, HDAC4 or SMRT down-regulation resulted in increased histone H3 acetylation at the proximal p21 promoter locus. These studies identify HDAC4 as a novel regulator of colon cell proliferation through repression of p21.

Class I histone deacetylase expression has independent prognostic impact in human colorectal cancer: specific role of class I histone deacetylases in vitro and in vivo

PURPOSE

Recently, several studies reported a strong functional link between histone deacetylases (HDAC) and the development of tumors of the large intestine. However, despite the importance of these molecules, comparably little is known on expression patterns and functions of specific HDAC isoforms in colorectal cancer.

EXPERIMENTAL DESIGN

We characterized class I HDAC isoform expression patterns in a cohort of 140 colorectal carcinomas by immunohistochemistry. In addition, effects of HDAC inhibition by valproic acid and suberoylanilide hydroxamic acid, and specific HDAC isoform knockdown by short interfering RNA, were investigated in a cell culture model.

RESULTS

We found class I HDACs highly expressed in a subset of colorectal carcinomas with positivity for HDAC1 in 36.4%, HDAC2 in 57.9%, and HDAC3 in 72.9% of cases. Expression was significantly enhanced in strongly proliferating (P = 0.002), dedifferentiated (P = 0.022) tumors. High HDAC expression levels implicated significantly reduced patient survival (P = 0.001), with HDAC2 expression being an independent survival prognosticator (hazard ratio, 2.6; P = 0.03). Short interfering RNA-based inhibition of HDAC1 and HDAC2 but not HDAC3 suppressed growth of colon cancer cells in vitro, although to a lesser extent than chemical HDAC inhibitors did.

CONCLUSIONS

The strong prognostic impact of HDAC isoforms in colorectal cancer, the interactions of HDACs with tumor cell proliferation and differentiation in vivo, and our finding that HDACs are differentially expressed in colorectal tumors suggest that the evaluation of HDAC expression in clinical trials for HDAC inhibitors might help to identify a patient subgroup who will exceptionally profit from such a treatment.

PIK3CA mutation/PTEN expression status predicts response of colon cancer cells to the epidermal growth factor receptor inhibitor cetuximab

Cetuximab is a monoclonal antibody that targets the human epidermal growth factor receptor (EGFR). Although approved for use in EGFR-overexpressing advanced colorectal cancer, recent studies have shown a lack of association between EGFR overexpression and cetuximab response, requiring the identification of novel biomarkers predictive of response to this agent. To do so, 22 colon cancer cell lines were screened for cetuximab response in vitro and sensitive and resistant lines were identified. In sensitive cell lines, cetuximab induced a G(0)-G(1) arrest without inducing apoptosis. Notably, cetuximab-sensitive but not cetuximab-resistant cell lines were preferentially responsive to EGF-stimulated growth. Whereas neither EGFR protein/mRNA expression nor gene copy number correlated with cetuximab response, examination of the mutation status of signaling components downstream of EGFR showed that cell lines with activating PIK3CA mutations or loss of PTEN expression (PTEN null) were more resistant to cetuximab than PIK3CA wild type (WT)/PTEN-expressing cell lines (14 +/- 5.0% versus 38.5 +/- 6.4% growth inhibition, mean +/- SE; P = 0.008). Consistently, PIK3CA mutant isogenic HCT116 cells showed increased resistance to cetuximab compared with PIK3CA WT controls. Furthermore, cell lines that were PIK3CA mutant/PTEN null and Ras/BRAF mutant were highly resistant to cetuximab compared with those without dual mutations/PTEN loss (10.8 +/- 4.3% versus 38.8 +/- 5.9% growth inhibition, respectively; P = 0.002), indicating that constitutive and simultaneous activation of the Ras and PIK3CA pathways confers maximal resistance to this agent. A priori screening of colon tumors for PTEN expression status and PIK3CA and Ras/BRAF mutation status could help stratify patients likely to benefit from this therapy.

