Peroxisomes in human colon carcinomas. A cytochemical and biochemical study

Peroxisomal cholesterol metabolism regulates yap-signaling, which maintains intestinal epithelial barrier function and is altered in Crohn's disease

Intestinal epithelial cells line the luminal surface to establish the intestinal barrier, where the cells play essential roles in the digestion of food, absorption of nutrients and water, protection from microbial infections, and maintaining symbiotic interactions with the commensal microbial populations. Maintaining and coordinating all these functions requires tight regulatory signaling, which is essential for intestinal homeostasis and organismal health. Dysfunction of intestinal epithelial cells, indeed, is linked to gastrointestinal disorders such as irritable bowel syndrome, inflammatory bowel disease, and gluten-related enteropathies. Emerging evidence suggests that peroxisome metabolic functions are crucial in maintaining intestinal epithelial cell functions and intestinal epithelium regeneration and, therefore, homeostasis. Here, we investigated the molecular mechanisms by which peroxisome metabolism impacts enteric health using the fruit fly Drosophila melanogaster and murine model organisms and clinical samples. We show that peroxisomes control cellular cholesterol, which in turn regulates the conserved yes-associated protein-signaling and contributes to intestinal epithelial structure and epithelial barrier function. Moreover, analysis of intestinal organoid cultures derived from biopsies of patients affected by Crohn's Disease revealed that the dysregulation of peroxisome number, excessive cellular cholesterol, and inhibition of Yap-signaling are markers of disease and could be novel diagnostic and/or therapeutic targets for treating Crohn's Disease. Our studies provided mechanistic insights on peroxisomal signaling in intestinal epithelial cell functions and identified cholesterol as a novel metabolic regulator of yes-associated protein-signaling in tissue homeostasis.

Peroxisomal trans-2-enoyl-CoA inhibits proliferation, migration and invasion of hepatocellular carcinoma cells

OBJECTIVES

Peroxisomal trans-2-enoyl-CoA reductase (PECR) encodes proteins related to fatty acid metabolism and synthesis. It has been confirmed that PECR has decreased expression in colon cancer and breast cancer, while the role of PECR in liver cancer is unknown. We aimed to study the role and mechanism of PECR in the genesis and development of liver cancer.

METHODS

In this study, the expression of PECR was queried in the Cancer Genome Atlas Database and Western Blotting and RT-PCR experiments were carried out in paired liver cancer tissues to detect the expression of PECR. Functional tests were evaluated by cell count kit-8 (CCK-8), Flow cytometry, wound healing assay, Transwell, migration. In vivo study, we constructed a nude mouse tumorigenic model to observe the effect of PECR on the proliferation of liver cancer. And the tumor body of the mouse was taken out for histochemistry (IHC). Multiple Cox regression was used to analyze the correlation between PECR and Clinicopathology.

RESULTS

We confirmed that the overexpression of PECR inhibited the proliferation, migration and invasion of hepatocellular carcinoma and promoted the apoptosis of hepatocellular carcinoma. The low expression group of PECR promoted the proliferation and metastasis of liver cancer. In vivo, overexpression of PECR inhibits the proliferation of mouse tumors. In addition, the mechanism study shows that PECR may indirectly affect the proliferation of hepatocellular carcinoma cells through ERK pathway.

CONCLUSION

In general, PECR may be a new diagnostic marker and a potential therapeutic target for hepatocellular carcinoma.

Identification of an at-risk subpopulation with high immune infiltration based on the peroxisome pathway and TIM3 in colorectal cancer

Background

Peroxisomes are pivotal metabolic organelles that exist in almost all eukaryote cells. A reduction in numbers and enzymatic activities of peroxisomes was found in colon adenocarcinomas. However, the role of peroxisomes or the peroxisome pathway in colorectal cancer (CRC) is not defined.

Methods

In the current study, a peroxisome score was calculated to indicate the activity of the peroxisome pathway using gene set variant analysis based on transcriptomic datasets. CIBERSORTx was chosen to infer enriched immune cells for tumors among subgroups. The SubMap algorithm was applied to predict its sensitivity to immunotherapy.

