PubMed Health⌕ Search

Biomedical subjects

Mitch Dowsett

Publications and source records attributed to Mitch Dowsett.

At least 73 records · Page 4Linked to original sources
PubMed2004

Phytoestrogen concentrations in serum and spot urine as biomarkers for dietary phytoestrogen intake and their relation to breast cancer risk in European prospective investigation of cancer and nutrition-norfolk.

Subjects of this study consisted of 333 women (aged 45-75 years) drawn from a large United Kingdom prospective study of diet and cancer, the European Prospective Investigation of Cancer and Nutrition-Norfolk study. Using newly developed gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry methods incorporating triply (13)C-labeled standards, seven phytoestrogens (daidzein, genistein, glycitein, O-desmethylangolensin, equol, enterodiol, and enterolactone) were measured in 114 spot urines and 97 available serum samples from women who later developed breast cancer. Results were compared with those from 219 urines and 187 serum samples from healthy controls matched by age and date of recruitment. Dietary levels were low, but even so, mean serum levels of phytoestrogens were up to 600 times greater than postmenopausal estradiol levels. Phytoestrogen concentrations in spot urine (adjusted for urinary creatinine) correlated strongly with that in serum, with Pearson correlation coefficients > 0.8. There were significant relationships (P < 0.02) between both urinary and serum concentrations of isoflavones across increasing tertiles of dietary intakes. Urinary enterodiol and enterolactone and serum enterolactone were significantly correlated with dietary fiber intake (r = 0.13-0.29). Exposure to all isoflavones was associated with increased breast cancer risk, significantly so for equol and daidzein. For a doubling of levels, odds ratios increased by 20-45% [log(2) odds ratio = 1.34 (1.06-1.70; P = 0.013) for urine equol, 1.46 (1.05-2.02; P = 0.024) for serum equol, and 1.22 (1.01-1.48; P = 0.044) for serum daidzein]. These estimates of risk are similar to those established for estrogens and androgens in postmenopausal breast cancer but need confirmation in larger studies.

Adult↗
PubMed2003

Comparison of the selective estrogen receptor modulator arzoxifene (LY353381) with tamoxifen on tumor growth and biomarker expression in an MCF-7 human breast cancer xenograft model.

Arzoxifene (ARZ) is a selective estrogen receptor (ER) modulator with greater bioavailability than raloxifene which is being developed as treatment for breast cancer. We have used an in vivo model of hormone-sensitive breast cancer to study the growth-inhibitory and pharmacodynamic effects of ARZ in comparison with the most widely used antiestrogen, tamoxifen (TAM). We compared the abilities of ARZ and TAM to antagonize the estrogen (E2)-dependent growth of MCF-7 human breast cancer xenografts in oophorectomized athymic mice. At four different time points over 28 days, we studied their time-related pharmacodynamic effects on biomarkers of tumor growth (cell proliferation/death measured by Ki-67 and apoptosis scores), cell cycle activity (cyclin D1 and p27(kip1)), and hormone-regulated gene expression (ERalpha, progesterone receptor, and pS2). Although maximal growth inhibition was seen after E2 withdrawal, ARZ and TAM induced significant and similar inhibition of E2-stimulated tumor growth. Inhibition of growth was reflected by changes in the tumor growth index (ratio posttreatment/pretreatment Ki-67/apoptosis scores). ARZ and TAM resulted in a significant (P < 0.001) increase in ER expression and reduction in progesterone receptor expression, whereas changes in cyclin D1 score were inversely related to p27(kip1) score. A significant but delayed biological effect was observed with a 10-fold lower dose of ARZ. These results show that ARZ is an effective antagonist of E2-stimulated breast cancer growth with similar growth-inhibitory and pharmacodynamic effects to TAM in this model.

Animals↗
PubMed2003

Phase II study of the efficacy and tolerability of two dosing regimens of the farnesyl transferase inhibitor, R115777, in advanced breast cancer.

