Progastrin-induced secretion of insulin-like growth factor 2 from colonic myofibroblasts stimulates colonic epithelial proliferation in mice

Progastrin: An Overview of Its Crucial Role in the Tumorigenesis of Gastrointestinal Cancers

Defining predictive biomarkers for targeted therapies and optimizing anti-tumor immune response is a main challenge in ongoing investigations. Progastrin has been studied as a potential biomarker for detecting and diagnosing various malignancies, and its secretion has been associated with cell proliferation in the gastrointestinal tract that may promote tumorigenesis. Progastrin is a precursor molecule of gastrin, synthesized as pre-progastrin, converted to progastrin after cleavage, and transformed into amidated gastrin via biosynthetic intermediates. In cancer, progastrin does not maturate in gastrin and becomes a circulating and detectable protein (hPG80). The development of cancer is thought to be dependent on the progressive dysregulation of normal signaling pathways involved in cell proliferation, thus conferring a growth advantage to the cells. Understanding the interaction between progastrin and the immune system is essential for developing future cancer strategies. To that end, the present review will approach the interlink between gastrointestinal cancers and progastrin by exploring the underlying molecular steps involved in the initiation, evolution, and progression of gastrointestinal cancers. Finally, this review will focus on the clinical applications of progastrin and investigate its possible use as a diagnostic and prognostic tumor circulating biomarker for disease progression and treatment effectiveness, as well as its potential role as an innovative cancer target.

Identifying key regulators of the intestinal stem cell niche

The intestinal tract is lined by a single layer of epithelium that is one of the fastest regenerating tissues in the body and which therefore requires a very active and exquisitely controlled stem cell population. Rapid renewal of the epithelium is necessary to provide a continuous physical barrier from the intestinal luminal microenvironment that contains abundant microorganisms, whilst also ensuring an efficient surface for the absorption of dietary components. Specialised epithelial cell populations are important for the maintenance of intestinal homeostasis and are derived from adult intestinal stem cells (ISCs). Actively cycling ISCs divide by a neutral drift mechanism yielding either ISCs or transit-amplifying epithelial cells, the latter of which differentiate to become either absorptive lineages or to produce secretory factors that contribute further to intestinal barrier maintenance or signal to other cellular compartments. The mechanisms controlling ISC abundance, longevity and activity are regulated by several different cell populations and signalling pathways in the intestinal lamina propria which together form the ISC niche. However, the complexity of the ISC niche and communication mechanisms between its different components are only now starting to be unravelled with the assistance of intestinal organoid/enteroid/colonoid and single-cell imaging and sequencing technologies. This review explores the interaction between well-established and emerging ISC niche components, their impact on the intestinal epithelium in health and in the context of intestinal injury and highlights future directions and implications for this rapidly developing field.

Gastrin exerts a protective effect against myocardial infarction via promoting angiogenesis

Background

It is known that increased gastrin concentration is negatively correlated with cardiovascular mortality, and plasma gastrin levels are increased in patients after myocardial infarction (MI). However, whether gastrin can play a protective role in MI remains unknown.

Methods

Adult C57BL/6 mice were subjected to ligation of the left anterior descending coronary artery (LAD) and subcutaneous infusion of gastrin (120 μg/Kg body weight/day, 100 μL in the pump) for 28 days after MI. Plasma gastrin concentrations were measured through an ELISA detection kit. Mice were analyzed by echocardiography after surgery. CD31 and VEGF expression were quantified using immunofluorescence staining or/and western blot to assess the angiogenesis in peri-infarct myocardium. Capillary-like tube formation and cell migration assays were performed to detect gastrin-induced angiogenesis.