Results

The patients with a relatively low peroxisome score and high level of T-cell immunoglobulin and mucin domain 3 (TIM-3) presented the worse overall survival than others. Moreover, low peroxisome scores were associated with high infiltration of lymphocytes and poor prognosis in those CRC patients. Thus, a PER^LowTIM3^High CRC risk subpopulation was identified and characterized by high immune infiltration. The results also showed that CD8 T cells and macrophages highly infiltrated tumors of the PER^LowTIM3^High group, regardless of consortium molecular subtype and microsatellite instability status. This subgroup had the highest tumor mutational burden and overexpression of immune checkpoint genes. Further, the PER^LowTIM3^High group showed a higher probability of responding to programmed cell death protein-1-based immunotherapy. In addition, genes involved in peroxisomal metabolic processes in CRC were also investigated since peroxisome is a rather pleiotropic and highly metabolic organelle in cell. The results indicated that only those genes involved in fatty acid alpha oxidation could be used to stratify CRC patients as similar as peroxisome pathway genes.

Conclusions

We revealed the favorable prognostic value of the peroxisome pathway in CRC and provided a new CRC stratification based on peroxisomes and TIM3, which might be helpful for CRC diagnostics and personalized treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-09085-9.

Differential Expression of Peroxisomal Proteins in Distinct Types of Parotid Gland Tumors

Salivary gland cancers are rare but aggressive tumors that have poor prognosis and lack effective cure. Of those, parotid tumors constitute the majority. Functioning as metabolic machinery contributing to cellular redox balance, peroxisomes have emerged as crucial players in tumorigenesis. Studies on murine and human cells have examined the role of peroxisomes in carcinogenesis with conflicting results. These studies either examined the consequences of altered peroxisomal proliferators or compared their expression in healthy and neoplastic tissues. None, however, examined such differences exclusively in human parotid tissue or extended comparison to peroxisomal proteins and their associated gene expressions. Therefore, we examined differences in peroxisomal dynamics in parotid tumors of different morphologies. Using immunofluorescence and quantitative PCR, we compared the expression levels of key peroxisomal enzymes and proliferators in healthy and neoplastic parotid tissue samples. Three parotid tumor subtypes were examined: pleomorphic adenoma, mucoepidermoid carcinoma and acinic cell carcinoma. We observed higher expression of peroxisomal matrix proteins in neoplastic samples with exceptional down regulation of certain enzymes; however, the degree of expression varied between tumor subtypes. Our findings confirm previous experimental results on other organ tissues and suggest peroxisomes as possible therapeutic targets or markers in all or certain subtypes of parotid neoplasms.

Toxicity and Anticancer Potential of Karwinskia: A Review

Karwinskia genus consists of shrubs and small trees. Four toxic compounds have been isolated from Karwinskia plants, which were typified as dimeric anthracenones and named T496, T514, T516, and T544. Moreover, several related compounds have been isolated and characterized. Here we review the toxicity of the fruit of Karwinskia plants when ingested (accidentally or experimentally), as well as the toxicity of its isolated compounds. Additionally, we analyze the probable antineoplastic effect of T514. Toxins cause damage mainly to nervous system, liver, lung, and kidney. The pathophysiological mechanism has not been fully understood but includes metabolic and structural alterations that can lead cells to apoptosis or necrosis. T514 has shown selective toxicity in vitro against human cancer cells. T514 causes selective and irreversible damage to peroxisomes; for this reason, it was renamed peroxisomicine A1 (PA1). Since a significant number of malignant cell types contain fewer peroxisomes than normal cells, tumor cells would be more easily destroyed by PA1 than healthy cells. Inhibition of topoisomerase II has also been suggested to play a role in the effect of PA1 on malignant cells. More research is needed, but the evidence obtained so far indicates that PA1 could be an effective anticancer agent.

