Prostaglandin E2 receptors EP2 and EP4 are down-regulated in human mononuclear cells after injury

BACKGROUND

Recent characterization of prostaglandin receptor subtypes shows that each is critical to cellular functions and operates through separate signaling pathways that may explain differing effects of prostanoids. This study aimed to determine whether prostaglandin receptors EP2 and EP4 are modulated after injury and to evaluate the effect of prostaglandin E(2) (PGE(2)) addition and blockade on EP receptor expression.

METHODS

Peripheral blood mononuclear cells (PBMCs) isolated from 10 patients sustaining fracture or burn injury and 10 control subjects were stimulated with lipopolysaccharide +/- NS-398, an inhibitor of PGE(2) production. Samples were evaluated for production of PGE(2), tumor necrosis factor--alpha, and leukotriene B(4) as well as mRNA expression of EP receptors and COX-2. EP receptor expression was also evaluated after treating control PBMCs with PGE(2).

RESULTS

PBMCs from injured patients exhibited significant increases in PGE(2) production and COX-2 mRNA compared with control subjects, and these increases were inhibited by NS-398. In contrast, EP2 and EP4 receptors were markedly down-regulated after injury and NS-398 restored expression to control levels. Decreased EP2 and EP4 receptor expression after injury was replicated by coincubation of PBMCs with PGE(2).

CONCLUSIONS

Specific PGE(2) receptors are down-regulated after injury and NS-398 reverses this response. Furthermore, PGE(2) mediates EP2 and EP4 down-regulation. These data suggest that specific EP receptor subtypes may provide critical targets for augmenting the immune response after injury in humans.

An essential role for Src kinase in ErbB receptor signaling through the MAPK pathway

ErbB receptor tyrosine kinases are activated by multiple ligands such as epidermal growth factor (EGF) and neuregulins (NRGs), leading to stimulation of intracellular signaling pathways, including the mitogen-activated protein kinase (MAPK) cascade. We show here that Src kinase is essential for rapid EGF- and NRG-induced MAPK activation when the breast carcinoma cell lines T47D and SKBR3 are stimulated with low concentrations of ligand. In the presence of the pharmacological inhibitor CGP77675, which specifically blocks the activity of Src family kinases, ligand-induced MAPK activation was almost completely blocked at 5 min. Although this block was only transient, inactivation of Src suppressed ligand-induced transcription from a MAPK-responsive promoter. At the molecular level, the initial inhibition of MAPK by Src inactivation correlated with impaired ligand-induced Shc phosphorylation. Surprisingly, Src inhibition affected neither association of Shc with ErbB receptors nor phosphorylation of receptor-bound Shc. Thus, ErbB signaling requires the engagement of a novel Src-dependent route to MAPK, to trigger its rapid activation and subsequent efficient stimulation of transcription.

Macrophage effector mechanisms in melanoma in an experimental study

BACKGROUND

The tumor-bearing state is known to induce immune dysfunction that contributes to increased infectious complications and tumor progression. However, the mechanisms underlying this immunosuppression remain unclear.

HYPOTHESIS

Macrophage (MO) dysfunction may play a role in tumor-induced immunosuppression.

DESIGN AND MAIN OUTCOME MEASURES

Using a murine model, this study investigated the effects of melanoma growth on peritoneal macrophage effector molecule and prostaglandin production, MO-mediated cytotoxicity, and candidacidal mechanisms. Female C57BL/6 mice were inoculated with 106 B16 melanoma cells or a salt solution subcutaneously. Mice were euthanized 3 weeks later and peritoneal MOs were harvested and assayed for nitric oxide, superoxide anion, tumor necrosis factor alpha, and prostaglandin E(2)production. Macrophage-mediated cytotoxicity against B16 melanoma targets and MO candidacidal mechanisms were also measured.

RESULTS

Macrophage production of nitric oxide, superoxide anion, and tumor necrosis factor alpha were significantly decreased, while prostaglandin E(2)production was increased in MOs from melanoma-bearing mice. Concomitantly, MO-mediated cytotoxicity and candidacidal mechanisms were significantly impaired.

CONCLUSIONS

Melanoma growth leads to decreased MO effector molecule production, increased prostaglandin E(2)production, and impaired MO cytotoxic and candidacidal mechanisms. These results may help explain the observed increased infectious complications in the tumor-bearing host. Strategies aimed at restoring MO function may have therapeutic potential.

