A metabolic atlas of mouse aging

Humans are living longer, but this is accompanied by an increased incidence of age-related chronic diseases. Many of these diseases are influenced by age-associated metabolic dysregulation, but how metabolism changes in multiple organs during aging in males and females is not known. Answering this could reveal new mechanisms of aging and age-targeted therapeutics. In this study, we describe how metabolism changes in 12 organs in male and female mice at 5 different ages. Organs show distinct patterns of metabolic aging that are affected by sex differently. Hydroxyproline shows the most consistent change across the dataset, decreasing with age in 11 out of 12 organs investigated. We also developed a metabolic aging clock that predicts biological age and identified alpha-ketoglutarate, previously shown to extend lifespan in mice, as a key predictor of age. Our results reveal fundamental insights into the aging process and identify new therapeutic targets to maintain organ health.

The aging tumor metabolic microenvironment

Despite the higher incidence of cancer with increasing age, few preclinical or clinical studies incorporate age. This, coupled with an aging world population, requires that we improve our understanding of how aging affects cancer development, progression, and treatment. One key area will be how the tumor microenvironment (TME) changes with age. Metabolite levels are an essential component of the TME, and they are affected by the metabolic requirements of the cells present and systemic metabolite availability. These factors are affected by aging, causing different TME metabolic states between young and older adults. In this review, we will summarize what is known about how aging impacts the TME metabolic state, and suggest how we can improve our understanding of it.

Differential integrated stress response and asparagine production drive symbiosis and therapy resistance of pancreatic adenocarcinoma cells

The pancreatic tumor microenvironment drives deregulated nutrient availability. Accordingly, pancreatic cancer cells require metabolic adaptations to survive and proliferate. Pancreatic cancer subtypes have been characterized by transcriptional and functional differences, with subtypes reported to exist within the same tumor. However, it remains unclear if this diversity extends to metabolic programming. Here, using metabolomic profiling and functional interrogation of metabolic dependencies, we identify two distinct metabolic subclasses among neoplastic populations within individual human and mouse tumors. Furthermore, these populations are poised for metabolic cross-talk, and in examining this, we find an unexpected role for asparagine supporting proliferation during limited respiration. Constitutive GCN2 activation permits ATF4 signaling in one subtype, driving excess asparagine production. Asparagine release provides resistance during impaired respiration, enabling symbiosis. Functionally, availability of exogenous asparagine during limited respiration indirectly supports maintenance of aspartate pools, a rate-limiting biosynthetic precursor. Conversely, depletion of extracellular asparagine with PEG-asparaginase sensitizes tumors to mitochondrial targeting with phenformin.

Methionine restriction forces Epstein-Barr virus out of latency

EBV gene expression is repressed during viral latency to prevent an immune response, but it is not known how metabolism contributes to this silencing. In this issue of Cell Metabolism, Guo et al. describe how methionine restriction reactivates the expression of EBV genes, offering new therapeutic approaches against EBV-driven diseases.

The Metabolic Relationship Between Viral Infection and Cancer

Viruses are fundamental tools in cancer research. They were used to discover the first oncogenes in the 1970s, and they are now being modified for use as antitumor therapeutics. Key to both of these oncogenic and oncolytic properties is the ability of viruses to rewire host cell metabolism. In this review, we describe how viral oncogenes alter metabolism to increase the synthesis of macromolecules necessary for both viral replication and tumor growth. We then describe how understanding the specific metabolic requirements of virus-infected cells can help guide strategies to improve the efficacy of oncolytic viruses, and we highlight immunometabolism and tumor microenvironment research that could also increase the therapeutic benefits of oncolytic viruses. We also describe how studies describing the therapeutic effects of dietary nutrient restriction in cancer can suggest new avenues for research into antiviral therapeutics.

Asparagine couples mitochondrial respiration to ATF4 activity and tumor growth

Mitochondrial respiration is critical for cell proliferation. In addition to producing ATP, respiration generates biosynthetic precursors, such as aspartate, an essential substrate for nucleotide synthesis. Here, we show that in addition to depleting intracellular aspartate, electron transport chain (ETC) inhibition depletes aspartate-derived asparagine, increases ATF4 levels, and impairs mTOR complex I (mTORC1) activity. Exogenous asparagine restores proliferation, ATF4 and mTORC1 activities, and mTORC1-dependent nucleotide synthesis in the context of ETC inhibition, suggesting that asparagine communicates active respiration to ATF4 and mTORC1. Finally, we show that combination of the ETC inhibitor metformin, which limits tumor asparagine synthesis, and either asparaginase or dietary asparagine restriction, which limit tumor asparagine consumption, effectively impairs tumor growth in multiple mouse models of cancer. Because environmental asparagine is sufficient to restore tumor growth in the context of respiration impairment, our findings suggest that asparagine synthesis is a fundamental purpose of tumor mitochondrial respiration, which can be harnessed for therapeutic benefit to cancer patients.