A New Prognostic Risk Model Based on PPAR Pathway-Related Genes in Kidney Renal Clear Cell Carcinoma

OBJECTIVE

This study is aimed at using genes related to the peroxisome proliferator-activated receptor (PPAR) pathway to establish a prognostic risk model in kidney renal clear cell carcinoma (KIRC).

METHODS

For this study, we first found the PPAR pathway-related genes on the gene set enrichment analysis (GSEA) website and found the KIRC mRNA expression data and clinical data through TCGA database. Subsequently, we used R language and multiple R language expansion packages to analyze the expression, hazard ratio analysis, and coexpression analysis of PPAR pathway-related genes in KIRC. Afterward, using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) website, we established the protein-protein interaction (PPI) network of genes related to the PPAR pathway. After that, we used LASSO regression curve analysis to establish a prognostic survival model in KIRC. Finally, based on the model, we conducted correlation analysis of the clinicopathological characteristics, univariate analysis, and multivariate analysis.

RESULTS

We found that most of the genes related to the PPAR pathway had different degrees of expression differences in KIRC. Among them, the high expression of 27 genes is related to low survival rate of KIRC patients, and the high expression of 13 other genes is related to their high survival rate. Most importantly, we used 13 of these genes successfully to establish a risk model that could accurately predict patients' prognosis. There is a clear correlation between this model and metastasis, tumor, stage, grade, and fustat.

CONCLUSIONS

To the best of our knowledge, this is the first study to analyze the entire PPAR pathway in KIRC in detail and successfully establish a risk model for patient prognosis. We believe that our research can provide valuable data for future researchers and clinicians.

A New Prognostic Risk Model Based on PPAR Pathway-Related Genes in Kidney Renal Clear Cell Carcinoma

Objective

This study is aimed at using genes related to the peroxisome proliferator-activated receptor (PPAR) pathway to establish a prognostic risk model in kidney renal clear cell carcinoma (KIRC).

Methods

For this study, we first found the PPAR pathway-related genes on the gene set enrichment analysis (GSEA) website and found the KIRC mRNA expression data and clinical data through TCGA database. Subsequently, we used R language and multiple R language expansion packages to analyze the expression, hazard ratio analysis, and coexpression analysis of PPAR pathway-related genes in KIRC. Afterward, using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) website, we established the protein-protein interaction (PPI) network of genes related to the PPAR pathway. After that, we used LASSO regression curve analysis to establish a prognostic survival model in KIRC. Finally, based on the model, we conducted correlation analysis of the clinicopathological characteristics, univariate analysis, and multivariate analysis.

Results

We found that most of the genes related to the PPAR pathway had different degrees of expression differences in KIRC. Among them, the high expression of 27 genes is related to low survival rate of KIRC patients, and the high expression of 13 other genes is related to their high survival rate. Most importantly, we used 13 of these genes successfully to establish a risk model that could accurately predict patients' prognosis. There is a clear correlation between this model and metastasis, tumor, stage, grade, and fustat.

Conclusions

To the best of our knowledge, this is the first study to analyze the entire PPAR pathway in KIRC in detail and successfully establish a risk model for patient prognosis. We believe that our research can provide valuable data for future researchers and clinicians.

Three novel hub genes and their clinical significance in clear cell renal cell carcinoma

Purpose. To investigate the association of biomarkers correlated with clinical stages and survival of clear cell renal cell carcinoma (ccRCC).

Methods. The GSE36895 dataset was downloaded and differentially expressed or methylated genes were analyzed. Hub genes were identified with weighted gene co-expression network analysis (WGCNA) and protein-protein interaction network (PPI), and validated with TCGA database and our own tissues. The biological processes of hub genes were further explored by functional enrichment analysis. Survival analyses were also performed. The underlying mechanisms for ccRCC development were detected with Gene set enrichment analyses.

