A cohort study of local excision followed by adjuvant therapy incorporating a contact X-ray brachytherapy boost instead of radical resection in 180 patients with rectal cancer

AIM

Recent data have suggested near-equivalent oncological results when treating early rectal cancer by local excision followed by radio- ± chemotherapy rather than salvage radical surgery. The aim of this retrospective study was to assess the use of contact X-ray brachytherapy within this paradigm.

METHOD

All patients had undergone local excision and were referred to our radiotherapy centre for treatment with contact X-ray brachytherapy. Postoperative (chemo)radiotherapy was also given in their local hospital in most cases. Variables assessed were local excision method, postoperative therapy received, follow-up duration, disease-free survival, salvage surgery and stoma-free survival.

RESULTS

In total, 180 patients with a median age of 70 (range 36-99) years were assessed. Following local excision, pT stages were pT1 = 131 (72%), pT2 = 44 (26%), pT3 = 5 (2%). All patients received contact X-ray brachytherapy boosting at our centre and, in addition, 110 received chemoradiotherapy and 60 received radiotherapy alone. After a median follow-up of 36 months (range 6-48), 169 patients (94%) remained free of local recurrence. Of the 11 patients with local recurrence (three isolated nodal), five underwent salvage abdominoperineal excision. Eight patients developed distant disease, of whom five underwent metastasis surgery. At last included follow-up 173 (96%) patients were free of all disease and 170 (94%) were stoma free.

CONCLUSIONS

Contact therapy can be offered in addition to external beam radio (±chemo) therapy instead of radical surgery as follow-on treatment after local excision of early rectal cancer. This combination can provide equivalent outcomes to radical surgery. The added value of contact therapy should be formally assessed in a clinical trial.

RETRACTED: IP1867B suppresses the insulin-like growth factor 1 receptor (IGF1R) ablating epidermal growth factor receptor inhibitor resistance in adult high grade gliomas

This article has been retracted at the request of the Editor-in-Chief due to concerns regarding the legitimacy of images and data presented in the paper. Though a corrigendum (Can. Lett. Vol. 469, 2020, pages 524-535) was previously published to address some of these concerns, this corrigendum has also been found to contain errors and therefore cannot stand. Specific concerns are listed below. The Editor and Publisher received a letter from the University of Portsmouth alerting us to an investigation into alleged research misconduct. The University concluded their investigation with external experts and determined that misconduct did take place in relation to the research involved in this paper. Upon our separate investigation, it has been determined that the paper headline relies on showing that there was considerable reduction of IGF1R, IL6R and EGFR post treatment in all cell lines. During review, it was determined that this cannot be concluded from the presented data. For example, in SEBTA-003 the EGFR levels go up and there is no difference in IGFR1. It is apparent from Fig 4d that in the SEBTA-003 cell line the EGFR level does not go down, which is stated in the Results section on page 32, it is rather going up. The data for IGFR1 are inconclusive and there are concerns regarding the blot. The general implications would be that the effects of the drug IP1867B does not seem to be the same for all tested cell lines, and this should have been discussed in detail by the authors. Additionally, in subsequent experiments (Fig. 4g and h) the SEBTA-003 cell line (no reduction of EGFR, rather increased expression) and the other 3 cell lines (reduction of EGFR) show similar responses. This is particularly evident in Fig. 4g: Two cell lines are compared, SEBTA-003 (increased EGFR expression) and UP-029 (decreased EGFR expression), both behave similarly after exposure to drugs. The corrigendum (https://doi.org/10.1016/j.canlet.2019.10.002) issue is with respect to the Supplemental Figure 6i EGFR, particularly panel IP1867B. The Corrigendum states that the left part is a cut out of the very right part. If so, the bands for IP1867B should show the same staining pattern - but they do not. Also, in the Corrigendum, there are incorrect mentions between day 14 in the Figure and day 19 in the Figure legend. All authors were informed of the retraction in advance. Drs. Pritchard and Duckworth agreed to the retraction. The corresponding author, Dr Hill, did not agree to the retraction. No response had been received from Drs. Mihajluk, Simms, Reay, Madureira, Howarth, Murray, Nasser and Pilkinton at the time of the retraction being published.

Contact X-ray Brachytherapy as an Adjunct to a Watch and Wait Approach is an Affordable Alternative to Standard Surgical Management of Rectal Cancer for Patients with a Partial Clinical Response to Chemoradiotherapy

AIMS

Emerging evidence suggests that contact X-ray brachytherapy (CXB) may increase the clinical complete response rate and durability when administered after standard chemoradiotherapy in patients with rectal cancer. The addition of CXB in partial responders is therefore probably cost-effective. The affordability of widening access to CXB in the UK, however, has not been evaluated.

MATERIALS AND METHODS

Decision analytical modelling with Monte Carlo simulation was used to evaluate long-term costs for the management of patients with rectal cancers who were given a CXB boost when a clinical complete response was not initially achieved following chemoradiotherapy in order to facilitate a watch and wait approach. A third-party payer (National Health Service) perspective was adopted, probabilistic sensitivity analysis was carried out and a scenario analysis was performed to investigate the effect of the number of referral centres and number of patients treated with CXB.

RESULTS

We estimate that 818 (95% confidence interval 628-1021) patients per year are eligible for CXB as an adjunct to a watch and wait approach in England and Wales. As this management is less costly than surgical management for each individual patient, the more patients treated, the more affordable the technology. Even if as few as 125 patients are treated nationally in 15 centres, the cost of implementing this technology would be less than £4 million. If the average number of patients treated in each centre is 30, this technology would be cost saving within 5 years.

CONCLUSIONS

The cost of CXB is not prohibitive according to the National Institute for Health and Care Excellence threshold for implementation of new technology and may even be cost saving within 5 years compared with standard surgical management, depending on the uptake of the technology and the number of referral centres.

