PubMed Health⌕ Search

Biomedical subjects

P Stanton

Publications and source records attributed to P Stanton.

At least 19 recordsLinked to original sources
PubMed2006

Low expression of HER2 protein in breast cancer is biologically significant.

HER2 status is routinely tested using immunohistochemistry or FISH following the licensing of a therapeutic agent targeting HER2. However, neither of these methods provides quantitative information relating to the 70-80% of patients with levels of expression lower than the assay detection thresholds. In this study, radioimmunohistochemistry was used to detect quantitative HER2 protein expression in 178 breast cancers. Survival analysis was performed, as were correlations with known prognostic variables and with overexpression of other HER family members. It is demonstrated that the populations expressing very high and very low levels of HER2 are each associated with increased risk of cancer-specific death on survival analysis (p = 0.0043). The group with low levels of HER2 was more likely to be of higher grade, EGFR-positive and ER/HER3/HER4-negative. HER2-positive cases were frequently ER-negative/HER3-positive, whilst cases with normal HER2 expression were often ER-positive/HER4-positive. The aggressive nature of the tumour group with low HER2 expression may be explained by actions of other HER family members, particularly EGFR, but whether these or other factors have a negative regulatory effect on HER2 expression remains to be determined.

Adult↗
PubMed2001

Evaluating HER2 amplification and overexpression in breast cancer.

The development of Herceptin (Trazumatab) makes testing for HER2 status important for choosing optimal therapy in breast cancer. This study addresses the precision, accuracy, and reproducibility of HER2 assays. HER2 was assessed retrospectively by immunohistochemistry (IHC) with Dako 'Herceptest', by IHC with the monoclonal antibody CB11, and by fluorescence in situ hybridization (FISH, PathVysion), in a series of 216 formalin-fixed breast carcinomas including 191 for which quantitative HER2 data from radioimmunohistochemistry (Q-IHC) were available. All tests were scored independently by two observers. Positivity rates varied between Herceptest (12.6%), FISH (19.4%), and CB11 IHC (28.5%). Kappa values showed that IHC-based tests were more susceptible to inter-observer variation (kappa=0.67 and 0.74 for Herceptest and CB11, respectively) than FISH (kappa=0.973). Overall test accuracy (see the Materials and methods section) for CB11 IHC (83.8%) was lower than Herceptest (87.4%) or FISH (93.2%). FISH predicted p185 HER2 overexpression (determined by Q-IHC) better (concordance index C.Ind. 0.90) than CB11 IHC (C.Ind.=0.85) or Herceptest (C.Ind.=0.81). Of 42 cases with gene amplification by FISH, 67% were positive in the Herceptest (2+ or 3+) vs. 83% with CB11. Of 174 cases negative by FISH, 96% were negative in the Herceptest and 68% with CB11. In conclusion, FISH is the most accurate, reproducible, and precise predictor of HER2 overexpression in routine diagnostic laboratories.

Antibodies, Monoclonal↗
PubMed2001

Competitive health policies and community health.

Since 1992 there have been fundamental changes in health care policy in Victoria, Australia, as the state government moves to competitive market models of service delivery and the measurement of service provision through output based funding. The introduction of competitive relationships to the public health system has had a major impact in the primary health care sector, particularly on community health centres. Most community health centres in Victoria have traditionally been semi-independent agencies controlled by community based committees of management. Such policies have had huge implications for the management and organisation of these agencies, as they have led to different patterns of service delivery and different models of management practice, often devaluing traditional philosophical perspectives of 'primary health care practice'. Although many agencies have embraced change as providing opportunities for growth and development and to have more influence in the provision of mainstream public health care, primary health care models of practice should be supported for their intrinsic and increasing value.

Community Health Centers↗
PubMed2001

HER2 as a prognostic and predictive marker for breast cancer.

