Search PubMed⌕ Search

Biomedical subjects

P C Vincent

Publications and source records attributed to P C Vincent.

At least 19 recordsLinked to original sources
PubMed2000

Hypermethylation of E-cadherin in leukemia.

E-cadherin gene is often termed a "metastasis suppressor" gene because the E-cadherin protein can suppress tumor cell invasion and metastasis. Inactivation of the E-cadherin gene occurs in undifferentiated solid tumors by both genetic and epigenetic mechanisms; however, the role of E-cadherin in hematologic malignancies is only now being recognized. E-cadherin expression is essential for erythroblast and normoblast maturation, yet expression is reduced or absent in leukemic blast cells. This study examined the messenger RNA (mRNA) and protein expression of the E-cadherin gene in bone marrow and blood samples from normal donors and patients with leukemia. We found that all normal donor samples expressed E-cadherin mRNA, whereas both samples of acute myelogenous leukemia and chronic lymphocytic leukemia had a significant reduction or absence of expression. However, normal blast counterparts expressed only a low level of E-cadherin surface protein. Sodium bisulphite genomic sequencing was used to fully characterize the methylation patterns of the CpG island associated with the E-cadherin gene promoter in those samples with matched DNA. All of the normal control samples were essentially unmethylated; however, 14 of 18 (78%) of the leukemia samples had abnormal hypermethylation of the E-cadherin CpG island. In fact both alleles of the E-cadherin gene were often hypermethylated. We conclude the E-cadherin gene is a common target for hypermethylation in hematologic malignancies.

Base Sequence↗
PubMed2000

Galileo's peers.

Explore the source record for details and available documents.

Australia↗
PubMed1999

Concurrent DNA hypermethylation of multiple genes in acute myeloid leukemia.

Hypermethylation in cancer often occurs in CpG islands that span the promoter regions of tumor suppressor genes. However, it is not clear if hypermethylation is limited to single target genes or if multiple genes are simultaneously methylated. To understand the extent of aberrant de novo methylation, we have analyzed the methylation pattern of a number of tumor-related genes in leukemia from the same cohort of patients. We used bisulfite genomic sequencing to characterize the methylation pattern of the CpG islands associated with the calcitonin, estrogen receptor, E-cadherin, p15, p16, Rb, GST-Pi, and HIC1 genes in the bone marrow from 9 normal and 20 patients with acute myeloid leukaemia (AML). All of the normal control samples were essentially unmethylated for each of the eight tumor-related genes studied. In contrast, 19 of 20 (95%) of the AML patients had an abnormal methylation pattern in at least one gene, and 15 of 20 (75%) had abnormal methylation patterns in two or more of the target genes. We conclude that there is a general deregulation of CpG island methylation in leukemia and that hypermethylation is not limited to single genes, but a number of genes are methylated concurrently. Moreover, the subset of genes that are commonly methylated in leukemia appear to be cancer type specific.

Acute Disease↗
PubMed1999

Relapse in chronic myeloid leukemia after bone marrow transplantation: biomathematical modeling as a new approach to understanding pathogenesis.

A biomathematical model was developed to simulate relapse development in patients with chronic myeloid leukemia (CML) following bone marrow transplantation (BMT). The purpose of this study was to better understand the pathophysiology of the time evolution of CML relapse and to provide means whereby the outcomes of patients with CML relapse can be projected and treatment modified accordingly. The model consists of three parallel series of catenated compartments representing granulopoiesis in normal (donor) cells from the marrow, in CML cells from the marrow, and in CML cells from extramedullary sites. It was assumed that CML stem cells were resistant to feedback control and that CML-derived neutrophils, as well as normal neutrophils, exercised feedback regulation of normal stem cells. The known longer generation times for CML neutrophil precursors compared with normal neutrophil precursors were used, and it was assumed that 10(7) pluripotential stem cells were infused with BMT. The model was evaluated for its ability to simulate the reappearance of CML (Philadelphia chromosome positive) metaphases in the marrow and the recovery pattern in the blood neutrophil count in six patients who had relapsed following BMT (allogeneic in three patients, allogeneic with T-cell depletion in two patients, and syngeneic in one patient). The variables tested included the site of origin of the CML stem cells responsible for relapse (marrow alone versus marrow and extramedullary sites), the minimum number of CML stem cells responsible for relapse, and the time delay between BMT and the onset of relapse. Model profiles based on the observed values were obtained in each case. The simulations pointed to the fact that relapse began from a small number of CML cells in medullary and extramedullary sites. The time delay between BMT and the onset of relapse varied from 15 to 240 days. We suggest that this biomathematical model should be further investigated as a possible means of predicting outcome and guiding the treatment for patients with CML relapsing after BMT.

Adult↗
PubMed1999

Cancer-specific region of hypermethylation identified within the HIC1 putative tumour suppressor gene in acute myeloid leukaemia.