The stomach in health and disease

The stomach is traditionally regarded as a hollow muscular sac that initiates the second phase of digestion. Yet this simple view ignores the fact that it is the most sophisticated endocrine organ with unique physiology, biochemistry, immunology and microbiology. All ingested materials, including our nutrition, have to negotiate this organ first, and as such, the stomach is arguably the most important segment within the GI tract. The unique biological function of gastric acid secretion not only initiates the digestive process but also acts as a first line of defence against food-borne microbes. Normal gastric physiology and morphology may be disrupted by Helicobacter pylori infection, the most common chronic bacterial infection in the world and the aetiological agent for most peptic ulcers and gastric cancer. In this state-of-the-art review, the most relevant new aspects of the stomach in health and disease are addressed. Topics include gastric physiology and the role of gastric dysmotility in dyspepsia and gastroparesis; the stomach in appetite control and obesity; there is an update on the immunology of the stomach and the emerging field of the gastric microbiome. H. pylori-induced gastritis and its associated diseases including peptic ulcers and gastric cancer are addressed together with advances in diagnosis. The conclusions provide a future approach to gastric diseases underpinned by the concept that a healthy stomach is the gateway to a healthy and balanced host. This philosophy should reinforce any public health efforts designed to eradicate major gastric diseases, including stomach cancer.

bak deletion stimulates gastric epithelial proliferation and enhances Helicobacter felis-induced gastric atrophy and dysplasia in mice

Helicobacter infection causes a chronic superficial gastritis that in some cases progresses via atrophic gastritis to adenocarcinoma. Proapoptotic bak has been shown to regulate radiation-induced apoptosis in the stomach and colon and also susceptibility to colorectal carcinogenesis in vivo. Therefore we investigated the gastric mucosal pathology following H. felis infection in bak-null mice at 6 or 48 wk postinfection. Primary gastric gland culture from bak-null mice was also used to assess the effects of bak deletion on IFN-γ-, TNF-α-, or IL-1β-induced apoptosis. bak-null gastric corpus glands were longer, had increased epithelial Ki-67 expression, and contained fewer parietal and enteroendocrine cells compared with the wild type (wt). In wt mice, bak was expressed at the luminal surface of gastric corpus glands, and this increased 2 wk post-H. felis infection. Apoptotic cell numbers were decreased in bak-null corpus 6 and 48 wk following infection and in primary gland cultures following cytokine administration. Increased gastric epithelial Ki-67 labeling index was observed in C57BL/6 mice after H. felis infection, whereas no such increase was detected in bak-null mice. More severe gastric atrophy was observed in bak-null compared with C57BL/6 mice 6 and 48 wk postinfection, and 76% of bak-null compared with 25% of C57BL/6 mice showed evidence of gastric dysplasia following long-term infection. Collectively, bak therefore regulates gastric epithelial cell apoptosis, proliferation, differentiation, mucosal thickness, and susceptibility to gastric atrophy and dysplasia following H. felis infection.

Epithelial cell shedding and barrier function: a matter of life and death at the small intestinal villus tip

The intestinal epithelium is a critical component of the gut barrier. Composed of a single layer of intestinal epithelial cells (IECs) held together by tight junctions, this delicate structure prevents the transfer of harmful microorganisms, antigens, and toxins from the gut lumen into the circulation. The equilibrium between the rate of apoptosis and shedding of senescent epithelial cells at the villus tip, and the generation of new cells in the crypt, is key to maintaining tissue homeostasis. However, in both localized and systemic inflammation, this balance may be disturbed as a result of pathological IEC shedding. Shedding of IECs from the epithelial monolayer may cause transient gaps or microerosions in the epithelial barrier, resulting in increased intestinal permeability. Although pathological IEC shedding has been observed in mouse models of inflammation and human intestinal conditions such as inflammatory bowel disease, understanding of the underlying mechanisms remains limited. This process may also be an important contributor to systemic and intestinal inflammatory diseases and gut barrier dysfunction in domestic animal species. This review aims to summarize current knowledge about intestinal epithelial cell shedding, its significance in gut barrier dysfunction and host-microbial interactions, and where research in this field is directed.

The clinical presentation and management of carcinoid heart disease

Carcinoid heart disease is a major cause of morbidity and mortality in patients with metastatic neuroendocrine tumours (NETs). Although cases of carcinoid syndrome and severe carcinoid heart disease requiring urgent intervention are well described, many patients with significant carcinoid heart disease may have insidious symptoms or even be asymptomatic. As haemodynamically significant carcinoid heart disease may be clinically silent, specific and individualised considerations must be made as to the most appropriate clinical criteria and time point at which surgical valve replacement should be undertaken in patients with carcinoid heart disease.

Signaling mediated by the NF-κB sub-units NF-κB1, NF-κB2 and c-Rel differentially regulate Helicobacter felis-induced gastric carcinogenesis in C57BL/6 mice

The classical nuclear factor-kappaB (NF-κB) signaling pathway has been shown to be important in a number of models of inflammation-associated cancer. In a mouse model of Helicobacter-induced gastric cancer, impairment of classical NF-κB signaling in the gastric epithelium led to the development of increased preneoplastic pathology, however the role of specific NF-κB proteins in Helicobacter-associated gastric cancer development remains poorly understood. To investigate this C57BL/6, Nfkb1^−/−, Nfkb2^−/− and c-Rel^−/− mice were infected with Helicobacter felis for 6 weeks or 12 months. Bacterial colonization, gastric atrophy and preneoplastic changes were assessed histologically and cytokine expression was assessed by qPCR. Nfkb1^−/− mice developed spontaneous gastric atrophy when maintained for 12 months in conventional animal house conditions. They also developed more pronounced gastric atrophy after short-term H. felis colonization with a similar extent of preneoplasia to wild-type (WT) mice after 12 months. c-Rel^−/− mice developed a similar degree of gastric atrophy to WT mice; 3 of 6 of these animals also developed lymphoproliferative lesions after 12 months of infection. Nfkb2^−/− mice developed minimal gastric epithelial pathology even 12 months after H. felis infection. These findings demonstrate that NF-κB1- and NF-κB2-mediated signaling pathways differentially regulate the epithelial consequences of H. felis infection in the stomach, while c-Rel-mediated signaling also appears to modulate the risk of lymphomagenesis in gastric mucosa-associated lymphoid tissue.