Differential expression of intestinal membrane transporters in cholera patients

Vibrio cholerae causes the cholera disease through secretion of cholera toxin (CT), resulting in severe diarrhoea by modulation of membrane transporters in the intestinal epithelium. Genes encoding membrane-spanning transporters identified as being differentially expressed during cholera disease in a microarray screening were studied by real-time PCR, immunohistochemistry and in a CaCo-2 cell model. Two amino acid transporters, SLC7A11 and SLC6A14, were upregulated in acute cholera patients compared to convalescence. Five other transporters were downregulated; aquaporin 10, SLC6A4, TRPM6, SLC23A1 and SLC30A4, which have specificity for water, serotonin (5-HT), magnesium, vitamin C and zinc, respectively. The majority of these changes appear to be attempts of the host to counteract the secretory response. Our results also support the concept that epithelial cells are involved in 5-HT signalling during acute cholera.

Dietary non-digestible carbohydrates promote L-cell differentiation in the proximal colon of rats

One of the challenges in type 2 diabetes treatment is to ensure pancreas functionality with gut peptides such as glucagon-like peptide-1 (GLP-1). We have recently shown that the endogenous GLP-1 production is promoted by dietary non-digestible carbohydrates (oligofructose), the higher GLP-1 secretion could participate in the control of obesity and associated disorders. This experimental study was designed to highlight the mechanisms of endogenous increase of GLP-1 following non-digestible carbohydrate feeding. Male Wistar rats were fed a standard diet (70.4 g/100 g total carbohydrates; controls) or the same diet supplemented with oligofructose (10 g/100 g diet) for 4 weeks. GLP-1-producing L-cells of the colon were quantified by immunohistochemistry. GLP-1 was quantified by ELISA, and proglucagon, neurogenin 3 and NeuroD mRNA were measured in the colon by quantitative RT-PCR. The number of GLP-1-expressing cells was doubled in the proximal colon of oligofructose-treated rats, a phenomenon correlated with the increase in proglucagon mRNA and peptide content in the tissue. Moreover, oligofructose increased the number of enteroendocrine L-cells in the proximal colon by a mechanism involving up-regulation of two differentiation factors: neurogenin 3 and NeuroD. It is the first demonstration that nutrients fermented in the gut may promote L-cell differentiation in the proximal colon, a phenomenon contributing to a higher endogenous GLP-1 production. These results suggest a new mechanism by which dietary fibres may lower food intake and fat mass development.

Cross-feeding between Bifidobacterium longum BB536 and acetate-converting, butyrate-producing colon bacteria during growth on oligofructose

In vitro coculture fermentations of Bifidobacterium longum BB536 and two acetate-converting, butyrate-producing colon bacteria, Anaerostipes caccae DSM 14662 and Roseburia intestinalis DSM 14610, with oligofructose as the sole energy source, were performed to study interspecies interactions. Two clearly distinct types of cross-feeding were identified. A. caccae DSM 14662 was not able to degrade oligofructose but could grow on the fructose released by B. longum BB536 during oligofructose breakdown. R. intestinalis DSM 14610 could degrade oligofructose, but only after acetate was added to the medium. Detailed kinetic analyses of oligofructose breakdown by the last strain revealed simultaneous degradation of the different chain length fractions, in contrast with the preferential degradation of shorter fractions by B. longum BB536. In a coculture of both strains, initial oligofructose degradation and acetate production by B. longum BB536 took place, which in turn also allowed oligofructose breakdown by R. intestinalis DSM 14610. These and similar cross-feeding mechanisms could play a role in the colon ecosystem and contribute to the combined bifidogenic/butyrogenic effect observed after addition of inulin-type fructans to the diet.

IL-6 protects enterocytes from hypoxia-induced apoptosis by induction of bcl-2 mRNA and reduction of fas mRNA

Interleukin-6 (IL-6) has been shown to rescue enterocytes from hypoxia-induced apoptosis when given orally following hemorrhagic shock. In vitro models using an intestinal epithelial cell line (IEC-6) cultured with lipopolysaccharide (LPS) under low O2 conditions, to mimic intestinal conditions, show that these cells also undergo apoptosis, which can be reduced by subsequent culture with IL-6. To examine further the mechanisms of rescue, we cultured normal rat intestinal epithelial cells (IEC-6) under both normoxic and hypoxic conditions and analyzed their responses to LPS and IL-6. We showed that IEC-6 expressed IL-6 receptor on its surface. Further, IEC-6 cells could be rescued from hypoxia-induced apoptosis by co-culture with IL-6. RNase protection assay (RPA) examination revealed that under hypoxic conditions, IEC-6 cells that were resistant to apoptosis showed reduced fas expression and increased bcl-2 expression after co-culture with LPS+IL-6.