In recent years investigators have looked at the human epidermal growth factor receptor-2 (HER2), which is overexpressed in 20%-30% of breast cancer patients, with regard to its role as a prognostic and predictive factor. Although many studies have suggested that HER2 overexpression may be associated with a poor clinical outcome, other studies have not fully supported this observation. The inconsistencies between studies may be due in part to discrepancies between different HER2 testing methods. To overcome this problem, a radioimmunohistochemical method was developed to quantitatively measure HER2 overexpression levels in breast tumor samples. The application of this method demonstrated that 85% of all breast tumor samples expressed HER2 at levels greater than normal. Of these, 23% expressed HER2 at levels between 45 and 480 times greater than normal, and this was associated with poor clinical outcome. The investigation of HER2 status as a predictor of response to therapy has also yielded many conflicting results. Overall, it appears that HER2 overexpression may correlate with resistance to hormonal therapy, sensitivity to anthracycline-based chemotherapy and resistance to CMF. With the development of targeted anti-HER2 therapies, assessment of HER2 status will be important in stratifying patients to the most appropriate treatment regimens.

Antibodies, Monoclonal↗
PubMed2001

The value of the human epidermal growth factor receptor-2 (HER2) as a prognostic marker.

The prognosis for patients with breast cancer is determined by well-established pathological features associated with biological aggressiveness, histological grade, tumour size and nodal involvement. These remain the key determinants, despite the identification of numerous other potential biological markers. The use of prognostic indices, such as the Nottingham Prognostic Index (NPI), which combines and weights these factors, enables clinicians to predict outcome with a certain amount of accuracy. Approximately 20-30% of breast cancers express very high quantities of the human epidermal growth factor receptor-2 (HER2) protein and this is almost always associated with gene amplification. With the use of sensitive techniques, such as the radio-immunohistochemical method (rIHC) described herein, to quantify HER2 protein levels, up to a further 50% of such cancers will be found to express the HER2 receptor at least 4-fold higher than normal breast cells. Adding HER2 expression to the NPI helps to determine more accurately the prognosis for individual patients, particularly those with node-negative disease. Overall, the main value of HER2 measurement is likely to be in the prediction of response to therapies targeting the HER2 gene and protein.

Breast Neoplasms↗
PubMed2001

The value of the human epidermal growth factor receptor-2 (HER2) as a prognostic marker.

The prognosis for patients with breast cancer is determined by well-established pathological features associated with biological aggressiveness, histological grade, tumour size and nodal involvement. These remain the key determinants, despite the identification of numerous other potential biological markers. The use of prognostic indices, such as the Nottingham Prognostic Index (NPI), which combines and weights these factors, enables clinicians to predict outcome with a certain amount of accuracy. Approximately 20-30% of breast cancers express very high quantities of the human epidermal growth factor receptor-2 (HER2) protein and this is almost always associated with gene amplification. With the use of sensitive techniques, such as the radio-immunohistochemical method (rIHC) described herein, to quantify HER2 protein levels, up to a further 50% of such cancers will be found to express the HER2 receptor at least 4-fold higher than normal breast cells. Adding HER2 expression to the NPI helps to determine more accurately the prognosis for individual patients, particularly those with node-negative disease. Overall, the main value of HER2 measurement is likely to be in the prediction of response to therapies targeting the HER2 gene and protein.

Journal Article↗
PubMed2000

Communication at millimetre-submillimetre wavelengths using a ceramic ribbon

Following the discovery by Kao and Hockman that ultra-low-loss optical fibres could be made from pure silica through the elimination of impurities, the ability to guide signals effectively at optical wavelengths has been assured. But there remains an important region of the spectrum--from 30 to 3,000 GHz (the millimetre-submillimetre band)--where low-loss waveguides are unknown. The main problem here in finding low-loss solids is no longer one of eliminating impurities, but is due to the presence of intrinsic vibration absorption bands. And the use of highly conducting materials is also precluded owing to high skin-depth losses in this part of the spectrum. Here we show that a combination of material and waveguide geometry can circumvent these difficulties. We adopt a ribbon-like structure with an aspect ratio of 10:1, fabricated from ceramic alumina (Coors' 998 Alumina), and the resulting waveguide has an attenuation factor of less than 10 dB km(-1) in the millimetre-submillimetre band. This attenuation is more than 100 times smaller than that of a typical ceramic (or other dielectric) circular rod waveguide and is sufficient for immediate application.