Results

We found that gastrin administration significantly ameliorated MI-induced cardiac dysfunction and reduced fibrosis at 28 days in post-MI hearts. Additionally, gastrin treatment significantly decreased cardiomyocyte apoptosis and increased angiogenesis in the infarct border zone without influencing cardiomyocyte proliferation. In vitro results revealed that gastrin up-regulated the PI3K/Akt/vascular endothelial growth factor (VEGF) signaling pathway and promoted migration and tube formation of human coronary artery endothelial cells (HCAECs). Cholecystokinin 2 receptor (CCK₂R) mediated the protective effect of gastrin since the CCK₂R blocker CI988 attenuated the gastrin-mediated angiogenesis and cardiac function protection.

Conclusion

Our data revealed that gastrin promoted angiogenesis and improved cardiac function in post-MI mice, highlighting its potential as a therapeutic target candidate.

The role of butyrate in surgical and oncological outcomes in colorectal cancer

Butyrate is a short-chain fatty acid produced by colonic gut bacteria as a result of fermentation of dietary fibers. In the colon, butyrate is a major energy substrate and contributes to the nutritional support and proliferation of a healthy mucosa. It also promotes the intestinal barrier function by enhancing mucus production and tight junctions. In addition to its pro-proliferative effect in healthy colonocytes, butyrate inhibits the proliferation of cancer cells. The antineoplastic effect of butyrate is associated with the inhibitory effect of butyrate on histone deacetylase (HDAC) enzymes, which promote carcinogenesis. Due to the metabolic shift of cancer cells toward glycolysis, unused butyrate accumulates and inhibits procarcinogenic HDACs. In addition, recent studies suggest that butyrate may improve the healing of colonic tissue after surgery in animal models, specifically at the site of reconnection of colonic ends, anastomosis, after surgical resection. Here, we review current evidence on the impact of butyrate on epithelial integrity and colorectal cancer and present current knowledge on data that support its potential applications in surgical practice.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

NF-κB2 signalling in enteroids modulates enterocyte responses to secreted factors from bone marrow-derived dendritic cells

Alternative pathway NF-κB signalling regulates susceptibility towards developing inflammatory bowel disease (IBD), colitis-associated cancer and sepsis-associated intestinal epithelial cell apoptosis and shedding. However, the cell populations responsible for the perturbed alternative pathway NF-κB signalling in intestinal mucosal pathology remain unclear. In order to investigate the contribution of the epithelial compartment, we have tested whether NF-κB2 regulated transcription in intestinal epithelial cells controls the intestinal epithelial response to cytokines that are known to disrupt intestinal barrier permeability. Enteroids were generated from the proximal, middle and distal regions of small intestine (SI) from C57BL/6J wild-type mice and displayed region-specific morphology that was maintained during sub-culture. Enteroids treated with 100 ng/mL TNF were compared with corresponding regions of SI from C57BL/6J mice treated systemically with 0.33 mg/kg TNF for 1.5 h. TNF-induced apoptosis in all regions of the intestine in vitro and in vivo but resulted in Paneth cell degranulation only in proximal tissue-derived SI and enteroids. TNF also resulted in increased enteroid sphericity (quantified as circularity from two-dimensional bright field images). This response was dose and time-dependent and correlated with active caspase-3 immunopositivity. Proximal tissue-derived enteroids generated from Nfκb2^−/− mice showed a significantly blunted circularity response following the addition of TNF, IFNγ, lipopolysaccharide (LPS) activated C57BL/6J-derived bone marrow-derived dendritic cells (BMDC) and secreted factors from LPS-activated BMDCs. However, Nfκb1^−/− mouse-derived enteroids showed no significant changes in response to these stimuli. In conclusion, the selection of SI region is important when designing enteroid studies as region-specific identity and response to stimuli such as TNF are maintained in culture. Intestinal epithelial cells are at least partially responsible for regulating their own fate by modulating NF-κB2 signalling in response to stimuli known to be involved in multiple intestinal and systemic diseases. Future studies are warranted to investigate the therapeutic potential of intestinal epithelial NF-κB2 inhibition.

