In vitro differentiation of HT-29 M6 mucus-secreting colon cancer cells involves a trychostatin A and p27KIP1-inducible transcriptional program of gene expression

Anti-Cancerous Potential of Polysaccharides Derived from Wheat Cell Culture

There is a global need to discover effective anti-cancerous compounds from natural sources. Cultivated wheat cells can be a valuable source of non-toxic or low toxic plant-derived polysaccharides. In this study, we evaluated the anti-cancer ability of seven fractions of wheat cell culture polysaccharides (WCCPSs) in the HCT-116 colon cancer cell line. Almost all (6/7) fractions had an inhibitory effect on the proliferation of colon cancer cells, and two fractions (A-b and A-f) had considerable therapeutic indexes. The WCCPS fractions induced cell cycle arrest in the G1 phase and induced different rates of apoptosis (≤48%). Transmission and scanning electron microscopy revealed that WCCPS fractions caused apoptotic changes in the nucleus and cytoplasm, including damage to mitochondria and external morphological signs of apoptosis. In addition, the WCCPSs induced an increase in the levels of Bax, cytochrome c, and caspases 8 and 3, indicating that cell death progressed through intrinsic and extrinsic pathways of apoptosis. Furthermore, some fractions caused a significant decrease of c-Myc, b-catenin, NFkB2, and HCAM (CD 44) levels, indicating enhanced cell differentiation. Thus, for the first time, our results provide a proof of concept of the anti-cancer capacity of WCCPS fractions in colorectal cancer.

Reversing chemorefraction in colorectal cancer cells by controlling mucin secretion

Fifteen percent of colorectal cancer (CRC) cells exhibit a mucin hypersecretory phenotype, which is suggested to provide resistance to immune surveillance and chemotherapy. We now formally show that CRC cells build a barrier to chemotherapeutics by increasing mucins’ secretion. We show that low levels of KChIP3, a negative regulator of mucin secretion (Cantero-Recasens et al., 2018), is a risk factor for CRC patients’ relapse in a subset of untreated tumours. Our results also reveal that cells depleted of KChIP3 are four times more resistant (measured as cell viability and DNA damage) to chemotherapeutics 5-fluorouracil + irinotecan (5-FU+iri.) compared to control cells, whereas KChIP3-overexpressing cells are 10 times more sensitive to killing by chemotherapeutics. A similar increase in tumour cell death is observed upon chemical inhibition of mucin secretion by the sodium/calcium exchanger (NCX) blockers (Mitrovic et al., 2013). Finally, sensitivity of CRC patient-derived organoids to 5-FU+iri. increases 40-fold upon mucin secretion inhibition. Reducing mucin secretion thus provides a means to control chemoresistance of mucinous CRC cells and other mucinous tumours.

Investigation of the Effect of Zebularine in Comparison to and in Combination with Trichostatin A on p21Cip1/Waf1/ Sdi1, p27Kip1, p57Kip2, DNA Methyltransferases and Histone Deacetylases in Colon Cancer LS 180 Cell Line

BACKGROUND

The heart of the cell cycle regulatory machine is a group of enzymes named cyclin-dependent kinases (Cdks). The active form of these enzymes includes a kinase and its partner, a cyclin. The regulation of cyclin-Cdk complexes is provided by Cdk inhibitors (CKIs) such as Cip/Kip family comprising p21Cip1/Waf1/Sdi1, p27Kip1, and p57Kip2. The hypermethylation and deacetylation of Cip/Kip gene family seem to be frequent in numerous cancers. It has been indicated that increased expression of DNMTs and HDACs contributes to cancer induction. Previously, we reported the effect of DNA demethylating agents and histone deacetylase inhibitors on histone deacetylase 1, DNA methyltransferase 1, and CIP/KIP family in colon cancer. The current study was designed to evaluate the effect of zebularine in comparison to and in combination with trichostatin A (TSA) on p21Cip1/Waf1/Sdi1, p27Kip1, p57Kip2, DNA methyltransferases (DNMT1, 3a and 3b) and histone deacetylases (HDAC1, 2, and 3) genes expression, cell growth inhibition and apoptosis induction in colon cancer LS 180 cell line.