Journal Article↗
PubMed2000

Employment relationships in Victorian public hospitals: the Kennett years.

From 1992 to 1999, the Kennett government in Victoria moved to competitive market models of service delivery and the measurement of service provision through casemix funding. Public hospital managers were given greater accountability for the costs and provision of service delivery and a new range of service providers, many from the private sector, entered the public health market. The decentralisation of the industrial relations system led to new developments in bargaining that brought both opportunities and problems. In the Victorian public health system there was an increasing emphasis on decentralisation in both service provision and employment relations. In this paper I suggest that there were contradictions in these developments for government, and new challenges and difficulties for employers, employees and trade unions.

Contract Services↗
PubMed1999

Radiation-related arterial disease.

Arterial occlusive disease has been recognized in association with radiation arteriopathy and, rarely, with spontaneous arterial disruption. This association results from the greater role of radiation therapy in the current management of malignant diseases coupled with longer patient survival and the lengthy latency period between radiation and clinical manifestations of radiation arteriopathy. Experience with six patients having radiation-associated arterial disease was retrospectively reviewed. There were four men and two women, with a mean age of 51 years (range, 36-74). Arteries exposed to radiation include two carotids, three subclavians, one coronary, and one femoral. The time from radiation therapy until clinical arterial disease was a mean of 14.3 years (range, 4-30). Operative repairs with polytetrafluoroethylene and saphenous vein bypass grafts were performed in four patients, stent placement in one patient, and one patient had spontaneous carotid disruption that ultimately was treated with ligation. In conclusion, elective bypass can be performed safely and successfully for arterial occlusive disease in a previously irradiated artery. In contrast, life-threatening arterial disruption secondary to radiation arteriopathy usually requires concomitant exposure to a source of bacterial contamination, and ligation may be the best choice to prevent recurrent hemorrhage.

Adult↗
PubMed1996

Specific mutations near the amino terminus of double-stranded RNA-dependent protein kinase (PKR) differentially affect its double-stranded RNA binding and dimerization properties.

The amino-terminal region of the double-stranded (ds) RNA-dependent protein kinase, PKR, has been shown to mediate both dsRNA binding and protein dimerization. To critically examine if PKR dimerization is dependent on dsRNA binding, we generated a series of mutants that are incapable of binding dsRNA. Some, but not all, of these mutants retained the ability to dimerize, as shown by a two-hybrid transcriptional activation assay in vivo and a chemical cross-linking assay in vitro. These mutants were used further to demonstrate that the translational inhibitory activity of PKR in vivo requires dsRNA binding; PKR mutants that dimerized but did not bind dsRNA could not inhibit the translation of a transfected reporter gene.

Amino Acid Sequence↗
PubMed1995

A radioresistant variant derived from a human neuroblastoma cell line is less prone to radiation-induced apoptosis.

By subjecting radiosensitive human neuroblastoma IMR 32 cells to a regime of fractionated X-irradiation, a radioresistant variant, XRIMR 32, was obtained. Radiation resistance of XRIMR 32 cells was demonstrated by clonogenic and spheroid regrowth delay assays. The XRIMR 32 cultures were phenotypically unstable, with the resistant phenotype being lost after 3 passages in the absence of radiation-selective pressure, but a monoclonal cell line (clone F) was established that maintained its resistance over 35 passages without irradiation. Flow cytometry showed that exponentially growing IMR 32, XRIMR 32, and clone F cells all had very similar cell cycle distributions. Studies of initial DNA damage and repair, using the technique of neutral filter elution, revealed no differences between these lines. Chromosomal damage, as measured by micronucleus frequency following irradiation, was also seen to be very similar. However, studies of apoptosis following irradiation showed significantly higher levels of apoptosis in IMR 32 cells, compared to the resistant lines. This was true at all time points studied between 6 and 42 h after irradiation. p53 status was examined in the IMR 32 and clone F cells. No mutations were detected in exons 5-8 of the cDNA. Both lines showed increased p53 expression after irradiation. These data are consistent with the evolution of cellular resistance as a possible mechanism for the evolution of cellular radioresistance during protracted radiation regimes. However, the molecular mechanism responsible for the increased radioresistance remains to be discovered.

