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Biomedical subjects

G V Sherbet

Publications and source records attributed to G V Sherbet.

At least 19 recordsLinked to original sources
PubMed2005

Hormonal influences on cancer progression and prognosis.

Cell differentiation, proliferation, apoptosis, and cell motility are induced and regulated by a host of growth factors, vitamins, and hormones. The mode of function of these modifiers of biological response, the signaling pathways that they activate, and the interacting pathways that can influence the biological outcome have been the focus of attention. Especially recognized and discussed in this review is the deregulation of their function, leading to abnormalities in cell proliferation, alteration of intercellular adhesive cohesion, remodeling of the extracellular matrix, and invasive behavior and metastatic deposition that are so characteristic of tumor development and progression, which strongly underscores the concept of molecular progression of cancer constructed on the basis of the relationship between genetic changes and the biological events associated with cancer progression. The molecular changes associated with hormone- and vitamin-driven responses and the deregulation of the expression and function of their target genes seem to correlate with specific biological events linked with cancer invasion and progression, and these findings could lead to the establishment of new markers of progression and to the development of new strategies for patient management. The scope of this work has been restricted by design and is dictated by the field of interest of the author's laboratory, but it is hoped that this field would be regarded adequately to reflect the wide genre of scientific interest in this field of human disease.

Animals↗
PubMed2003

Differential regulation of Notch signal transduction in leukaemia and lymphoma cells in culture.

The transduction of Notch signal plays an intricate role in cell differentiation and pathogenesis of haematological malignancies as well as in certain congenital conditions. We found no genomic changes in either gene in 34 leukaemic samples and 25 leukaemia and lymphoma cell lines. The functionality of Notch signalling was tested using HES1 gene activation. We show that Notch signalling is differentially regulated in T-acute lymphoblastic leukaemia (ALL) and B-lymphoma cells. The Notch pathway is intact in a majority of B-lymphoma cell lines, but EBNA2, which mimics notch function, can occasionally activate the pathway. In contrast, the Notch pathway is constitutively active in T-ALL. This is the first demonstration of a distinction between B-lymphomas and T-cell leukaemias in the functioning of the Notch-signalling pathway. This might be related to their pathogenesis.

Cell Line, Tumor↗
PubMed2003

Prediction of nodal spread of breast cancer by using artificial neural network-based analyses of S100A4, nm23 and steroid receptor expression.

The expression of tumour promoter gene S100A4, metastasis suppressor gene nm23, oestrogen and progesterone receptors, and tumour grade and size have been investigated for their potential to predict breast cancer progression. The molecular and cellular data have been analysed using artificial neural networks to determine the potential of these markers to predict the presence of metastatic tumour in the regional lymph nodes. This study shows that tumour grade and size are poor predictors. The relative expression of S100A4 and nm23 genes is the single most effective predictor of nodal status. Inclusion of oestrogen- and progesterone-receptor status with tumour grade and size markers improves prediction; however, there may be some overlap between steroid receptors and molecular markers. This study also underscores the power of artificial neural network techniques to predict the potential of primary breast cancers to spread to axillary lymph nodes. This could aid the clinician in determining whether invasive procedures of axially node dissection can be obviated and whether conservative forms of treatment might be appropriate in the management of the patient.

Adult↗
PubMed2001

Oxidative stress signalling in the apoptosis of Jurkat T-lymphocytes.

The pathways of transduction of oxidative stress signals have been studied using the Jurkat T cell model. The oxidative stress was induced by exposure of the cells to 100 microM H(2)O(2). DNA damage was detected within 15 min after commencement of treatment. DNA damage repair occurred within about 1 h in cells exposed to oxidative stress for 15 min. In continuous exposure to stress, DNA repair was slower and control levels of DNA integrity were not reached. DNA repair did not involve gene transcription. H(2)O(2) at 100 microM caused cell death by necrosis as well as by apoptosis. Both these processes were induced by 15 min exposure to the stress stimulus. However, some important differences were found between necrosis and apoptosis. Necrosis was more rapid, began within an hour of treatment and continued to increase during the full duration of the experiment. But apoptosis was seen after 4 h from treatment and was conspicuous between 6 and 20 h after the start of treatment. The necrotic phase preceded apoptosis, although these did show an overlap. In the necrotic phase, Bcl-2, Caspase 8 genes were down regulated. The 6-20 h phase characterised by a marked increase in apoptosis is accompanied by the up regulation of both Bcl-2 and Caspase genes. Expression of the Fas and p53 genes was not altered in either phase. We also analysed the levels of expression of the scavenging genes whose gene products are involved in detoxification. No modulation of the antioxidant enzymes, catalase, Cu/Zn superoxide dismutase and glutathione peroxidase was detectable.