Acute WNT signalling activation perturbs differentiation within the adult stomach and rapidly leads to tumour formation

A role for WNT signalling in gastric carcinogenesis has been suggested due to two major observations. First, patients with germline mutations in adenomatous polyposis coli (APC) are susceptible to stomach polyps and second, in gastric cancer, WNT activation confers a poor prognosis. However, the functional significance of deregulated WNT signalling in gastric homoeostasis and cancer is still unclear. In this study we have addressed this by investigating the immediate effects of WNT signalling activation within the stomach epithelium. We have specifically activated the WNT signalling pathway within the mouse adult gastric epithelium via deletion of either glycogen synthase kinase 3 (GSK3) or APC or via expression of a constitutively active β-catenin protein. WNT pathway deregulation dramatically affects stomach homoeostasis at very short latencies. In the corpus, there is rapid loss of parietal cells with fundic gland polyp (FGP) formation and adenomatous change, which are similar to those observed in familial adenomatous polyposis. In the antrum, adenomas occur from 4 days post-WNT activation. Taken together, these data show a pivotal role for WNT signalling in gastric homoeostasis, FGP formation and adenomagenesis. Loss of the parietal cell population and corresponding FGP formation, an early event in gastric carcinogenesis, as well as antral adenoma formation are immediate effects of nuclear β-catenin translocation and WNT target gene expression. Furthermore, our inducible murine model will permit a better understanding of the molecular changes required to drive tumourigenesis in the stomach.

CD24 is expressed in gastric parietal cells and regulates apoptosis and the response to Helicobacter felis infection in the murine stomach

CD24 is expressed in the putative stem cells within several tissues and is overexpressed in gastric and colonic adenocarcinomas. Perturbed CD24 expression may therefore alter the response of gastrointestinal epithelia to damage-inducing stimuli that induce cancer. We have investigated the effects of CD24 deletion on gastric responses to Helicobacter felis infection and γ-irradiation using CD24-null mice. Gastric CD24 expression was determined by immunohistochemistry in C57BL/6 mice. Female CD24-null and C57BL/6 mice were infected with H. felis for 6 wk, and inflammation, proliferation, apoptosis, and parietal cell numbers were assessed in gastric tissue sections. Apoptosis and proliferation were analyzed on a cell-positional basis in stomach, small intestine, and colon of CD24-null and C57BL/6 mice following γ-irradiation. Apoptosis was also assessed in HT29 cells following CD24 siRNA transfection. Of CD24-positive cells in the gastric corpus, 98% were H(+)-K(+)-ATPase-expressing parietal cells. CD24-null mice showed more prominent gastric H. felis colonization than C57BL/6 mice but displayed a marked reduction in corpus inflammation, reduced Ki67 labeling, and less gastric atrophy 6 wk following infection. Corpus apoptosis was elevated in CD24-null mice, but this did not increase further with H. felis infection as observed in C57BL/6 mice. More apoptotic cells were found following γ-irradiation in the stomach, small intestine, and colon of CD24-null mice and following CD24 knockdown in vitro. In conclusion, CD24 is expressed in gastric parietal cells, where it modulates gastric responses to H. felis and γ-radiation. CD24 also regulates susceptibility to apoptosis in the distal murine gastrointestinal tract.

Local barrier dysfunction identified by confocal laser endomicroscopy predicts relapse in inflammatory bowel disease

OBJECTIVES

Loss of intestinal barrier function plays an important role in the pathogenesis of inflammatory bowel disease (IBD). Shedding of intestinal epithelial cells is a potential cause of barrier loss during inflammation. The objectives of the study were (1) to determine whether cell shedding and barrier loss in humans can be detected by confocal endomicroscopy and (2) whether these parameters predict relapse of IBD.

METHODS

Confocal endomicroscopy was performed in IBD and control patients using intravenous fluorescein to determine the relationship between cell shedding and local barrier dysfunction. A grading system based on appearances at confocal endomicroscopy in humans was devised and used to predict relapse in a prospective pilot study of 47 patients with ulcerative colitis and 11 patients with Crohn's disease.

RESULTS

Confocal endomicroscopy in humans detected shedding epithelial cells and local barrier defects as plumes of fluorescein effluxing through the epithelium. Mouse experiments demonstrated inward flow through some leakage-associated shedding events, which was increased when luminal osmolarity was decreased. In IBD patients in clinical remission, increased cell shedding with fluorescein leakage was associated with subsequent relapse within 12 months after endomicroscopic examination (p<0.001). The sensitivity, specificity and accuracy for the grading system to predict a flare were 62.5% (95% CI 40.8% to 80.4%), 91.2% (95% CI 75.2 to 97.7) and 79% (95% CI 57.7 to 95.5), respectively.

CONCLUSIONS

Cell shedding and barrier loss detected by confocal endomicroscopy predicts relapse of IBD and has potential as a diagnostic tool for the management of the disease.

The relative contribution of NSAIDs and Helicobacter pylori to the aetiology of endoscopically-diagnosed peptic ulcer disease: observations from a tertiary referral hospital in the UK between 2005 and 2010

BACKGROUND

Recent data from Western countries indicate that the aetiology of peptic ulcer disease (PUD) is changing as the prevalence of Helicobacter pylori is decreasing while the use of low-dose aspirin (LDA, ≤325 mg/day) is increasing.

AIM

To investigate the changing aetiology and demographics of PUD in a well-characterised patient cohort at a large tertiary hospital in the UK between July 2005 and June 2010.

METHODS

Patients diagnosed with PUD following endoscopy were categorised as non-steroidal anti-inflammatory drug (NSAID)-users or non-users, and their H. pylori status determined. Comparisons between NSAID-users and non-users, and between non-aspirin NSAID-users and LDA-users were summarised using counts and corresponding percentages (for categorical variables) and means and standard deviations (for continuous variables).

RESULTS

Overall, 386 patients were enrolled; 57% used NSAIDs (51% LDA only) and 43% were non-users. 57% of the whole cohort was H. pylori-positive (including 66% with duodenal ulcers and 47% with gastric ulcers). Compared with non-users, NSAID-users were older (mean age 68 vs. 61 years) and fewer were H. pylori-positive (52% vs. 63%). LDA-users were older (mean age 71 vs. 62 years) and more likely to be H. pylori-positive (61% vs. 41%) than those using non-aspirin NSAIDs. Twelve per cent of the patients were neither using NSAIDs nor were H. pylori-positive.

CONCLUSIONS

The NSAIDs, particularly LDA, were most commonly associated with PUD in this cohort. Our findings are compatible with the decline in the prevalence of H. pylori-positive PUD and increase in non-NSAID, non-H. pylori PUD previously reported.

Review article: cellular and molecular mechanisms of NSAID-induced peptic ulcers

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) are some of the most prescribed drugs worldwide and have now probably overtaken Helicobacter pylori as the most common cause of gastrointestinal injury in Western countries. Further understanding of the pathogenesis of NSAID-induced ulcers is important to enable the development of novel and effective preventive strategies.