HMGB1: an overview of its versatile roles in the pathogenesis of colorectal cancer

BACKGROUND

In recent years, the high mobility group box-1 (HMGB1) protein, a damage-associated molecular pattern (DAMP) molecule, has been found to play multifunctional roles in the pathogenesis of colorectal cancer. Although much attention has been given to the diagnostic and prognostic values of HMGB1 in colorectal cancer, the exact functional roles of the protein as well as the mechanistic pathways involved have remained poorly defined. This systematic review aims to discuss what is currently known about the roles of HMGB1 in colorectal cancer development, growth and progression, and to highlight critical areas for future investigations. To achieve this, the bibliographic databases Pubmed, Scopus, Web of Science and ScienceDirect were systematically screened for articles from inception till June 2018, which address associations of HMGB1 with colorectal cancer.

CONCLUSIONS

HMGB1 plays multiple roles in promoting the pathogenesis of colorectal cancer, despite a few contradicting studies. HMGB1 may differentially regulate disease-related processes, depending on the redox status of the protein in colorectal cancer. Binding of HMGB1 to various protein partners may alter the impact of HMGB1 on disease progression. As HMGB1 is heavily implicated in the pathogenesis of colorectal cancer, it is crucial to further improve our understanding of the functional roles of HMGB1 not only in colorectal cancer, but ultimately in all types of cancers.

Fibroblasts Impact Goblet Cell Responses to Lactic Acid Bacteria After Exposure to Inflammatory Cytokines and Mucus Disruptors

Scope

Mucus produced by goblet cells contributes to gut barrier function. Lactic acid bacteria (LAB) have been shown to impact mucus production. It is not completely known whether mucus production is influenced by the abundantly present fibroblasts in the intestine.

Methods and results

The influence of fibroblasts on mucus‐related genes including mucin‐2 (MUC2), trefoil factor 3 (TFF3), resistin‐like molecule β (RETNLB), carbohydrate sulfotransferase 5 (CHST5), and galactose‐3‐O‐sulfotransferase 2 (GAL3ST2) is examined after co‐culture of LS174T‐goblet cells and CCD‐18Co colonic fibroblasts in the presence and absence of LAB‐strains known to impact mucus function. This is also tested after exposure to TNF‐α, IL‐13, or the mucin synthesis inhibitor tunicamycin (Tm). Effects of fibroblasts are treatment duration‐ and bacterial species‐dependent under homeostatic conditions. During TNF‐α challenge, fibroblasts reverse Lactobacillus (L.) rhamnosus CCFM237‐elicited declined TFF3 expression. After IL‐13 exposure, L. rhamnosus CCFM237 and L. fermentum CCFM787 attenuate enhanced TFF3 and RETNLB expression, respectively, only in the presence of fibroblasts. LAB has no effects on Tm‐induced decreased expression of goblet cell‐related genes regardless of the presence of fibroblasts.

Conclusion

It is demonstrated that goblet cell–fibroblast crosstalk impacts mucus synthesis and influences the effects of LAB on goblet cell‐related genes. Effects are LAB‐species and stressor dependent.

The G-protein coupled receptor 56, expressed in colonic stem and cancer cells, binds progastrin to promote proliferation and carcinogenesis

Overexpression of human progastrin increases colonic mucosal proliferation and colorectal cancer progression in mice. The G-protein coupled receptor 56 (GPR56) is known to regulate cell adhesion, migration, proliferation and stem cell biology, but its expression in the gut has not been studied. We hypothesized that the promotion of colorectal cancer by progastrin may be mediated in part through GPR56. Here, we found that GPR56 expresses in rare colonic crypt cells that lineage trace colonic glands consistent with GPR56 marking long-lived colonic stem-progenitor cells. GPR56 was upregulated in transgenic mice overexpressing human progastrin. While recombinant human progastrin promoted the growth and survival of wild-type colonic organoids in vitro, colonic organoids cultured from GPR56^−/− mice were resistant to progastrin. We found that progastrin directly bound to, and increased the proliferation of, GPR56-expressing colon cancer cells in vitro, and proliferation was increased in cells that expressed both GPR56 and the cholecystokinin-2 receptor (CCK2R). In vivo, deletion of GPR56 in the mouse germline abrogated progastrin-dependent colonic mucosal proliferation and increased apoptosis. Loss of GPR56 also inhibited progastrin-dependent colonic crypt fission and colorectal carcinogenesis in the azoxymethane (AOM) mouse model of colorectal cancer. Overall, we found that progastrin binds to GPR56 expressing colonic stem cells, which in turn promotes their expansion, and that this GPR56-dependent pathway is an important driver and potential new target in colorectal carcinogenesis.