SARS-CoV-2 infection rewires host cell metabolism and is potentially susceptible to mTORC1 inhibition

Viruses hijack host cell metabolism to acquire the building blocks required for replication. Understanding how SARS-CoV-2 alters host cell metabolism may lead to potential treatments for COVID-19. Here we profile metabolic changes conferred by SARS-CoV-2 infection in kidney epithelial cells and lung air-liquid interface (ALI) cultures, and show that SARS-CoV-2 infection increases glucose carbon entry into the TCA cycle via increased pyruvate carboxylase expression. SARS-CoV-2 also reduces oxidative glutamine metabolism while maintaining reductive carboxylation. Consistent with these changes, SARS-CoV-2 infection increases the activity of mTORC1 in cell lines and lung ALI cultures. Lastly, we show evidence of mTORC1 activation in COVID-19 patient lung tissue, and that mTORC1 inhibitors reduce viral replication in kidney epithelial cells and lung ALI cultures. Our results suggest that targeting mTORC1 may be a feasible treatment strategy for COVID-19 patients, although further studies are required to determine the mechanism of inhibition and potential efficacy in patients.

The pandemic of COVID-19, caused by SARS-CoV-2 infection, warrants immediate investigation for therapy options. Here the authors show, using epithelial and air-liquid interface cultures, that SARS-CoV-2 hijacks host cell metabolism to facilitate viral replication, and that inhibition of mTORC1, a master metabolic regulator, suppresses viral replication.

A pilot window-of-opportunity study of preoperative fluvastatin in localized prostate cancer

Background

Statins inhibit HMG-CoA reductase, the rate-limiting enzyme of the mevalonate pathway. Epidemiological and pre-clinical evidence support an association between statin use and delayed prostate cancer (PCa) progression. Here, we evaluated the effects of neoadjuvant fluvastatin treatment on markers of cell proliferation and apoptosis in men with localized PCa.

Methods

Thirty-three men were treated daily with 80 mg fluvastatin for 4–12 weeks in a single-arm window-of-opportunity study between diagnosis of localized PCa and radical prostatectomy (RP) (ClinicalTrials.gov: NCT01992042). Percent Ki67 and cleaved Caspase-3 (CC3)-positive cells in tumor tissues were evaluated in 23 patients by immunohistochemistry before and after treatment. Serum and intraprostatic fluvastatin concentrations were quantified by liquid chromatography-mass spectrometry.

Results

Baseline characteristics included a median prostate-specific antigen (PSA) level of 6.48 ng/mL (IQR: 4.21–10.33). The median duration of fluvastatin treatment was 49 days (range: 27–102). Median serum low-density lipoprotein levels decreased by 35% after treatment, indicating patient compliance. Median PSA decreased by 12%, but this was not statistically significant in our small cohort. The mean fluvastatin concentration measured in the serum was 0.2 μM (range: 0.0–1.1 μM), and in prostatic tissue was 8.5 nM (range: 0.0–77.0 nM). At these concentrations, fluvastatin induced PCa cell death in vitro in a dose- and time-dependent manner. In patients, fluvastatin treatment did not significantly alter intratumoral Ki67 positivity; however, a median 2.7-fold increase in CC3 positivity (95% CI: 1.9–5.0, p = 0.007) was observed in post-fluvastatin RP tissues compared with matched pre-treatment biopsy controls. In a subset analysis, this increase in CC3 was more pronounced in men on fluvastatin for >50 days.

Conclusions

Fluvastatin prior to RP achieves measurable drug concentrations in prostatic tissue and is associated with promising effects on tumor cell apoptosis. These data warrant further investigation into the anti-neoplastic effects of statins in prostate tissue.

