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Biomedical subjects

R Clarke

Publications and source records attributed to R Clarke.

At least 127 records · Page 7Linked to original sources
PubMed1995

Effect of estrogen withdrawal on energy-rich phosphates and prediction of estrogen dependence monitored by in vivo 31P magnetic resonance spectroscopy of four human breast cancer xenografts.

The effect of estrogen withdrawal on energy metabolism was studied in four human breast cancer xenografts: the estrogen-dependent MCF-7 and ZR75-1 and the estrogen-independent ZR75/LCC-3 and MDA-MB-231. The tumors were grown in ovariectomized nude mice with a s.c. implanted estrogen pellet. After Gompertzian growth was verified, the estrogen pellet was removed from half of the animals. In vivo 31P magnetic resonance spectroscopy of the tumors was performed 1 day before and on days 2, 6, and 14 after estrogen removal. Estrogen withdrawal induced a significant increase in the nucleoside triphosphate:Pi ratio in the two estrogen-dependent xenografts, whereas this ratio remained unchanged in the estrogen-independent tumors. In ZR75/LCC-3 tumors a slight decrease in nucleoside triphosphate:Pi was observed following onset of estrogen stimulation after initial growth without estrogen. Extracts of freeze-clamped tumors prepared 14 days after estrogen removal were analyzed for ATP and phosphocreatine content. Our findings suggest a correlation between estrogen withdrawal and the steady-state concentrations of ATP, phosphocreatine, and Pi in human breast cancer xenografts. Discrimination analysis of the pretherapeutic spectra enabled us to identify the tumor line and the estrogen dependence of the tumors in 80-90% of all cases.

Animals↗
PubMed1995

Hormone dependence of breast cancer cells and the effects of tamoxifen and estrogen: 31P NMR studies.

Many breast tumors appear to progress from estrogen-dependent growth to a more malignant phenotype characterized by estrogen-independent growth, antiestrogen resistance, and a high metastatic potential. Utilizing 31P NMR spectroscopy on human breast cancer cells growing in vitro, we have investigated the effects of 17 beta-estradiol and tamoxifen on the metabolic/bioenergetic spectra of a series of human breast cancer cells that vary in their estrogen and antiestrogen responsiveness. A comparison of baseline spectra associates higher levels of phosphodiesters and UDP-glucosides (e.g. UDP-glucose, UDP-N-acetylglucosamine), and lower phosphocholine/glycerylphosphocholine and phosphocholine/phosphoethanolamine ratios, with the acquisition of estrogen-independent growth in estrogen receptor expressing cells. No metabolic changes are clearly associated with the metastatic phenotype. Whilst estrogen treatment produces no consistently significant spectral changes in any of the cell lines, the estrogen-independent and estrogen-responsive MCF7/MIII cell line responds to tamoxifen treatment by significantly increasing all spectral resonances 30%-40% above baseline values. This may reflect a tamoxifen-induced change to a more differentiated or apoptotic phenotype, or an attempt by the cells to reverse the inhibitory effects of the drug. The ability to detect metabolic changes in response to tamoxifen by NMR spectroscopy may provide a novel means to identify those tumors that are responsive to antiestrogen therapy.

Adenocarcinoma↗
PubMed1995

Reversible hepatic dysfunction in association with cyclophosphamide therapy.

A 5.5-year-old child with nephrotic syndrome was treated with cyclophosphamide. After 9 weeks of therapy she developed jaundice and abnormal liver function tests. No infective aetiology was found and the abnormal liver function tests resolved within 5 weeks of discontinuing cyclophosphamide. Cyclophosphamide has rarely been reported to cause liver dysfunction, but not in children treated for nephrotic syndrome, and paediatricians should therefore be aware of its potential for inducing reversible hepatic dysfunction.

Child, Preschool↗
PubMed1995

Use of a monoclonal antibody to ovine IgE for fly strike studies in sheep.

A new monoclonal raised against sheep IgE was used to examine sera and wound exudates from sheep which had been struck by Lucilia cuprina in the field. The antibody was also used to detect the presence of IgE in sera and skin sections from sheep which had been artificially infected with fly larvae 3 times. Neither total, nor L. cuprina specific circulating IgE could be detected in serum or wound exudates from struck sheep. Cell bound IgE was, however, identified by the monoclonal in skin sections from struck sheep and from a control sheep which had not been struck. No difference in the number of IgE positive cells was observed between the control and 2 of the 3 artificially infected sheep, and none of the latter showed an increase in IgE positive cells even after 3 infections. One sheep showed twice as many IgE positive cells as the other treated sheep and the third larval infection was difficult to establish and limited in size and severity. This suggests a relationship between innate resistance to strike and the number of IgE positive cells present in skin.

Animals↗
PubMed1995

FMS mutations in patients following cytotoxic therapy for lymphoma.