Apoptosis↗
PubMed1999

Stathmin is involved in S100A4-mediated regulation of cell cycle progression.

S100A4 is a cell proliferation- and cancer metastasis-related gene. Previous studies have shown that over-expression of S100A4 drives the cells into the S-phase of the cell cycle, with concomitant enhancement of p53 detection. This has led to the postulate that S100A4 could be controlling cell cycle progression by sequestering p53 and abrogating its G1-S checkpoint control. Cells induced by S100A4 to enter the S-phase do successfully negotiate the G2-M checkpoint control. Here we show that S100A4 is also involved in the regulation of control at this checkpoint. Stathmin is known to be associated, together with p53 in controlling G2-M transition. We present evidence that the expression of S100A4 and stathmin genes is up regulated in exponentially growing HeLa cells. They are down regulated in parallel when cell proliferation is inhibited by hyperthermia and 4-hydroxynonenal (4-HNE). We postulate that S100A4 might directly induce stathmin up regulation to enable cells to enter into mitosis. Since wild-type p53 is known to down regulate stathmin expression, we further postulate this might also involve S100A4-mediated sequestration of p53. The expression of heme oxygenase (HO-1), a stress-response protein, has been used to monitor effects of hyperthermia, 12-O-tetradecanoly phorbol 13-acetate (TPA) and 4-HNE. All these treatments induced HO-1 and also when cells growing in serum-deficiency were restored with full serum. HO-1 induction occurred irrespective of S100A4 expression status. HO-1 gene has responsive elements for many angiogenic agents and induces marked neovascularisation of tumours. We suggest therefore that S100A4 may not possess angiogenic properties.

3T3 Cells↗
PubMed1999

DNA ploidy and cell cycle distribution of breast cancer aspirate cells measured by image cytometry and analyzed by artificial neural networks for their prognostic significance.

Chromosomal abnormalities are commonly associated with cancer, and their importance in the pathogenesis of the disease has been well recognized. Also recognized in recent years is the possibility that, together with chromosomal abnormalities, DNA ploidy of breast cancer aspirate cells, measured by image cytometric techniques, may correlate with prognosis of the disease. Here, we have examined the use of an artificial neural network to predict: 1) subclinical metastatic disease in the regional lymph nodes and 2) histological assessment, through the analysis of data obtained by image cytometric techniques of fine needle aspirates of breast tumors. The cellular features considered were: 1) DNA ploidy measured in terms of nuclear DNA content as well as by cell cycle distribution; 2) size of the S-phase fraction; and 3) nuclear pleomorphism. A further objective of the study was to analyze individual markers in terms of impact significance on predicting outcome in both cases. DNA ploidy, indicated by cell cycle distribution, was found markedly to influence the prediction of nodal spread of breast cancer, and nuclear pleomorphism to a lesser degree. Furthermore, a comparison between histological assessment and artificial neural network prediction shows a closer correlation between the neural approach and the development of further metastases as indicated in subsequent follow-up, than does histological assessment. These data demonstrate that artificial neural networks are capable of providing powerful and reliable indicators of possible lymph node metastasis, using measurements of cellular features alone.

Breast Neoplasms↗
PubMed1998

Heat shock modulates the expression of the metastasis associated gene MTS1 and proliferation of murine and human cancer cells.

Mts1 is a metastasis-associated gene of the S-100 gene family and codes for a Ca2+-binding protein. It is highly expressed in murine and human cancers of high invasive and metastatic potential. Recent work has shown that the mts1 protein might be involved in cell cycle regulation. An upregulation of its expression drives cells into the S phase, together with an enhanced expression of p53 phosphoprotein, which has led to the suggestion that mtsl protein might be sequestering p53 thereby abrogating the G1-S checkpoint control normally exerted by p53. Preliminary studies showed that expression of mts1 is downregulated by hyperthermia. We present evidence that in murine BL6 melanoma cells and human HUT cells that hyperthermia downregulates the mts1 gene. It is also downregulated in heat-resistant variants of the B16 melanoma and HUT cells. In parallel, there is a decrease in the size of the S phase fraction and an increase in the doubling time of cells. Cell subjected to hyperthermia show an 2- to 3.5-fold increase in the expression of HSP28 which has been shown to possess a proliferation inhibitory action. It is postulated that a complete regulatory loop involving mtsl, p53, and HSP28 might be involved in cell proliferation.