Results. A total of 1624 differentially expressed genes were analyzed by WGCNA and 6 co-expressed gene modules were identified. Three hub genes (EHHADH, ACADM and AGXT2) were met the criterion of both WGCNA and PPI networks analysis, which showed highest negative association with pathological T stage (r = - 0.45, p = 0.01) and tumor grade (r = - 0.45, p = 0.01). The downregulation of these hub genes was validated with using both TCGA database and samples harvested at our institute The biological processes that hub genes involved, such as metabolic process (p = 9.63E - 09), oxidation-reduction process (p = 1.05E - 08) and oxidoreductase activity (p = 1.72E - 04), were revealed. Survival analysis showed a higher expression or lower methylation of these hub genes, a longer survival of ccRCC patients. ccRCC samples with higher expression of hub genes were enriched in gene sets correlated with signaling like biosynthesis of unsaturated fatty acids, butanoate metabolism, and PPAR signaling pathway.

Conclusions. We identified three novel tumor suppressors associated with pathological T stage and overall survival of ccRCC. They might be potential as individualized therapeutic targets and diagnostic biomarkers for ccRCC.

The peroxisome: an update on mysteries 2.0

Peroxisomes are key metabolic organelles, which contribute to cellular lipid metabolism, e.g. the β-oxidation of fatty acids and the synthesis of myelin sheath lipids, as well as cellular redox balance. Peroxisomal dysfunction has been linked to severe metabolic disorders in man, but peroxisomes are now also recognized as protective organelles with a wider significance in human health and potential impact on a large number of globally important human diseases such as neurodegeneration, obesity, cancer, and age-related disorders. Therefore, the interest in peroxisomes and their physiological functions has significantly increased in recent years. In this review, we intend to highlight recent discoveries, advancements and trends in peroxisome research, and present an update as well as a continuation of two former review articles addressing the unsolved mysteries of this astonishing organelle. We summarize novel findings on the biological functions of peroxisomes, their biogenesis, formation, membrane dynamics and division, as well as on peroxisome-organelle contacts and cooperation. Furthermore, novel peroxisomal proteins and machineries at the peroxisomal membrane are discussed. Finally, we address recent findings on the role of peroxisomes in the brain, in neurological disorders, and in the development of cancer.

Hypoxia signaling pathways: modulators of oxygen-related organelles

Oxygen (O2) is an essential substrate in cellular metabolism, bioenergetics, and signaling and as such linked to the survival and normal function of all metazoans. Low O2 tension (hypoxia) is a fundamental feature of physiological processes as well as pathophysiological conditions such as cancer and ischemic diseases. Central to the molecular mechanisms underlying O2 homeostasis are the hypoxia-inducible factors-1 and -2 alpha (HIF-1α and EPAS1/HIF-2α) that function as master regulators of the adaptive response to hypoxia. HIF-induced genes promote characteristic tumor behaviors, including angiogenesis and metabolic reprogramming. The aim of this review is to critically explore current knowledge of how HIF-α signaling regulates the abundance and function of major O2-consuming organelles. Abundant evidence suggests key roles for HIF-1α in the regulation of mitochondrial homeostasis. An essential adaptation to sustained hypoxia is repression of mitochondrial respiration and induction of glycolysis. HIF-1α activates several genes that trigger mitophagy and represses regulators of mitochondrial biogenesis. Several lines of evidence point to a strong relationship between hypoxia, the accumulation of misfolded proteins in the endoplasmic reticulum, and activation of the unfolded protein response. Surprisingly, although peroxisomes depend highly on molecular O2 for their function, there has been no evidence linking HIF signaling to peroxisomes. We discuss our recent findings that establish HIF-2α as a negative regulator of peroxisome abundance and suggest a mechanism by which cells attune peroxisomal function with O2 availability. HIF-2α activation augments peroxisome turnover by pexophagy and thereby changes lipid composition reminiscent of peroxisomal disorders. We discuss potential mechanisms by which HIF-2α might trigger pexophagy and place special emphasis on the potential pathological implications of HIF-2α-mediated pexophagy for human health.