MYC Interacts with the G9a Histone Methyltransferase to Drive Transcriptional Repression and Tumorigenesis

MYC is an oncogenic driver that regulates transcriptional activation and repression. Surprisingly, mechanisms by which MYC promotes malignant transformation remain unclear. We demonstrate that MYC interacts with the G9a H3K9-methyltransferase complex to control transcriptional repression. Inhibiting G9a hinders MYC chromatin binding at MYC-repressed genes and de-represses gene expression. By identifying the MYC box II region as essential for MYC-G9a interaction, a long-standing missing link between MYC transformation and gene repression is unveiled. Across breast cancer cell lines, the anti-proliferative response to G9a pharmacological inhibition correlates with MYC sensitivity and gene signatures. Consistently, genetically depleting G9a in vivo suppresses MYC-dependent tumor growth. These findings unveil G9a as an epigenetic regulator of MYC transcriptional repression and a therapeutic vulnerability in MYC-driven cancers.

Extracellular Matrix Remodeling Regulates Glucose Metabolism through TXNIP Destabilization

The metabolic state of a cell is influenced by cell-extrinsic factors, including nutrient availability and growth factor signaling. Here, we present extracellular matrix (ECM) remodeling as another fundamental node of cell-extrinsic metabolic regulation. Unbiased analysis of glycolytic drivers identified the hyaluronan-mediated motility receptor as being among the most highly correlated with glycolysis in cancer. Confirming a mechanistic link between the ECM component hyaluronan and metabolism, treatment of cells and xenografts with hyaluronidase triggers a robust increase in glycolysis. This is largely achieved through rapid receptor tyrosine kinase-mediated induction of the mRNA decay factor ZFP36, which targets TXNIP transcripts for degradation. Because TXNIP promotes internalization of the glucose transporter GLUT1, its acute decline enriches GLUT1 at the plasma membrane. Functionally, induction of glycolysis by hyaluronidase is required for concomitant acceleration of cell migration. This interconnection between ECM remodeling and metabolism is exhibited in dynamic tissue states, including tumorigenesis and embryogenesis.

Statin-Induced Cancer Cell Death Can Be Mechanistically Uncoupled from Prenylation of RAS Family Proteins

The statin family of drugs preferentially triggers tumor cell apoptosis by depleting mevalonate pathway metabolites farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), which are used for protein prenylation, including the oncoproteins of the RAS superfamily. However, accumulating data indicate that activation of the RAS superfamily are poor biomarkers of statin sensitivity, and the mechanism of statin-induced tumor-specific apoptosis remains unclear. Here we demonstrate that cancer cell death triggered by statins can be uncoupled from prenylation of the RAS superfamily of oncoproteins. Ectopic expression of different members of the RAS superfamily did not uniformly sensitize cells to fluvastatin, indicating that increased cellular demand for protein prenylation cannot explain increased statin sensitivity. Although ectopic expression of HRAS increased statin sensitivity, expression of myristoylated HRAS did not rescue this effect. HRAS-induced epithelial-to-mesenchymal transition (EMT) through activation of zinc finger E-box binding homeobox 1 (ZEB1) sensitized tumor cells to the antiproliferative activity of statins, and induction of EMT by ZEB1 was sufficient to phenocopy the increase in fluvastatin sensitivity; knocking out ZEB1 reversed this effect. Publicly available gene expression and statin sensitivity data indicated that enrichment of EMT features was associated with increased sensitivity to statins in a large panel of cancer cell lines across multiple cancer types. These results indicate that the anticancer effect of statins is independent from prenylation of RAS family proteins and is associated with a cancer cell EMT phenotype.Significance: The use of statins to target cancer cell EMT may be useful as a therapy to block cancer progression. Cancer Res; 78(5); 1347-57. ©2017 AACR.

Abstract 3543: Targeting the metabolic mevalonate pathway with statins as anti-breast cancer agents