Animals↗
PubMed1998

Characterization of a splice variant of metastasis-associated h-mts1 (S100A4) gene expressed in human infiltrating carcinomas of the breast.

The h-mts1 (S100A4) is a member of the S100 gene family, coding for a calcium-binding protein. It is a metastasis-associated gene whose expression shows strong correlation with the proliferative potential and invasive and metastatic ability of cancers. In a proportion of human intraductal carcinomas of the breast, a shorter variant h-mts1 transcript (h-mts1v) of approximately 450 nucleotides is expressed. We have characterized the transcript using reverse transcriptase-polymerase chain reaction employing exon-specific oligonucleotides. We show here that the noncoding exon 1a/1b is lost in the variant cDNA. Exons 2 and 3, which code for the protein, seem to be present in the variant isoform. The RT-PCR products obtained using exons 2- and 3-specific oligonucleotides showed a high degree of sequence homology with exons 2 and 3 of the h-mts1 gene. The expression of the variant transcript could be influencing disease progression, albeit not as effectively as the normal unspliced h-mts1 transcript.

Base Sequence↗
PubMed1998

Expression of metastasis-associated genes h-mts1 (S100A4) and nm23 in carcinoma of breast is related to disease progression.

The murine 18A2/mts1 and its human homolog h-mts1 (S100A4), encoding a Ca2+-binding protein belonging to the S-100 family, are associated with high invasive and metastatic potentials of murine tumors, human tumor cell lines in vitro, and human tumors growing as xenografts. The nm23 is a putative metastasis-suppressor gene whose expression has been found to correlate inversely with the metastatic potential of some forms of human cancer. The products of both human genes alter cytoskeletal dynamics, with antagonistic effects. In view of the equivocal association of nm23 with the metastatic potential of human cancer, we suspected that the relative expression of h-mts1 and nm23 might reflect tumor progression more accurately than either of them alone. We describe here the expression of these genes in infiltrating ductal carcinomas of the breast and show that high h-mts1 expression is associated with metastatic spread to the regional lymph nodes. The expression of nm23 on its own did not show a statistically significant inverse correlation with nodal spread. However, the expression status of the two genes, taken together, correlated strongly with the occurrence of nodal metastases. Breast cancers with no detectable expression of h-mts1 were found to be estrogen and progesterone receptor positive. Expression of h-mts1 was not related to tumor differentiation. The clinical data, together with the state of expression of steroid receptors and the expression levels of h-mts1 and nm23 genes, were analyzed using artificial neural networks for accuracy in predicting nodal spread of the carcinomas. These analyses support the conclusion that, overall, h-mts1 expression appears to be associated with and indicative of more aggressive disease. Complemented with nm23, h-mts1 could provide a powerful marker of breast cancer prognosis.

Adult↗
PubMed1997

Artificial neural networks in cancer research.

The concept of artificial neural networks dates back to the early part of this century. However, their use in biological and medical research has only vastly proliferated during the last few years. It is now clear that these networks, which attempt to emulate functions of the human brain, can play a vital role in the field of cancer research, where they could be used in the diagnosis, prognosis and patient management stages of cancer evaluation. This paper presents a review of the underlying theory behind artificial neural networks and gives a broad overview of their many areas of application within the cancer field. This is achieved through the prognostic analysis of prostate cancer markers, the non-invasive diagnosis of lymph node involvement in breast cancer patients and the assessment of image cytometric data for predicting the metastatic potential of breast cancer.

Biomarkers, Tumor↗
PubMed1996

Homologous recombination in variants of the B16 murine melanoma with reference to their metastatic potential.