PURPOSE: R115777 is an orally active farnesyl transferase inhibitor that specifically blocks farnesylation of proteins involved in growth-factor-dependent cell-signal-transduction pathways. We conducted a phase II study in 76 patients with advanced breast cancer. PATIENTS AND METHODS: Two cohorts of patients were recruited sequentially. The first cohort (n = 41) received a continuous dosing [CD] regimen of R115777 400 or 300 mg bid. The second cohort (n = 35) received 300 mg bid in a cyclical regimen of 21 days of treatment followed by 7 days of rest (intermittent dosing [ID]). RESULTS: In the CD cohort, four patients (10%) had a partial response (PR) and six patients (15%) had stable disease at > or = 24 weeks (SD). In the ID cohort, five patients (14%) had a PR and three patients (9%) had prolonged SD. The first six patients in the CD cohort treated at 400 mg bid all developed grade 3 to 4 neutropenia, so the subsequent 35 patients were treated at 300 mg bid. The incidence of hematologic toxicity was significantly lower in the ID than in the CD (300-mg bid) cohort: grade 3 to 4 neutropenia (14% v 43%; P =.016) and grade 3 to 4 thrombocytopenia (3% v 26%; P =.013). One patient in the ID cohort developed grade 2 to 3 neurotoxicity compared with 15 patients in the CD cohort (3% v 37%; P =.0004). CONCLUSION: The farnesyl transferase inhibitor R115777 has demonstrated clinical activity in patients with metastatic breast cancer, and the ID regimen has a significantly improved therapeutic index compared with the CD regimen.

Administration, Oral↗
PubMed2003

Enhanced estrogen receptor (ER) alpha, ERBB2, and MAPK signal transduction pathways operate during the adaptation of MCF-7 cells to long term estrogen deprivation.

The mechanisms involved in resistance to estrogen deprivation are of major importance for optimal patient therapy and the development of new drugs. Long term culture of MCF-7 cells in estrogen (E2)-depleted medium (long term estrogen deprivation; LTED) results in hypersensitivity to E2 coinciding with elevated levels of estrogen receptor (ER) alpha phosphorylated on Ser118 and MAPK, together with several of its downstream targets associated previously with ERalpha phosphorylation. Our data suggest elevated MAPK activity results from enhanced ERBB2 expression in the LTED cells versus the wild-type (wt), and treatment with the tyrosine kinase inhibitor ZD1839 revealed increased sensitivity in both transcription and proliferation assays. Similarly the MEK inhibitor U0126 decreased transcription and proliferation in the LTED cells and reduced their sensitivity to the proliferative effects of E2, while having no effect on the wt. However, the complete suppression of MAPK activity in the LTED cells did not inhibit ERalpha Ser118 phosphorylation suggesting that ER activity remained ligand-dependant. The LTED cells also expressed elevated levels of insulin-like growth factor-1R, and inhibition of phosphatidylinositol 3-kinase activity with LY294002 reduced basal ERalpha transactivation by 70% in the LTED cells compared with the wt. However, LY294002 had no effect on ERalpha Ser118 phosphorylation. These data suggest that although elevated levels of MAPK occur during LTED and influence the phenotype, this is unlikely to be the sole pathway operating to achieve adaptation.

Adaptation, Physiological↗
PubMed2003

Cell filtration-laser scanning cytometry for the characterisation of circulating breast cancer cells.

BACKGROUND: Epithelial cells may be detected in the circulation of the majority of patients with metastatic breast cancer. Quantification of such presumptive cancer cells might allow for the monitoring of patients with early or late stage disease as an early index of relapse. Additionally, biomarker analysis may allow a more rational approach to therapeutics. We have developed a new method for the detection and characterisation of these cells. METHODS: Blood was filtered through polycarbonate membranes containing cylindrical pores, 8 microm in diameter. All the red cells and a large majority of the white blood cells passed through the filter while the larger epithelial cells were trapped. Cells on the membrane were fixed in ethanol, stained with propidium iodide and anti-pan-cytokeratin-FITC (to identify epithelial cells). The filters were then examined by laser scanning cytometry (LSC), which allowed enumeration and localisation of cells. RESULTS: With normal blood spiked with cells from breast carcinoma cell lines, 99.9% of the leukocytes passed through the membrane, while close to 100% of the epithelial cells were trapped, with a detection limit of less than one epithelial cell/ml of blood. All of 20 samples from patients with widespread metastatic disease contained cytokeratin-positive cells with the morphological characteristics of carcinoma cells, the number of cells ranging from 0.2 to 5.7/ml of blood. CONCLUSIONS: Cell filtration-LSC is a viable technique for detecting and studying breast carcinoma cells in peripheral blood.