Abnormal DNA methylation has been found to be a common feature in cancer cells, although the mechanism of this alteration remains poorly understood. HIC1 is a putative tumour suppressor gene on chromosome 17p13.3 and is hypermethylated in a number of cancers including leukaemia. In this study, using bisulphite genomic sequencing, we have identified a 'boundary' sequence within the HIC1 CpG island that shows a marked junction between methylated and unmethylated DNA in normal haematopoietic cells. Surprisingly, this boundary of differential methylation lies exactly between the intron 2 and exon 3 junction. In contrast to normal haematopoietic cells, hypermethylation extends past this boundary at a high frequency (83%) in newly diagnosed acute myeloid leukaemias (AML). Identification of the hypermethylated boundary sequence not only provides the first step in understanding the mechanisms that normally protect CpG islands from de novo methylation but also may prove to be a useful cancer-specific marker.

Acute Disease↗
PubMed1998

Increased DNA methyltransferase expression in leukaemia.

Aberrant DNA methylation has been observed consistently in many human tumours, in particular in the CpG islands of tumour suppressor genes, but the underlying mechanism of these changes remains unclear. To determine whether DNA methyltransferase expression is increased in leukaemia, we developed a standardised competitive RT-PCR assay to measure the level of DNA methyltransferase transcripts. Using this assay on bone marrow RNA samples from 12 patients with acute leukaemia, we observed a 4.4-fold mean increase in the level of DNA methyltransferase mRNA compared with normal bone marrow. These results support but do not prove the hypothesis that an increase in DNA methyltransferase activity is associated with malignant haematological diseases and may constitute a key step in carcinogenesis.

Adult↗
PubMed1997

Extensive DNA methylation spanning the Rb promoter in retinoblastoma tumors.

The retinoblastoma gene (Rb) is one of the best characterized tumor suppressor genes, and its inactivation is associated with a number of cancers. Previous studies have shown, by restriction enzyme analysis, that the promoter region of the Rb gene is methylated in a significant proportion of primary retinoblastoma tumors. We now report the first detailed methylation sequence analysis of the CpG island spanning the retinoblastoma promoter from hypermethylated retinoblastoma tumors. Our results show methylation is not confined to a specific CpG site, as detected by restriction enzyme studies, but extends to essentially all 27 CpG dinucleotides spanning the retinoblastoma CpG island, including the core promoter. The methylation pattern from each tumor DNA sample is different, ranging from densely to sparsely methylated profiles. Single CpG sites, in particular the E2F transcription factor binding site, as well as blocks of CpGs, were undermethylated in some tumor samples. Possible interference of methylation could be due to the binding of sequence-specific protein factors at these sites in the tumor cells. This study highlights that the dynamics of DNA methylation in cancer cells are clearly different from normal cells and gives an insight into the mechanism of abnormal methylation of CpG islands in cancer cells.

Base Sequence↗
PubMed1995

Apoptosis and the assessment of radiation injury.

Apoptosis is a necessary form of cell death for all multicellular organisms and is controlled by the action of genes that initiate, facilitate or inhibit the process. In addition to physiological triggers, apoptosis can follow cellular injury, such as exposure to ionizing radiation. Cell death following radiation serves as a means by which the possibility of cells surviving with potentially harmful genomic damage can be reduced. Apoptosis can be identified in tissues shortly after whole body radiation; but apoptotic cells are rapidly cleared by phagocytosis, and apoptosis is unlikely to serve as a useful long-term marker of previous radiation exposure.

Animals↗
PubMed1992

Binding of proteins from embryonic and differentiated cells to a bidirectional promoter contained within a CpG island.

We have analysed binding sites of nuclear protein factors to a CpG island (HTF9), which contains the promoter for a pair of overlapping, divergently-transcribed "housekeeping" genes. Using DNaseI protection assays with extracts from a range of differentiated and undifferentiated cell lines, including mouse embryonic stem (ES) and embryonal carcinoma (EC) cells, we located multiple protein binding sites on HTF9. Most of the sites were outside the defined core promoter and could bind to previously identified transcription factors. These included constitutive, inducible and apparently tissue-specific factors in an extremely asymmetric array relative to the transcription start sites of the two genes. A number of sites showed different binding specificities or affinities in different cell types, including ES cells. However, we found no factors that were specific for both ES and EC cells, and no protein-binding site protected exclusively in undifferentiated embryonic cells.

3T3 Cells↗
PubMed1991

Characterization of endocrine-rich monolayers of human fetal pancreas that display reduced immunogenicity.

Fibroblast-free insulin-secreting monolayers of human fetal pancreas (14-20 wk of gestation) were formed by plating isletlike cell clusters (ICCs) obtained from partially digested pancreases on plates coated with bovine corneal matrix. Human fetal pancreatic cells, freshly digested with collagen, displayed a 17-fold response to human peripheral blood lymphocytes (HPBLs) in mixed-lymphocyte culture. After 14 days in culture, monolayers derived from ICCs exhibited a smaller, twofold response to HPBLs. By comparison, in monolayers produced from single-cell suspensions, fibroblast overgrowth remained a problem. The endocrine component of the monolayers was 65 +/- 13 and 43 +/- 8%, respectively, with the number of beta-cells being 51 and 9%. Cells from both monolayers displayed increased insulin release when exposed to 10 mM theophylline, 10 mM Ca2+, and 0.6-1.3 microM 12-O-tetradecanoylphorbol-13-acetate but not to 20 mM glucose. Monolayers derived from ICCs synthesized DNA, proinsulin, and protein. This study showed that it is possible to establish an endocrine-rich monolayer of human fetal pancreas that has greatly reduced immunogenicity. The existence of residual activity to HPBLs suggests some additional form of immunosuppression is required to prevent rejection of this tissue when grafted into diabetic patients. Subculturing and cryopreservation may also be needed to achieve adequate numbers of beta-cells for clinical transplantation.