Overlapping CRE and E-box promoter elements can independently regulate COX-2 gene transcription in macrophages

Macrophage cyclooxygenase-2 (COX-2) transcription is mediated through the collaboration of different promoter elements. Here, the role of an overlapping cyclic AMP responsive element (CRE)/E-box was investigated. Nuclear proteins bound both the CRE and E-box, which synergized with other promoter elements to induce COX-2 transcription. Endotoxin induced binding of nuclear proteins to the CRE and E-box and each element independently induced higher COX-2 transcription levels than the overlapping CRE/E-box. Transcription factors associated with the CRE binding complex included c-Jun and CRE binding protein and with the E-box binding complex USF-1; their overexpression significantly induced COX-2 transcription. Therefore, both CRE and E-box promoter elements regulate COX-2 transcription in macrophages.

Suppression of macrophage nitric oxide production by melanoma: mediation by a melanoma-derived product

The tumour-bearing state is known to induce immune dysfunction that contributes to increased infectious complications and tumour progression. However, the mechanisms underlying this immunosuppression remain unclear. This study investigated in a murine model the effects of melanoma growth on nitric oxide (NO) production by peritoneal macrophages in vivo and in vitro. B16 and K1735 melanoma cells were inoculated subcutaneously into C57BL/6 and C3H/HeN mice, respectively. Stimulated NO production by elicited peritoneal macrophages was examined in control and melanoma- bearing mice. An in vitro system was established to assess the effects of co-culturing melanoma cells (B16 and K1735) or melanoma-conditioned medium with normal peritoneal macrophages on subsequent NO production. NO production was significantly suppressed in macrophages from melanoma-bearing mice. Co-culture of normal macrophages with melanoma cells in a transwell system or with melanoma-conditioned media in vitro reproduced the defects observed in vivo without affecting macrophage viability, pointing to a melanoma-derived product as the basis for the observed suppression of NO production. This inhibition required RNA and protein synthesis and was dose and time dependent. Using inhibition profiles and neutralizing antibodies, it was demonstrated that this melanoma inhibitory activity was distinct from known NO inhibitors. Preliminary characterization attributed this activity to a melanoma-secreted protein moiety.

Behavioral and electrophysiological responses of Arhopalus tristis to burnt pine and other stimuli

The exotic longhorn beetle Arhopalus tristis is a pest of pines, particularly those damaged by fire, and a major export quarantine issue in New Zealand. Actinograph recordings of caged individuals showed that males and females were most active from dusk to midnight. Olfactometer experiments indicated that females moved upwind toward odors from burnt pine (80%, N = 75), compared to unburnt pine (20%). Oviposition choice tests showed that eggs were predominantly laid on burnt logs (79%, N = 20), compared to unburnt logs. Beetles were trapped by funnel traps baited with burnt (mean catch per trap 7.8) and unburnt (mean catch 4.1 per trap) pine bark from inside a screen cage (4 x 3 m), while unbaited traps had a mean catch 0.1 beetles (N = 8 replicates). The treatment of burnt pine bark with a 1:1:2 mixture of green leaf volatiles (E)-2-hexen-1-ol and (E)-2-hexenal) in mineral oil as a repellent reduced trap catch by fivefold in a similar experiment (mean catches of 1.2 beetles per trap to burnt pine bark plus repellent treatment and 6.2 beetles per trap to burnt pine bark alone). The treatment of burnt pine bark with this solution also reduced oviposition by 98.5% (mean eggs per log of 11.1 on burnt pine and 0.3 on burnt pine plus repellent), indicating that oviposition cues have the potential to be significantly disrupted. The electrophysiological responses of adult beetles were recorded to a range of odorants. Normalized responses to monoterpenes known to occur in Pinus radiata ranged from about 20 to about 150, with alpha-terpineol giving the greatest responses in both sexes. Green leaf volatiles also gave high responses. The potential exists to improve the management of this insect using chemical cues in various ways.