AIMS

To provide an update on recent advances in our understanding of the cellular and molecular mechanisms involved in the development of NSAID-induced ulcers.

METHODS

A Medline search was performed to identify relevant literature using search terms including 'nonsteroidal anti-inflammatory drugs, aspirin, gastric ulcer, duodenal ulcer, pathogenesis, pharmacogenetics'.

RESULTS

The mechanisms of NSAID-induced ulcers can be divided into topical and systemic effects and the latter may be prostaglandin-dependent (through COX inhibition) or prostaglandin-independent. Genetic factors may play an important role in determining individual predisposition.

CONCLUSIONS

The pathogenesis of NSAID-induced peptic ulcers is complex and multifactorial. Recent advances in cellular and molecular biology have highlighted the importance of various prostaglandin-independent mechanisms. Pharmacogenetic studies may provide further insights into the pathogenetic mechanisms of NSAID-induced ulcers and help identify patients at increased risk.

Review article: Strategies to determine whether hypergastrinaemia is due to Zollinger-Ellison syndrome rather than a more common benign cause

BACKGROUND

As there is considerable overlap between the fasting serum gastrin concentrations found in Zollinger-Ellison syndrome and various common conditions such as Helicobacter pylori infection and acid suppressing medication use, establishing the cause of hypergastrinaemia in individual cases can sometimes be difficult.

AIM

To review the causes of hypergastrinaemia and the role of additional non-invasive investigations in hypergastrinaemic patients.

METHODS

Review of articles following a Pubmed search.

RESULTS

As gastrinomas may cause serious complications and be potentially life threatening, investigation of hypergastrinaemic patients should particularly focus on confirming or refuting the diagnosis of Zollinger-Ellison syndrome. Establishing the cause of hypergastrinaemia may be difficult when there is only a mild-to-moderate elevation of fasting serum gastrin concentration and concurrent treatment with proton pump inhibitor drugs and the presence of H. pylori infection can both confuse the clinical picture. A variety of provocative tests are therefore useful for establishing whether a hypergastrinaemic patient has a gastrinoma and current evidence suggests that the secretin test should be used first line.

CONCLUSIONS

We suggest an algorithm for the investigation of patients found to have an elevated fasting serum gastrin concentration and address the roles of gastrin stimulation tests in current clinical practice.

Gastrin increases mcl-1 expression in type I gastric carcinoid tumors and a gastric epithelial cell line that expresses the CCK-2 receptor

Elevated serum concentrations of the hormone gastrin are associated with the development of gastric carcinoid tumors, but the mechanisms of tumor development are not fully understood. We hypothesized that the antiapoptotic effects of gastrin may be implicated and have therefore investigated the role of antiapoptotic members of the bcl-2 family of proteins. AGS-G(R) human gastric carcinoma cells stably transfected with the CCK-2 receptor were used to assess changes in the expression of bcl-2 family members following gastrin treatment and the function of mcl-1 during apoptosis was investigated by use of small-interfering RNA (siRNA). Treatment of AGS-G(R) cells with 10 nM gastrin for 6 h caused maximally increased mcl-1 protein abundance. Gastrin-induced mcl-1 expression was inhibited by the transcription inhibitor actinomycin D and by the protein synthesis inhibitor cycloheximide. Downstream signaling of mcl-1 expression occurred via the CCK-2 receptor, protein kinase C, and MAP kinase pathways, but not via PI 3-kinase. Transfection with mcl-1 siRNA significantly suppressed mcl-1 protein expression and abolished the antiapoptotic effects of gastrin on serum starvation-induced apoptosis. Mcl-1 protein expression was also specifically increased in the type I enterochromaffin-like cell carcinoid tumors of 10 patients with autoimmune atrophic gastritis and hypergastrinemia. Gastrin therefore signals via the CCK-2 receptor, protein kinase C, and MAP kinase to induce expression of antiapoptotic mcl-1 in AGS-G(R) cells, and mcl-1 expression is also increased in human hypergastrinemia-associated type I gastric carcinoid tumors. Gastrin-induced mcl-1 expression may therefore be an important mechanism contributing toward type I gastric carcinoid development.

Altered gastric corpus expression of tissue inhibitors of metalloproteinases in human and murine Helicobacter infection

BACKGROUND

Matrix metalloproteinases (MMPs) have roles in inflammation and other processes relevant to the architectural disturbances seen in the gastric mucosa in response to Helicobacter pylori infection. Upregulation of MMPs has been reported in H pylori infection, but there are no detailed reports regarding altered production of their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs).

AIMS

To investigate changes in the abundance of TIMPs in human gastric corpus mucosa and murine stomach in Helicobacter infection, and to study cellular sources in man.

METHODS

Gastric corpus biopsy samples were assessed for abundance of mRNA or protein for TIMP-1 to -4 by real-time quantitative PCR or western blotting, respectively. Antral and corpus biopsies were processed for histology, H pylori status and inflammatory scoring. Cellular sources of TIMP-1, -3 and -4 were examined by indirect immunohistochemistry. Circulating gastrin was measured by radioimmunoassay. Also, abundance of TIMP-1, -3 and -4 mRNA in the stomach of Helicobacter felis infected mice post-infection was compared with that of uninfected control animals.

RESULTS

Compared with uninfected patients, mRNA and protein for TIMP-1, -3 and -4 were significantly more abundant in the gastric corpus of H pylori infected subjects. Gastric TIMP expression did not differ significantly between hyper- and normogastrinaemic subjects within the H pylori negative and positive groups. There was no difference in mRNA abundance for MMP-3 or -8. Immunohistochemistry showed TIMP proteins localised to gastric epithelial, stromal cells and inflammatory cells. Murine H felis infection was associated with upregulation of TIMP-1 and -3 mRNA.

CONCLUSIONS

Helicobacter infection is associated with upregulation of specific TIMPs (TIMP-1 and -3) in glandular epithelium and stroma. It is suggested that increased expression of specific protease inhibitors in the corpus mucosa may exert important effects on extracellular matrix remodelling and influence the outcome of H pylori infection.