Apoptosis↗
PubMed1995

The interferon-inducible double-stranded RNA-activated protein kinase self-associates in vitro and in vivo.

The interferon-inducible double-stranded (ds) RNA-activated protein kinase (PKR) exhibits antiviral, anticellular, and antitumor activities. The mechanisms of its enzymatic activation by autophosphorylation and of the observed transdominant inhibitory phenotype of enzymatically inactive mutants have invoked PKR dimerization. Here we present direct evidence in support of PKR-PKR interaction. We show that radiolabeled PKR can specifically interact with matrix-bound unlabeled PKR in the absence of dsRNA. The self-association activity resides, in part, in the N-terminal region of 170 residues, which also constitutes the dsRNA-binding domain (DRBD). DRBD can bind to matrix-bound PKR or to matrix-bound DRBD. Dimerization of DRBD was directly demonstrated by chemical crosslinking. Affinity chromatography and electrophoretic mobility supershift assays demonstrated that mutants that fail to bind dsRNA can still exhibit protein-protein interaction. The PKR-PKR interaction could also be observed in a two-hybrid transcriptional activation assay in mammalian cells and consequently is likely to be an important feature of PKR activity in vivo.

Biopolymers↗
PubMed1995

The cyclic AMP response elements of the genes for angiotensin converting enzyme and phosphoenolpyruvate carboxykinase (GTP) can mediate transcriptional activation by CREM tau and CREM alpha.

The potential of the CREM family of proteins to activate transcription of the genes encoding the testis-specific isozyme of angiotensin converting enzyme (ACET) and the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (GTP) (PEPCK) (EC 4.1.1.32) were investigated. Both CREM tau and CREM alpha bind efficiently to the putative cyclic AMP response element (CRE) present in the ACET gene (CRET) and to the CRE in the PEPCK gene. In HepG2 cells, the CRE was required for the strong stimulation by CREM tau of the expression of a chimeric PEPCK (-210 to +73)-chloramphenicol acetyl transferase (CAT) gene. The CRE could be mutated to the CRET sequence without losing the stimulatory effects of CREM tau. However, a similar chimeric gene driven by the regulatory region of the ACET gene, which contains the CRET site, could only be stimulated by CREM tau when its imperfect TATA element was mutated to an authentic TATA. Surprisingly, CREM alpha, an alleged inhibitor of CRE-mediated transcription, stimulated the expression of both PEPCK-CAT and ACET-CAT genes in HepG2 cells, a process which required the presence of the CRE and the CRET sites, respectively. In contrast, when the same CRE elements were used to drive the transcription of a chimeric gene containing the thymidine kinase promoter linked to the CAT structural gene, CREM alpha inhibited its expression in HepG2 and JEG3 cells. The expression of the same chimeric gene, however, was stimulated by CREM alpha in F9 embryonal carcinoma cells. These results demonstrated that the nature of the transcriptional effects of CREM isoforms on CRE-mediated transcription depends on the specific gene, the specific cell type and the promoter context of the CRE site.

Animals↗
PubMed1994

Role of the amino-terminal residues of the interferon-induced protein kinase in its activation by double-stranded RNA and heparin.