NS-398 Treatment after Trauma Modifies NF-κB Activation and Improves Survival

Prostaglandin E(2) (PGE(2)) production after trauma contributes to immune alterations that increase susceptibility to infections. We hypothesize that blocking PGE(2) with NS-398, a selective COX-2 inhibitor, will modulate this response and improve outcome. This study evaluated the effect of NS-398 given over 7 days on proinflammatory cytokines, intracellular signaling, and survival after a septic challenge. Balb/C mice (n = 8/group) were given 10 mg/kg NS-398 intraperitoneally over 7 days, starting after anesthesia or trauma (femur fracture + 40% hemorrhage). Four groups, anesthesia + vehicle (C), anesthesia + NS-398 (CN), trauma + vehicle (T), or trauma + NS-398 (TN), were studied. On Day 7 after trauma, mice were sacrificed, serum was collected, and splenic macrophages were evaluated for PGE(2), LTB(4), IL-6, TNF-alpha, and NO production. Additionally, macrophage COX-2 mRNA, IkappaB-alpha, and NF-kappaB were evaluated. In a separate study, mice (n = 10-11/group) were traumatized and given NS-398 over 7 days, and then cecal ligation and puncture (CLP) were performed. Mice were then followed for survival over 10 days (via log-rank test). NS-398 treatment of injured mice decreased PGE(2) production compared to T (3.9 +/- 0.3 vs 3.1 +/- 0.4 pg/microg protein), and significantly decreased IL-6, NO, and TNF-alpha production. NS-398 treatment also attenuated COX-2 mRNA levels and NF-kappaB activation. These cellular events correlate with a significant survival advantage in TN versus T mice after CLP. These data suggest that a specific COX-2 inhibitor not only suppresses PGE(2), but normalizes proinflammatory cytokines after trauma through changes that may partly be mediated via transcriptional events. This correlates with significantly increased survival in TN mice given a septic challenge and suggests that COX-2 inhibitors contribute to modulating the inflammatory response and improving survival after trauma.

Malnutrition-induced macrophage apoptosis

BACKGROUND

Human and murine studies suggest protein-calorie malnutrition (PCM) results in significant host immunosuppression resulting in increased morbidity and mortality. Apoptosis has been implicated as an important mediator in the immunosuppression observed in several disease states. This study was designed to characterize macrophage apoptosis in a murine model of PCM and investigate components that regulate the apoptotic process, such as protein kinase C (PKC) and Bcl-2 activity.

METHODS

Swiss-Webster mice (n = 50) were randomly assigned to receive either a control (24% protein) or a PCM diet (0% protein) for 7 days. Peritoneal macrophages were harvested and detection of apoptosis was performed by terminal deoxy-transferase-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) and propidium iodide DNA staining under baseline and pro-apoptotic conditions. Pro-apoptotic conditions included cells treated with tumor necrosis factor-alpha (TNF-alpha) (10 ng/mL), interferon-gamma (IFN-gamma) (10 ng/mL), and a combination of both agents. In addition, levels of PKC activity and expression of Bcl-2 and p53 protein were measured.

RESULTS

Peritoneal macrophages from PCM mice had a significantly greater amount of apoptosis at baseline and under stimulated conditions compared with controls. Levels of PCM apoptosis were elevated at baseline by TUNEL staining compared with macrophages from the control group (16.5% +/- 1.4%, versus 4.5% +/- 1.1%, P <.01). In addition, peritoneal macrophages from the malnourished animals were significantly more susceptible to the apoptotic effect of TNF-alpha and the effects of INF-gamma (27.3% +/- 2.1% and 31% +/- 1.4%) compared with control mice (5.5% +/- 0.7% and 7.2% +/- 0.5%, P <.01), respectively. Again, an increase in the baseline apoptosis rate was demonstrated in peritoneal macrophages from PCM mice compared with control fed mice (13.2% +/- 4.4% versus 4.3% +/- 3.1%, P <.01) as measured by propidium iodide staining. The combination of agents, TNF-alpha and INF-gamma, resulted in an additive apoptotic effect in the malnourished host compared with the control animals (43.4% +/- 4.7% versus 10.5% +/- 2.2%, P <.01), respectively. Furthermore, there was a significant decrease in the mean total PKC activity in the malnourished macrophages compared with results in controls (110,000 +/- 8000 versus 60,000 +/- 4000 cpm, P <.01). Similar changes were also observed in PKC cytosolic and membrane activity between both groups. In addition, Bcl-2 protein expression was significantly decreased in PCM animals compared with control animals.