Image-guided genomics of phenotypically heterogeneous populations reveals vascular signalling during symbiotic collective cancer invasion

Phenotypic heterogeneity is widely observed in cancer cell populations. Here, to probe this heterogeneity, we developed an image-guided genomics technique termed spatiotemporal genomic and cellular analysis (SaGA) that allows for precise selection and amplification of living and rare cells. SaGA was used on collectively invading 3D cancer cell packs to create purified leader and follower cell lines. The leader cell cultures are phenotypically stable and highly invasive in contrast to follower cultures, which show phenotypic plasticity over time and minimally invade in a sheet-like pattern. Genomic and molecular interrogation reveals an atypical VEGF-based vasculogenesis signalling that facilitates recruitment of follower cells but not for leader cell motility itself, which instead utilizes focal adhesion kinase-fibronectin signalling. While leader cells provide an escape mechanism for followers, follower cells in turn provide leaders with increased growth and survival. These data support a symbiotic model of collective invasion where phenotypically distinct cell types cooperate to promote their escape.

The mechanisms linking phenotypic heterogeneity to collective cancer invasion are unclear. Here the authors develop an image-guided genomic technique to select and amplify leader and follower cells from in vitro invading cell packs and find a cooperative symbiotic relationship between these two cell populations.

Targeting progastrin enhances radiosensitization of colorectal cancer cells

A high percentage of advanced rectal cancers are resistant to radiation. Therefore, increasing the efficacy of radiotherapy by targeting factors involved in radioresistance seems to be an attractive strategy. Here we demonstrated that the pro-hormone progastrin (PG), known to be over-expressed in CRC, and recognized as a pro-oncogenic factor, is a radioresistance factor that can be targeted to sensitize resistant rectal cancers to radiations. First, we observed an increase in PG mRNA expression under irradiation. Our results also demonstrated that down-regulating PG mRNA expression using a shRNA strategy, significantly increases the sensitivity to irradiation (IR) in a clonogenic assay of different colorectal cancer cell lines. We also showed that the combination of PG gene down-regulation and IR strongly inhibits tumours progression in vivo. Then, we demonstrated that targeting PG gene radiosensitizes cancer cells by increasing radio-induced apoptosis shown by an increase in annexin V positive cells, caspases activation and PARP cleavage. We also observed the up-regulation of the pro-apoptotic pathway, JNK and the induction of the expression of pro-apoptotic factors such as BIM. In addition, we demonstrated in this study that inhibition of PG gene expression enhances radiation-induced DNA damage. Our data also suggest that, in addition to increase radio-induced apoptosis, targeting PG gene also leads to the inhibition of the survival pathways, AKT and ERK induced by IR. Taken together, our results highlight the role of PG in radioresistance and provide a preclinical proof of concept that PG represents an attractive target for sensitizing resistant rectal tumours to irradiation. .

Mesenchymal-epithelial signalling in tumour microenvironment: role of high-mobility group Box 1