Breast Neoplasms↗
PubMed2003

Measurement of proliferation marker Ki67 in breast tumour FNAs using laser scanning cytometry in comparison to conventional immunocytochemistry.

BACKGROUND: A variety of markers, including Ki67, estrogen receptors (ER), and progesterone receptors (PgR), are frequently measured in fine needle aspirates from human breast carcinomas. Previously, we demonstrated the use of laser scanning cytometry (LSC) for the measurement of Ki67, ER, and PgR in a human breast carcinoma cell line, MCF7 (21). In the present study, we investigated the expression of Ki67 in breast tumour fine needle aspirates (FNAs) using LSC and compared the results to the data obtained using conventional immunocytochemistry (ICC). METHODS: A total of 11 sets of cytospins of FNAs taken from breast tumours at various stages of tamoxifen treatment were used. For LSC, the cytospins were stained for Ki67 with fluorescein using immunofluorescence; the nuclei were counterstained with propidium iodide. A parallel set of cytospins was stained using horseradish peroxidase and diaminobenzidine and scored manually by conventional light microscopy. RESULTS: Values for Ki67 obtained using the LSC were generally lower than ICC scores. The changes in Ki67 measured by the LSC were almost all parallel to those obtained by manual scoring of immunocytochemical stains. CONCLUSIONS: It should be possible to use LSC for the routine measurement of Ki67 marker in FNAs from human breast carcinomas.

Biomarkers, Tumor↗
PubMed2003

Origin and characteristics of adverse events in aromatase inhibition therapy for breast cancer.

Estrogen is critical in the progression and probably also in the initiation of breast tumors. Two classes of pharmacologic agents currently used in the treatment of estrogen receptor-positive breast tumors are the selective estrogen receptor modulators such as tamoxifen that block the interaction of estrogen with its cognate receptor, and the aromatase inhibitors (AIs) that block the final enzymatic step in the estrogen biosynthetic pathway. Recent data from first-line phase III trials in postmenopausal patients with hormone receptor-positive or -unknown metastatic breast cancer suggest that AIs are at least equivalent to or more effective than tamoxifen in this setting. As a result AIs are being evaluated in the adjuvant setting and may eventually displace tamoxifen as the endocrine therapy of choice for postmenopausal patients with breast cancer. Among the side effects of therapy that were observed in metastatic trials, AIs have shown less vascular and uterine adverse events than tamoxifen. Some concern exists, however, regarding their effect on lipid metabolism and bone turnover. To be acceptable for adjuvant treatment, AIs will have to show not only an advantage in efficacy, but also that any concerns from potential side effects may be managed appropriately. This article reviews the safety profile of AIs, discussing events related to their chemical structure, their specificity, and the effects of estrogen deprivation on target organs.

Antineoplastic Agents, Hormonal↗
PubMed2003

Efforts to link biological and clinical breast cancer research.

Important issues that underpin efforts to link new biological data on breast cancer to clinical research are considered. While animal models have been helpful in drug development, the changes in some key markers (oestrogen receptor and Ki67) in response to hormonal therapy are very different in patients. To predict that benefit of therapy in biomarker-defined subgroups requires the parallel study of a randomized control arm. Biomarker analyses have reduced statistical power compared with whole trials. Neoadjuvant therapy is an advantageous scenario to link biological and clinical research.

Biomarkers, Tumor↗
PubMed2003

Role of biologic markers in patient selection and application to disease prevention.