We have previously reported that the amino-terminal residues 1-34 of the interferon-induced protein kinase (RNA-activated) (PKR) are necessary for its binding to and activation by double-stranded RNA (dsRNA) (Patel, R. C., and Sen, G. C. (1992) J. Biol. Chem. 267, 7671-7676). Here, we report that the amino-terminal 24 residues are indispensable for these properties of the enzyme. The replacement of these residues with 14 unrelated residues fully restored the protein's dsRNA binding activity, but only partially restored the enzyme activity. Mutation of residues 18 and 19 revealed their importance in determining the affinity of PKR for dsRNA and its ability to phosphorylate eukaryotic initiation factor 2 alpha. These mutations, however, did not affect PKR's autophosphorylation activity. Deletion mutants that failed to bind to and be activated by dsRNA could be fully activated by the alternative activator, heparin. Thus, activation of PKR by dsRNA and heparin is mediated through different mechanisms that require different domains of the protein.

Amino Acid Sequence↗
PubMed1994

Epidermal growth factor receptor expression by human squamous cell carcinomas of the head and neck, cell lines and xenografts.

Epidermal growth factor receptor (EGFR) overexpression has been associated frequently with squamous cell carcinomas (SCC) and SCC cell lines. In most cases the level of EGFR on the tumours from which the cell lines were derived has not been determined, nor have EGFR levels been determined for xenograft tumours from the cell lines. In this study we determined EGFR expression on a new series of head and neck SCC (SCCHN)-derived cell lines, which were obtained from tumours representing a spectrum of malignant progression, and two cell strains derived from erythroplakia premalignant lesions. The level of EGFR on cell lines was determined by [125I]EGF competitive binding assays. EGFR levels on some of the original tumours and xenografts of the cell lines were determined on cryosections by a competitive binding assay based on [125I]EGFR1, an EGFR-specific monoclonal antibody. EGFR expression on the tumour cryosections was compared with expression on cryosections of skin and buccal mucosa. Eight of the ten tumour cell lines had elevated EGFR. Two of the tumour-derived cell lines and the two erythroplakia-derived cell strains expressed EGFR at levels similar to that detected on normal keratinocytes in tissue culture. Only two of the tumours overexpressed EGFR when compared with normal tissue. The other tumours had levels similar to that detected on the basal layers of skin or buccal mucosa. The xenografts expressed EGFR, as did the original tumours, even though they were derived from cell lines that displayed significant overexpression of EGFR. This study suggests that most tumours have a latent potential to overexpress EGFR which is realised in tissue culture.

Animals↗
PubMed1993

Relationship of endothelial cell proliferation to tumor vascularity in human breast cancer.

Current studies of tumor angiogenesis rely on the concept that endothelium proliferates 30-40 times faster in tumors than in normal tissues. This evidence is based on histological autoradiographic data largely from animal studies. To assess endothelial cell proliferation in human cancer we used the more sensitive and specific technique of immunohistochemistry. We measured the frequency and distribution of endothelial cell proliferation and examined their relationship to tumor cell proliferation. For the first time, we also correlated endothelial and tumor cell proliferation with tumor vascularity. Twenty breast carcinomas from patients exposed to bromodeoxyuridine 3-8 h prior to surgery were double immunostained using antibodies to CD31 (as a marker of endothelium) and bromodeoxyuridine (as a marker of proliferation). The labeling index (LI) for both tumor and endothelial cells was determined and tumor vascularity was assessed by counting the number of CD31 positive vessels. Endothelial cell proliferation was predominantly at the tumor periphery while tumor cell proliferation occurred throughout the lesion. The mean LIs for endothelium and tumor were 2.2% (range, 0.8-5.3) and 7.3% (range, 1.3-17.1), respectively. There was no correlation between tumor and endothelial cell LI (P = 0.414) or between the tumor LI or endothelial cell LI and tumor vascularity (P = 0.08 and P = 0.39, respectively). These findings suggest that previous studies in animal tumors have significantly overestimated endothelial cell proliferation and that its importance in tumor angiogenesis may be related more to continual remodeling and migration of vessels than to proliferation alone.

Adult↗