Point mutations at codons 301 and 969 of the FMS proto-oncogene have been reported in both myelodysplasia (MDS) and acute myeloid leukaemia (AML). We report here the incidence of such mutations in patients at risk of developing secondary MDS and AML. Peripheral blood DNA from 70 patients in remission from lymphoma was screened for mutations by oligonucleotide (ONH) using mutant specific probes. Codon 969 mutations were detected in 11 of the 70 (15.7%) cases. No codon 301 mutations were detected. Five of these mutations were confirmed using an independent technique (single nucleotide primer extension analysis, SNPE) and a further mutation was detected in a single patient using single-stranded conformational polymorphism analysis (SSCP). No codon 969 mutations were detected in 62 lymphoma biopsy specimens from these patients or from three patients with detectable FMS mutations where pre-therapy marrow was investigated by ONH. No mutations at either codons 301 or 969 were detected by ONH in 61 normal controls. Somatic mutations at codon 969 of the FMS gene occur commonly following cytotoxic therapy for lymphoma and their detection indicates the presence of a clonally expanded population of abnormal cells.

Adult↗
PubMed1995

Non-neoplastic glandular structures in bone marrow: a technical artefact.

A case of non-neoplastic glandular structures embedded in the centre of a bone marrow trephine biopsy is described. This is a hitherto unreported phenomenon. These glandular structures originated from the dermal sweat gland and represented an artefactual lesion produced by the biopsy procedure. The importance of considering the possibility of non-neoplastic glandular structures in bone marrow is stressed, in order to avoid a misdiagnosis of metastatic adenocarcinoma.

Adenocarcinoma↗
PubMed1995

Bovine tuberculosis in a free-ranging mule deer (Odocoileus hemionus) from Montana.

A survey of 41 mule deer (Odocoileus hemionus) and three white-tailed deer (O. virginianus) for bovine tuberculosis was conducted on a Montana (USA) cattle ranch from 2 November 1993 through January 1994. Gross and microscopic lesions typical of tuberculosis were present in tonsil and lymph nodes of the head, thorax, and abdomen of one adult female mule deer. Additionally, a single microgranuloma considered morphologically suggestive of tuberculosis was present in one lymph node of the head of a second mule deer. Mycobacterial isolates from lymph nodes of the head and thorax of the first deer were identified as Mycobacterium bovis.

Animals↗
PubMed1994

Resistance to TNF-alpha and adriamycin in the human breast cancer MCF-7 cell line: relationship to MDR1, MnSOD, and TNF gene expression.

The molecular basis of cross-resistance to tumor necrosis factor (TNF) and Adriamycin has been investigated using the breast adenocarcinoma cell line MCF7/p, its Adriamycin-resistant counterpart MCF7AdrR, and the MDR1 gene-transduced MCF-7 cells (MCF7/MDR1). While the parental cell line MCF7/p was TNF-sensitive, MCF7AdrR was TNF-resistant. The TNF resistance exhibited by MCF7AdrR cells was not due to a lack of TNF receptor expression because both cell lines express comparable levels of p75 and p55 receptors as revealed by immunofluorescence analysis. NF-kappa B translocation, which is an essential transducing signal of the TNF-induced lysis pathway, does not appear to be involved in this resistance as assessed by gel shift experiments. In order to determine the role of MDR1 gene expression in the development of this cross-resistance, MCF7/p cells transfected by the MDR1 gene were examined. Our data showed that the expression of the MDR1 gene in these cells resulted in a relative resistance of these cells to Adriamycin without affecting their susceptibility to TNF killing. The implication of the manganese superoxide dismutase and endogenous TNF expression in the cross-resistance by MCF7AdrR cells to Adriamycin and TNF has also been investigated. Northern blot analysis indicated that following TNF stimulation, the expression of 4-kilobase and 1-kilobase manganese superoxide dismutase mRNAs were 9- to 10-fold induced in MCF7AdrR cells as compared to MCF7/p and MCF7/MDR1 cells. This suggests a possible involvement of this enzyme in the Adriamycin-induced resistance to TNF. Although TNF-treatment of MCF7/p and MDR-cells induced endogenous TNF expression in these cells, the level of mRNA induction was selectively enhanced in MCF7AdrR cells (7- to 8-fold greater in MCF7AdrR cells as compared to MCF7/p and MCF7/MDR1 cells). Collectively, these data indicate that the expression of the MDR1 gene in MCF7/p cells following gene transfection is not sufficient for the acquisition of TNF resistance by MCF7/MDR1 cells. Furthermore, our data provide the first evidence that Adriamycin-induced resistance to TNF in MCF7AdrR cells may, in part, involve an overexpression of endogenous TNF and manganese superoxide dismutase genes.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Anti-proliferative and anti-estrogenic effects of ICI 164,384 and ICI 182,780 in 4-OH-tamoxifen-resistant human breast-cancer cells.