Hypergastrinemia increases gastric epithelial susceptibility to apoptosis

Plasma concentrations of the hormone gastrin are elevated by Helicobacter pylori infection and by gastric atrophy. It has previously been proposed that gastrin acts as a cofactor during gastric carcinogenesis and hypergastrinemic transgenic INS-GAS mice are prone to developing gastric adenocarcinoma, particularly following H. pylori infection. We hypothesised that the increased risk of carcinogenesis in these animals may partly result from altered susceptibility of gastric epithelial cells to undergo apoptosis. Gastric corpus apoptosis was significantly increased 48 h after 12Gy gamma-radiation in mice rendered hypergastrinemic by transgenic (INS-GAS) or pharmacological (omeprazole treatment of FVB/N mice) methods and in both cases the effects were inhibited by the CCK-2 receptor antagonist YM022. However, no alteration in susceptibility to gamma-radiation-induced gastric epithelial apoptosis was observed in mice overexpressing progastrin or glycine-extended gastrin. Apoptosis was also significantly increased in gastric corpus biopsies obtained from H. pylori-infected humans with moderate degrees of hypergastrinemia. We conclude that hypergastrinemia specifically renders cells within the gastric corpus epithelium more susceptible to induction of apoptosis by radiation or H. pylori. Altered susceptibility to apoptosis may therefore be one factor predisposing to gastric carcinogenesis in INS-GAS mice and similar mechanisms may also be involved in humans.

Pathogenesis of gastrinomas associated with multiple endocrine neoplasia type 1

Deletion of the second allele of the tumour suppressor gene MEN1 is assoiated with development of duodenal gastrin‐secreting microtumours in MEN1

Radiation-induced gastric epithelial apoptosis occurs in the proliferative zone and is regulated by p53, bak, bax, and bcl-2

Unlike the small intestine and colon where gamma-radiation-induced apoptosis has previously been well characterized, the response of murine gastric epithelium to gamma-radiation has not been investigated in detail. Apoptosis was therefore assessed on a cell positional basis in gastric antral and corpus glands from adult male mice following gamma-radiation. Maximum numbers of apoptotic cells were observed in both antrum and corpus at 48 h and at radiation doses greater than 12 Gy. However, the number of apoptotic cells observed in the gastric epithelium was much lower than observed in the small intestine or colon after similar doses of radiation. Hematoxylin and eosin, caspase 3 immunohistochemistry, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling detected similar numbers and cell positional distributions of apoptotic cells, hence hematoxylin and eosin was used for subsequent studies. The highest numbers of apoptotic cells were observed at cell positions 5-6 in the antrum and cell positions 15-18 in the corpus. These distributions coincided with the distributions of PCNA-labeled proliferating cells, but not with the distributions of H(+)-K(+)-ATPase-labeled parietal cells or TFF2-labeled mucous neck cells. Decreased numbers of apoptotic gastric epithelial cells were observed in p53-null, bak-null, and bax-null mice compared with wild-type counterparts 6 and 48 h after 12 Gy gamma-radiation. Significantly increased numbers of apoptotic gastric epithelial cells were observed in bcl-2-null mice compared with wild-type littermates 6 h after 12 Gy gamma-radiation. Radiation therefore induces apoptosis in the proliferative zone of mouse gastric epithelium. This response is regulated by the expression of p53, bak, bax, and bcl-2.

Review article: Pathogenesis and management of gastric carcinoid tumours

BACKGROUND

Gastric carcinoid tumours are rare, but are increasing in incidence.

AIM

To discuss tumour pathogenesis and outline current approaches to patient management.

METHODS

Review of published articles following a Pubmed search.

RESULTS

Although interest in gastric carcinoids has increased since it was recognized that they are associated with achlorhydria, to date there is no definite evidence that humans taking long-term acid suppressing medication are at increased risk. Type I tumours are associated with autoimmune atrophic gastritis and hypergastrinaemia, type II are associated with Zollinger-Ellison syndrome, multiple endocrine neoplasia-1 and hypergastrinaemia and sporadic type III carcinoids are gastrin-independent and carry the worst prognosis. Careful investigation of these patients is required, particularly to identify the tumour type, the source of hypergastrinaemia and the presence of metastases. Treatment can be directed at the source of hypergastrinaemia if type I or II tumours are still gastrin responsive and not growing autonomously. Type III tumours should be treated surgically.

CONCLUSIONS

Advances in our understanding of the pathogenesis of gastric carcinoids have led to recent improvements in investigation and management. Challenges remain in identifying the genetic and environmental factors, in addition to hypergastrinaemia, that are responsible for tumour development in susceptible patients.

COOH-terminal 26-amino acid residues of progastrin are sufficient for stimulation of mitosis in murine colonic epithelium in vivo

Transgenic mice (hGAS) that overexpress human progastrin are more susceptible than wild-type mice (FVB/N) to the induction of colonic aberrant crypt foci (ACF) and adenomas by the chemical carcinogen azoxymethane. We have previously shown significantly increased levels of colonic mitosis in hGAS compared with FVB/N mice after gamma-radiation. To investigate whether the effects of progastrin observed in hGAS colon require the presence of other forms of circulating gastrin, we have crossed hGAS (hg(+/+)) with gastrin knockout (G(-/-)) mice to generate mice that express progastrin and no murine gastrin (G(-/-)hg(+/+)). After azoxymethane, G(-/-)hg(+/+) mice developed significantly more ACF than control G(-/-)hg(-/-) mice (which do not express any forms of gastrin). G(-/-)hg(+/+) mice also exhibited significantly increased colonic mitosis both before and after exposure to 8 Gray Gy gamma-radiation or 50 mg/kg azoxymethane compared with G(-/-)hg(-/-). Treatment of G(-/-)hg(-/-) mice with synthetic progastrin (residues 21-101 of human preprogastrin) or G17 extended at its COOH terminus corresponding to the COOH-terminal 26-amino-acid residues of human preprogastrin (residues 76-101, G17-CFP) resulted in continued colonic epithelial mitosis after gamma-radiation, whereas glycine-extended gastrin-17 and the COOH-terminal tryptic fragment of progastrin [human preprogastrin-(96-101)] had no effect. Immunoneutralization with an antibody against G17-CFP before gamma-radiation significantly decreased colonic mitosis in G(-/-)hg(+/+) mice to levels similar to G(-/-)hg(-/-). We conclude that progastrin does not require the presence of other forms of gastrin to exert proliferative effects on colonic epithelia and that the portion of the peptide responsible for these effects is contained within amino acid residues 76-101 of human preprogastrin.

