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Biomedical subjects

Patricia S Steeg

Publications and source records attributed to Patricia S Steeg.

At least 19 recordsLinked to original sources
PubMed2006

Combined breast ductal lavage and ductal endoscopy for the evaluation of the high-risk breast: a feasibility study.

BACKGROUND AND OBJECTIVES: Evaluation of the ductal epithelium of the breast at increased risk for breast cancer is needed to define the carcinogenic pathway, for risk assessment, and to improve selection of women for chemoprevention therapy. We studied the feasibility of combining breast ductal endoscopy with ductal lavage in the high-risk contralateral breast of women with ipsilateral breast cancer for the evaluation of high-risk ducts and acquisition of ductal epithelial cells for analysis. METHODS: Breast ducts were studied by ductal lavage and ductal endoscopy, and epithelial cell content studied cytologically and quantitatively. RESULTS: Twenty-five subjects and 44 ducts, including 22 (50.0%) which did not produce nipple aspirate fluid (NAF), were studied. Cellular atypia was present in five subjects. Ductal endoscopy was performed on 1 or more ducts in 24 subjects. Structural changes were noted in 63.6% of the ducts, most commonly fibrous stranding or bridging. Ductal sampling with endoscopic brush and coil sampling devices provided additional cellular samples of relatively pure ductal epithelial content (> or = 91% purity) in 8/11 subjects. CONCLUSIONS: Breast ductal endoscopy combined with ductal lavage represents a feasible approach for characterizing the ducts and ductal epithelium of the high-risk breast, especially in a research setting.

Adult↗
PubMed2006

c-Met ectodomain shedding rate correlates with malignant potential.

PURPOSE: Many proteins are proteolytically released from the cell surface by a process known as ectodomain shedding. Shedding occurs under normal physiologic conditions and can be increased in certain pathologies. Among the many receptors for which ectodomain shedding has been shown is c-Met, the hepatocyte growth factor (HGF) receptor tyrosine kinase. HGF stimulates mitogenesis, motogenesis, and morphogenesis in a variety of cellular targets during development, homeostasis, and tissue regeneration. Inappropriate HGF signaling resulting in unregulated cell proliferation, motility, and invasion occurs in several human malignancies. This can occur through paracrine signaling, autocrine loop formation, receptor mutation, gene amplification, or gene rearrangement, accompanied frequently with overexpression of ligand and/or receptor proteins. We hypothesized that c-Met overexpression in cancer might result in increased ectodomain shedding, and that its measure could be a useful biomarker of tumor progression. EXPERIMENTAL DESIGN: We developed a sensitive electrochemiluminescent immunoassay to quantitate c-Met protein in cell lysates, culture supernatants, and biological samples. RESULTS: A survey of cultured cell models of oncogenic transformation revealed significant direct correlations (P < 0.001, t test or ANOVA) between malignant potential and the rate of c-Met ectodomain shedding that was independent of steady-state receptor expression level. Moreover, weekly plasma and urine samples from mice harboring s.c. human tumor xenografts (n = 4 per group) displayed soluble human c-Met levels that were measurable before tumors became palpable and that correlated directly with tumor volume (R2 > 0.92, linear regression). CONCLUSIONS: For a variety of human cancers, c-Met ectodomain shedding may provide a reliable and practical indicator of malignant potential and overall tumor burden.

Animals↗
PubMed2006

Rab11a differentially modulates epidermal growth factor-induced proliferation and motility in immortal breast cells.

The development of cancer prevention strategies depends on the elucidation of molecular pathways underlying oncogenesis. In a previous proteomic study of matched normal breast ducts and Ductal Carcinoma in Situ (DCIS), we identified overexpression of Rab11a in DCIS. Rab11a is not well studied in cancer, but is known to regulate the recycling of internalized cell surface proteins and receptors from the early endosome through the trans-Golgi network. Using immunohistochemistry, we confirmed our observation, noting increased Rab11a expression in 19 of 22 (86%) DCIS cases compared to matched normal breast epithelium. To study the function of Rab11a, immortal, nontumorigenic MCF10A breast cells were stimulated with ligands to the EGF receptor (EGFR) after transfection with empty vector (control), Rab11a, or a S25N dominant-negative (DN) Rab11a. Using an iodinated ligand:receptor recycling assay, transfection of Rab11a accelerated, while DN-Rab11a postponed EGFR recycling in vitro. The signaling and in vitro phenotypic consequences of Rab11a expression and function were studied. Transfection of DN-Rab11a increased Erk1/2 activation downstream of EGF, but exerted no effect on the Akt pathway. Expression of DN-Rab11a inhibited MCF10A proliferation by 50-60%, and also inhibited anchorage-dependent colonization. Notably, DN-Rab11a transfection increased motility toward EGFR ligands. The data provide a first demonstration that Rab11a modulates EGFR recycling, and promotes the proliferation but inhibits the motility of an immortal breast line, consistent with the DCIS phenotype.

