In vitro models for the identification and characterization of tumor-promoting and protective factors for colon carcinogenesis

The untapped potential of cell culture in disentangling insect-microbial relationships

Cell culture is a powerful technique for the investigation of molecular mechanisms fundamental to health and disease in a diverse array of organisms. Cell lines offer several advantages, namely their simplistic approach and high degree of reproducibility. One field where cell culture has proven particularly useful is the study of the microbiome, where cell culture has led to the illumination of microbial influences on host immunity, nutrition, and physiology. Thus far, researchers have focused cell culture work predominantly on humans, but the growing field of insect microbiome research stands to benefit greatly from its application. Insects constitute one of Earth's most diverse and ancient life forms and, just as with humans, possess microbiomes with great significance to their health. Insects, which play critical roles in supporting food security and ecological stability, are facing increasing threats from agricultural intensification, climate change, and pesticide use. As the microbiome is closely tied to host health, gaining a more robust understanding is of increasing importance. In this review, we assert that the cultivation and utilization of insect gut cell lines in microbiome research will bridge critical knowledge gaps essential for informing insect management practices in a world under pressure.

Patient-Derived Organoids of Colorectal Cancer: A Useful Tool for Personalized Medicine

Colorectal cancer is one of the most important malignancies worldwide, with high incidence and mortality rates. Several studies have been conducted using two-dimensional cultured cell lines; however, these cells do not represent a study model of patient tumors very well. In recent years, advancements in three-dimensional culture methods have facilitated the establishment of patient-derived organoids, which have become indispensable for molecular biology-related studies of colorectal cancer. Patient-derived organoids are useful in both basic science and clinical practice; they can help predict the sensitivity of patients with cancer to chemotherapy and radiotherapy and provide the right treatment to the right patient. Regarding precision medicine, combining gene panel testing and organoid-based screening can increase the effectiveness of medical care. In this study, we review the development of three-dimensional culture methods and present the most recent information on the clinical application of patient-derived organoids. Moreover, we discuss the problems and future prospects of organoid-based personalized medicine.

Benzo(a)pyrene-induced cytotoxicity, cell proliferation, DNA damage, and altered gene expression profiles in HT-29 human colon cancer cells

In the US alone, around 60,000 lives/year are lost to colon cancer. In order to study the mechanisms of colon carcinogenesis, in vitro model systems are required in addition to in vivo models. Towards this end, we have used the HT-29 colon cancer cells, cultured in Dulbecco's Modified Eagle Medium (DMEM), which were exposed to benzo(a)pyrene (BaP), a ubiquitous and prototypical environmental and dietary toxicant at 1, 10, 100 nM and 1, 5, 10, and 25 μM concentrations for 96 h. Post-BaP exposure, growth, cytotoxicity, apoptosis, and cell cycle changes were determined. The BaP metabolite concentrations in colon cells were identified and measured. Furthermore, the BaP biotransformation enzymes were studied at the protein and mRNA levels. The BaP exposure-induced damage to DNA was assessed by measuring the oxidative damage to DNA and the concentrations of BaP-DNA adducts. To determine the whole repertoire of genes that are up- or downregulated by BaP exposure, mRNA transcriptome analysis was conducted. There was a BaP exposure concentration (dose)-dependent decrease in cell growth, cytotoxicity, and modulation of the cell cycle in the treatment groups compared to untreated or dimethylsulfoxide (DMSO: vehicle for BaP)-treated categories. The phase I biotransformation enzymes, CYP1A1 and 1B1, showed BaP concentration-dependent expression. On the other hand, phase II enzymes did not exhibit any marked variation. Consistent with the expression of phase I enzymes, elevated concentrations of BaP metabolites were generated, contributing to the formation of DNA lesions and stable DNA adducts, which were also BaP concentration-dependent. In summary, our studies established that biotransformation of BaP contributes to cytotoxicity, proliferation of tumor cells, and alteration of gene expression by BaP. • Benzo(a)pyrene (BaP) is an environmental and dietary toxicant. • BaP causes cytotoxicity in cultured HT-29 colon cancer cells. • mRNA transcriptome analyses revealed that BaP impacts cell growth, cell cycle, biotransformation, and DNA damage.

