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C S Potten

Publications and source records attributed to C S Potten.

At least 19 recordsLinked to original sources
PubMed2001

Expression of Id helix-loop-helix proteins in colorectal adenocarcinoma correlates with p53 expression and mitotic index.

Id helix-loop-helix (HLH) proteins function as regulators of cell growth and differentiation and when overexpressed can induce malignant transformation. In a series of 34 cases of primary human colorectal adenocarcinoma, immunoreactivity for Id1, Id2, and Id3 was found to be significantly elevated in tumor compared with normal mucosa (P = 0.001 for Id1 and Id2; P = 0.002 for Id3). No elevation of Id expression was observed in 17 cases of adenoma. Expression of Id1 and to a lesser extent of Id2 was correlated with mitotic index (P = 0.005 for Id1; P = 0.042 for Id2) in human adenocarcinomas, and expression of all three Id proteins was correlated with p53 immunoreactivity (a marker of mutational 'inactivation' of p53 function; P = 0.002 for Id1; P = 0.006 for Id2; P = 0.016 for Id3). In normal intestinal mucosa of p53-null mice and in spontaneous tumors arising in Min+/- mice, expression of all three Id proteins was also found to be up-regulated. Antisense oligonucleotide blockade of Id protein expression inhibited the proliferation of human adenocarcinoma cells. Enforced, ectopic expression of the E47 basic HLH (bHLH) protein in human adenocarcinoma cell lines efficiently sequestered endogenous Id proteins as Id-bHLH heterodimers, as shown by coimmunoprecipitation and subcellular colocalization studies. This led to growth arrest of the cells. Enforced overexpression of a mutant E47 protein, deficient in transactivation and DNA binding function, also partially inhibited cell growth. Taken together, these data imply that deregulated expression of Id proteins in colorectal adenocarcinoma arises at least in part as a consequence of loss of p53 function and contributes to the uncontrolled proliferation of tumor cells in colorectal cancer.

Adenocarcinoma↗
PubMed2001

1,2-Dimethylhydrazine-induced colon carcinoma and lymphoma in msh2(-/-) mice.

BACKGROUND: Defective mismatch repair (MMR) in humans is particularly associated with familial colorectal cancer, but defective repair in mice is generally associated with lymphoma in the absence of experimental exposure to carcinogens. Loss of MMR also confers resistance to the toxic effects of methylating agents. We investigated whether resistance to methylation contributes to increased susceptibility to colorectal cancer in mice by exposing mice with defects in the MMR gene msh2 to a methylating agent. METHODS: Tumor incidence and time of death in msh2(+/+), msh2(+/-), and msh2(-/-) mice were analyzed after weekly exposure (until tumor appearance) to the methylating agent 1,2-dimethylhydrazine (DMH). Chemically induced and spontaneous tumors were characterized by frequency, type, and location. The tumor incidence in untreated and treated mice of each genotype was compared by a Mann-Whitney U test. Carcinogen-induced apoptosis in histologic sections of small and large intestines was also determined. All statistical tests were two-sided. RESULTS: Homozygous inactivation of the msh2 gene statistically significantly accelerated (P<.0001) death due to the development of DMH-induced colorectal tumors and lymphomas. Rates of death from DMH-induced colorectal adenocarcinoma were similar in msh2 heterozygous and wild-type mice, but only msh2 heterozygotes (msh(+/-)) developed additional, noncolorectal malignancies (notably trichofolliculoma [two of 21], angiosarcoma of the kidney capsule [two of 21], and lymphoma [one of 21]), suggesting that heterozygosity for msh2 slightly increases DMH susceptibility. DMH induced apoptosis in small intestinal and colonic epithelial crypts that was dependent on active msh2. CONCLUSIONS: Inactivation of msh2 allows the proliferation of gastrointestinal tract cells damaged by methylating agents. Furthermore, MMR constitutes a powerful defense against colorectal cancer induced by DNA methylation.

1,2-Dimethylhydrazine↗
PubMed2001

Ageing of murine small intestinal stem cells.