Genomic instability has been accepted as providing a phenotypic variety of malignant cells within a developing tumour. Defects in genetic recombination can often lead to phenotypic differences; therefore, it is possible that metastatic variant cell lines exhibit their particular phenotype as a result of an altered ability to catalyse homologous recombination. We have investigated recombination efficiency in B16 melanoma metastatic variants, using a plasmid, pDR, as a recombination substrate. The plasmid contains two truncated, nontandem but overlapping segments of the neomycin resistance gene (neo 1 and neo 2), separated by the functional gpt gene unit. Only a successful recombination of the two neo segments will generate a functionally intact neomycin gene. Extrachromosomal recombination here was a transient measure of the cells to recombine the neo fragments in an intra- or intermolecular manner. Extrachromosomal recombination frequencies were higher in the high metastasis variants (BL6, ML8) compared with the low metastatic F1 cells. On the other hand, the frequency of chromosomal recombination (after plasmid integration) was higher for the low metastasis (F1) cell line compared with the highly metastatic variants, BL6 and ML8. Since the recombination assay measures only successful recombination events, we have interpreted the observed higher incidence of chromosomal recombination in the low metastatic variant line as indicative of a more stable genome. Similarly, a higher inherent instability in the genome of the high metastasis variants would render these less efficient at producing and maintaining successful recombination events, and this was found to be true by Southern analysis. The results presented show that frequency of recombination may be adduced as evidence for implicating genomic instability in the generation of variant cell populations during metastatic spread. Such an interpretation is also compatible with the Nowell hypothesis for tumour progression.

Animals↗
PubMed1996

The detection of nodal metastasis in breast cancer using neural network techniques.

Identification and treatment of involved axillary lymph nodes is important in the planning of strategies for adjuvant treatments of breast cancer. With the advent of the National Health Service Screening Programme, an increasing number of women with the disease are detected at an early stage, when the lymph nodes are not involved. In whom, therefore, is it necessary to carry out a formal axillary dissection? Are there accurate surrogates for lymph node involvement in the form of tumour markers or characteristics? This study, carried out on over 81 patients, examines the use of neural networks to predict the involvement of lymph nodes using readily available clinical and pathological data and also more specialized markers of possible prognostic significance. The study shows that neural networks are capable of providing strong indicators as to lymph node status using only basic measurements of the primary breast tumour. However, accuracy can be improved by the addition of less common markers.

Biomarkers, Tumor↗
PubMed1994

Induction of 18A2/mts1 gene expression and its effects on metastasis and cell cycle control.

The metastasis associated 18A2/mtsI gene was inserted into the mammalian expression vector pMAMneo placing it under the control of the dexamethasone-inducible MMTV promoter. The construct was transfected into dexamethasone receptor negative F1 and receptor positive F10 cells of the B16 murine melanoma. The transferred gene was switched on in two transfectant clones of F10, by exposure to 10(-6) M dexamethasone, but not in clones of the receptor negative F1 line. One of the F10 transfectant clones (F10-192/10) was characterized further. A 13.5-fold increase in 18A2/mts1 transcripts was found in this clone upon exposure to dexamethasone. There was also a seven-fold increase in lung colonization in an experimental metastasis assay, together with increased expression of depolymerized tubulin and enhanced detection of p53 protein. The number of cells in the S phase increased by 2.5-fold following dexamethasone treatment of the clone. These data suggest a direct involvement of the 18A2/mts1 gene in lung colonization by the tumor cells. The 18A2/mts1 protein promotes tubulin depolymerization, sequesters the p53 phosphoprotein, and induces the cells to enter the S phase, but the relevance of these in the metastatic process remains to be elucidated.

Animals↗
PubMed1994

Metastasis-associated mts1 gene expression correlates with increased p53 detection in the B16 murine melanoma.

MTS1 is a metastasis-associated gene highly expressed in high-metastasis tumors. Here we show that the expression of the suppressor gene p53 protein correlates with mts1 expression. In murine melanoma B16-F1 cells, alpha-melanocyte-stimulating hormone up-regulated mts1 and increased p53 positivity in immunohistochemical tests. In B16-ML8 cells, retinoic acid reduced mts1 expression together with a reduction of p53 positivity. The variation of p53 in association with mts1 gene expression suggests that the mts1 product might interact with and stabilize p53. Taxol-induced aneuploidy increased the proportion of G0G1 phase cells, increased p53 positivity, and down-regulated mts1. This suggests that mts1 transcription may have been negatively regulated, possibly on account of the stabilization of microtubules by taxol. We postulate that the control of G1-S transition by p53 could be due to p53 sequestration by mts1, leading to microtubule depolymerization and signaling entry, into the S phase. Thus, a coordinated function of mts1 and p53 may be involved not only in uncontrolled growth but also in cytoskeletal depolymerization that could lead to cancer invasion.