Glucose deprivation, hypoxia and acidosis are characteristic features of the central core of most solid tumours. Myofibroblasts are stromal cells present in many such solid tumours, including those of the colon, and are known to be involved in all stages of tumour progression. HMGB1 is a nuclear protein with an important role in nucleosome stabilisation and gene transcription; it is also released from immune cells and is involved in the inflammatory process. We report that the microenvironmental condition of glucose deprivation is responsible for the active release of HMGB1 from various types of cancer cell lines (HT-29, MCF-7 and A549) under normoxic conditions. Recombinant HMGB1 (10 ng/ml) triggered proliferation in myofibroblast cells via activation of PI3K and MEK1/2. Conditioned medium collected from glucose-deprived HT-29 colon cancer cells stimulated the migration and invasion of colonic myofibroblasts, and these processes were significantly inhibited by immunoneutralising antibodies to HMGB1, RAGE and TLR4, together with specific inhibitors of PI3K and MEK1/2. Our data suggest that HMGB1 released from cancer cells under glucose deprivation is involved in stimulating colonic myofibroblast migration and invasion and that this occurs through the activation of RAGE and TLR4, resulting in the activation of the MAPK and PI3K signalling pathways. Thus, HMGB1 might be released by cancer cells in areas of low glucose in solid tumours with the resulting activation of myofibroblasts and is a potential therapeutic target to inhibit solid tumour growth.

Paracrine tumor signaling induces transdifferentiation of surrounding fibroblasts

Growth stimuli in cancer growth resemble those exhibited in wound healing. However, the process of nemosis is absent in cancer-associated fibroblasts (CAFs), which remain constitutively active. CAFs are present in almost all solid tumors but are most abundant in breast, prostate and pancreatic cancers. TGF-β1, TGF-β2, PDGF, IL-6, bFGF, reactive oxide species and protein kinase C are considered the key players in tumor-induced transdifferentiation of surrounding fibroblasts. Full-extent transdifferentiation was obtained only when the medium contained TGF-β1 or TGF-β2 (with or without other factors), whereas PDGF, bFGF or IL-6 (each alone) induced only partial transdifferentiation. Recent evidence suggests that the fibroblasts associated with primary cancers differ from those associated with metastases. The metastases-associated fibroblasts are converted by a metastasis-specific spectrum of factors. A large portion of paracrine tumor signaling is mediated by cancer cell-derived vesicles termed exosomes and microvesicles. The cancer cell-derived exosomes contain abundant and diverse proteomes and a number of signaling factors (TGF-ß1, TGF-ß2, IL-6, MMP2 and MMP9), particularly under hypoxic conditions. In contrast to the traditional view, the clonal expansion and selection of neoplastic cells should not be viewed outside the host body context. It is vital for a neoplastic cell to achieve the ability to re-program host body cells into CAFs and by this influence to modulate its microenvironment and receive positive feedback for growth and drug resistance. Neoplastic cells, which fail to develop such capacity, do not pass critical barriers in tumorigenesis and remain dormant and benign.

Murine Models of Helicobacter (pylori or felis)-associated Gastric Cancer

Gastric adenocarcinoma is the fifth most common cancer and third most common cause of cancer-related death in the world. The majority of these cancers develop in genetically susceptible individuals who are chronically infected with the Gram-negative bacterium Helicobacter pylori. Often these individuals have also been exposed to certain environmental factors that increase susceptibility, such as dietary components. Murine models of Helicobacter-induced gastric cancer are valuable tools for investigating the mechanisms responsible for the stepwise pathological changes of chronic atrophic gastritis, intestinal metaplasia, dysplasia and gastric adenocarcinoma. Helicobacter felis colonization greatly accelerates the development of gastric neoplasia in mice, and causes pathologies similar to those observed with Helicobacter pylori-associated gastric carcinogenesis in humans. These mouse models are therefore useful for investigating genetic and environmental factors that may be involved in the pathogenesis and treatment of gastric cancer. Detailed in these protocols are procedures for inducing Helicobacter-associated carcinogenesis in mice as well as the histological analysis and interpretation of gastric pathology in these animals.