MATERIALS AND METHODS

The colon cancer LS 180 cell line was cultured and treated with zebularine and TSA. To determine cell viability, apoptosis, and the relative expression level of the genes, MTT assay, cell apoptosis assay, and qRT-PCR were done respectively.

RESULTS

Both compounds significantly inhibited cell growth, and induced apoptosis. Furthermore, both compounds increased p21Cip1/Waf1/Sdi1, p27Kip1, and p57Kip2 significantly. Additionally, zebularine and TSA decreased DNMTs and HDACs gene expression respectively.

CONCLUSION

The zebularine and TSA can reactivate the CIP/KIP family through inhibition of DNMTs and HDACs genes activity.
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Self-organized intestinal epithelial monolayers in crypt and villus-like domains show effective barrier function

Intestinal organoids have emerged as a powerful in vitro tool for studying intestinal biology due to their resemblance to in vivo tissue at the structural and functional levels. However, their sphere-like geometry prevents access to the apical side of the epithelium, making them unsuitable for standard functional assays designed for flat cell monolayers. Here, we describe a simple method for the formation of epithelial monolayers that recapitulates the in vivo-like cell type composition and organization and that is suitable for functional tissue barrier assays. In our approach, epithelial monolayer spreading is driven by the substrate stiffness, while tissue barrier function is achieved by the basolateral delivery of medium enriched with stem cell niche and myofibroblast-derived factors. These monolayers contain major intestinal epithelial cell types organized into proliferating crypt-like domains and differentiated villus-like regions, closely resembling the in vivo cell distribution. As a unique characteristic, these epithelial monolayers form functional epithelial barriers with an accessible apical surface and physiologically relevant transepithelial electrical resistance values. Our technology offers an up-to-date and novel culture method for intestinal epithelium, providing an in vivo-like cell composition and distribution in a tissue culture format compatible with high-throughput drug absorption or microbe-epithelium interaction studies.

In vivo regulation of colonic cell proliferation, differentiation, apoptosis, and P27Kip1 by dietary fish oil and butyrate in rats

We have shown that dietary fish oil is protective against experimentally induced colon cancer, and the protective effect is enhanced by coadministration of pectin. However, the underlying mechanisms have not been fully elucidated. We hypothesized that fish oil with butyrate, a pectin fermentation product, protects against colon cancer initiation by decreasing cell proliferation and increasing differentiation and apoptosis through a p27(Kip1)-mediated mechanism. Rats were provided diets of corn or fish oil, with/without butyrate, and terminated 12, 24, or 48 hours after azoxymethane (AOM) injection. Proliferation (Ki-67), differentiation (Dolichos Biflorus Agglutinin), apoptosis (TUNEL), and p27(Kip1) (cell-cycle mediator) were measured in the same cell within crypts in order to examine the coordination of cell cycle as a function of diet. DNA damage (N(7)-methylguanine) was determined by quantitative IHC analysis. Dietary fish oil decreased DNA damage by 19% (P = 0.001) and proliferation by 50% (P = 0.003) and increased differentiation by 56% (P = 0.039) compared with corn oil. When combined with butyrate, fish oil enhanced apoptosis 24 hours after AOM injection compared with a corn oil/butyrate diet (P = 0.039). There was an inverse relationship between crypt height and apoptosis in the fish oil/butyrate group (r = -0.53, P = 0.040). The corn oil/butyrate group showed a positive correlation between p27(Kip1) expression and proliferation (r = 0.61, P = 0.035). These results indicate the in vivo effect of butyrate on apoptosis and proliferation is dependent on dietary lipid source. These results demonstrate the presence of an early coordinated colonocyte response by which fish oil and butyrate protects against colon tumorigenesis.