Calcium-Binding Proteins↗
PubMed1994

Metastasis-associated mts1 gene expression is down-regulated by heat shock in variant cell lines of the B16 murine melanoma.

Tumour cells are more heat sensitive than corresponding normal cells but the reasons for this are poorly understood. Here we report that induction of heat shock proteins was associated with a down-regulation of the metastasis associated mts1 gene in BL6-B16 murine melanoma cells, and the heat-resistant HTG variant of the BL6 line. Melanocyte stimulating hormone, which does not affect B16 cell proliferation but upregulates mts1 expression, only marginally enhanced heat shock protein expression in F1 cells as determined by immunohistochemical methods. Retinoic acid, which inhibits cell proliferation and down-regulates the mts1 gene, reduced heat shock protein expression in the ML8-B16 variant line. This suggests that the changes in the heat shock protein expression reported here may be cell proliferation related. Heat shock proteins are known to stabilize microtubules, whereas mts1 has been implicated in their depolymerization. Taxol, which stabilizes microtubules and arrests cells at the G1 phase of the cell cycle, down-regulated mts1 gene expression in both F1 and ML8 lines. Taxol also reduced heat shock protein expression in ML8 cells. These data suggest opposing functions of heat shock proteins and the mts1 gene in microtubule polymerization, and may provide a rationale for the use of hyperthermia as a treatment for tumours.

Animals↗
PubMed1994

Overexpression of the 18A2/mts1 gene and down-regulation of the TIMP-2 gene in invasive human glioma cell lines in vitro.

Invasion of the reconstituted extracellular matrix composite, Matrigel, by eight human glioma-derived cell lines and human fetal brain cells was assessed in vitro using 8 microns polycarbonate filters in a modified Boyden migration chamber. With the exception of one low grade glioma derived cell line, all lines studied proved to be invasive while normal fetal brain cells failed to invade. This invasive potential was independent of the histological grade of the tumour from which the cell lines originated. In addition, the expression of the metastasis-associated gene 18A2/mts1 as well as the tissue inhibitor of metalloproteinases-2 (TIMP-2) was analysed in each of the glioma-derived cell lines. The 18A2/mts1 was expressed in all the cells studied with the exception of fetal brain cells and the low grade non-invasive glioma derived IPRK-7 cell line. The 18A2/mts1 related genes coding for the S100 subfamily of calcium binding proteins were found to be differentially and overexpressed in invasive cell lines. TIMP-2 was expressed only in non-invasive cell lines. These results suggest that the 18A2/mts1 and TIMP-2 genes could play an important role in the invasive behaviour of human glioma cells in vitro.

Blotting, Northern↗
PubMed1993

DNA repair and repair fidelity in metastatic variants of the B16 murine melanoma.

We have examined the concept of genomic instability in relation to the metastatic progression of low (F1) and high metastasis (BL6, ML8) clones of the B16 mouse melanoma, by using a mutation assay, and DNA strand break repair and repair fidelity assays. The frequency of induced ouabain resistant colonies between the variant cell lines was consistent with the difference between their metastatic properties. Survival data for X-irradiation and bleomycin were similar among the 3 cell lines. When X-rays or bleomycin were used to induce strand breakage, no difference was detectable in either the rate or extent of DNA repair using the techniques of alkaline unwinding and alkaline elution for total strand breaks, and neutral elution for double strand breaks. DNA repair fidelity was measured using the PMH16 plasmid. A Kpn I restriction site was used to introduce a break within the gpt gene of the plasmid, prior to transfection. We found that approximately 100% and approximately 65% of the highly metastatic ML8 and Bl6 clones, respectively, religated the gene with the required fidelity, compared with only approximately 25% of the low metastasis F1 clones. In summary, the metastatic variants show similar sensitivities to X-irradiation and bleomycin, but a differential response to EMS. This difference is not reflected in any subsequent DNA strand break religation, but the variants do differ in their fidelity of repair. However, although the fidelity of DNA religation is related to metastatic potential, it is not consistent with the mutation frequency data.

Animals↗