Cancer-associated fibroblasts in digestive tumors

The significant influence of tumor stroma on malignant cells has been extensively investigated in this era of targeted therapy. The tumor microenvironment, as a dynamic system, is orchestrated by various cells including tumor vascular composing cells, inflammatory cells and fibroblasts. As a major and important component in tumor stroma, increasing evidence has shown that spindle-shaped cancer-associated fibroblasts (CAFs) are a significant modifier of cancer evolution, and promote tumorigenesis, tumor invasion and metastasis by stimulating angiogenesis, malignant cell survival, epithelial-mesenchymal transition (EMT) and proliferation via direct cell-to-cell contact or secretion of soluble factors in most digestive solid tumors. CAFs are thought to be activated, characterized by the expression of α-smooth muscle actin, fibroblast activated protein, fibroblast specific protein, vimentin, fibronectin, etc. They are hypothesized to originate from normal or aged fibroblasts, bone marrow-derived mesenchymal cells, or vascular endothelial cells. EMT may also be an important process generating CAFs, and most probably, CAFs may originate from multiple cells. A close link exists between EMT, tumor stem cells, and chemo-resistance of tumor cells, which is largely orchestrated by CAFs. CAFs significantly induce immunosuppression, and may be a prognostic marker in various malignancies. Targeted therapy toward CAFs has displayed promising anticancer efficacy, which further reinforces the necessity to explore the relationship between CAFs and their hosts.

Cathelicidin suppresses colon cancer development by inhibition of cancer associated fibroblasts

BACKGROUND

Cathelicidin (LL-37 in humans and mCRAMP in mice) represents a family of endogenous antimicrobial and anti-inflammatory peptides. Cancer-associated fibroblasts can promote the proliferation of colon cancer cells and growth of colon cancer tumors.

METHODS

We examined the role of cathelicidin in the development of colon cancer, using subcutaneous human HT-29 colon-cancer-cell-derived tumor model in nude mice and azoxymethane- and dextran sulfate-mediated colon cancer model in C57BL/6 mice. We also determined the indirect antitumoral mechanism of cathelicidin via the inhibition of epithelial-mesenchymal transition (EMT) of colon cancer cells and fibroblast-supported colon cancer cell proliferation.

RESULTS

Intravenous administration of cathelicidin expressing adeno-associated virus significantly reduced the size of tumors, tumor-derived collagen expression, and tumor-derived fibroblast expression in HT-29-derived subcutaneous tumors in nude mice. Enema administration of the mouse cathelicidin peptide significantly reduced the size and number of colonic tumors in azoxymethane- and dextran sulfate-treated mice without inducing apoptosis in tumors and the adjacent normal colonic tissues. Cathelicidin inhibited the collagen expression and vimentin-positive fibroblast expression in colonic tumors. Cathelicidin did not directly affect HT-29 cell viability, but did significantly reduce tumor growth factor-β1-induced EMT of colon cancer cells. Media conditioned by the human colonic CCD-18Co fibroblasts promoted human colon cancer HT-29 cell proliferation. Cathelicidin pretreatment inhibited colon cancer cell proliferation mediated by media conditioned by human colonic CCD-18Co fibroblasts. Cathelicidin disrupted tubulin distribution in colonic fibroblasts. Disruption of tubulin in fibroblasts reduced fibroblast-supported colon cancer cell proliferation.

CONCLUSION

Cathelicidin effectively inhibits colon cancer development by interfering with EMT and fibroblast-supported colon cancer cell proliferation.

Novel roles of gastrin

The existence of the hormone gastrin in the distal stomach (antrum) has been known for almost 110 years, and the physiological function of this amidated peptide in regulating gastric acid secretion via the CCK2 receptor is now well established. In this brief review we consider important additional roles of gastrin, including regulation of genes encoding proteins such as plasminogen activator inhibitors and matrix metalloproteinases that have important actions on extracellular matrix remodelling. These actions are, at least in part, effected by paracrine signalling pathways and make important contributions to maintaining functional integrity of the gastric epithelium. Recent studies also provide support for the idea that gastrin, in concert with other hormones, could potentially contribute a post-prandial incretin effect. We also review recent developments in the biology of other gastrin gene products, including the precursor progastrin, which causes proliferation of the colonic epithelium and in certain circumstances may induce cancer formation. Glycine-extended biosynthetic processing intermediates also have proliferative effects in colonic mucosa and in some oesophageal cancer cell lines. Whether these additional gene products exert their effects through the CCK2 receptor or a separate entity is currently a matter of debate.