Breast Neoplasms↗
PubMed2006

In vivo MRI of cancer cell fate at the single-cell level in a mouse model of breast cancer metastasis to the brain.

Metastasis (the spread of cancer from a primary tumor to secondary organs) is responsible for most cancer deaths. The ability to follow the fate of a population of tumor cells over time in an experimental animal would provide a powerful new way to monitor the metastatic process. Here we describe a magnetic resonance imaging (MRI) technique that permits the tracking of breast cancer cells in a mouse model of brain metastasis at the single-cell level. Cancer cells that were injected into the left ventricle of the mouse heart and then delivered to the brain were detectable on MR images. This allowed the visualization of the initial delivery and distribution of cells, as well as the growth of tumors from a subset of these cells within the whole intact brain volume. The ability to follow the metastatic process from the single-cell stage through metastatic growth, and to quantify and monitor the presence of solitary undivided cells will facilitate progress in understanding the mechanisms of brain metastasis and tumor dormancy, and the development of therapeutics to treat this disease.

Animals↗
PubMed2006

Translational approaches using metastasis suppressor genes.

Cancer metastasis is a significant contributor to breast cancer patient morbidity and mortality. In order to develop new anti-metastatic therapies, we need to understand the biological and biochemical mechanisms of metastasis. Toward these efforts, we and others have studied metastasis suppressor genes, which halt metastasis in vivo without affecting primary tumor growth. The first metastasis suppressor gene identified was nm23, also known as NDP kinase. Nm23 represents the most widely validated metastasis suppressor gene, based on transfection and knock-out mouse strategies. The biochemical mechanism of metastasis suppression via Nm23 is unknown and likely complex. Two potential mechanisms include binding proteins and a histidine kinase activity. Elevation of Nm23 expression in micrometastatic tumor cells may constitute a translational strategy for the limitation of metastatic colonization in high risk cancer patients. To date, medroxyprogesterone acetate (MPA) has been identified as a candidate compound for clinical testing.

Animals↗
PubMed2006

Reaction of geldanamycin and C17-substituted analogues with glutathione: product identifications and pharmacological implications.

17-Dimethylaminoethylamino-17-demethoxygeldanamycin (DMAG) and 17-allylamino-17-demethoxygeldanamycin (17-AAG) are two derivatives of geldanamycin (GA) that are currently undergoing clinical evaluation as anticancer agents. These agents bind to heat shock protein 90 (hsp90), resulting in the destabilization of client proteins and inhibition of tumor growth. In a search for the mechanism of hepatotoxicity, which is a dose-limiting toxicity for these agents, we found that GA and its derivatives, 17-AAG and 17-DMAG, react chemically (i.e., nonenzymatically) with glutathione (GSH). A combination of liquid chromatography/electrospray ionization/mass spectrometry and nuclear magnetic resonance analyses were used to identify the product of this reaction as a GSH adduct in which the thiol group of GSH is substituted in the 19-position of the benzoquinone ring. The reaction proceeds rapidly with GA and 17-DMAG (half-lives of approximately 1.5 and 36 min, respectively) and less rapidly with 17-AAG and its major metabolite, 17-AG (half-lives of approximately 9.8 and 16.7 h). The reaction occurs at pH 7.0, 37 degrees C, and a physiological concentration of GSH, indicating that cellular GSH could play a role in modulating the cellular toxicity of these agents and therefore be a factor in their mechanism of differential toxicity. Moreover, reactions with thiol groups of critical cellular proteins could be important to the mechanism of toxicity with this class of anticancer agents.

Antibiotics, Antineoplastic↗
PubMed2005

Medroxyprogesterone acetate elevation of Nm23-H1 metastasis suppressor expression in hormone receptor-negative breast cancer.