CONCLUSIONS

Thus, peritoneal macrophages from PCM mice exhibit significantly greater levels of apoptosis at baseline and when stimulated with pro-apoptotic agents compared with controls. The propensity of macrophages from PCM mice to undergo apoptosis may be attributable in part to decreased PKC activity and Bcl-2 protein expression. These findings may help to explain the associated immune dysfunction observed in malnutrition.

Redundancy in the signaling pathways and promoter elements regulating cyclooxygenase-2 gene expression in endotoxin-treated macrophage/monocytic cells

Macrophage expression of cyclooxygenase-2 (COX-2), the inducible isoform of COX, is up-regulated by pro-inflammatory stimuli both in vivo and in vitro. Here we investigated the mechanisms regulating COX-2 gene expression in macrophage/monocytic cells. Lipopolysaccharide (LPS) is known to induce de novo COX-2 mRNA expression in these cells. Transient cotransfections with a COX-2 promoter-luciferase construct and different expression vectors showed that LPS up-regulates COX-2 transcription through both mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) pathways. Cotransfections with expression vectors for dominant negative mutants of MAPK and PKC isoforms did not suppress the effects of LPS on COX-2. Electrophoretic mobility shift assays and transient transfection experiments with deleted and mutated variants of a COX-2 promoter-luciferase construct showed that NFkappaB, NF-IL6, and CRE promoter sites mediate gene transcription independently in response to LPS treatment. In these experiments, isolated NFkappaB, NF-IL6, and CRE promoter sites were less effective than the intact promoter in mediating COX-2 transcription. Cotransfections with mutated COX-2 promoter-luciferase constructs and expression vectors showed that each one of these promoter elements can be activated by LPS through both MAPK and PKC pathways to induce gene expression. In summary, there is redundancy in the signaling pathways and promoter elements regulating COX-2 transcription in endotoxin-treated cells of macrophage/monocytic lineage.

The influence of restricted calorie intake on peritoneal macrophage function

Malnutrition leads to immune dysfunction with greatly increased morbidity. However, restrictive dietary regimens are also known to preserve immune function in autoimmune-susceptible mice. The macrophage (Mø) is central to both immune effector and autoregulatory functions and is critical to host-defense mechanisms. The aim of this study was to investigate the effect of calorie restriction on Mø functions in mice. Female, 6- to 8-wk-old, Swiss Webster mice were randomized to ad libitum feeding for 7 or 21 d (n = 10 mice/group), restricted feeding (13.5 to 14.0 g/cage/d; n = 10) for 7 d, or restricted feeding (16.5 to 17.0 g/cage/d; n = 10) for 21 d. These restrictions were equivalent to a decrease in calorie intake of 21.9% and 5.1%, respectively, over 7 and 21 d. All mice were allowed free access to water. On days 8 and 22, respectively, the mice were killed, and peritoneal Møs were isolated by lavage and adhered to 96-well polystyrene tissue-culture-treated plates. After stimulation with lipopolysaccharide, supernatant prostaglandin E2 and interleukin-6 levels were measured by enzyme-linked immunosorbent assay. Supernatant NO2- in response to stimulation with lipopolysaccharide and interferon-gamma was determined by the Greiss reaction. Prostaglandin E2 production was significantly elevated in peritoneal Møs from the calorie-restricted mice compared with the ad-libitum-fed mice after 7 d. After 21 d, production of both prostaglandin E2 and nitric oxide was significantly increased (P < 0.05) in peritoneal Møs from the restricted mice compared with the ad-libitum-fed mice. These results indicate that calorie restriction influences immune function by altering prostaglandin E2 and nitric oxide generation by Møs.

Effect of TNF gene depletion on liver regeneration after partial hepatectomy in mice

BACKGROUND

Tumor necrosis factor-alpha (TNF) is thought to act as a stimulator for initiating hepatocyte proliferation after partial hepatectomy (PH). At the same time, TNF induces a series of inflammatory responses that may be detrimental for the liver and other remote organs. The purpose of this study was to investigate the effect of TNF on the pathophysiologic state after PH.

METHODS

Wild-type (TNF+/+) and TNF-deficient (TNF-/-) mice underwent 70% PH. Hepatocyte proliferation was assessed by bromodeoxyuridine labeling and mitotic index. Liver function was evaluated by alanine aminotransferase (ALT) and total bilirubin levels in serum after PH. Myeloperoxidase activity in the liver and lung was measured as a marker for neutrophil activation.