Carcinoma-associated fibroblasts provide operational flexibility in metastasis

Malignant cancer cells do not act as lone wolves to achieve metastasis, as they exist within a complex ecosystem consisting of an extracellular matrix scaffold populated by carcinoma-associated fibroblasts (CAFs), endothelial cells and immune cells. We recognize local (primary tumor) and distant ecosystems (metastasis). CAFs, also termed myofibroblasts, may have other functions in the primary tumor versus the metastasis. Cellular origin and tumor heterogeneity lead to the expression of specific markers. The molecular characteristics of a CAF remain in evolution since CAFs show operational flexibility. CAFs respond dynamically to a cancer cell's fluctuating demands by shifting profitable signals necessary in metastasis. Local, tissue-resident fibroblasts and mesenchymal stem cells (MSCs) coming from reservoir sites such as bone marrow and adipose tissue are the main progenitor cells of CAFs. CAFs may induce awakening from metastatic dormancy, a major cause of cancer-specific death. Cancer management protocols influence CAF precursor recruitment and CAF activation. Since CAF signatures represent early changes in metastasis, including formation of pre-metastatic niches, we discuss whether liquid biopsies, including exosomes, may detect and monitor CAF reactions allowing optimized prognosis of cancer patients.

Activation of pro-oncogenic pathways in colorectal hyperplastic polyps

Background

In contrast to sessile serrated adenomas and traditional serrated adenomas which are associated with a significant cancer risk, the role of hyperplastic polyps (HP) in colorectal carcinogenesis as well as the molecular mechanisms underlying their development remain controversial and still need to be clarified. Several reports suggest that a subset of HP may represent precursor lesions of some colorectal cancers. However, biomarkers are needed to identify the subset of HP that may have a malignant potential. The hormone precursor, progastrin (PG) has been involved in colon carcinogenesis and is known to activate pro-oncogenic pathways such as the ERK or the STAT3 pathway. We therefore analyzed PG expression and the activation of these signaling factors in HP.

Methods

We retrospectively analyzed PG expression as well as the phosphorylation of ERK and STAT3 by immunohistochemistry in HP from 48 patients.

Results

Mean percentages of epithelial cells positive for PG or phospho-ERK were respectively, 31% and 33% in HP and were significantly higher in these lesions compared to normal colon (3%, p = 0.0021 and 7%, p = 0.0008, respectively). We found a significant correlation between PG and phospho-ERK expression in HP with ERK activation significantly stronger in lesions with high progastrin expression (p = 0.015). In contrast, STAT3 was not significantly activated in HP compared to normal colon and we did not observe a significant correlation with PG expression.

Conclusions

HP overexpressing PG that have the highest activation of the ERK pathway might reflect less latent lesions that might have a malignant potential.

Na+/Ca2+ exchangers regulate the migration and proliferation of human gastric myofibroblasts

Gastrointestinal myofibroblasts are contractile, electrically nonexcitable, transitional cells that play a role in extracellular matrix production, in ulcer healing, and in pathophysiological conditions they contribute to chronic inflammation and tumor development. Na+/Ca2+ exchangers (NCX) are known to have a crucial role in Ca2+ homeostasis of contractile cells, however, no information is available concerning the role of NCX in the proliferation and migration of gastrointestinal myofibroblasts. In this study, our aim was to investigate the role of NCX in the Ca2+ homeostasis, migration, and proliferation of human gastrointestinal myofibroblasts, focusing on human gastric myofibroblasts (HGMs). We used microfluorometric measurements to investigate the intracellular Ca2+ and Na+ concentrations, PCR analysis and immunostaining to show the presence of the NCX, patch clamp for measuring NCX activity, and proliferation and migration assays to investigate the functional role of the exchanger. We showed that 53.0±8.1% of the HGMs present Ca2+ oscillations, which depend on extracellular Ca2+ and Na+, and can be inhibited by NCX inhibitors. NCX1, NCX2, and NCX3 were expressed at both mRNA and protein levels in HGMs, and they contribute to the intracellular Ca2+ and Na+ homeostasis as well, regardless of the oscillatory activity. NCX inhibitors significantly blocked the basal and insulin-like growth factor II-stimulated migration and proliferation rates of HGMs. In conclusion, we showed that NCX plays a pivotal role in regulating the Ca2+ homeostasis, migration, and proliferation of HGMs. The inhibition of NCX activity may be a potential therapeutic target in hyperproliferative gastric diseases.