BACKGROUND: Reestablishment of metastasis suppressor gene expression may constitute a therapeutic strategy for high-risk breast cancer patients. We previously showed that medroxyprogesterone acetate (MPA), a progestin that has been tested as treatment for advanced breast cancer, elevates expression of the Nm23-H1 metastasis suppressor gene in hormone receptor-negative metastatic human breast carcinoma cell lines in vitro via a glucocorticoid receptor-based mechanism. Here, we tested whether MPA treatment inhibits metastatic colonization of a hormone receptor-negative breast cancer cell line in vivo. METHODS: We tested the soft-agar colony-forming efficiency of untransfected MDA-MB-231T human breast carcinoma cells and MDA-MB-231T cells transfected with antisense Nm23-H1 in the presence and absence of MPA. Pharmacokinetic studies were used to establish dose and injection schedules that led to MPA serum levels in mice similar to those achievable in humans. For in vivo studies, nude mice were injected intravenously with MDA-MB-231T cells. After 4 weeks, mice were randomized to control or MPA arms. Endpoints included incidence, number, and size of gross pulmonary metastases; Nm23-H1 protein expression in gross metastases; and side effects. All statistical tests were two-sided. RESULTS: MPA reduced colony formation of MDA-MB-231T cells by 40%-50% but had no effect on colony formation of Nm23-H1 antisense transfectants. Metastases developed in 100% (95% confidence interval [CI] = 78% to 100% and 77% to 100%, respectively) of control mice injected with MDA-MB-231T cells. In two independent experiments, only 73% (95% CI = 45% to 92%) and 64% (95% CI = 35% to 87%) of mice injected with 2 mg of MPA developed metastases. Mice injected with 2 mg of MPA showed reductions in the mean numbers, per mouse, of all metastases and of large (>3 mm) metastases (P = .04 and .013, respectively). Nm23-H1 was expressed at high levels in 43% of pulmonary metastases in MPA-treated mice but only 13% of metastases in untreated mice. Mice receiving at least 1-mg doses of MPA gained more weight than control-treated mice but exhibited no bone density alterations or abnormal mammary fat pad histology. CONCLUSION: Our preclinical results show that MPA appears to elevate Nm23-H1 metastasis suppressor gene expression, thereby reducing metastatic colonization. The data suggest a new use for an old agent in a molecularly defined subset of breast cancer patients.

Animals↗
PubMed2005

Metastasis gets site specific.

Organ-specific homing and colonization of cancer cells are important and interesting features of metastasis. Molecular programs that contribute to this tropism may be elucidated through gene expression profiling with DNA microarrays. Using experimentally derived breast cancer cells that home specifically to bone or to lung, several investigators have concluded that distinct alterations in gene expression underlie metastasis to these sites. Minn et al. (2005) report a set of genes involved in lung-specific metastasis of breast cancer; the authors have determined the functional contribution of several genes to the metastatic cascade, as well as the relevance of these genes to human disease.

Breast Neoplasms↗
PubMed2005

Breast cancer metastasis to the central nervous system.

Clinically symptomatic metastases to the central nervous system (CNS) occur in approximately 10 to 15% of patients with metastatic beast cancer. CNS metastases are traditionally viewed as a late complication of systemic disease, for which few effective treatment options exist. Recently, patients with Her-2-positive breast tumors who were treated with trastuzumab have been reported to develop CNS metastases at higher rates, often while responding favorably to treatment. The blood:brain barrier and the unique brain microenvironment are hypothesized to promote distinct molecular features in CNS metastases that may require tailored therapeutic approaches. New research approaches using cell lines that reliably and preferentially metastasize in vivo to the brain have been reported. Using such model systems, as well as in vitro analogs of blood-brain barrier penetration and tissue-based studies, new molecular leads into this disease are unfolding.

Antibodies, Monoclonal↗
PubMed2005

Nm23-H1 metastasis suppressor expression level influences the binding properties, stability, and function of the kinase suppressor of Ras1 (KSR1) Erk scaffold in breast carcinoma cells.

Metastatic disease is a significant contributor to cancer patient mortality. We previously reported that the Kinase Suppressor of Ras1 (KSR1) scaffold protein for the Erk mitogen-activated protein kinase pathway coimmunoprecipitated the metastasis suppressor protein Nm23-H1. We now hypothesize that altered expression levels of Nm23-H1 influence the binding properties, stability, and function of the KSR1 scaffold. Increased coimmunoprecipitation of Hsp90 with KSR1 was observed in either stable or transient transfectants of nm23-H1 in MDA-MB-435 human breast carcinoma cells. Similar trends were also observed in the cytoplasmic and nuclear fractions of cells. Cells expressing high levels of Nm23-H1 exhibited increased KSR1 degradation in the presence of either cycloheximide or an Hsp90-directed drug currently in clinical trial, 17-allylamino-17-demethoxygeldanamycin (17-AAG). In agreement with KSR1 degradation data, high-Nm23-H1-expression cells were preferentially inhibited in anchorage-independent colonization assays by 17-AAG. KSR1 scaffold binding patterns are dynamic in both the cytoplasmic and nuclear compartments, modulated by metastasis suppressor expression. Metastasis suppressor expression levels can impact traditional signaling pathways, such as the Erk pathway, resulting in altered tumor cell sensitivity to cancer therapeutics.