Most organs of the body comprise populations of cells that are committed to specialized functions and that are renewed from small numbers of uncommitted progenitor or 'stem' cells. Stem cells are of central importance in the study of ageing because any senescent decline in the number or functional competence of stem cells will impair the capacity for renewal and turnover of committed cells, with potentially serious consequences for tissue homeostasis. The intestinal epithelium represents an excellent model system for the study of stem cells. Its spatial and hierarchical organisation allows the study of the function or characteristic of a given cell according to its position within the crypt. Hence, the stem cells which are located at the 4th-5th cell position from the bottom can be studied together with their daughter cells, as they divide and differentiate while migrating along the crypt-villus axis. The ability of the stem cells to undergo apoptosis and the capacity to regenerate the epithelium following injury were investigated in mice of different ages. Stem cells from older animals showed an increased apoptotic response following exposure to low doses of ionising radiation. The regenerative capacity was estimated by measuring the crypt survival levels and the growth rate of surviving crypts after high doses of irradiation. Surviving crypts in the older mice, suggesting an impairment in the damage recognition/response mechanisms, were both fewer and smaller than in young mice. The growth rate of surviving crypts was determined by measuring the crypt area and the number of cells/crypt at various times after 14 Gy irradiation. There was a growth delay of between half and one day in the older mice, and they subsequently grew more slowly. The number of cells susceptible to regenerate a crypt was also estimated. Surprisingly, they appear to be more numerous in the older mice. These studies indicate important age-related alterations in the capacity of the stem cells to regenerate the crypts after radiation-induced damage. The molecular bases of these changes are currently being investigated. Preliminary data showed alteration in the level of p53 and p21 expression, suggesting an age-related defect in the capacity to recognize damage and initiate apoptosis or repair.

Animals↗
PubMed2001

Caspase activation during spontaneous and radiation-induced apoptosis in the murine intestine.

The aim of this study was to characterize the activation of caspase-3 along the crypt/villus axis in the normal and irradiated intestine and to compare active caspase-3 expression with existing apoptosis detection techniques. Small and large intestine were removed from mice at various time points after exposure to 8 Gy gamma-radiation. Positive apoptotic cells stained with an antibody against active caspase-3, haematoxylin and eosin (H&E) or TUNEL were scored in histological sections of small and large intestinal crypts and villi. In the control intestine, active caspase-3 expression was rarely observed; however, expression was markedly increased following exposure to radiation and was predominantly confined to apoptotic bodies. Measurement of apoptosis in intestinal crypts using active caspase-3 expression gave similar results to apoptosis detected from H&E-stained sections. In the normal villus, active caspase-3 expression was observed infrequently and did not significantly increase following radiation, consistent with a lack of apoptotic body formation from H&E sections. This study indicates that caspase-3 is activated in intestinal crypts but not in villi following gamma-radiation. Active caspase-3 detection compared favourably with existing immunological techniques, suggesting that it is a suitable alternative method for apoptosis quantification.

Animals↗
PubMed2001

In vitro labelling studies and the measurement of epithelial cell proliferative activity in the human oral cavity.

Samples (110) of human mandibular gingiva and buccal mucosa, harvested from patients undergoing third-molar surgery, were subjected to in vitro labelling with tritiated thymidine, bromodeoxyuridine, or a sequential double-labelling technique comprising tritiated thymidine followed by bromodeoxyuridine, in order to determine the efficacy of a new incubation labelling technique, and to characterize S-phase labelling indices in human oral mucosa. Whilst, there were no demonstrable differences in labelling indices obtained by single thymidine, single bromodeoxyuridine or double labelling, there was a significant difference between anatomical sites, with higher S phase labelling observed in buccal mucosa (mean LI 11.7) than mandibular gingiva (mean LI 8.5; P<0.01). There was, however, no significant correlation between individual labelling indices and patient age, sex or the time of day when tissue was harvested. The in vitro labelling technique provides a reliable and quantifiable method of characterizing proliferative labelling indices in the human oral cavity. Further investigation is being carried out to profile wider age and anatomical ranges and to utilize the double-labelling technique to calculate S-phase durations and cell-cycle times. These profiles may have a future role in the assessment of oral mucous membrane disease.

Adolescent↗
PubMed2001

Effect of photoreactivating light on UV radiation-induced alterations in human skin.

BACKGROUND/AIMS: Photoreactivating light (PRL) after ultraviolet radiation (UVR) exposure causes photoreversal of cyclobutane pyrimidine dimers through the activation of photolyase. Although photoreversal has been demonstrated in the "three kingdoms of life," its existence in man remains controversial. We sought evidence for photoreversal in man. METHODS AND RESULTS: Seven subjects were spot-irradiated at two sites with 4 minimal erythema doses (MED) of solar-simulating UVR. Of the two sites, one was then immediately exposed to a PRL source. Epidermal biopsies were taken immediately after exposure. No significant difference in the quantity of pyrimidine dimers was detected comparing the "UVR only" site to the "UVR, PRL-exposed" site. Biopsies were repeated 24 h later and no significant difference in p53 protein expression or dendritic cell number was detected. However, the "UVR, PRL-exposed" site showed a greater reduction in pyrimidine dimer quantity. CONCLUSIONS: We found no evidence for a direct effect of PRL causing photoreversal of UVR-induced pyrimidine dimers in man. Our results do, however, suggest that some indirect effect of PRL may enhance pyrimidine dimer repair in the 24-h period following UVR exposure.