RESULTS

No differences were observed in liver regeneration or hepatocyte proliferation between TNF+/+ and TNF-/- mice. The survival of TNF-/- mice on day 1 after PH was significantly higher than that of TNF+/+ mice, but both groups had similar survival thereafter. The ALT level was significantly higher in TNF+/+ mice 6 hours after PH and myeloperoxidase activities in both liver and lung were markedly elevated in TNF+/+ mice compared with TNF-/- mice.

CONCLUSIONS

These findings demonstrate that TNF gene-depleted mice do not demonstrate delayed liver regeneration but do suppress neutrophil activation after PH compared with results in wild-type (TNF +/+) mice.

Use of multidimensional assessment to provide testimony on behalf of residents in a life-care home

City administrators challenged a life-care home's tax-exempt status. A successful, empirically-based case was made based on data collected by gerontological nurses using the Iowa Self-Assessment Inventory (ISAI) and related instruments (Mini-Mental State Examination [MMSE], Instrumental Activities of Daily Living Scale [IADLS], and Physical Self-Maintenance Scale [PSMS]) to describe the life-care population. Testimony by gerontological nurses included comparisons between these life-care residents and statewide data on elderly individuals currently residing in nursing homes and in the community. The data they presented showed not only that this life-care home provided a high quality of life, but also saved society substantial amounts of money in government-funded services that would otherwise be provided to residents of this home. The judge ruled in favor of continuing tax-exempt status for this life-care home because credible evidence clearly demonstrated that taxpayer savings from the services provided to life-care home residents and the life-care commitment dramatically outweighed the taxpayer costs associated with lost tax revenues.

Prostaglandins regulate melanoma-induced cytokine production in macrophages

Tumor-secreted products can affect macrophage cytokine expression and in that way alter the immune response. Prostaglandins (PGs) are found in the tumor microenvironment and have been associated with local and regional immunosuppression. We investigated whether tumor-secreted factors could induce PG synthesis in macrophages and whether these PGs could alter macrophage production of immunoregulatory cytokines. In both murine and human models, melanoma conditioned medium (MCM) induced macrophage production of PGE(2), IL-6, and TNF-alpha. PGE(2) production increased over 24 h and was accompanied by an increase in cyclooxygenase-2 (COX-2) expression, while COX-1 expression remained unchanged. In the presence of 10 microM NS398, a selective COX-2 inhibitor, MCM-stimulated PGE(2) synthesis was almost completely suppressed, while production of IL-6 and TNF-alpha proteins and mRNA also was partially abrogated. In the murine model, 200 microM NS398 resulted in more significant inhibition of cytokine protein and mRNA production. Although MCM induced NFkappaB and NF-IL-6 activation, neither dose of NS398 altered this effect. We conclude that melanoma-secreted products stimulate COX-2 expression and PGE(2) synthesis in macrophages and that inhibition of COX-2-derived PG synthesis results in partial abrogation of macrophage cytokine production.

Blocking prostaglandin E2 after trauma attenuates pro-inflammatory cytokines and improves survival

Major injury leads to impaired immune responses and increases the risk of infectious complications. Following trauma, increased prostaglandin E2 (PGE2) levels may be important in immunodysregulation. We hypothesized that blocking PGE2 with NS-398, a selective COX-2 inhibitor, during the first 24 h after injury may modify the immune response and protect the host from a subsequent septic challenge. BALB/c mice were given NS-398 (10 mg/kg) immediately after injury, at 12, and at 24 h after sham injury or trauma (femur fracture and 40% hemorrhage). On day 7 after injury, splenic macrophages were evaluated for cytokine production and COX-2 mRNA. In a separate study mice were injured, then given 3 doses of NS-398. After 7 days, cecal ligation and puncture was performed and mice were followed for survival. Traumatized mice given NS-398 had a significant survival advantage compared with trauma mice alone (P < 0.001). Macrophages from traumatized mice showed increased COX-2 mRNA and proinflammatory cytokines compared with controls (P < 0.05), whereas treatment of injured mice with NS-398 significantly decreased proinflammatory cytokine production (P < 0.05) and COX-2 mRNA. Therefore NS-398 given within 24 h of injury suppressed PGE2 through inhibition of cyclooxygenase, in addition to decreasing proinflammatory cytokines, and providing a survival advantage to the host.

Pancreatic anastomotic failure after pancreaticoduodenectomy

BACKGROUND

Pancreatic anastomotic failure has historically been regarded as one of the most feared complications after pancreaticoduodenectomy.