NOTCH3 signaling regulates MUSASHI-1 expression in metastatic colorectal cancer cells

MUSASHI-1 (MSI-1) is a well-established stem cell marker in both normal and malignant colon cells and it acts by positively regulating the NOTCH pathway through inactivation of NUMB, a NOTCH signaling repressor. To date, the mechanisms of regulation of MSI-1 levels remain largely unknown. Here, we investigated the regulation of MSI-1 by NOTCH signaling in colorectal cancer cell lines and in primary cultures of colorectal cancer metastases. Stimulation by the NOTCH ligand DLL4 was associated with an increase of MSI-1 mRNA and protein levels, and this phenomenon was prevented by the addition of an antibody neutralizing NOTCH2/3 but not NOTCH1. Moreover, forced expression of activated NOTCH3 increased MSI-1 levels, whereas silencing of NOTCH3 by short hairpin RNA reduced MSI-1 levels in both colorectal cancer cells and CRC tumor xenografts. Consistent with these findings, enforced NOTCH3 expression or stimulation by DLL4 increased levels of activated NOTCH1 in colorectal cell lines. Finally, treatment of colorectal cancer cells with anti-NOTCH2/3 antibody increased NUMB protein while significantly reducing formation of tumor cell spheroids. This novel feed-forward circuit involving DLL4, NOTCH3, MSI-1, NUMB, and NOTCH1 may be relevant for regulation of NOTCH signaling in physiologic processes as well as in tumor development. With regard to therapeutic implications, NOTCH3-specific drugs could represent a valuable strategy to limit NOTCH signaling in the context of colorectal cancers overexpressing this receptor.

Development of intestinal organoids as tissue surrogates: cell composition and the epigenetic control of differentiation

Intestinal organoids are multicellular crypt-like structures that can be derived from adult intestinal stem cells (ISCs), embryonic stem cells (ESCs) or induced pluripotent stem cells (IPSCs). Here we show that intestinal organoids generated from mouse ESCs were enriched in ISCs and early progenitors. Treatment of these organoids with a γ-secretase inhibitor increased Math1 and decreased Hes1 expression, indicating Notch signaling regulates ISC differentiation in these organoids. Lgr5 and Tert positive ISCs constituted approximately 10% and 20% of the organoids. As found in native tissue, Lgr5 and Tert expressing cells resolved into two discreet populations, which were stable over time. Intestinal organoids derived from cancer-prone Apc(Min/+) mice showed similar numbers of ISCs, but had reduced Math1 expression, indicating a suppressed secretory cell differentiation potential (as found in intestinal tissue). Apc(Min/+) organoids were used to screen epigenetically active compounds for those that increased Math1 expression and organoid differentiation (including HDAC inhibitors, Sirtuin (SIRT) modulators and methyltransferase inhibitors). Broad-spectrum HDAC inhibitors increased both Math1 and Muc2 expression, indicating an ability to promote the suppressed secretory cell differentiation pathway. Other epigenetic compounds had a diverse impact on cell differentiation, with a strong negative correlation between those that activated the secretory marker Muc2 and those that activated the absorptive cell marker Fabp2. These data show that ESC-derived intestinal organoids can be derived in large numbers, contain distinct ISC types and can be used to screen for agents that promote cell differentiation through different lineage pathways.