Comprehensive polar metabolomics and lipidomics profiling discriminates the transformed from the non-transformed state in colon tissue and cell lines

Colorectal cancer (CRC) is the fourth most lethal disease worldwide. Despite an urgent need for therapeutic advance, selective target identification in a preclinical phase is hampered by molecular and metabolic variations between cellular models. To foster optimal model selection from a translational perspective, we performed untargeted ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry-based polar metabolomics and lipidomics to non-transformed (CCD841-CON and FHC) and transformed (HCT116, HT29, Caco2, SW480 and SW948) colon cell lines as well as tissue samples from ten colorectal cancer patients. This unveiled metabolic signatures discriminating the transformed from the non-transformed state. Metabolites involved in glutaminolysis, tryptophan catabolism, pyrimidine, lipid and carnitine synthesis were elevated in transformed cells and cancerous tissue, whereas those involved in the glycerol-3-phosphate shuttle, urea cycle and redox reactions were lowered. The degree of glutaminolysis and lipid synthesis was specific to the colon cancer cell line at hand. Thus, our study exposed pathways that are specifically associated with the transformation state and revealed differences between colon cancer cell lines that should be considered when targeting cancer-associated pathways.

Comprehensive characterization of the effects of ellagic acid and urolithins on colorectal cancer and key-associated molecular hallmarks: MicroRNA cell specific induction of CDKN1A (p21) as a common mechanism involved

SCOPE

Ellagitannins, ellagic acid, and the colonic metabolites urolithins (Uros) exhibit anticancer effects against colon cells, but a comprehensive molecular analysis has not been done. Herein, we used a panel of cell lines to first time evaluate the antiproliferative properties and accompanying molecular responses of two ellagitannin metabolites mixtures mimicking the situation in vivo and of each individual metabolite.

METHODS AND RESULTS

We examined cell growth, cell cycle, apoptosis, and the expression of related genes and microRNAs (miRs) in a panel of nonmalignant and malignant colon cell lines. Regardless of the composition, the mixed metabolites similarly inhibited proliferation, induced cycle arrest, and apoptosis. All the metabolites contributed to these effects, but Uro-A, isourolithin A, Uro-C, and Uro-D were more potent than Uro-B and ellagic acid. Despite molecular differences between the cell lines, we discerned relevant changes in key cancer markers and corroborated the induction of CDKN1A (cyclin-dependent kinase inhibitor 1A gene (p21, Cip1); encoding p21) as a common step underlying the anticancer properties of Uros. Interestingly, cell-unique downregulation of miR-224 or upregulation of miR-215 was found associated with CDKN1A induction.

CONCLUSION

Physiologically relevant mixtures of Uros exert anticancer effects against colon cancer cells via a common CDKN1A upregulatory mechanism. Other associated molecular responses are however heterogeneous and mostly cell-specific.

Combined genotoxic effects of a polycyclic aromatic hydrocarbon (B(a)P) and an heterocyclic amine (PhIP) in relation to colorectal carcinogenesis

Colorectal neoplasia is the third most common cancer worldwide. Environmental factors such as diet are known to be involved in the etiology of this cancer. Several epidemiological studies have suggested that specific neo-formed mutagenic compounds related to meat consumption are an underlying factor involved in the association between diet and colorectal cancer. Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) are known mutagens and possible human carcinogens formed at the same time in meat during cooking processes. We studied the genotoxicity of the model PAH benzo(a)pyrene (B(a)P) and HCA 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), alone or in mixture, using the mouse intestinal cell line Apc^Min/+, mimicking the early step of colorectal carcinogenesis, and control Apc^+/+ cells. The genotoxicity of B(a)P and PhIP was investigated using both cell lines, through the quantification of B(a)P and PhIP derived DNA adducts, as well as the use of a genotoxic assay based on histone H2AX phosphorylation quantification. Our results demonstrate that heterozygous Apc mutated cells are more effective to metabolize B(a)P. We also established in different experiments that PhIP and B(a)P were more genotoxic on Apc^Min/+ cells compared to Apc^+/+. Moreover when tested in mixture, we observed a combined genotoxicity of B(a)P and PhIP on the two cell lines, with an increase of PhIP derived DNA adducts in the presence of B(a)P. Because of their genotoxic effects observed on heterozygous Apc mutated cells and their possible combined genotoxic effects, both B(a)P and PhIP, taken together, could be implicated in the observed association between meat consumption and colorectal cancer.

