Newly defined aberrant crypt foci as a marker for dysplasia in the rat colon

Recent Advances in Implantation-Based Genetic Modeling of Biliary Carcinogenesis in Mice

Simple Summary

Biliary tract cancer (BTC) is often refractory to conventional therapeutics and is difficult to diagnose in the early stages. In addition, the pathogenesis of BTC is not fully understood, despite recent advances in cancer genome analysis. To address these issues, the development of fine disease models is critical for BTC. Although still limited in number, there are various platforms for genetic models of BTC owing to newly emerging technology. Among these, implantation-based models have recently drawn attention for their convenience, flexibility, and scalability. To highlight the relevance of this approach, we comprehensively summarize the advantages and disadvantages of BTC models developed using diverse approaches. Currently available research data on intra- and extrahepatic cholangiocarcinoma and gallbladder carcinoma are presented in this review. This information will likely help in selecting the optimal models for various applications and develop novel innovative models based on these technologies.

Abstract

Epithelial cells in the biliary system can develop refractory types of cancers, which are often associated with inflammation caused by viruses, parasites, stones, and chemicals. Genomic studies have revealed recurrent genetic changes and deregulated signaling pathways in biliary tract cancer (BTC). The causal roles have been at least partly clarified using various genetically engineered mice. Technical advances in Cre-LoxP technology, together with hydrodynamic tail injection, CRISPR/Cas9 technology, in vivo electroporation, and organoid culture have enabled more precise modeling of BTC. Organoid-based genetic modeling, combined with implantation in mice, has recently drawn attention as a means to accelerate the development of BTC models. Although each model may not perfectly mimic the disease, they can complement one another, or two different approaches can be integrated to establish a novel model. In addition, a comparison of the outcomes among these models with the same genotype provides mechanistic insights into the interplay between genetic alterations and the microenvironment in the pathogenesis of BTCs. Here, we review the current status of genetic models of BTCs in mice to provide information that facilitates the wise selection of models and to inform the future development of ideal disease models.

Two intertwined compartments coexisting in sporadic conventional colon adenomas

Sporadic conventional colon adenomas are microscopically built of 2 intertwined compartments: one on top, harboring the dysplastic tissue that defines their histo-biomolecular attributes, and the other below, composed of non-dysplastic crypts with corrupted shapes (CCS). The CCS of 306 colon adenomas revealed asymmetric, haphazardly-distributed proliferating cell-domains (PC). In contrast, the PC-domains in normal controls were symmetric, being limited to the lower thirds of the crypts. In 28% out of 501 sporadic conventional adenomas, foci of p53-upregulated dysplastic tissue were found. The CCS in 30% of 108 sporadic adenomas showed p53-upregulated single cells, suggesting mounting somatic mutations. No p53-upregulated cells were found in the crypts of controls. In polypoid adenomas, the mucosa of the stalk without dysplastic tissue on top disclosed CCS with asymmetrical PC-domains and single p53-upregulated cells. The latter observations suggested that CCS had developed prior to and not after the growth of the dysplastic tissue on top. CCS were also found below colon adenomas in carcinogen-treated rats. It is concluded that the 2 intertwined histo-biological compartments of sporadic conventional colon adenomas are probably interdependent components. These findings may open new directions aimed to uncover the link between the normal colonic mucosa and the histogenesis of, conventional adenomas.

Organoid-based ex vivo reconstitution of Kras-driven pancreatic ductal carcinogenesis