Calcium↗
PubMed1990

Pig fetal pancreatic monolayers. A model of potential use in transplantation.

Endocrine-rich monolayers of pig fetal pancreas that are free of fibroblasts have been established with the ultimate aim of providing guidelines for the culture of the human equivalent. The immunogenic potential of the monolayers--hence their capacity to be grafted--has also been analyzed. Fetuses ranging from 50 to 90 days were used, and, following digestion with collagenase (4 mg/ml, 15-20 min), the pancreatic suspension was plated onto tissue culture vessels containing RPMI 1640. The fetal calf serum concentration was kept low (5%) initially to inhibit fibroblast proliferation, but subsequently increased to 7%. Monolayers from a typical litter of 8-10 fetal pigs produced 6-8 x 10(8) viable epithelial cells by day 10 of culture, of which 75% were endocrine cells. This represents an 8-fold increase in a two-week period. The ratio of beta:alpha:delta:pancreatic polypeptide cells was 19:33:18:5. These monolayers synthesized both DNA, (pro)insulin and protein, and displayed increased insulin release when exposed to 10 mM theophylline, 10 mM Ca2+ and 1.3 microM 12-0-tetradecanoyl-phorbol-13-acetate. Static stimulation with 20 mM glucose however, did not elicit a response in insulin secretion. These cells displayed no reaction to allogeneic lymphocytes in a mixed lymphocyte culture, whereas freshly obtained porcine epithelial cells did. Methods may need to be found to increase the proportion of B cells in this enriched endocrine cell population. In general however, guidelines have been established that may be useful in developing a monolayer of human fetal pancreatic cells with the eventual aim of transplantation. The reduction in immunogenicity of the pig fetal pancreatic cells suggests that they too might be a potential source for transplantation.

Animals↗
PubMed1989

Cytogenetic abnormalities in benign lymphoid hyperplasia: a dual-parameter study using chromosome analysis and flow cytometry.

This is a prospective study of lymphoid tissue showing benign reactive hyperplasia (18 lymph nodes and 2 tonsils), using cytogenetic analysis of cells stimulated with T- or B-cell mitogens. The reason for this study was the detection of an abnormal chromosomal population in cells from an enlarged lymph node excised from a 7-year-old female who on further investigation was found to be clinically well and after one year's close follow-up had not developed any further signs or symptoms of malignancy. In addition, DNA content was measured by flow cytometry (FCM) on fresh cell suspensions in 17 cases and fixed cell suspensions in 3 cases. Structural and numerical clonal chromosome abnormalities were found in 9 of the 20 samples, but no common specific defect was identified. FCM showed an abnormal DNA content in 10 of the 20 samples studied; 3 of these showed clonal chromosome abnormalities. Surface membrane immunoglobulin studies were carried out on 15 of the 20 samples using cell suspensions and frozen tissue sections. In 5 of the 15 cases, monoclonal surface immunoglobulin was detected. There was no direct correlation between the surface membrane immunoglobulin studies and the chromosome and FCM analyses. We conclude that aneuploidy is a common feature in reactive lymphoid tissue, but both cytogenetics and FCM are needed to identify it.

Aneuploidy↗
PubMed1989

Characterization of cell lines derived from a multiply aneuploid human bladder transitional-cell carcinoma, UCRU-BL-13.

A series of cultured cell lines (designated UCRU-BL-13) has been established from different serial passages of a multiply aneuploid human bladder transitional-cell carcinoma xenografted in nude mice. Serial passage of the xenografts in vivo and of the cell lines in vitro was accompanied by shifts in the tumor ploidy, with dominance of different major peaks. Despite this, the expression of tumor markers remained constant, and consistent chromosomal markers were observed both in the 8th xenograft passage and in a subline in tissue culture established over a year apart. Chromosomal numbers reflected the predominant aneuploid peaks observed; consistent numerical and structural changes included a marker derived from chromosome 1, 8p-, -10, 11q+, and 17q+. The cell line derived from the initial xenograft comprised a mixture of transitional, adenocarcinoma and squamous carcinoma cells in early passage, but adenocarcinoma cells were absent from later passages. The lines expressed the B-blood-group antigen, histocompatibility antigens, receptors for transferrin and EGF, and reacted with a series of monoclonal antibodies (MAbs) directed to malignant human epithelial cell lines. These lines provide a model for studying the evolution of tumor heterogeneity and drug resistance in bladder carcinoma exhibiting multiple aneuploidy.

Aneuploidy↗
PubMed1989

Hodgkin's disease.

Explore the source record for details and available documents.

Hodgkin Disease↗