Review article: How useful are the rodent animal models of gastric adenocarcinoma?

Gastric cancer is the second most common cause of cancer-related mortality world-wide. In most cases, it develops via the pre-malignant stages of atrophic gastritis, intestinal metaplasia and dysplasia, following Helicobacter pylori infection of susceptible individuals. A number of rodent models have recently provided valuable insights into the host, bacterial and environmental factors involved in gastric carcinogenesis. Wild-type rodents do not develop gastric adenocarcinoma, but early studies showed that the disease could be induced in several rodent species by chemical carcinogens. More recently, it has been demonstrated that gastric adenocarcinoma can be induced in Mongolian gerbils by H. pylori infection and in C57BL/6 mice by long-term H. felis infection. These models have allowed the importance of Helicobacter virulence genes, host factors, such as gender, strain and immune response, and environmental factors, such as dietary salt, to be explored. A number of transgenic mice with alterations in various pathways, including the immune response, gastrin biosynthesis, parietal cell development, growth factors and tumour suppressors, have also provided models of various stages of gastric carcinogenesis. One model that has proved to be particularly valuable is the hypergastrinaemic INS-GAS mouse, in which gastric carcinoma develops spontaneously in old animals, but the process is greatly accelerated by Helicobacter infection.

The importance of p53-independent apoptosis in the intestinal toxicity induced by raltitrexed (ZD1694, Tomudex): genetic differences between BALB/c and DBA/2 mice

The thymidylate synthase inhibitor raltitrexed (ZD1694, Tomudex) induces greater intestinal toxicity, manifested as diarrhea and weight loss, in BALB/c than in DBA/2 mice. No convincing pharmacokinetic or pharmacodynamic reason for this strain difference has been established. We have investigated whether this strain difference in response to raltitrexed is related to differential susceptibilities of intestinal mucosae to undergo apoptosis and also whether p53 expression, a critical factor in 5-fluorouracil-induced intestinal apoptosis and toxicity, modulates this response. Ten mg/kg or 100 mg/kg raltitrexed were administered as single or double i.p. injections 24 h apart to BALB/c, DBA/2, and p53-/- mice. Apoptosis, mitosis, and tissue damage were assessed in intestinal epithelium, and animal weight was recorded. BALB/c mice developed diarrhea and weight loss following 100 mg/kg x2 raltitrexed, whereas DBA/2 mice did not. BALB/c mice were more sensitive than DBA/2 to induction of small-intestinal and colonic apoptosis 24 h following 100 mg/kg raltitrexed. Inhibition of mitosis was equivalent in both strains. Both strains showed histopathological damage to the small intestine after 100 mg/kg x2 raltitrexed, but only BALB/c mice demonstrated colonic damage. p53-null mice showed the same level of small intestinal apoptosis as their wild-type counterparts 24 h after 100 mg/kg x1 raltitrexed and also the same levels of intestinal toxicity 3, 5, and 7 days after 100 mg/kg x2 raltitrexed. Thus, BALB/c mice were more susceptible to induction of intestinal apoptosis by raltitrexed than DBA/2 mice and also demonstrated more histopathological damage in the colon correlating with the induction of diarrhea and weight loss. In contrast to 5-fluorouracil, the intestinal apoptosis and toxicity induced by raltitrexed were p53-independent.

Bcl-w is an important determinant of damage-induced apoptosis in epithelia of small and large intestine

The potential role of the bcl-2 relative bcl-w as a physiological regulator of apoptosis in intestinal epithelia has been investigated. Immunoblots for bcl-w with new monoclonal antibodies revealed that it was expressed in the small intestine and colon, among other murine tissues, as well as in six human tumour cell lines of epithelial origin, including two colon carcinoma lines. To assess whether bcl-w regulates either spontaneous or damage-induced apoptosis in the small intestine or colon, apoptosis in intestinal crypts of bcl-w -/- and wild-type mice was quantified microscopically on a cell positional basis. Spontaneous apoptosis within crypt epithelia was not significantly increased by loss of bcl-w, in either the small intestine or midcolon. However, after treatment with the cytotoxic drug 5-fluorouracil or with gamma-radiation, the bcl-w-null animals exhibited substantially more apoptosis than their wild-type counterparts in both tissues. The greatest enhancement of apoptosis attributable to the absence of bcl-w (up to sixfold) occurred in the small intestine. Hence, bcl-w is an important determinant of damage-induced apoptosis in intestinal epithelia, and unlike bcl-2, which regulates only colonic apoptosis, plays a major role in small intestinal epithelium.

New directions in the treatment of colorectal cancer: a look to the future

Today, adjuvant 5-fluorouracil based therapy is known to significantly reduce the relapse rates and the risks of dying from resected colon cancer; chemotherapy approximately doubles overall survival of advanced colorectal cancer and second line treatment prolongs the survival of patients compared with best supportive care. At the molecular level a number of key genes are often mutated in cancer of the colon and some of these key regulators of apoptosis are discussed (p53 and bcl-2 family of proteins). Dihydropyrimidine dehydrogenase (DPD) activity may be a potential factor controlling fluorouracil (FU) responsiveness at the tumoral level and its importance is stressed. The rationale of combining FU with DPD inhibitors is fairly strong. Ethynyluracil, UFT and S1 pursue this strategy while capecitabine has another the rationale. Drug resistance should be at least partially overcome by combination chemotherapy (FU plus mitomycin, oxaliplatin, irinotecan) and combined modality (FU+RT) regimens. Improved surgical techniques and radiotherapy have substantially decreased local failure rates for rectal cancers. Finally, innovative treatment modalities such as anti-angiogenetic and antimetastatic agents, farnesyl transferase inhibitors, vaccine and gene therapy are in early clinical trials.