Aromatase inhibitors (AIs) are now under investigation for the treatment of early stage breast cancer and for disease prevention as alternatives to standard treatment with tamoxifen. Currently identified genetic risk factors of breast cancer include BRCA-1/BRCA-2 mutations, ATM mutations, and history of high estrogen levels, as evidenced by plasma analyses and/or dense bones. To date, estrogen receptor (ER) and progesterone receptor (PgR) status has predictive value for determining response to therapy in patients with hormone receptor-positive breast cancer (ER+ and/or PgR+ tumors). Recent studies have shown AIs to be safer and more effective than tamoxifen in postmenopausal women with advanced disease. Some data suggest that letrozole may be a more effective treatment than tamoxifen for patients with ER+ and/or PgR+ early breast cancers expressing ErbB-1 and/or ErbB-2. Changes in cell proliferation markers (e.g., S-phase fraction and Ki67 antigen), plasma lipid levels, and the bone resorption marker C-terminal peptide are biomarkers that have been evaluated for preventive and prognostic value in breast cancer patients and normal volunteers. Results from biomarker screens can be used to define inclusion criteria for clinical trials and eventually to individualize treatment. Gene expression profiling (microarray analysis), i.e., genomic and proteomic studies, will probably advance the discovery of new biomarkers for breast cancer prevention and treatment.

Antineoplastic Agents↗
PubMed2003

Current perspectives on HER2 testing: a review of national testing guidelines.

Knowledge of HER2 status is a prerequisite when considering a patient's eligibility for Herceptin (trastuzumab) therapy. Accurate assessment of HER2 status is essential to ensure that all patients who may benefit from Herceptin are correctly identified. There are several assays available to determine HER2 status: the most common in routine clinical practice are immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Various factors can affect the results achieved with these assays, including the assay antibody/probe, the methodology and the experience of personnel. Many countries have implemented national testing guidelines in an attempt to standardize testing procedures and make results more accurate. These guidelines vary in the level of detail and the number of recommendations. This review looks at areas of consensus between the different national testing guidelines and highlights where errors may arise during the testing procedure. The key point underlined by this review is that whatever method is used to test for HER2 status, the technology must be validated first, and there must be regular internal and external quality control and quality assurance procedures.

Algorithms↗
PubMed2003

Human epidermal growth factor receptor-2 and hormonal therapies: clinical implications.

Estrogen-targeted therapies such as administration of tamoxifen or aromatase inhibitors are among the most important treatment strategies in the modern management of breast cancer. Despite initial responses in the metastatic setting and prolonged disease-free intervals in the adjuvant setting, many patients subsequently become resistant to these agents. Human epidermal growth factor receptor-2 (HER2) is a transmembrane glycoprotein receptor that is overexpressed in 13%-30% of human breast cancers. There are experimental data suggesting an important role for HER2 in de novo and acquired resistance to endocrine therapies. These experimental data are discussed in this article, as are clinical data addressing the role of HER2 in resistance to endocrine therapy in the adjuvant, neoadjuvant, and metastatic settings. Responses and benefit from tamoxifen appear to be impaired in patients in whom HER2 is overexpressed. In contrast, early data from the neoadjuvant setting suggest that responses to aromatase inhibitors may be maintained in patients with HER2 overexpression.

Antineoplastic Agents, Hormonal↗
PubMed2003

Preoperative models to evaluate endocrine strategies for breast cancer.