Quantitative Proteomics Reveals the Roles of Peroxisome-associated Proteins in Antiviral Innate Immune Responses

Compared with whole-cell proteomic analysis, subcellular proteomic analysis is advantageous not only for the increased coverage of low abundance proteins but also for generating organelle-specific data containing information regarding dynamic protein movement. In the present study, peroxisome-enriched fractions from Sendai virus (SeV)-infected or uninfected HepG2 cells were obtained and subjected to quantitative proteomics analysis. We identified 311 proteins that were significantly changed by SeV infection. Among these altered proteins, 25 are immune response-related proteins. Further bioinformatic analysis indicated that SeV infection inhibits cell cycle-related proteins and membrane attack complex-related proteins, all of which are beneficial for the survival and replication of SeV within host cells. Using Luciferase reporter assays on several innate immune-related reporters, we performed functional analysis on 11 candidate proteins. We identified LGALS3BP and CALU as potential negative regulators of the virus-induced activation of the type I interferons.

Butyrate modulates antioxidant enzyme expression in malignant and non-malignant human colon tissues

The induction of antioxidant enzymes is an important mechanism in colon cancer chemoprevention, but the response of human colon tissue to butyrate, a gut fermentation product derived from dietary fiber, remains largely unknown. Therefore, our study investigated the effect of a butyrate treatment on catalase (CAT) and superoxide dismutase (SOD2) in matched human colon tissues of different transformation stages (n = 3-15 in each group) ex vivo. By performing quantitative real-time PCR, Western blot, and spectrophotometric measurements, we found an increase in SOD2 at expression and activity level in colonic adenocarcinomas (mRNA: 1.96-fold; protein: 1.41-fold, activity: 1.8-fold; P < 0.05). No difference was detectable for CAT between normal, adenoma, and carcinoma colon tissues. Treatment of normal colon epithelium (12 h) with a physiologically relevant concentration of butyrate (10 mM) resulted in a significant increase (P < 0.05) in CAT mRNA (1.24-fold) and protein (1.39-fold), without affecting the enzymatic activity. Consequently, preliminary experiments failed to show any protective effect of butyrate against H2 O2 -mediated DNA damage. Despite a significantly lowered SOD2 transcript (0.51-fold, P < 0.01) and, to a lesser extent, protein level (0.86-fold) after butyrate exposure of normal colon cells, the catalytic activity was significantly enhanced (1.19-fold, P < 0.05), suggesting an increased protection against tissue superoxide radicals. In malignant tissues, greater variations in response to butyrate were observed. Furthermore, both enzymes showed an age-dependent decrease in activity in normal colon epithelium (CAT: r = -0.49, P = 0.09; SOD2: r = -0.58, P = 0.049). In conclusion, butyrate exhibited potential antioxidant features ex vivo but cellular consequences need to be investigated more in depth.

Selenium as a chemopreventive agent in experimentally induced colon carcinogenesis

AIM: To elucidate the chemopreventive efficacy of selenium during experimentally induced colon carcinogenesis.

METHODS: Thirty-two male wistar rats were divided into four groups: group I (normal control); group II [1,2-dimethylhydrazine (DMH) treated]; group III (selenium treated); and group IV (DMH + selenium treated). Groups II and IV were given subcutaneous injections of DMH (30 mg/kg body weight) every week for 20 wk. Selenium, in the form of sodium selenite, was given to groups III and IV at 1 ppm in drinking water ad libitum for 20 wk. At the end of the study, rats were sacrificed and their colons were analyzed for the development of tumors, antioxidant enzyme levels and histological changes.

RESULTS: 100% of the DMH treated rats developed tumors, which was reduced to 60% upon simultaneous selenium supplementation. Similarly, tumor multiplicity decreased to 1.1 following selenium supplementation to DMH treated rats. Levels of lipid peroxidation, glutathione-S-transferase, superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) decreased following DMH treatment, whereas levels of glutathione (GSH) and glutathione reductase (GR) significantly increased in DMH treated rats. Selenium administration to DMH treated rats led to an increase in the levels of lipid peroxidation, SOD, catalase, glutathione-S-transferase and GPx, but decreased the levels of GSH and GR. Histopathological studies on DMH treated rats revealed dysplasia of the colonic histoarchitecture, which showed signs of improvement following selenium treatment.