Lessons from genetically engineered animal models. VII. Apoptosis in intestinal epithelium: lessons from transgenic and knockout mice

Apoptosis plays an important role in homeostasis of intestinal epithelia and is also a stress response to toxic stimuli. Transgenic and knockout mice have provided insights into the regulation of intestinal epithelial apoptosis that could not have been obtained by cell culture techniques. Two broad types of apoptosis have been characterized: spontaneous apoptosis, which occurs continuously at low levels in the normal, unstressed intestine, and stress-induced apoptosis, which occurs after genotoxic insult such as exposure to gamma radiation or DNA-damaging drugs. Spontaneous apoptosis occurs at the base of the crypt at or near the position of epithelial stem cells. Knockout studies have shown that spontaneous apoptosis is independent of p53 and Bax in both small and large intestine, whereas Bcl2 only regulates spontaneous apoptosis in the colon. Little is known about the regulation of the specialized form of cell death at the villus tip. In contrast, knockout studies have demonstrated that both p53 and Bcl2 are important regulators of stress-induced apoptosis but that there are significant differences between early and late time points. Bax plays only a minor role in the regulation of stress-induced apoptosis. The cumulative effect of stress-induced apoptosis on tissue architecture is not straightforward, and cell cycle arrest also plays a critical role. Nevertheless, p53 is an important determinant of the histopathological damage induced by 5-fluorouracil in murine intestinal epithelium. These studies have important implications for the development of more effective treatment for inflammatory bowel disease and cancer.

Balb/c mice as a preclinical model for raltitrexed-induced gastrointestinal toxicity

Raltitrexed (RTX) is an antifolate thymidylate synthase (TS) inhibitor used for the treatment of advanced colorectal cancer. RTX induces proliferating tissue toxicities that are largely confined to the intestine, with diarrhea being a severe side effect in a small but significant minority of patients. Similarly, weight loss and diarrhea were observed in BALB/c mice, and a maximum tolerated dose (MTD) was determined as approximately 5-10 mg/kg/day x 5 days. At an equivalent dose of 10 mg/kg/day x 5 days (dl-5), DBA2 mice lost considerably less weight, leading to a higher MTD (>500 mg/kg/day x 5 days), and there was no evidence of diarrhea. Histopathological consequences of damage, such as changes in small intestinal crypt architecture and villus atrophy induced by the 10-mg/kg/day dose, were greater and of longer duration in BALB/c mice. A higher dose of RTX (100 mg/kg/day x 5) induced weight loss and histopathological damage similar to that seen in BALB/c mice (10 mg/kg/ day x 5) but was of later onset, nadir, and recovery. Small changes to the colon were only observed in BALB/c mice. Pretreatment levels of plasma thymidine, deoxyuridine (approximately 1 microM), and folate (approximately40 ng/ml) were similar in both mouse strains. A single injection of radiolabeled RTX (5 mg/kg/ day) did not lead to any marked difference 24 h later in the total drug concentration and distribution of polyglutamates (comprising 70-80% of drug extracted) in the liver, kidney, and intestinal epithelium (large and small intestine) between the two mouse strains. Further studies used a RIA to measure RTX polyglutamate formation in tissues at various times and drug doses. This led to the conclusion that, although there was a higher accumulation of RTX in BALB/c small intestinal epithelium (days 4-6), it may be an effect secondary to another undetermined cause of increased drug sensitivity. This model represents a vehicle by which the etiology and treatment of severe clinical toxicity induced by RTX may be evaluated.

Damage-induced apoptosis in intestinal epithelia from bcl-2-null and bax-null mice: investigations of the mechanistic determinants of epithelial apoptosis in vivo

The influence of bcl-2 and bax expression on apoptotic cell death in mouse intestinal epithelia was assessed using homozygously null mice. Apoptosis was induced in vivo by the enterotoxin 5-fluorouracil (5FU) or by gamma-irradiation and its cell positional incidence was assessed. 5FU and gamma-radiation treated bax-null mice surprisingly showed no reductions in apoptotic yield in the small intestine or midcolon at 4.5 h at cell positions in which both agents had previously been shown to strongly induce p53 protein expression. The colonic epithelia of 5FU treated bcl-2-null mice showed elevated levels of apoptosis at 4.5 h: from 48 apoptotic events in wild-type mice to 273 in the nulls, scoring 200 half crypts. The increase occurred specifically in the cell positions considered to harbour colonic stem cells, at the base of crypts, where there is selective expression of bcl-2. There was a modest but significant increase in apoptosis in the small intestine of the bcl-2-null mice although the epithelia of wild-type mice here are not immunohistochemically positive for bcl-2 protein. These findings show that bcl-2 plays a key role in determining the sensitivity of colonic stem cells to damage-induced death but that bax is not responsible for the p53-dependent induction of apoptosis in this context.

Chemically-induced apoptosis: p21 and p53 as determinants of enterotoxin activity

The relationship between toxin-induced apoptosis and longer-term (> 72 h) intestinal toxicity was investigated in vivo using p53 wild type (+/+) and 'knockout' (-/-) mice. The enterotoxic antimetabolite 5-fluorouracil (5-FU) induced acute p53-dependent apoptosis in the crypts of both small intestine and midcolon. Although the amount of apoptosis was the same order of magnitude at its peak (24 h) at both 40 and 400 mg/kg 5-FU, only 400 mg/kg 5-FU brought about changes in the integrity of the gut after 96 h. These were characterised by the loss of epithelial cells from crypts and villi. Only after 400 mg/kg 5-FU were mitotic index and DNA synthesis significantly suppressed in both small intestinal and midcolonic crypts. This correlated with a prolonged, p53-dependent expression of p21(waf-1/cip1). In p53 null (-/-) mice significant reductions in 5-FU-induced apoptosis and relief from the inhibition of cell cycle progression permitted retention of crypt integrity after 5-FU. Thus, quantitative measures of acute apoptosis in vivo did not accurately predict subsequent pathological changes in the gut. Rather, p53-dependent inhibition of cell cycle progression together with cell loss by apoptosis caused a loss of crypt integrity. Importantly, the tissue toxicity of 5-fluorouracil was genetically determined at a locus (p53) separate from that directly associated with toxin action. The selectivity of toxin action is therefore also determined by events 'downstream' of those associated with the direct mode of action of the toxin.