Adult↗
PubMed2001

Cell migration and organization in the intestinal crypt using a lattice-free model.

We present a novel class of spatial models of cell movement and arrangement applied to the two-dimensional cellular organization of the intestinal crypt. The model differs from earlier approaches in using a dynamic movement on a lattice-free cylindrical surface. Cell movement is a consequence of mitotic activity. Cells interact by viscoelastic forces. Voronoi tessellation permits simulations of individual cell boundaries. Simulations can be compared with experimental data obtained from cell scoring in sections. Simulation studies show that the model is consistent with the experimental results for the spatial distribution of labelling indices, mitotic indices and other observed phenomena using a fixed number of stem cells and a fixed number of transit cell divisions.

Animals↗
PubMed2001

High-risk colorectal adenomas and serum insulin-like growth factors.

BACKGROUND: This study investigated the hypothesis that circulating levels of insulin-like growth factor (IGF) I and its main binding protein (IGFBP-3) predict for the presence of colorectal adenomas, surrogate markers of colorectal cancer risk. METHODS: Within the Flexi-Scope Trial (healthy volunteers aged 55-64 years), at one study centre, IGF-I and IGFBP-3 levels in serum samples collected prospectively from 442 attendants were measured. Of these, 100 individuals underwent a complete screening colonoscopy. There were 47 normal examinations, while in 11 examinations low-risk adenomas and in 42 examinations high-risk adenomas were identified. Estimates of relative risk (RR) for the adenomatous stages were calculated by means of unconditional logistic regression, adjusting for known risk factors. RESULTS: Mean serum IGF-I and IGFBP-3 levels were similar in individuals with a normal colonoscopy finding and in those with low-risk adenomas. By contrast, the mean(s.d.) serum IGF-I level was increased (190(53) versus 169(54) microg/l; P = 0.06) and the serum IGFBP-3 concentration was significantly decreased (3.22(0.60) versus 3.47(0.62) mg/l; P = 0.05) in individuals with high-risk adenomas compared with levels in those with normal colonoscopy and low-risk adenomas combined. Levels were unaffected by removal of the adenomas. With high-risk adenoma as the dependent factor, regression models demonstrated a significant positive association with IGF-I after controlling for IGFBP-3 (RR per one standard deviation (1s.d.) change 4.39 (95 per cent confidence interval (c.i.) 1.31-14.7); P = 0.02) and, independently, an inverse association with IGFBP-3 after adjustment for IGF-I (RR per 1s.d. change 0.41 (95 per cent c.i. 0. 20-0.82); P = 0.01). CONCLUSION: These findings suggest that circulating IGF-I and IGFBP-3 levels are related to future colorectal cancer risk and, specifically, may predict adenoma progression.

Adenoma↗
PubMed2001

Blockade of growth factor receptors in ductal carcinoma in situ inhibits epithelial proliferation.

BACKGROUND: Ductal carcinoma in situ (DCIS) expresses c-erbB-2 receptor and epidermal growth factor receptor (EGFR). The aim of this study was to determine whether blocking of c-erbB-2 receptor with a humanized monoclonal antibody, 4D5 (HerceptinTM), or of EGFR with an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), ZD1839 (IressaTM), would decrease epithelial proliferation in DCIS. METHODS: DCIS tissue from 18 women undergoing surgery was implanted into 16 to 20 athymic nude mice per experiment (eight xenografts per mouse). Treatment commenced 2 weeks after implantation and consisted either of twice-weekly intraperitoneal injections of 4D5 10 mg/kg or of daily gavage with ZD1839 at 100-200 mg/kg for 14 days; appropriate controls were included. Xenografts were removed on days 14, 21 and 28. Proliferation was assessed by counting 1000 epithelial cells after Ki67 immuno- staining. RESULTS: ZD1839 inhibited proliferation compared with that in controls after 14 days (P < 0.01), whereas 4D5 did not. CONCLUSION: Proliferation in DCIS was decreased by EGFR tyrosine kinase inhibition but not by c-erbB-2 receptor blockade. ZD1839, an orally active and selective EGFR-TKI, has potential as adjuvant therapy in DCIS.

Adult↗
PubMed2001

Paradoxical elevations in serum IGF-II and IGF binding protein-2 in acromegaly: insights into the regulation of these peptides.