CONCLUSION: The study suggests the antioxidative potential of selenium is a major factor in providing protection from development of experimentally induced colon carcinogenesis.

Loss of Peroxisomes Causes Oxygen Insensitivity of the Histochemical Assay of Glucose-6-Phosphate Dehydrogenase Activity to Detect Cancer Cells

Oxygen insensitivity of carcinoma cells and oxygen sensitivity of non-cancer cells in the histochemical assay of glucose-6-phosphate dehydrogenase (G6PD) enables detection of carcinoma cells in unfixed cell smears or cryostat sections of biopsies. The metabolic background of oxygen insensitivity is still not understood completely. In the present study, rat hepatocytes, rat hepatoma cells (FTO-2B), and human colon carcinoma cells (HT29) were used to elucidate these backgrounds. The residual activity in oxygen was 0%, 55%, and 80% in hepatocytes, hepatoma cells, and colon carcinoma cells, respectively. N-ethylmaleimide (NEM), a blocker of SH-groups, did not affect G6PD activity in both carcinoma cell types but reduced G6PD activity in hepatocytes by 40%. Ultrastructural localization of G6PD activity was exclusively in the cytoplasm of carcinoma cells, but in hepatocytes both in cytoplasm and peroxisomes. NEM abolished peroxisomal G6PD activity only. Histochemical assay of catalase activity demonstrated absence of peroxisomes in both carcinoma cell lines. It is concluded that absence of SH-sensitive G6PD activity in peroxisomes in cancer cells is responsible for the oxygen-insensitivity phenomenon.

Proteomic analysis of a preneoplastic phenotype in ovarian surface epithelial cells derived from prophylactic oophorectomies

OBJECTIVE

To study the pattern of protein expression associated with a predisposition to develop ovarian cancer.

METHODS

Prophylactic oophorectomy is used to prevent ovarian carcinoma in high-risk populations who have a strong family history of breast/ovarian cancer. In ovarian specimens of these women, the ovarian surface epithelium (OSE), which is tissue of origin of epithelial ovarian cancer, often shows altered morphology, growth patterns and differentiation features that are believed to be preneoplastic. This study has used a proteomic approach, based on two-dimensional gel electrophoresis and mass spectrometry, to compare the protein profiles of OSE from women with a history of familial ovarian cancer (FH-OSE), i.e., at least two first-degree relatives with such cancer and/or testing positive for BRCA1 mutations, to those without such history (NFH-OSE).

RESULTS

Of >1500 protein spots, there were 8 proteins whose levels were significantly altered in FH-OSE. Three were known ovarian tumor associated proteins, others were novel changes. A number of the alterations seen were accompanied with protein modifications and have not been previously reported. There was a predominance of sequences related to the stress response pathway. Differential expression of selected genes was confirmed by Western blotting and real-time reverse transcription polymerase chain reaction.

CONCLUSIONS

Our findings define the OSE phenotype of women at a high risk of developing ovarian cancer. Protein alterations seen in these tissues may represent an early, irreversible, non-mutational step in ovarian epithelial neoplastic progression and may be potential early and sensitive markers for the evaluation of cancer risk.

Tumour-related enzyme alterations in the clear cell type of human renal cell carcinoma identified by two-dimensional gel electrophoresis

To identify tumour-related enzyme alterations we have used 2D-gels to analyse the proteome from dissected malignant and benign kidney areas from patients with clear-cell-type renal carcinoma. The expression of 12 proteins was diminished in tumour. Four proteins were characterized by mass spectrometry and were identified as enoyl-CoA hydratase, alpha-glycerol-3-phosphate dehydrogenase, aldehyde dehydrogenase 1 and aminoacylase-I.