Functional cell models of the gut and their applications in food microbiology--a review

Animal experimentation has a long tradition for risk assessment of new drugs before they reach the clinic. To reduce expensive animal experimentation, attempts have been made to build inexpensive and convenient intestinal functional cell models to study toxicity and bioavailability of new substances along with providing relevant models to study interactions between the host, pathogens and intestinal microflora. We review the available cell lines and models of the intestine and their potential uses. Tumor derived cell lines such as Caco-2, T84 and HT-29 are widely used despite many drawbacks, which are discussed with respect to complexity of the gut, where various cell types interact with commensal microbiota and gut-associated lymphoid tissue. To address this complexity, 3D models of human and animal gut represent a promising in vitro system to mimic in vivo situation without the use of transformed cell lines.

TRAIL induces apoptosis in human colorectal adenoma cell lines and human colorectal adenomas

PURPOSE

Recombinant human (rh) tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potential new anticancer drug which can induce apoptosis in colorectal cancer cell lines. The aim of this study was to investigate whether it is possible to induce apoptosis in human adenoma cell lines and human adenomas using rhTRAIL.

EXPERIMENTAL DESIGN

Two human adenoma cell lines were exposed to 0.1 microg/mL of rhTRAIL for 5 hours. Apoptosis and caspase activation in cell lines were evaluated using immunocytochemistry, fluorimetric caspase assays, and Western blotting. Short-term explant cultures were established from freshly removed human adenomas (n = 38) and biopsies of normal colon epithelium (n = 15), and these were incubated for 5 hours in the presence or absence of 1 microg/mL of rhTRAIL. Apoptosis was determined in paraffin-embedded tissue using morphologic criteria and cleaved caspase-3 staining.

RESULTS

In the adenoma cell lines, rhTRAIL induced up to 55% apoptosis. This coincided with caspase-8 and caspase-3 activation and could be inhibited by a pan-caspase inhibitor. rhTRAIL induced caspase-dependent apoptosis in adenomas with high-grade dysplasia (n = 21) compared with the paired untreated counterparts (apoptotic index, 34 +/- 5% versus 17 +/- 2%, mean +/- SE; P = 0.002), but not in adenomas with low-grade dysplasia (n = 17) or in normal colon epithelium (n = 15).

CONCLUSIONS

Colorectal adenoma cell lines and adenomas with high-grade dysplasia are sensitive to rhTRAIL-induced apoptosis, whereas normal colon epithelium is not. This suggests the potential application of rhTRAIL in the treatment of adenomas with high-grade dysplasia.

Apc10.1: an ApcMin/+ intestinal cell line with retention of heterozygosity

APC10.1 is a new intestinal cell line derived from ApcMin/+ mice that retains both the heterozygous Apc genotype and a nonactivated Wnt signaling pathway and displays an early neoplastic phenotype. Although tumorigenic both in immunodepressed and in immunocompetent syngeneic mice, it requires a high cell dose and a long latency. Its epithelial/intestinal origin is shown, in a gene expression profile, by the expression of epithelial transcripts (such as cytokeratin and laminin isoforms) and of developmental regulatory genes (such as Tcf-4, Hnf3beta, p21, Ihh, Hes1) necessary for, or involved in, the maintenance of intestinal stem cells. The lack of activation of the Wnt cascade in APC10.1 cells is shown both by the expression profile of Wnt target genes and by the standard TCF reporter assay. APC10.1 cell line is a novel in vitro model that can contribute to a better understanding of the clinical evolution of familial adenomatous polyposis and to finding of new prophylactic and therapeutic approaches. Supplementary material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html.

ESTABLISHMENT OF A LONG-TERM CULTURE SYSTEM FOR RAT COLON EPITHELIAL CELLS

The aim of this study was to establish a long-term culture system for rat colon epithelial cells. Colonic crypts were isolated by incubating a 4-cm-long rat colon segment cut longitudinally with an ethylenediaminetetraacetic acid [disodium salt]-containing buffer, taken up in conditioned medium from the normal rat kidney fibroblast cell line NRK (i.e., the supernatant of pure NRK cultures), directly plated on mitomycin C-treated NRK cells and subcultured with conditioned medium from NRK cells. Cells started to migrate out of the crypts shortly after plating them on NRK feeder layers. Some of the crypts fell apart during the isolation procedure, whereas the vast majority of them did it within 1 to 2 h after plating. The cells proliferated extremely slowly but continuously over a period of 4 mo and were epithelial because they expressed cytokeratin 19 and were stained by crystal violet at pH 2.8. In conclusion, the experimental system described in this study allows to maintain rat colon epithelial cells for up to 4 mo in culture and can be used to study the effects of a variety of tumor-modulating factors on growth and gene expression of normal colon epithelial cells in vitro.