METHODS

We reviewed our recent experience (59 cases), March 1994 to December 1998, with pancreaticoduodenectomy and compared preoperative and intraoperative characteristics as well as outcomes in those patients who experienced (n = 10) versus those who did not experience a postoperative pancreatic leak (n = 49). Information was retrospectively collected from hospital records, office records, and interviews with patients.

RESULTS

The clinical leak rate in this series was 8.5%. There were no significant differences in preoperative or intraoperative characteristics comparing those with versus those without a postoperative pancreatic leak. Only 1 of 10 patients with a postoperative pancreatic leak required reoperation to manage the leak. Those with a pancreatic leak had more other postoperative complications (median 2 versus 0 complications per patient, P = 0.01) and longer hospital duration compared with those without a leak (median 13 versus 23 days, P<0.01). Overall mortality in the series was 3.4%; no mortalities occurred as a result of a pancreatic leak.

CONCLUSIONS

In the 1990s pancreatic anastomotic leak remains a potentially lethal problem after pancreaticoduodenectomy. Pancreatic leakage after pancreaticoduodenectomy is associated with other postoperative complications and a longer hospital stay.

Predictive factors associated with axillary lymph node metastases in T1a and T1b breast carcinomas: analysis in more than 900 patients

BACKGROUND

Axillary lymph node metastasis (ALNM) represents the single most important prognostic indicator in patients diagnosed with breast cancer. The proportion of < or = 1-cm (T1a, T1b) invasive breast carcinomas is increasing. The incidence and predictive factors associated with ALNM in patients with < or = 1-cm tumors remains unclear and the role of axillary lymph node dissection in these patients has been questioned. The purpose of this study was to determine clinical and pathologic factors predictive of ALNM in patients with < or = 1-cm invasive breast carcinomas by univariate and multivariate analyses.

STUDY DESIGN

Review analysis from a prospective database identified patients with < or = 1-cm invasive breast cancers treated at our institution between 1990 and 1996. All patients underwent a resection of the primary tumor and axillary lymph node dissections. Routine patient and tumor characteristics evaluated included: age, race, tumor size, histologic grade, estrogen and progesterone receptor status, and lymphatic and vascular invasion. Univariate and multivariate analyses were performed. Adjusted odds ratios (OR) and 95% confidence intervals (CI) are presented.

RESULTS

A total of 919 patients were identified in this study with tumors < or = 1 cm. These included 199 patients (21.7%) with T1a tumors and 720 patients (78.3%) with T1b tumors. ALNM was detected in 165 patients with an overall incidence of 18.0%. Of the ALNM group, 32 patients (19.4%) had T1a tumors and 133 patients (80.6%) had T1b tumors. Four variables were found to be significant in univariate analysis. These included: increasing tumor size, poor histologic grade, presence of lymphatic or vascular invasion, and younger age of the patient. An increase in tumor size was associated with a significant risk of ALNM (OR = 2.66, 95% CI = 1.28 to 5.75; p = 0.01). Poor tumor grade and the presence of lymphatic or vascular invasion were also associated with an increased risk of ALNM (OR = 2.69, p = 0.003 and OR = 5.52, p = 0.0001, respectively). Patients with ALNM were more likely to have a tumor grade of 3 (25.0% ALNM versus 12.5% node-negative, p = 0.004) and lymphatic or vascular invasion (16.9% ALNM versus 3.5% node-negative, p < 0.0001). In multivariate analysis, an increased risk of ALNM was demonstrated with increasing tumor size (0.1-cm increments), poor histologic grade, and younger age.

CONCLUSIONS

This study investigated clinical and pathologic factors influencing ALNM in patients with T1a and T1b breast carcinomas. We have identified three factors by multivariate analysis as significant independent predictors of ALNM in this group of patients. These include increasing tumor size, poor histologic grade, and younger age. Given the significant amount of ALNM demonstrated in this study (overall 18%) and the inability to identify a subgroup of patients that had an acceptable low risk of ALNM, the complete omission of assessing the axilla for metastatic disease in patients with small breast cancers cannot be advocated. Our recommendation for patients diagnosed with T1a and T1b tumors is to have their axilla investigated for metastatic disease either by traditional axillary lymph node dissections or by intraoperative lymphatic mapping and sentinel lymph node biopsy techniques.