The relationships between p53-dependent apoptosis, inhibition of proliferation, and 5-fluorouracil-induced histopathology in murine intestinal epithelia

The relationship between acute (<36 h) induction of apoptosis and longer-term (>72 h) intestinal histopathology was systematically investigated in vivo using p53 wild-type (+/+) and null (-/-) mice. Administration of the enterotoxin 5-fluorouracil (5-FU) at either 40 or 400 mg/kg to BDF1 mice induced an acute p53-dependent apoptosis in the crypts of both small intestine and midcolon. Although the amount of apoptosis was of the same order of magnitude at its peak (24 h) at both doses, only 400 mg/kg 5-FU brought about histopathological changes to the gut after 96 h, quantified as losses of crypt and villus cellularity. Only after the administration of 400 mg/kg 5-FU were mitotic index and DNA synthesis significantly suppressed in both small intestinal and midcolonic crypts at 24 h. This correlated with a prolonged, p53-dependent expression of p21waf-1/cip1. In p53 null (-/-) mice, significant reductions in both 5-FU-induced apoptosis and inhibition of cell cycle progression allowed retention of crypt integrity 96 h after 5-FU. These results show that quantitative measures of acute apoptosis in vivo may not accurately predict subsequent pathological changes in the gut. Rather, p53-dependent inhibition of cell cycle progression, together with cell loss by apoptosis, caused a loss of crypt integrity. Importantly, the tissue toxicity of 5-FU was genetically determined at a locus (p53) separate from that directly associated with drug action.

Radiation-induced p53 and p21WAF-1/CIP1 expression in the murine intestinal epithelium: apoptosis and cell cycle arrest

p53-dependent expression of p21WAF-1/CIP1 has been studied in murine intestinal epithelium after exposure to ionizing radiation. In un-irradiated small intestine, neither p53 nor p21WAF-1/CIP1 could be detected by immunohistochemistry. After irradiation (8 Gy), there was a time- and dose-dependent increase in the expression of both proteins. In the small bowel, the positional expression of p53 and p21WAF-1/CIP1 was similar but not coincident. Both proteins could be observed throughout the crypts with greatest frequency of expression over the first 15 cell positions, which includes the stem cell population (approximately positions 3 to 5) and the proliferating, transit cell population (approximately positions 5 to 15). p53-positive cells were primarily distributed toward the base of the crypt relative to p21WAF-1/CIP1. Subdivision of the p53-positive cell population revealed that the cells with strongest p53 immunoreactivity were positioned farther toward the base of the crypt, and their distribution was approximately coincident with the frequency distribution of apoptotic cells. Cells that were either weakly or moderately immunoreactive for p53 were located toward the middle of the crypt and were approximately coincident with the distribution of p21WAF-1/CIP1. The numbers of both p53- and p21WAF-1/CIP1-positive cells declined steadily with time, and by 6 days after irradiation there were very few immunoreactive cells to observe. Radiation-induced increase in p53 and p21WAF-1/CIP1 expression was not detected in mice homozygously null for p53. Expression of p21WAF-1/CIP1 and incorporation of tritiated thymidine were found to be mutually exclusive. In the large bowel, p21WAF-1/CIP1 and p53 expression were observed along the entire length of the colonic crypts after irradiation (8 Gy), and, unlike in the small intestine, this expression was not only maintained but increased over 72 hours. p21WAF-1/CIP1 immunoreactivity was detected in large intestine epithelium up to 6 days after irradiation. The differential expression of p21WAF-1/CIP1, observed between the large and small bowel and within the small intestinal crypts, is discussed.

The intestinal epithelial stem cell: the mucosal governor

All epithelial cells in the small and large intestine are thought to originate from stem cells located towards the base of the crypts of Lieberkühn. To-date, there are no specific intestinal stem cell markers, hence stem cell properties can only be inferred. A range of experimental techniques have been employed including cell position mapping, radiation regeneration (clonogenic) assays, chimeric and transgenic mice. This review discusses the implications of experiments performed using these techniques in order to deduce the number, location and functional properties of stem cells. Stem cell homeostasis is maintained by cell proliferation and death 'through apoptosis'. The various growth and matrix factors and genes which may control these processes, and be important for stem cell function, are discussed along with their carcinogenic and clinical implications.

The intestinal epithelial stem cell: the mucosal governor

All epithelial cells in the small and large intestine are thought to originate from stem cells located towards the base of the crypts of Lieberkühn. To-date, there are no specific intestinal stem cell markers, hence stem cell properties can only be inferred. A range of experimental techniques have been employed including cell position mapping, radiation regeneration (clonogenic) assays, chimeric and transgenic mice. This review discusses the implications of experiments performed using these techniques in order to deduce the number, location and functional properties of stem cells. Stem cell homeostasis is maintained by cell proliferation and death 'through apoptosis'. The various growth and matrix factors and genes which may control these processes, and be important for stem cell function, are discussed along with their carcinogenic and clinical implications.

Inhibition by uridine but not thymidine of p53-dependent intestinal apoptosis initiated by 5-fluorouracil: evidence for the involvement of RNA perturbation

The epithelia from the crypts of the intestine are exquisitely sensitive to metabolic perturbation and undergo cell death with the classical morphology of apoptosis. Administration of 40 mg/kg 5-fluorouracil (5-FU) to BDF-1 p53+/+ mice resulted in an increase in p53 protein at cell positions in the crypts that were also those subjected to an apoptotic cell death. In p53-/- mice apoptosis was almost completely absent, even after 24 hr. 5-FU is a pyrimidine antimetabolite cytotoxin with multiple mechanisms of action, including inhibition of thymidylate synthase (TS), which gives rise to DNA damage, and incorporation into RNA. The inhibition of TS can be increased by coadministration of folinic acid and can be abrogated by administration of thymidine. The incorporation of 5-FU into RNA is inhibited by administration of uridine. p53-Dependent cell death induced by 5-FU was only inhibited by administration of uridine. Uridine had no effect on the apoptosis initiated by 1 Gy of gamma-radiation. Although thymidine abrogated apoptosis induced by the pure TS inhibitor Tomudex, it had no effect on 5-FU-induced apoptosis, and coadministration of folinic acid did not increase apoptosis. The data show that 5-FU-induced cell death of intestinal epithelial cells is p53-dependent and suggests that changes in RNA metabolism initiate events culminating in the expression of p53.

Apoptosis and gastrointestinal pharmacology

Apoptosis is a fundamental biological process that regulates cell number and removes cells that are neoplastic or infected by viruses. This review summarises present knowledge of the mechanisms and genetic regulation of apoptosis in the gastrointestinal tract and highlights areas of pharmacological relevance. In the intestine, apoptosis occurs in the crypt and possibly at the villus tip. Abnormal apoptosis plays a role in a number of gastrointestinal disease including colorectal cancer. The effects of cytotoxic drugs, chemical carcinogens, nonsteroidal anti-inflammatory drugs, short-chain fatty acids, bile salts and anthraquinolones on apoptosis in the gastrointestinal tract are reviewed.