Intestinal microbiome and digoxin inactivation: meal plan for digoxin users?

There is an increasing interest in the role of intestinal microbiome in human diseases and therapeutic agents' bioavailability, activity and toxicity. Epidemiological data show that the bioavailability of digoxin, a widely used agent for heart disease, varies among individuals. The inactivation of digoxin was found when it was incubated with gut bacterium Eggerthella lenta in vitro decades ago. However, the underlying mechanisms of digoxin inactivation are still unclear. A recent study using animal models uncovered this mystery, which suggested that arginine supplements might be a potential intervention in increasing digoxin activity by inhibiting the expression of cardiac glycoside reductase gene operons that inactivated digoxin. This perspective summarizes the connections among the intestinal microbiome, the digoxin inactivation, the metabolism of arginine. We also discuss several issues yet to be addressed in the future, making better strategies in the application of dietary arginine supplements for digoxin users.

Progastrin stimulates colonic cell proliferation via CCK2R- and β-arrestin-dependent suppression of BMP2

BACKGROUND & AIMS

Progastrin stimulates colonic mucosal proliferation and carcinogenesis through the cholecystokinin 2 receptor (CCK2R)-partly by increasing the number of colonic progenitor cells. However, little is known about the mechanisms by which progastrin stimulates colonic cell proliferation. We investigated the role of bone morphogenetic proteins (BMPs) in progastrin induction of colonic cell proliferation via CCK2R.

METHODS

We performed microarray analysis to compare changes in gene expression in the colonic mucosa of mice that express a human progastrin transgene, gastrin knockout mice, and C57BL/6 mice (controls); the effects of progastrin were also determined on in vitro colonic crypt cultures from cholecystokinin 2 receptor knockout and wild-type mice. Human colorectal and gastric cancer cells that expressed CCK2R were incubated with progastrin or Bmp2; levels of β-arrestin 1 and 2 were knocked down using small interfering RNAs. Cells were analyzed for progastrin binding, proliferation, changes in gene expression, and symmetric cell division.

RESULTS

The BMP pathway was down-regulated in the colons of human progastrin mice compared with controls. Progastrin suppressed transcription of Bmp2 through a pathway that required CCK2R and was mediated by β-arrestin 1 and 2. In mouse colonic epithelial cells, down-regulation of Bmp2 led to decreased phosphorylation of Smads1/5/8 and suppression of inhibitor of DNA binding 4. In human gastric and colorectal cancer cell lines, CCK2R was necessary and sufficient for progastrin binding and induction of proliferation; these effects were blocked when cells were incubated with recombinant Bmp2. Incubation with progastrin increased the number of CD44(+), bromodeoxyuridine+, and NUMB(+) cells, indicating an increase in symmetric divisions of putative cancer stem cells.

CONCLUSIONS

Progastrin stimulates proliferation in colons of mice and cultured human cells via CCK2R- and β-arrestin 1 and 2-dependent suppression of Bmp2 signaling. This process promotes symmetric cell division.

A Speculative Role for Stromal Gastrin Signaling in Development and Dissemination of Pancreatic Ductal Adenocarcinoma

The peptide growth factor gastrin and its receptor, the G-protein coupled cholecystokinin receptor type B (CCK_BR), play an integral role in the growth and progression of pancreatic ductal adenocarcinoma (PDAC). Gastrin immunoreactivity is found in the fetal pancreas but its expression is not detected in normal pancreas after birth, except when it is re-expressed in malignant lesions.