Expression and prognostic significance of catalase in malignant mesothelioma

BACKGROUND

Free radicals and antioxidant enzymes (AOEs) may play a critical role in cell proliferation and in the resistance of malignant cells against cytotoxic drugs and radiation. Malignant mesothelioma is a resistant tumor with high levels of manganese superoxide dismutase, a central superoxide scavenging AOE. In the current study, the authors assessed the expression and prognostic role of catalase, an important hydrogen peroxide scavenging AOE, in malignant pleural mesothelioma.

METHODS

Catalase expression was investigated by immunohistochemistry in 5 cases of nonmalignant healthy pleura and in tumor tissue of 32 mesothelioma patients, and by Western blot in 7 continuous human mesothelioma cell lines. The distribution of catalase in mesothelioma cells was assessed by immunoelectron microscopy. Furthermore, to investigate the effect of catalase inhibition in the drug resistance of these cells in vitro, the authors exposed mesothelioma cells with the highest catalase level to epirubicin with and without aminotriazole pretreatment.

RESULTS

Nonmalignant mesothelial cells showed no catalase immunoreactivity whereas most mesothelioma cases (24 of 32, 75%) were catalase positive, 17 cases (53%) showing moderate or high expression. Higher catalase expression in mesothelioma was associated with a better prognosis, mean survival rate from diagnosis being 6 and 24 months for negative/low expression and moderate/high expression, respectively. Furthermore, a coordinately high expression of both manganese-superoxide dismutase (Mn-SOD) and catalase predicted even more favorable outcome of the mesothelioma patients. Catalase also could be detected in all mesothelioma cell lines, the most resistant cell line showing the highest protein expression and compartmentalization of catalase mainly to peroxisomes. Aminotriazole inhibition of catalase had a marginal effect on the toxicity caused by epirubicin.

CONCLUSIONS

Catalase may have multifactorial effects in malignant cells; high catalase and/or coordinated high expression of Mn-SOD and catalase may decrease tumor progression by modulating the cellular redox state, but enhanced antioxidant capacity of mesothelioma cells also may protect tumor cells against exogenous oxidants, at least in vitro.

Peroxisome distribution along the crypt-villus axis of the guinea pig small intestine

Peroxisomes and peroxisomal enzyme expression were investigated biochemically and morphometrically in guinea pig intestinal epithelial cells at different stages of their migration along the crypt-villus axis. Epithelial cells were sequentially isolated along the axis and the specific activities of the peroxisomal enzymes catalase and acyl-CoA oxidase were found to be significantly higher in differentiated and mature cells situated at the villus tip and stem than in the crypt. Conversely, 1-alk-1'enyl, 2-acyl phospholipid (plasmalogen) concentration in the crypt and middle villus was significantly higher than in villus tip cells. Assay of alkyl DHAP synthase and fatty acyl CoA reductase (enzymes responsible for the production of plasmalogen precursors) showed no correlating activity gradient with plasmalogen concentration. Morphometric analysis revealed that peroxisomes were present even in the most immature stem cells, however, their number and volume and surface densities increased as the epithelial cell developed as did the proportion of elongated and vermiform peroxisomes to spherical structures. Senescent cells at the tip of the villus, however, showed a dramatic decrease in number of peroxisomes per cell possibly due to cellular degradation. We conclude that the peroxisomal compartment of the guinea pig small intestinal epithelial cell develops as a function of cell development possibly reflecting adaptation to maximise its metabolic capacity.

Leukaemia disease genes: large-scale cloning and pathway predictions

Retroviral insertional mutagenesis in BXH2 and AKXD recombinant inbred mice induces a high incidence of myeloid or B- and T-cell leukaemia and the proviral integration sites in the leukaemias provide powerful genetic tags for disease gene identification. Some of the disease genes identified by proviral tagging are also associated with human disease, validating this approach for human disease gene identification. Although many leukaemia disease genes have been identified over the years, many more remain to be cloned. Here we describe an inverse PCR (IPCR) method for proviral tagging that makes use of automated DNA sequencing and the genetic tools provided by the Mouse Genome Project, which increases the throughput for disease gene identification. We also use this IPCR method to clone and analyse more than 400 proviral integration sites from AKXD and BXH2 leukaemias and, in the process, identify more than 90 candidate disease genes. Some of these genes function in pathways already implicated in leukaemia, whereas others are likely to define new disease pathways. Our studies underscore the power of the mouse as a tool for gene discovery and functional genomics.