There are essentially two approaches to presurgical therapy. The first strategy is one in which the therapy is given to downstage the disease over a period of some 3-4 months. In these circumstances, biological studies can be conducted that can be associated with clinical response. The second strategy involves the institution of medical therapy before surgery with no delay to that surgery. This is essentially incidental and is not given with the aim of having a therapeutic benefit but rather for the biological study of the particular therapeutic approach. In the incidental therapy scenario, we have conducted a number of studies to evaluate the biological effects of raloxifene, idoxifene, fulvestrant (in comparison with tamoxifen), and the aromatase inhibitor 4-hydroxyandrostenedione. Significant reductions in proliferation were noted in all, as was down-regulation of estrogen receptor levels. The changes were most profound in those estrogen receptor-positive tumors that were also progesterone receptor positive, consistent with the greater clinical effect of these therapies in this population. This setting is particularly valuable for treatments in which there is no particular evidence for clinical benefit but in which the therapy is known to be safe. It is possible to evaluate potential resistance mechanisms by associating changes in Ki67 or apoptosis with the expression of the putative determinant of resistance in the short-term presurgical model.

Antineoplastic Agents, Hormonal↗
PubMed2003

Integration of signal transduction inhibitors with endocrine therapy: an approach to overcoming hormone resistance in breast cancer.

Recent evidence suggests that common molecular adaptations occur during resistance to both tamoxifen and estrogen deprivation that use various signal transduction pathways, often involving cross-talk with a retained and functional estrogen receptor (ER) protein. There appear to be several different levels at which this cross-talk may occur, including peptide growth factor signaling via the type 1 tyrosine kinase growth factor receptor family [epidermal growth factor receptor (EGFR) and HER2], which may become up-regulated during endocrine treatment, ultimately being harnessed by cells to allow them hormone-independent growth. ER may remain involved in cell growth with ligand-independent phosphorylation and activation via different intracellular mitogen-activated protein kinases. ER may also become involved in non-nuclear estrogen-dependent signaling via interaction with the phosphatidylinositol 3'-kinase/Akt cell survival pathway or may interact with the stress-activated protein kinase/c-Jun-NH(2)-terminal kinase pathway. Understanding these mechanisms will permit the optimal integration of new signal transduction inhibitors (STIs) into breast cancer therapy. Preclinical approaches that have shown promise include the use of EGFR tyrosine kinase inhibitors for hormone-resistant breast cancer cells that are dependent on either EGFR or HER2 signaling. Likewise, farnesyl transferase inhibitors, mitogen-activated protein kinase inhibitors, and cell cycle inhibitors have all shown activity in experimental breast cancer models. Emerging data suggest that STIs may be more effective when given in combination with endocrine therapy either to overcome resistance or to prevent/delay emergence of the resistance phenotype. Clinical trials are in progress to determine the safety and optimal schedule for each of the various STIs, and studies of STIs in combination with aromatase inhibitors have commenced in breast cancer to see whether the therapeutic response to endocrine therapy can be enhanced further.

Antineoplastic Agents, Hormonal↗
PubMed2003

Correlation between cyclooxygenase-2 expression and angiogenesis in human breast cancer.

PURPOSE: Cyclooxygenase (COX)-2 is overexpressed in breast cancer and may have a role in regulating tumor growth via effects on angiogenesis, cell proliferation, or apoptosis. This study aimed to derive data from human breast carcinomas to help substantiate or refute these relationships. EXPERIMENTAL DESIGN: We performed immunohistochemical analysis of a set of 86 breast tumors for COX-2, estrogen receptor (ER), progesterone receptor (PGR), HER-2, Ki67 (a marker of proliferation), and CD31 (an endothelial cell marker of angiogenesis). RESULTS: COX-2 protein expression was detected in 79% of all tumors studied, ER was detected in 79% of all tumors studied, PGR was detected in 73% of all tumors studied, and HER-2 was detected in 16% of all tumors studied. COX-2 protein expression did not significantly correlate with tumor size, grade, axillary lymph node status, or the presence of vascular invasion. A significant negative correlation (P < 0.001) was observed between ER and Ki67. COX-2 expression showed a significant linear correlation with CD31 staining (P < 0.001). No significant correlations were observed between COX-2 and ER, PGR, or HER-2. CONCLUSIONS: This study demonstrates a novel relationship between COX-2 expression and the neovasculature of human breast adenocarcinomas. If this is a functional relationship, it provides support for a potential therapeutic role of COX-2 inhibitors in human breast cancer tissue via their antiangiogenic properties.

Adult↗