The organoid culture technique has been recently applied to modeling carcinogenesis in several organs. To further explore its potential and gain novel insights into tumorigenesis, we here investigated whether pancreatic ductal adenocarcinoma (PDA) could be generated as subcutaneous tumors in immunocompromised nude mice, by genetic engineering of normal organoids. As expected, acute induction of KrasG12Din vitro occasionally led to development of tiny nodules compatible with early lesions known as pancreatic intraepithelial neoplasia (PanIN). KrasG12D-expressing cells were enriched after inoculation in the subcutis, yet proved rather declined during culture, suggesting that its advantage might depend on surrounding environments. Depletion of growth factors or concurrent Trp53 deletion resulted in its robust enrichment, invariably leading to development of PanIN or large high-grade adenocarcinoma, respectively, consistent with in vivo mouse studies for the same genotype. Progression from PanIN was also recapitulated by subsequent knockdown of common tumor suppressors, whereas the impact of Tgfbr2 deletion was only partially recapitulated, illustrating genotype-dependent requirement of the pancreatic niche for tumorigenesis. Intriguingly, analysis of tumor-derived organoids revealed that KrasG12D-expressing cells with spontaneous deletion of wild-type Kras were positively selected and exhibited an aging-related mutation signature in nude mice, mirroring the pathogenesis of human PDA, and that the sphere-forming potential and orthotopic tumorigenicity in syngenic mice were significantly augmented. These observations highlighted the relevance of the subcutis of nude mice in promoting PDA development despite its ectopic nature. Taken together, pancreatic carcinogenesis could be considerably recapitulated with organoids, which would probably serve as a novel disease model.

Shortcuts to intestinal carcinogenesis by genetic engineering in organoids

Inactivation of the Adenomatous polyposis coli (APC) gene is an initiating and the most relevant event in most sporadic cases of colorectal cancer, providing a rationale for using Apc‐mutant mice as the disease model. Whereas carcinogenesis has been observed only at the organism level, the recent development of the organoid culture technique has enabled long‐term propagation of intestinal stem cells in a physiological setting, raising the possibility that organoids could serve as an alternative platform for modeling colon carcinogenesis. Indeed, it is demonstrated in the present study that lentivirus‐based RNAi‐mediated knockdown of Apc in intestinal organoids gave rise to subcutaneous tumors upon inoculation in immunodeficient mice. Reconstitution of common genetic aberrations in organoids resulted in development of various lesions, ranging from aberrant crypt foci to full‐blown cancer, recapitulating multi‐step colorectal tumorigenesis. Due to its simplicity and utility, similar organoid‐based approaches have been applied to both murine and human cells in many investigations, to gain mechanistic insight into tumorigenesis, to validate putative tumor suppressor genes or oncogenes, and to establish preclinical models for drug discovery. In this review article, we provide a multifaceted overview of these types of approaches that will likely accelerate and advance research on colon cancer.

Chemoprevention by artesunate in a preclinical model of colorectal cancer involves down regulation of β-catenin, suppression of angiogenesis, cellular proliferation and induction of apoptosis

Use of anti-inflammatory drugs is well known to decrease the risk of colorectal cancer, one of the most common causes of cancer related mortality. In view of anti-inflammatory property of artesunate reported in various experimental models, the present study was carried out to evaluate its efficacy in rat model where colon carcinogenesis was induced by 1, 2 dimethylhydrazine (DMH). A time course study revealed that two injections of DMH given at an interval of one week resulted in appearance of multiple plaque lesions and aberrant crypt foci in the colon with a peak effect occurring at the end of 8 weeks. An efficacy study carried out with daily oral administration of artesunate (50 and 150 mg/kg) and aspirin (60 mg/kg) showed a marked reduction in pre-neoplastic changes with a significant decrease in the number of aberrant crypt foci, crypt multiplicity and restoration of histoarchitecture. Both the drugs down regulated β-catenin signaling, reduced the levels of angiogenic markers like VEGF, MMP-9 and inhibited cellular proliferation. The anti-cancer effect of these drugs was concomitant with the pro-apoptotic effect as revealed by increased DNA fragmentation, TUNEL positivity and Bax/Bcl₂ immunoreactivity. This is the first study to evaluate the inhibitory effect of artesunate on pre-neoplastic changes in colon where its chemopreventive effect was found to be comparable to that of aspirin. Our study strengthens the previous findings and shows that it has a preventive and therapeutic potential in the treatment of colon cancer.

Corrupted colonic crypt fission in carcinogen-treated rats

Background

The colonic crypts in rats reproduce themselves by symmetric fission at the base of the crypts, and proceeding upwards, generate two separate identical crypts. Recently we reported corrupted colonic crypt fission (CCCF) in rats with colonic carcinoma. Here we investigated whether CCCF also occurred in the colonic mucosa without carcinoma in carcinogen-treated rats.