Benzoquinones↗
PubMed2003

Dexamethasone and medroxyprogesterone acetate elevate Nm23-H1 metastasis suppressor gene expression in metastatic human breast carcinoma cells: new uses for old compounds.

PURPOSE: Long-term elevation of metastasis suppressor gene expression in micrometastases represents a novel therapeutic strategy for breast and other cancers. We searched for well-tolerated compounds that could elevate Nm23 metastasis suppressor expression in metastatic human breast cancer cell lines. EXPERIMENTAL DESIGN: MDA-MB-435 and MDA-MB-231 human breast carcinoma cells were treated with dexamethasone or medroxyprogesterone acetate (MPA) in cultures containing either charcoal-stripped serum or FCS. Aspects of nm23 expression and function were determined. RESULTS: Previous investigation of the nm23-H1 promoter suggested that glucocorticoids may contribute to the elevation of Nm23-H1 expression. Dexamethasone elevated Nm23-H1 and Nm23-H2 protein levels in two metastatic human breast carcinoma cell lines 2-3-fold over a 4-day time course when cultured in steroid-free culture medium, with high-dose inhibition, via a traditional transcriptional mechanism. Elevation of Nm23-H1 expression was not observed using FCS-containing culture medium, which contains endogenous levels of corticosteroids, limiting the potential in vivo use of dexamethasone. MPA was investigated as a glucocorticoid receptor agonist. MPA elevated breast carcinoma Nm23-H1 protein expression 3-fold over a 10 nM to 1 micro M dose range when cultured in steroid-free or FCS-containing medium, with a shorter time course. Elevation of Nm23-H1 expression in the presence of endogenous corticosteroids found in FCS involved a distinct, glucocorticoid receptor-dependent, posttranscriptional mechanism of action. MPA had no effect on proliferation in vitro but reduced the soft agar colonization of metastatic breast cancer cell lines by approximately 50%. CONCLUSIONS: MPA represents a first generation lead agent for the elevation of Nm23-H1 metastasis suppressor expression and the inhibition of metastatic colonization.

Agar↗
PubMed2003

Histidine kinases and histidine phosphorylated proteins in mammalian cell biology, signal transduction and cancer.

Intensive investigation of protein tyrosine, serine and threonine phosphorylation has lead to advances in signal transduction research and cancer treatment. This feature summarizes research on mammalian proteins exhibiting histidine phosphorylation. Histidine kinases are well known in prokaryotic and lower eukaryotic systems where they form the 'two-component' signal transduction system. The relative invisibility of histidine phosphorylation in mammalian cells may result from technical obstacles such as its acid lability, which precludes detection in electrophoretic systems, amino acid sequencing, etc. Emerging data have identified mammalian histidine kinases for the kinase suppressor of ras, a scaffold molecule for the Map kinase pathway, as well as histone H4, aldolase C and the beta-subunit of heterotrimeric G proteins. Additional mammalian proteins of interest to signal transduction and cancer research exhibit histidine phosphorylation, including P-selectin, annexin I and the 20S proteasome. Other candidate histidine phosphorylated proteins are identified. These data suggest the existence of another series of phosphorylation patterns in signal transduction.

Animals↗
PubMed2003

Proteomic approaches to the diagnosis, treatment, and monitoring of cancer.

The field of proteomics holds promise for the discovery of new biomarkers for the early detection and diagnosis of disease, molecular targets for therapy and markers for therapeutic efficacy and toxicity. A variety of proteomics approaches may be used to address these goals. Two-dimensional gel electrophoresis (2D-PAGE) is the cornerstone of many discovery-based proteomics studies. Technologies such as laser capture microdissection (LCM) and highly sensitive MS methods are currently being used together to identify greater numbers of lower abundance proteins that are differentially expressed between defined cell populations. Newer technologies such as reverse phase protein arrays will enable the identification and profiling of target pathways in small biopsy specimens. Surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) analysis enables the high throughput characterization of lysates from very few tumor cells or body fluids and may be best suited for diagnosis and monitoring of disease. Such technologies are expected to supplement our arsenal of mRNA-based assays, and we believe that in the future, entire cellular networks and not just a single deregulated protein will be the target of therapeutics and that we will soon be able to monitor the status of these pathways in diseased cells before, during and after therapy.

Biomarkers, Tumor↗