OBJECTIVE: Circulating insulin-like growth factor (IGF)-II and IGF binding protein-2 (IGFBP-2) are frequently altered, often in parallel, in numerous pathologies including neoplastic disease but little is known about their normal regulation. This study compared serum IGF-II and IGFBP-2 distributions between acromegalics and a large normal adult population to explore possible determinants. PATIENTS: Sixty acromegalic patients undergoing screening colonoscopy (age range 25-81 years); normative data from 306 healthy adults (age range 20-89 years). MEASUREMENTS: Serum IGF-I, IGF-II, IGFBP-2 and IGFBP-3 were measured in healthy adults and acromegalics. Mean growth hormone (GH) levels were obtained for acromegalic patients. Differences were compared using t-tests (unadjusted) and multiple regression models (adjusted for age and gender). Correlations were expressed as Pearson's coefficient (r). RESULTS: For acromegalic patients, GH was significantly correlated with IGF-I (r = 0.50; P < 0.001) and IGFBP-3 (r = 0.29; P = 0.03) but not IGF-II or IGFBP-2. Contrary to expectations, mean IGF-II and IGFBP-2 levels were significantly raised in the acromegalics compared with normals [adjusted mean difference (95% CI) = 226 (181, 271) microg/l and 305 (200, 410) microg/l, respectively]. Ten acromegalic patients had colorectal neoplasia but their presence did not contribute to the elevations in serum IGF-II and IGFBP-2. The (IGF-I + IGF-II)/IGFBP-3 molar ratios were remarkably constant in both healthy adults and acromegalics, but the relationships of the ligands individually with IGFBP-3 were not linear: as IGFBP-3 increased, IGF-I also increased whereas IGF-II initially increased but then decreased. IGFBP-2 did not correlate with IGF-II, but molar concentration significantly correlated with the IGF-II/IGFBP-3 molar ratio (r = 0.40; P = 0.001). CONCLUSIONS: Serum IGF-II and IGFBP-2 levels were paradoxically elevated in acromegalics, independent of the presence of colorectal neoplasia. The (IGF-I + IGF-II)/IGFBP-3 molar ratio appears to be pivotal in determining IGF-II values, which, in turn, expressed as a ratio of IGFBP-3, is related to IGFBP-2. These observations offer new insights into the regulation of these peptides.

Acromegaly↗
PubMed2001

Tanning salon exposure and molecular alterations.

BACKGROUND: Human studies of the short-term cellular effects of tanning salon exposures are lacking. Findings of such studies may prove extremely helpful in educating consumers considering or currently attending tanning salons. OBJECTIVE: Our purpose was to determine whether tanning salon exposure causes DNA alterations and p53 protein expression in epidermal keratinocytes and/or circulating peripheral lymphocytes. METHODS: Eleven subjects received 10 full-body tanning salon exposures over a 2-week period. UV-induced DNA cyclobutane pyrimidine dimers and p53 protein expression were examined, comparing pretreatment peripheral blood lymphocytes and epidermal biopsy specimens with analogous specimens obtained after the 10 tanning salon exposures. RESULTS: Cyclobutane pyrimidine dimers in DNA and p53 protein expression were detected in epidermal keratinocytes, but were absent in lymphocytes. CONCLUSION: Similar to outdoor sun exposure, short-term recreational tanning salon exposure causes molecular alterations believed essential in the development of skin cancer.

Adolescent↗
PubMed2001

Epidermal p53 response and repair of thymine dimers in human skin after a single dose of ultraviolet radiation: effects of photoprotection.

A cellular p53 response, DNA repair enzymes and melanin pigmentation are important strategies utilized by skin keratinocytes against impairment caused by ultraviolet radiation (UVR). In this study a double-immunofluorescence technique was used to investigate UVR-induced thymine dimers and p53 protein simultaneously. Four healthy volunteers were irradiated on both sides of their buttock skin with a single dose of solar-simulating UVR. One side was pretreated with a topical sunscreen. Biopsies from different time-points were immunostained for visualization of thymine dimers, p53 and proliferation. One single physiological dose of UVR generated widespread formation of thymine dimers throughout the epidermis 4h after irradiation. The level of thymine dimers decreased over time and was followed by a p53 response in the same cells. A late proliferative response was also found. The formation of thymine dimers, the p53 response and the late proliferative response were partially blocked by topical sunscreen. Large inter-individual differences in the kinetics of thymine dimer formation and repair as well as in the p53 response were evident in both sunscreen-protected and unprotected skin.

Adult↗
PubMed2001

Protection against mucosal injury by growth factors and cytokines.