The statin family of drugs target the mevalonate pathway and have been used for decades in the control of hypercholesterolemia, however recent evidence suggests these approved agents may also be useful as anti-cancer therapeutics (see our recent Nature Review Cancer article1). For example, statins can trigger tumor-specific apoptosis and two independent pre-op clinical trials in breast cancer, evaluating cholesterol-lowering doses of fluvastatin and atorvastatin, resulted in breast tumor shrinkage due to decreased growth and increased apoptosis. Our hypothesis is that statins have utility as anti-breast cancer agents. To maximize efficacy and speak to personalized medicine, our objectives are to develop biomarkers to distinguish which patients will benefit from the addition of statins to their treatment regimen and how best to use statins in combination with other agents to augment anti-tumor efficacy. To identify biomarkers of statin sensitivity we evaluated fluvastatin activity across a panel of BCa cell lines and showed that the basal, estrogen receptor-negative subtype were significantly sensitive to statin-induced apoptosis. As this included the difficult-to-treat triple negative BCa (TNBCa) we have extended this work and further evaluated a panel of TNBCa cell lines for statin sensitivity. From these results we are identifying features associated with robust apoptosis in response to statin exposure. To identify how best to use statins, we conducted two unbiased screens and have shown that blocking the restorative feedback response to statin exposure potentiates statin-induced apoptosis. This is reversible with exogenous mevalonate, reinforcing that this is an on-target effect. We also identified another approved agent, dipyridamole, as able to potentiate the anti-cancer activity of statins. Mechanistically we have shown that dipyridamole blocks the feedback response to statin exposure. We have extended these studies and shown that the combination of statins and dipyridamole is effective against TNBCa both in vitro and in vivo. Thus, we provide essential pre-clinical data to support the further evaluation of statins and dipyridamole in BCa.

Reference: Mullen, P.J. et al. The interplay between cell signalling and the mevalonate pathway in cancer. Nat Rev Cancer. 16, 718-731 (2016).

Citation Format: Jenna van Leeuwen, Aleksandra Pandyra, Carolyn Goard, Peter J. Mullen, Rosemary Yu, Linda Z. Penn. Targeting the metabolic mevalonate pathway with statins as anti-breast cancer agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3543. doi:10.1158/1538-7445.AM2017-3543

The interplay between cell signalling and the mevalonate pathway in cancer

The mevalonate (MVA) pathway is an essential metabolic pathway that uses acetyl-CoA to produce sterols and isoprenoids that are integral to tumour growth and progression. In recent years, many oncogenic signalling pathways have been shown to increase the activity and/or the expression of MVA pathway enzymes. This Review summarizes recent advances and discusses unique opportunities for immediately targeting this metabolic vulnerability in cancer with agents that have been approved for other therapeutic uses, such as the statin family of drugs, to improve outcomes for cancer patients.

Simvastatin induces mitochondrial dysfunction and increased atrogin-1 expression in H9c2 cardiomyocytes and mice in vivo

Simvastatin is effective and well tolerated, with adverse reactions mainly affecting skeletal muscle. Important mechanisms for skeletal muscle toxicity include mitochondrial impairment and increased expression of atrogin-1. The aim was to study the mechanisms of toxicity of simvastatin on H9c2 cells (a rodent cardiomyocyte cell line) and on the heart of male C57BL/6 mice. After, exposure to 10 μmol/L simvastatin for 24 h, H9c2 cells showed impaired oxygen consumption, a reduction in the mitochondrial membrane potential and a decreased activity of several enzyme complexes of the mitochondrial electron transport chain (ETC). The cellular ATP level was also decreased, which was associated with phosphorylation of AMPK, dephosphorylation and nuclear translocation of FoxO3a as well as increased mRNA expression of atrogin-1. Markers of apoptosis were increased in simvastatin-treated H9c2 cells. Treatment of mice with 5 mg/kg/day simvastatin for 21 days was associated with a 5 % drop in heart weight as well as impaired activity of several enzyme complexes of the ETC and increased mRNA expression of atrogin-1 and of markers of apoptosis in cardiac tissue. Cardiomyocytes exposed to simvastatin in vitro or in vivo sustain mitochondrial damage, which causes AMPK activation, dephosphorylation and nuclear transformation of FoxO3a as well as increased expression of atrogin-1. Mitochondrial damage and increased atrogin-1 expression are associated with apoptosis and increased protein breakdown, which may cause myocardial atrophy.

Immediate utility of two approved agents to target both the metabolic mevalonate pathway and its restorative feedback loop

New therapies are urgently needed for hematologic malignancies, especially in patients with relapsed acute myelogenous leukemia (AML) and multiple myeloma. We and others have previously shown that FDA-approved statins, which are used to control hypercholesterolemia and target the mevalonate pathway (MVA), can trigger tumor-selective apoptosis. Our goal was to identify other FDA-approved drugs that synergize with statins to further enhance the anticancer activity of statins in vivo. Using a screen composed of other FDA approved drugs, we identified dipyridamole, used for the prevention of cerebral ischemia, as a potentiator of statin anticancer activity. The statin-dipyridamole combination was synergistic and induced apoptosis in multiple myeloma and AML cell lines and primary patient samples, whereas normal peripheral blood mononuclear cells were not affected. This novel combination also decreased tumor growth in vivo. Statins block HMG-CoA reductase (HMGCR), the rate-limiting enzyme of the MVA pathway. Dipyridamole blunted the feedback response, which upregulates HMGCR and HMG-CoA synthase 1 (HMGCS1) following statin treatment. We further show that dipyridamole inhibited the cleavage of the transcription factor required for this feedback regulation, sterol regulatory element-binding transcription factor 2 (SREBF2, SREBP2). Simultaneously targeting the MVA pathway and its restorative feedback loop is preclinically effective against hematologic malignancies. This work provides strong evidence for the immediate evaluation of this novel combination of FDA-approved drugs in clinical trials.