Differences in the reducing power along the rat GI tract: lower antioxidant capacity of the colon

The ability of the gastrointestinal (GI) tract, as well as other tissues, to cope with reactive oxygen species (ROS) efflux in pathological events is determined partly by epithelial antioxidant levels. These levels are comprised of tissue antioxidant enzymes and low molecular weight antioxidants (LMWA). While glutathione levels and the activity of enzymatic antioxidants along the GI tract have been studied, the contribution of the overall LMWA to the total antioxidant capacity has not yet been determined. In this study the overall antioxidant activity in the mucosa/submucosa and muscularis/serosa of various sections along the small intestine and colon of the rat was evaluated by determining the reducing power, which reflects the total antioxidant activity derived from LMWA, using cyclic voltammetry. The activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase was also measured. The reducing power (total antioxidant activity) was higher in the mucosa/submucosa of the small intestine as compared to the mucosa/submucosa of the colon. Similarly, catalase and SOD activity in the mucosa/submucosa of the small intestine was significantly higher than in the mucosa/submucosa of the colon. Differences were also observed in the reducing power and SOD activity in the muscularis/serosa of the rat small intestine as compared to the colon. The low antioxidant capacity in the colon may facilitate reactive oxygen species (ROS)-mediated injury and lead to inflammatory diseases such as ulcerative colitis, specifically in the colon.

Studies on peroxisomes of colonic mucosa in Crohn's disease

The etiology and pathogenesis of Crohn's disease, a chronic inflammatory bowel pathology, have not been elucidated yet. In particular, the behavior of peroxisomes in inflamed colonic mucosa has not been investigated despite their important role in cellular oxidative metabolism. Using cytochemistry at the ultrastructural level, we have observed these catalase-positive organelles. In addition, biochemical analyses have revealed the specific activities of catalase and cyanide-insensitive acyl-CoA oxidase. Mucosal biopsy specimens from inflamed and noninflamed areas of Crohn's patients were compared to control biopsies. We found that Crohn's disease was marked by an important diminution in the peroxisomal frequency per cell unit area. If catalase activity was not affected by this pathology, cyanide-insensitive acyl-CoA oxidase, an enzyme of the peroxisomal beta-oxidation system, was found diminished in inflamed and in noninflamed areas. In conclusion, our results showed that Crohn's disease is accompanied by peroxisomal modifications but the number and the enzyme activities of colonic peroxisomes are less deeply altered in Crohn's disease than during neoplasia. This fact suggests that a relation may exist between the degree of peroxisomal deficiency and the clinical severity of colonic disease.

Peroxisomes and peroxisomal enzymes along the crypt-villus axis of the rat intestine

The development of peroxisomes and expression of their enzymes were investigated in differentiating intestinal epithelial cells during their migration along the crypt-villus axis. Sequential cell populations harvested by a low-temperature method were identified by microscopy, determination of alkaline phosphatase and sucrase activities and incorporation of [3H]-thymidine into DNA. Ultrastructural cytochemistry after staining for catalase activity, revealed the presence of peroxisomes in undifferentiated stem cells located in the crypt region. Morphometry indicated that the number of these organelles increased as intestinal epithelial cells differentiate. Catalase activity was higher in the crypt cells than in the mature enterocytes harvested from villus tips. On the other hand, an increasing gradient of activity was observed from crypts to villus tips for peroxisomal oxidases, i.e. fatty acyl coA oxidase, D-amino acid oxidase and polyamine oxidase. These findings indicate that biogenesis of peroxisomes occurs during migration of intestinal epithelial cells along the crypt-villus axis and that peroxisomal oxidases contribute substantially to the biochemical maturation of enterocytes.