The anatomy and relations of evidence-based medicine

Current tensions between evidence-based medicine (EBM) and some clinicians are counterproductive and unnecessary. The most contentious issues concern (a) the limitations of efficacy data from randomised trials as evidence; (b) differences in attitudes to medical diagnosis and clinical judgement; and (c) political concerns about the use of the concept of clinical evidence and guidelines to restrict physician autonomy. Health services research has evolved in response to a bureaucratic need to study health care, including clinical practice, in order to improve its effectiveness (defined mainly in terms of technological interventions), and to contain costs. Its perspective is from the top-down representing the interests of bureaucracy and managed care, and articulates with political demands for professional accountability and cost-containment. EBM has established its place as an important contributor to the methodological toolbox for health services research. There is a need for a corresponding coherent programme of clinical practice research which would locate EBM in the clinical environment beside quality assurance, the study of the appropriateness and effectiveness of interventions, and multidisciplinary research related to the art of medicine and supportive aspects of clinical care. EBM would then be seen as one organ in relation to many others making their contribution to the body of knowledge needed for clinical decisions and policy making. A 'centre for the study of clinical practice' would be an appropriate structure to support such a comprehensive programme of clinical practice research in a tertiary hospital. The bottom-up perspective of clinical practice research would complement the current top-down perspective of most health services research, providing information to doctors, patients and administrators concerning local quality of care and health outcomes, information which could also be aggregated for guidance of health policy makers. It would also represent the voice of the clinician in policy debates. Such a programme, located in the practice environment, would also foster mutual understanding, respect and cooperation between workers from different backgrounds.

ErbB2 potentiates breast tumor proliferation through modulation of p27(Kip1)-Cdk2 complex formation: receptor overexpression does not determine growth dependency

Overexpression of the ErbB2 receptor, a major component of the ErbB receptor signaling network, contributes to the development of a number of human cancers. ErbB2 presents itself, therefore, as a target for antibody-mediated therapies. In this respect, anti-ErbB2 monoclonal antibody 4D5 specifically inhibits the growth of tumor cells overexpressing ErbB2. We have analyzed the effect of 4D5-mediated ErbB2 inhibition on the cell cycle of the breast tumor cell line BT474. 4D5 treatment of BT474 cells resulted in a G(1) arrest, preceded by rapid dephosphorylation of ErbB2, inhibition of cytoplasmic signal transduction pathways, accumulation of the cyclin-dependent kinase inhibitor p27(Kip1), and inactivation of cyclin-Cdk2 complexes. Time courses demonstrated that 4D5 treatment redirects p27(Kip1) onto Cdk2 complexes, an event preceding increased p27(Kip1) expression; this correlates with the downregulation of c-Myc and D-type cyclins (proteins involved in p27(Kip1) sequestration) and the loss of p27(Kip1) from Cdk4 complexes. Similar events were observed in ErbB2-overexpressing SKBR3 cells, which exhibited reduced proliferation in response to 4D5 treatment. Here, p27(Kip1) redistribution resulted in partial Cdk2 inactivation, consistent with a G1 accumulation. Moreover, p27(Kip1) protein levels remained constant. Antisense-mediated inhibition of p27(Kip1) expression in 4D5-treated BT474 cells further demonstrated that in the absence of p27(Kip1) accumulation, p27(Kip1) redirection onto Cdk2 complexes is sufficient to inactivate Cdk2 and establish the G(1) block. These data suggest that ErbB2 overexpression leads to potentiation of cyclin E-Cdk2 activity through regulation of p27(Kip1) sequestration proteins, thus deregulating the G(1)/S transition. Moreover, through comparison with an ErbB2-overexpressing cell line insensitive to 4D5 treatment, we demonstrate the specificity of these cell cycle events and show that ErbB2 overexpression alone is insufficient to determine the cellular response to receptor inhibition.

Esophageal cancer: results of an American College of Surgeons Patient Care Evaluation Study

BACKGROUND

The last two decades have seen changes in the prevalence, histologic type, and management algorithms for patients with esophageal cancer. The purpose of this study was to evaluate the presentation, stage distribution, and treatment of patients with esophageal cancer using the National Cancer Database of the American College of Surgeons.

STUDY DESIGN

Consecutively accessed patients (n = 5,044) with esophageal cancer from 828 hospitals during 1994 were evaluated in 1997 for case mix, diagnostic tests, and treatment modalities.