Identifying molecular features that distinguish fluvastatin-sensitive breast tumor cells

Statins, routinely used to treat hypercholesterolemia, selectively induce apoptosis in some tumor cells by inhibiting the mevalonate pathway. Recent clinical studies suggest that a subset of breast tumors is particularly susceptible to lipophilic statins, such as fluvastatin. To quickly advance statins as effective anticancer agents for breast cancer treatment, it is critical to identify the molecular features defining this sensitive subset. We have therefore characterized fluvastatin sensitivity by MTT assay in a panel of 19 breast cell lines that reflect the molecular diversity of breast cancer, and have evaluated the association of sensitivity with several clinicopathological and molecular features. A wide range of fluvastatin sensitivity was observed across breast tumor cell lines, with fluvastatin triggering cell death in a subset of sensitive cell lines. Fluvastatin sensitivity was associated with an estrogen receptor alpha (ERα)-negative, basal-like tumor subtype, features that can be scored with routine and/or strong preclinical diagnostics. To ascertain additional candidate sensitivity-associated molecular features, we mined publicly available gene expression datasets, identifying genes encoding regulators of mevalonate production, non-sterol lipid homeostasis, and global cellular metabolism, including the oncogene MYC. Further exploration of this data allowed us to generate a 10-gene mRNA abundance signature predictive of fluvastatin sensitivity, which showed preliminary validation in an independent set of breast tumor cell lines. Here, we have therefore identified several candidate predictors of sensitivity to fluvastatin treatment in breast cancer, which warrant further preclinical and clinical evaluation.

MYC phosphorylation at novel regulatory regions suppresses transforming activity

Despite its central role in human cancer, MYC deregulation is insufficient by itself to transform cells. Because inherent mechanisms of neoplastic control prevent precancerous lesions from becoming fully malignant, identifying transforming alleles of MYC that bypass such controls may provide fundamental insights into tumorigenesis. To date, the only activated allele of MYC known is T58A, the study of which led to identification of the tumor suppressor FBXW7 and its regulator USP28 as a novel therapeutic target. In this study, we screened a panel of MYC phosphorylation mutants for their ability to promote anchorage-independent colony growth of human MCF10A mammary epithelial cells, identifying S71A/S81A and T343A/S344A/S347A/S348A as more potent oncogenic mutants compared with wild-type (WT) MYC. The increased cell-transforming activity of these mutants was confirmed in SH-EP neuroblastoma cells and in three-dimensional MCF10A acini. Mechanistic investigations initiated by a genome-wide mRNA expression analysis of MCF10A acini identified 158 genes regulated by the mutant MYC alleles, compared with only 112 genes regulated by both WT and mutant alleles. Transcriptional gain-of-function was a common feature of the mutant alleles, with many additional genes uniquely dysregulated by individual mutant. Our work identifies novel sites of negative regulation in MYC and thus new sites for its therapeutic attack.

Abstract C165: Breast cancer, statins, and 3-D cell culture

Statins are widely used to lower serum cholesterol levels. They act by inhibiting hydroxymethylglutaryl coenzyme A reductase (HMGCR), the rate-limiting step in the mevalonate pathway. Recent work also shows that statins could be used as anticancer therapeutics, particularly in breast cancer. This study presents a preliminary rationale for the use of statins as a therapy in breast cancer.

We characterized a panel of breast cancer cell lines for sensitivity to fluvastatin, using proliferation and cell-death assays. We also screened for differences in activity of the electron transport chain and glycolysis after fluvastatin treatment. We then began to expand on these results using 3D cell culture techniques to offer a more representative tumor model.