The effects of the anti-estrogens 4-hydroxytamoxifen (OHTam), ICI 164,384 and ICI 182,780 were tested on the MCF-7/LCC2 breast-carcinoma cell line, which grows significantly in the presence of OHTam and serves as a model for studying anti-estrogen resistance of estrogen-receptor-positive breast cancer. Cell proliferation and cathepsin-D secretion were strongly inhibited by either ICI 182,780 or ICI 164,384 alone or ICI 164,384 in combination with 17-beta-estradiol (E2) or OHTam. ICI 164,384 alone did not affect the cathepsin-D and pS2 mRNA levels, but antagonized the stimulatory effects of E2 or OHTam on these 2 mRNAs. OHTam was more effective than E2 in increasing cathepsin-D mRNA levels, supporting the idea that anti-estrogen-resistant breast cancer continues to overexpress cathepsin-D. These data show that the steroidal anti-estrogens ICI 164,384 and ICI 182,780 retain their ability to inhibit cell proliferation and the estrogen-responsiveness of cathepsin-D and pS2 genes in the OHTam-resistant MCF-7/LCC2 cell lines. These pure anti-estrogens may thus be efficient second-line treatments of some Tamoxifen-resistant tumors.

Antineoplastic Agents↗
PubMed1994

Effect of tamoxifen on the multidrug-resistant phenotype in human breast cancer cells: isobologram, drug accumulation, and M(r) 170,000 glycoprotein (gp170) binding studies.

We have performed isobologram analyses of the ability of tamoxifen (TAM) to alter the response to Adriamycin (ADR) and vinblastine (VBL) in human breast cancer cells. MCF-7 cells express functional receptors for estrogen and progesterone but do not express detectable levels of M(r) 170,000 glycoprotein (gp170). CL 10.3 and MCF-7ADR cells are MCF-7 variants which express gp170. CL 10.3 but not MCF-7ADR cells express functional steroid hormone receptors. Tamoxifen (1-2.5 microM) interacts synergistically with ADR and VBL in CL 10.3 and MCF-7ADR cells. TAM increases the cytotoxicity of VBL and ADR and the intracellular levels of [3H]VBL by approximately 2-3-fold. TAM also prevents the binding of [3H]azidopine to gp170. The ability of TAM to concurrently increase the cytotoxic effects of ADR and VBL, increase VBL accumulation, and inhibit the binding of azidopine to gp170 strongly implies that the synergistic effects of TAM are mediated through its effects on gp170. TAM produces an antagonistic to additive interaction with ADR and VBL in MCF-7 cells, and at high concentrations (5 microM) the synergy apparent in CL 10.3 and MCF-7ADR cells is lost. While TAM clearly has a significant potential for use as a chemosensitizing agent, the design of clinical trials may require careful consideration.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Psychosocial factors in the development and progression of breast cancer.

The factors responsible for the genesis of breast cancer remain unclear. Emerging, although controversial, evidence suggests that factors related to life-style, such as dietary fat or alcohol intake, or exposure to various forms of stressors, are associated with mammary tumorigenesis. The possible role of life-style factors in breast cancer is important in light of the fact that mortality to this disease is increasing in most countries and that development of curative therapies for breast cancer has not been forthcoming. Thus, determining the role of life-style factors in the onset and progression of breast cancer, particularly among individuals genetically vulnerable to breast cancer or women with breast cancer in remission, is critical to prevent this disease. We will review the three main hypotheses which have been suggested to link psychosocial factors to the etiology of cancer, emphasizing data obtained through animal models. Interpretation of the existing data suggests that the number of stressful life-events does not predict vulnerability to develop breast cancer or survival from it; a certain level of stress appears to protect from malignancies. The crucial factor affecting tumor growth is the interaction among stress, an individual's personality, and available psychosocial support, and the effect of this interaction on an individual's ability to cope with stress. In addition, other risk factors for breast cancer known to be closely associated with psychosocial factors, namely dietary fat and alcohol consumption, may interact with the effects of psychosocial factors on breast cancer.

Alcohol Drinking↗
PubMed1994

Hormonal carcinogenesis in breast cancer: cellular and molecular studies of malignant progression.

We have established and characterized a series of variant cell lines in which to identify the critical factors associated with E2-induced malignant progression, and the acquisition to tamoxifen resistance in human breast cancer. Sublines of the hormone-dependent MCF-7 cell line (MCF7/MIII and MCF7/LCC1) form stable, invasive, estrogen independent tumors in the mammary fat pads of ovariectomized athymic nude mice. These cells retain expression of both estrogen (ER) and progesterone receptors (PGR), but retain sensitivity to each of the major structural classes of antiestrogens. The tamoxifen-resistant MCF7/LCC2 cells retain sensitivity to the inhibitory effects of the steroidal antiestrogen ICI 182780. By comparing the parental hormone-dependent and variant hormone-independent cells, we have demonstrated an altered expression of some estrogen regulated genes (PGR, pS2, cathepsin D) in the hormone-independent variants. Other genes remain normally estrogen regulated (ER, laminin receptor, EGF-receptor). These data strongly implicate the altered regulation of a specific subset or network of estrogen regulated genes in the malignant progression of human breast cancer. Some of the primary response genes in this network may exhibit dose-response and induction kinetics similar to pS2, which is constitutively upregulated in the MCF7/MIII, MCF7/LCC1 and MCF7/LCC2 cells.

Adenocarcinoma↗