RESULTS

The mean age of patients was 67.3 years with a male to female ratio of 3:1; non-Hispanic Caucasians made up most patients. Only 16.6% reported no tobacco use. Dysphagia (74%), weight loss (57.3%), gastrointestinal reflux (20.5%), odynophagia (16.6%), and dyspnea (12.1%) were the most common symptoms. Approximately 50% of patients had the tumor in the lower third of the esophagus. Of all patients, 51.6% had squamous cell histology and 41.9% had adenocarcinoma. Barrett's esophagus occurred in 777 patients, or 39% of those with adenocarcinoma. Of those patients that underwent surgery initially, pathology revealed stage I (13.3%), II (34.7%), III (35.7%), and IV (12.3%) disease. For patients with various stages of squamous cell cancer, radiation therapy plus chemotherapy were the most common treatment modalities (39.5%) compared with surgery plus adjuvant therapy (13.2%). For patients with adenocarcinoma, surgery plus adjuvant therapy were the most common treatment methods. Disease-specific overall survival at 1 year was 43%, ranging from 70% to 18% from stages I to IV.

CONCLUSIONS

Cancer of the esophagus shows an increasing occurrence of adenocarcinoma in the lower third of the esophagus and is frequently associated with Barrett's esophagus. Choice of treatment was influenced by tumor histology and tumor site. Multimodality (neoadjuvant) therapy was the most common treatment method for patients with esophageal adenocarcinoma. The use of multimodality treatment did not appear to increase postoperative morbidity.

Effects of oncogenic ErbB2 on G1 cell cycle regulators in breast tumour cells

The ErbB2 receptor tyrosine kinase is overexpressed in a variety of human tumours. In order to understand the mechanism by which ErbB2 mediates tumour proliferation we have functionally inactivated the receptor using an intracellularly expressed, ER-targeted single-chain antibody (scFV-5R). Inducible expression of scFv-5R in the ErbB2-overexpressing SKBr3 breast tumour cell line leads to loss of plasma membrane localized ErbB2. Simultaneously, the activity of ErbB3, MAP kinase and PKB/Akt decreased dramatically, suggesting that active ErbB2/ErbB3 dimers are necessary for sustained activity of these kinases. Loss of functional ErbB2 caused the SKBr3 tumour cells to accumulate in the G1 phase of the cell cycle. This was a result of reduction in CDK2 activity, which was mediated by a re-distribution of p27Kip1 from sequestering complexes to cyclin E/CDK2 complexes. The level of c-Myc and D-cyclins, proteins involved in p27KiP1 sequestration, decreased in the absence of functional ErbB2. Ectopic expression of c-Myc led to an increase in D cyclin levels, CDK2 activity and resulted in a partial G1 rescue. We propose that c-Myc is a primary effector of ErbB2-mediated oncogenicity and functions to prevent normal p27Kip1 control of cyclinE/CDK2.

Glucocorticoid blockade does not abrogate tumor-induced cachexia

Cancer-induced cachexia is a common manifestation observed in patients with malignancies. Elevated levels of circulating glucocorticoids and interleukin-6 (IL-6) have been observed in cancer patients with cachexia and are implicated as major mediators in this process. The purpose of this study was to investigate the role of circulating glucocorticoid levels as primary mediators in cancer-induced cachexia. We evaluated whether inhibition of glucocorticoids with the receptor antagonist RU-486 could abrogate the detrimental wasting of muscle and adipose tissues seen in a well-characterized murine tumor-induced cachexia model. Mice (12/group) were randomized to control, tumor-bearing, control + vehicle, or tumor-bearing + glucocorticoid receptor antagonist groups. Circulating serum glucocorticoid and IL-6 levels were measured in addition to multiple body composition parameters, such as total body weight, lean body mass, and adipose content. The results of this study indicate a significant physiological alteration in the tumor-bearing host that causes severe and detrimental changes in body composition parameters. Regression analysis demonstrated a significant correlation between increased circulating glucocorticoid levels and alterations in body composition parameters. These observed defects were not abrogated with the administration of a glucocorticoid receptor antagonist. We therefore conclude that the untoward effects of tumor-induced cachexia are not mediated primarily by the peripheral effects of high circulating glucocorticoid levels but may involve a complex interaction with IL-6.