Mybl2, downregulated during colon epithelial cell maturation, is suppressed by miR-365

Altered profiles of gene expression reflect the reprogramming of intestinal epithelial cells during their maturation along the crypt-luminal axis. To focus on genes important in this process, and how they in turn are regulated, we identified 14 transcripts commonly downregulated in expression during lineage-specific maturation of the immortalized cell lines Caco-2 (absorptive), HT29Cl16E (goblet), and HT29Cl19A (secretory) induced by contact inhibition of growth or the short-chain fatty acid butyrate. One such gene, Mybl2 (Myb-related protein B), has been linked to the stem cell phenotype, and we report is also markedly suppressed in maturing cells along the crypt-luminal axis in vivo. Mybl2 is not significantly downregulated transcriptionally during colon cell maturation, but we identified a potential micro-RNA (miRNA)-binding sequence in the Mybl2 3'-untranslated region that mediates reporter gene suppression in differentiating colon cells. Accordingly, miRNAs predicted to bind this functional target are upregulated in differentiating colon epithelial cells in vitro and in vivo; expression of one of these, hsa-miR-365 (but not hsa-324-5p), suppresses Mybl2 protein expression in proliferating Caco-2 cells. These data demonstrate that miRNA silencing plays an important role in regulating gene expression in maturing colon epithelial cells, and that utilizing a target-centered approach, rather than profiling global miRNA expression, can identify physiologically relevant, functional miRNAs.

Role of epigenetics in liver-specific gene transcription, hepatocyte differentiation and stem cell reprogrammation

Controlling both growth and differentiation of stem cells and their differentiated somatic progeny is a challenge in numerous fields, from preclinical drug development to clinical therapy. Recently, new insights into the underlying molecular mechanisms have unveiled key regulatory roles of epigenetic marks driving cellular pluripotency, differentiation and self-renewal/proliferation. Indeed, the transcription of genes, governing cell-fate decisions during development and maintenance of a cell's differentiated status in adult life, critically depends on the chromatin accessibility of transcription factors to genomic regulatory and coding regions. In this review, we discuss the epigenetic control of (liver-specific) gene-transcription and the intricate interplay between chromatin modulation, including histone (de)acetylation and DNA (de)methylation, and liver-enriched transcription factors. Special attention is paid to their role in directing hepatic differentiation of primary hepatocytes and stem cells in vitro.

Mucins: a new family of epigenetic biomarkers in epithelial cancers

BACKGROUND

Epigenetic regulation of gene expression is a common feature of cancer development and progression. The search for new biomarkers and tools to detect cancer in its early stages has unveiled the usefulness of epigenetics and genes epigenetically regulated as potential targets. Among them, genes encoding mucins have been shown to be regulated by DNA methylation and histone modifications in epithelial cancer cells. These genes encode either secreted glycoproteins necessary for epithelial homeostasis or membrane-bound glycoproteins that participate in tumor progression.

OBJECTIVE

The important biological functions played by these large molecules in pathophysiology of the epithelia make them key genes to target to propose new therapeutic strategies and new diagnostic and/or prognostic tools in cancer.

RESULTS

In that context, the recent data regarding the epigenetic regulation of these genes are reported and their potential as biomarkers in cancer is discussed. Mucin genes are also potentially interesting to study as they may be regulated by miRNAs but also regulate miRNA activity.

CONCLUSION

Epigenetic regulation of mucin genes is at its dawn, but there is great potential in that research to (with new technologies and high-throughput methods) provide quickly new biomarkers (diagnostic and/or prognostic), help tumor identification/classification and propose new therapeutic targets to the clinician and pathologist.

Epigenetic influences on sensory regeneration: histone deacetylases regulate supporting cell proliferation in the avian utricle