This article provides an overview of published studies in which growth factors and cytokines were used to modify the sensitivity of intestinal stem cells to a dose of radiation. In these experiments, growth factors were used to manipulate the sensitivity of stem cells in the gastrointestinal tract to reduce the severity of gastrointestinal mucositis in cancer therapy patients. Transforming growth factor beta3, interleukin 11, and keratinocyte growth factor were used. All three agents, given according to appropriate protocols, can result in a threefold to fourfold increase in the number of intestinal stem cells that survive a dose of radiation therapy. This result was assessed by using the crypt microcolony assay of stem cell functional capacity. The changes in stem cell survival that were observed resulted in increased animal survival. This increased survival was taken as a surrogate for improvement in patient well-being. The severity of diarrhea, a marker of functional impairment, was concomitantly reduced.

Animals↗
PubMed2001

The relevance of apoptosis for cellular homeostasis and tumorigenesis in the intestine.

Intestinal epithelium is a rapidly renewing tissue in which cell homeostasis is regulated by a balance among proliferation, growth arrest, differentiation and apoptosis (programmed cell death). Until recently, studies on oncogenesis have focused on the regulation of cell proliferation. The recognition that apoptosis must be understood to comprehend how appropriate cell numbers are maintained and how alterations in any part of the equation can contribute to malignancy has led to an explosion of research in this field. The first half of this review gives an overview of morphology and mechanisms of apoptosis, emphasizing key areas of genetic control such as the bcl-2 family and p53. The second half of the review focuses on the role of apoptosis in normal cellular homeostasis and tumorigenesis in the gastrointestinal epithelium. The importance of understanding the molecular biology of apoptotic pathways in cancer therapy and future directions are also addressed.

Animals↗
PubMed2001

Apoptosis in oral mucosa: lessons from the crypt. A commentary.

The programmed removal of individual isolated cells from a tissue during development, in the adult steady state, and in pathological abnormalities, is an important regulated process that counter-balances the cells produced due to cell division, and compliments differentiation in the overall tissue homeostatic mechanisms. In stratified epithelium, apoptosis can sometimes be difficult to identify and end-labelling techniques such as TUNEL are difficult to optimise and validate. In the columnar epithelium of the small intestine, apoptosis is easy to recognise by virtue of the morphological changes seen in dying cells in routine paraffin sections. The dying cells fragment and the apoptotic fragments can be reliably counted. Because of the precise cell positional relationship between hierarchical status in the lineage and cell position in the tissue, the cell death can be related to the hierarchical status of the dying cells. In the normal steady state in healthy epithelium a small proportion of stem cells are constantly dying. This p53-independent apoptosis is interpreted as part of the homeostatic regulation of stem cell numbers. After exposure to low levels of genotoxic agents, such as radiation, some stem cells in this tissue are very susceptible to apoptosis induction in a p53-dependent fashion. This has been interpreted to be a genome protective mechanism that accounts at least in part for the unexpected low incidence of cancer in this rapidly proliferating, large mass of tissue within the gastrointestinal tract.

Adult↗
PubMed2001

The effects of repeated doses of keratinocyte growth factor on cell proliferation in the cellular hierarchy of the crypts of the murine small intestine.

Keratinocyte growth factor (KGF) administered on a daily basis for 3 or more days can result in dramatic changes in tissue architecture, particularly the thickness in oral epithelia, and can afford protection against the cytotoxic effects of radiation on the clonogenic stem cells in the crypts. This protection of intestinal stem cells (increased numbers of surviving crypts) is reflected in an increased survival of animals exposed to a lethal dose of irradiation. The mechanisms underlying these effects are not clear. The present experiments were designed to investigate the nature of any proliferative changes induced in the crypts of the small intestine by protracted exposure to KGF. Tritiated thymidine or bromodeoxyuridine labeling showed statistically significant increases in labeling in the stem cell zone of the crypt, with a concomitant reduction in labeling in the upper regions of the crypt corresponding to the late-dividing transit population. The increase in labeling in the lower regions of the crypt was also observed with Ki-67 staining, but the reduction in the upper regions of the crypt seen with tritiated thymidine was not observed with Ki-67. Metaphase arrest data suggest that the rate of progression through the cell cycle is essentially the same in KGF-treated animals as in controls, but there is a statistically significant increase in the number of mitotic events per crypt. Double labeling studies suggest that, at certain times of the day, there is a greater influx into S phase than efflux. The data overall indicate that KGF induces some complex proliferative changes in the intestinal crypts and are consistent with the hypothesis that the radioprotection may be afforded, at least in part, by a KGF-induced increase in stem cell numbers and/or increases in the number of stem cells in the S phase of the cell cycle. This alteration in the homeostasis of the crypt is compensated for by a foreshortening of the dividing transit lineage.

Animals↗