The panel of breast cancer cell lines showed a range of sensitivity to fluvastatin, with MTT50 for 72 h treatment varying from 0.7 μM for MDA-MB231 cells to 162.8 μM in BT474 cells. Interestingly, triple negative cell lines were in the sensitive range. Differences in cell cycle populations were also observed, with a representative panel of sensitive cells showing an increased G1/G0 arrest and decrease in S-phase population when compared to insensitive cell lines. Delving deeper, mitochondrial respiration was decreased in the sensitive cell lines. We also observed greater changes in morphology in the sensitive cell lines than the insensitive when grown in 3D cell culture, potentially offering more relevance to our observations.

These results confirm that there is a range of sensitivities to fluvastatin in breast cancer cell lines, allowing for further studies to determine the cause of these differences. The hints at metabolic differences could also lead to novel co-treatments with statins and greater therapeutic benefit.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C165.

Matrix metalloproteinases 2 and 9 in the cochlea: expression and activity after aminoglycoside exposition

The matrix metalloproteinases (MMPs) are a family of proteins involved in the remodelling and homeostasis of the extracellular matrix. These proteases have been well studied in the retina and the brain, marking their importance in neuronal cell survival and death [Chintala (2006) Exp Eye Res 82:5-12; Candelario-Jalil et al. (2009) Neuroscience 158:983-994]. The neuroepithelia of the eye and the inner ear share common characteristics. Therefore, we hypothesized that MMPs could play a similar role in the cochlea as described in the retina. We focused on the localization and function of MMP-2 and MMP-9 in the cochlea, by determining their expression and activity under normal conditions and after cochlear damage via aminoglycoside exposition. We examined their expression in 5-day-old Wistar rat cochleas by RT-PCR, real-time PCR, and Western blot. We used immunohistochemistry to investigate their location in the cochleas of adult C57BL/6 mice. We also determined whether or not the exposure of the organs of Corti to aminoglycosides would change MMP-2 and MMP-9 expression patterns. Western blotting identified MMP-2 and MMP-9 in neonatal spiral ganglion, stria vascularis, and to a lesser extent the organ of Corti. Neonatal mRNA expression of MMP-2 was approximately equivalent in all three tissues, while MMP-9 mRNA was highest in spiral ganglion. Immunohistochemistry showed MMP-2 primarily in adult spiral ganglion neurons and inner hair cells, while MMP-9 was found mainly in spiral ganglion neurons, inner hair cells and supporting cells. Organs of Corti treated with gentamicin for 24 h showed an upregulation of MMP-2 and MMP-9 proteins, but did not show a significant upregulation of mRNA expression 3, 6, 12, 24, and 36 h after gentamicin exposure. Inhibition of MMP activity in organs of Corti incubated with an MMP inhibitor in organotypic cultures resulted in hair cell death-suggesting that a basal level of MMP activity is required for hair cell survival.

Immunohistochemical detection of O-acetylated sialomucins in intestinal metaplasia and carcinoma of the stomach

Eighty-two selected gastric mucosal biopsy or resection specimens were stained both conventionally, to classify subtypes of intestinal metaplasia and carcinoma, and immunohistochemically with a mouse monoclonal antibody (MMM-17), raised against normal human colonic mucin, which has an affinity for di- and/or tri-O-acetylated sialomucin. The aims of the study were to reassess the prevalence of O-acetylated sialomucins in normal, metaplastic and carcinomatous gastric mucosa and to investigate whether the production of these mucins by intestinal metaplasia is related to its associated mucosal pathology. O-acetylated sialomucins were not seen in normal mucosa. They were, however, prevalent in all sub-types of metaplastic (64.8%) and carcinomatous (42.9%) mucosa. Type 1 intestinal metaplasia was significantly more likely to contain this type of mucin if Helicobacter pylori infection was identifiable in the adjacent gastric mucosa (81.0% v. 38.5%, P < 0.025). Type 3 showed a similar, albeit nonsignificant, relationship (100% v. 62.5%). O-acetylated sialomucins are, therefore, much more prevalent in gastric intestinal metaplasia and carcinoma than previously recognized by conventional staining techniques. The production of this type of mucin by intestinal metaplasia may reflect an adaptive response to alterations in the luminal environment such as an increase in bacterial content.

The dangers of electrocardiography in general practice

The use of the electrocardiograph by general practitioners was studied by scrutiny of 100 successive referrals to the Department of Clinical Electrophysiology. 31% of referrals were on patients with chronic, recurrent chest pain and a further 13% were on patients with a recent episode of acute chest pain. The ECG is of limited diagnostic value in patients with chest pain, and it may be both misleading and time-wasting when used inappropriately by general practitioners.