Methods

Filed Swiss-roll sections from 35 male rats (25 treated with 1,2-dimethyhydrazine (DMH) suspended in EDTA solution, and 10 EDTA-treated) were reviewed. CCCF were regarded those with either asymmetric basal fission, asymmetric lateral sprouting/lateral fission, basal dilatations, or spatial aberrations of the normal (vertical) axis.

Results

202 CCCF (38%) were recorded amongst 533 crypts with fission in DMH-treated rats, and only one CCCF (0.1%) was found amongst 571 crypts with fission in EDTA-treated rats (p<0.05). The basal aspect of four adenomas included in Swiss roll sections exhibited CCCF lined either with indigenous (non-dysplastic) epithelium or with dysplastic epithelium.

Conclusion

It was demonstrated that CCCF without dysplasia develop in carcinogen-treated SD rats. As judged by the figures presented, the possibility that the epithelium in those corrupted crypts was successively replaced by top-down growing dysplastic cells, could not be totally rejected. This is the first report showing that non-dysplastic CCCF may antedate the very early stages of colonic carcinogenesis in SD rats.

Activins and their related proteins in colon carcinogenesis: insights from early and advanced azoxymethane rat models of colon cancer

Background

Activin-A may exert pro- or anti-tumorigenic activities depending on cellular context. However, little is known about its role, or the other mature activin proteins, in colorectal carcinoma (CRC). This study measured the expression of activin βA- & βB-subunits, activin type IIA & IIB receptors, smads 2/3/4/6/7 and follistatin in CRC induced by azoxymethane (AOM) in rats. The results were compared with controls and disseminated according to the characteristics of histopathological lesions.

Methods

Eighty male Wistar rats were allocated into 20 controls and the remaining were equally divided between short ‘S-AOM’ (15 weeks) and long ‘L-AOM’ (35 weeks) groups following injecting AOM for 2 weeks. Subsequent to gross and histopathological examinations and digital image analysis, the expression of all molecules was measured by immunohistochemistry and quantitative RT-PCR. Activin-A, activin-B, activin-AB and follistatin were measured by ELISA in serum and colon tissue homogenates.

Results

Colonic pre-neoplastic and cancerous lesions were identified in both AOM groups and their numbers and sizes were significantly (P < 0.05) greater in the L-AOM group. All the molecules were expressed in normal colonic epithelial cells. There was a significantly (P < 0.05) greater expression of βA-subunit, IIB receptor and follistatin in both pre-neoplastic and cancerous tissues. Oppositely, a significant (P < 0.05) decrease in the remaining molecules was detected in both AOM groups. Metastatic lesions were only observed within the L-AOM group and were associated with the most significant alterations of all molecules. Significantly higher concentrations of activin-A and follistatin and lower activin-AB were also detected in both groups of AOM. Tissue and serum concentrations of activin-A and follistatin correlated positively, while tissue activin-AB inversely, and significantly with the numbers and sizes of colonic lesions.

Conclusions

Normal rat colon epithelial cells are capable of synthesising, controlling as well as responding to activins in a paracrine/autocrine manner. Colonic activin systems are pathologically altered during tumorigenesis and appear to be time and lesion-dependent. Activins could also be potential sensitive markers and/or molecular targets for the diagnosis and/or treatment of CRC. Further studies are required to illustrate the clinical value of activins and their related proteins in colon cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2914-9) contains supplementary material, which is available to authorized users.

Co-treatment with sulforaphane–zein microparticles enhances the chemopreventive potential of zinc in a 1,2-dimethylhydrazine induced colon carcinogenesis rat model

Hypothesis of the study was that zinc and sulforaphane will act on common targets MT and Nrf2 in colon, increasing their intracellular levels leading to improvement in DMH induced oxidative stress thereby hindering the process of colon carcinogenesis in rat.

Palonosetron attenuates 1,2-dimethyl hydrazine induced preneoplastic colon damage through downregulating acetylcholinesterase expression and up-regulating synaptic acetylcholine concentration

The present study was undertaken to evaluate the effect of palonosetron (PAL) against 1,2-dimethylhydrazine (DMH)-induced colon cancer.