The sensory hair cells of the cochlea and vestibular organs are essential for normal hearing and balance function. The mammalian ear possesses a very limited ability to regenerate hair cells and their loss can lead to permanent sensory impairment. In contrast, hair cells in the avian ear are quickly regenerated after acoustic trauma or ototoxic injury. The very different regenerative abilities of the avian vs. mammalian ear can be attributed to differences in injury-evoked expression of genes that either promote or inhibit the production of new hair cells. Gene expression is regulated both by the binding of cis-regulatory molecules to promoter regions as well as through structural modifications of chromatin (e.g., methylation and acetylation). This study examined effects of histone deacetylases (HDACs), whose main function is to modify histone acetylation, on the regulation of regenerative proliferation in the chick utricle. Cultures of regenerating utricles and dissociated cells from the utricular sensory epithelia were treated with the HDAC inhibitors valproic acid, trichostatin A, sodium butyrate, and MS-275. All of these molecules prevent the enzymatic removal of acetyl groups from histones, thus maintaining nuclear chromatin in a "relaxed" (open) configuration. Treatment with all inhibitors resulted in comparable decreases in supporting cell proliferation. We also observed that treatment with the HDAC1-, 2-, and 3-specific inhibitor MS-275 was sufficient to reduce proliferation and that two class I HDACs--HDAC1 and HDAC2--were expressed in the sensory epithelium of the utricle. These results suggest that inhibition of specific type I HDACs is sufficient to prevent cell cycle entry in supporting cells. Notably, treatment with HDAC inhibitors did not affect the differentiation of replacement hair cells. We conclude that histone deacetylation is a positive regulator of regenerative proliferation but is not critical for avian hair cell differentiation.

Characterization of a subpopulation of colon cancer cells with stem cell-like properties

The biology of the normal colonic mucosa suggests that colon cancer originates from normal colon stem cells. CD44 cancer stem cells have been identified in breast and prostate cancer, and we therefore examined whether CD44 similarly identified colon cancer stem cells. Initial assays found CD44(hi) colon tumor cells to have enhanced soft agar colony-forming ability. Subsequently, CD44(hi) cells isolated from 4 primary colon adenocarcinoma xenografts were found to be highly tumorigenic in immune deficient mice. CD44(hi) cells consistently formed tumors with 1,000 cells, and in multiple experiments, as few as 10 and 100 CD44(hi) cells formed tumors in 7/10 and 21/28 mice, respectively. In contrast, CD44(-) colon tumor cells were either nontumorigenic or 10-50-fold less tumorigenic. CD44(hi) cells could be serially passaged up to 4 times in vivo, suggesting self-renewal capacity, and formed tumors that recapitulated the heterogeneity of the original patient tumor. CD44(hi) cells were significantly enriched for nuclear activated beta-catenin, a key element in normal stem/progenitor cells and in early colon tumor progression. Bromodeoxyuridine (BrdU) labeling studies indicated that CD44(hi) cells divide slowly relative to the CD44(-) cells, suggesting their tumorigenicity is not simply due to faster proliferation. Aldehyde dehydrogenase (ALDH) sort further increased the tumorigenicity of CD44(hi) cells from 2/2 patient tumors, but CD133 tumor cells in our hands did not have increased tumorigenicity. Our observations indicate that CD44 is a marker of stem-like cells in colon cancer, and support the use of additional markers to further purify colon cancer stem cells.

Functions of p21 and p27 in the regenerating epithelial linings of the mouse small and large intestine

The epithelial linings of the small and large intestine are rapidly turned over and provide an ideal system for exploring links between differentiation and regulation of cell cycle exit. We utilized wild type, p21-/-, p27-/- and p21/p27-/- mice to address contributions of the Cdk inhibitors p21 and p27 to proliferation and differentiation in the mouse gastrointestinal tract. We did not detect any significant differences in proliferation, and all differentiated epithelial cell lineages were represented in all four genotypes. These data indicate that p21 and p27 do not play essential roles in the regulation of normal epithelial renewal in the intestine. These Cdk inhibitors are not needed in vivo for either assembly of Cdk/Cyclin complexes that drive active proliferation, or inhibition of Cdk/Cyclin complexes during cell cycle exit. However, expression of Cyclin D2 and to a lesser degree Cyclin D3 was reduced in p27-/- and p21/p27-/- mice, indicating a unique role for p27 in the regulation of these specific D-type Cyclins in vivo. In the absence of p27, reduced levels of Cyclin D2 and D3 may help to counteract increased proproliferative signals in the intestine.