[Palliative therapy concepts for pancreatic carcinoma]

The majority of patients with ductal pancreatic adenocarcinoma are already in a locally advanced or metastatic stage at the time of diagnosis and require palliative therapy. Interventional and operative measures are available for the restoration of biliary outflow in bile duct obstruction and the continuity of the upper intestinal lumen in duodenal or gastric outlet obstruction. In the presence of tumor-related pain, pain therapy according to the World Health Organization (WHO) scheme or a truncus coeliacus blockade, in cachexia a nutritional therapy and in thromboembolic events an anticoagulant therapy are used. An individualized palliative chemotherapy regimen should be selected for each patient, taking into account the patient's general condition and the side effects profile of the chemotherapeutic agents. Radiochemotherapy and local ablative therapies should currently only be used within the framework of studies. A palliative resection is not recommended according to current knowledge.

[Branch duct intraductal papillary mucinous neoplasm - contra resection]

Due to improvements in imaging modalities the diagnosis of branch duct intraductal papillary mucinous neoplasms (BD-IPMN) has been significantly increased in recent years. A BD-IPMN is frequently diagnosed as an incidental finding in asymptomatic patients. The optimal management of BD-IPMN is the subject of controversial discussions. Numerous studies have shown that an individualized therapeutic strategy with a follow-up observation of most BD-IPMNs is feasible and safe, considering age, comorbidities and patient preference. An accurate evaluation of BD-IPMN with a detailed anamnesis, high-resolution imaging techniques and endoscopic ultrasound is necessary. Symptomatic patients as well as patients with so-called high-risk stigmata should undergo resection. Asymptomatic patients with so-called worrisome features can either undergo surveillance or surgical resection, taking age and comorbidities into account. For BD-IPMN patients without high-risk stigmata and worrisome features and showing no symptoms, surveillance of the pancreatic lesion is the preferred approach. The high prevalence of BD-IPMN, limitations in differential diagnostics, an overestimation of the risk of malignancy due to an overrepresentation of symptomatic and suspected BD-IPMN in resected cohorts, an overestimated role of BD-IPMN as precursor lesions for pancreatic carcinoma and evidence of the safety of follow-up surveillance, underline the enormous importance of surveillance. Based on this and considering the background of a notable mortality and morbidity of pancreatic surgery, aggressive management with prophylactic surgical resection is not justified for all BD-IPMN, in particular for low-risk lesions.

Nuclear osteopontin-c is a prognostic breast cancer marker

BACKGROUND

Although Osteopontin has been known as a marker for cancer progression, the elevated production of this cytokine is not specific for cancer. We have identified the splice variant Osteopontin-c as being absent from healthy tissue but associated with about 75% of breast cancer cases. However, in previous studies of Osteopontin-c, follow-up information was not available.

METHODS

Here we have analysed 671 patients, comprising a cohort of 291 paraffin blocks plus a population-based case-control study of 380 arrayed breast tumor tissues.

RESULTS

We find that high staining intensity of nuclear Osteopontin-c is strongly associated with mortality in patients with early breast cancer. Cytosolic staining for exon 4, reflective of Osteopontin-a and -b also predicts poor outcome. By contrast, total Osteopontin does not correlate with prognosis. These diverse assessments of Osteopontin also do not correlate with each other, suggesting distinct expression patterns for the variant forms. Consistent with its role in tumor progression, not tumor initiation, Osteopontin-c is not correlated with proliferation markers (Ki-67, cyclin A, cyclin B, cyclin E and cyclin D), neither is it correlated with ER, PR or HER2.

CONCLUSIONS

The addition of Osteopontin-c immunohistochemistry to standard pathology work-ups may have prognostic benefit in early breast cancer diagnosis.

Osteopontin is a marker for cancer aggressiveness and patient survival

BACKGROUND

Only a fraction of molecular cancer markers identified in the scientific literature have found clinical use. Specifically, few predictors of invasiveness are established in diagnostics. Meta-analysis is a valuable tool for biomarker validation. Here, we evaluate Osteopontin as a marker for tumor aggressiveness (grade, stage, early progression) and patient survival.

METHODS

Publications through 2008 with the keywords 'osteopontin AND cancer' were retrieved. Titles and abstracts were screened for studies presenting original data on human subjects. This left 228 publications for data extraction. We applied categorical data analysis for testing the relationship between Osteopontin and a clinical variable.

RESULTS

Osteopontin ranks correlated with lower overall and disease-free/relapse-free survival in all tumors combined, as well as in lung cancer, breast cancer, prostate cancer, head and neck cancer, and liver cancer. Further, Osteopontin levels correlated with tumor grade and stage for all tumors combined and for several individual tumor types. Osteopontin levels were significantly associated with the early progression of eight cancers, independent in one, and inversely correlated in two.

CONCLUSIONS

Osteopontin is significantly associated with survival in several forms of cancer. Osteopontin levels are also markers for stage, grade, and early tumor progression in multiple cancers, reflecting a common molecular underpinning for distinct clinical measures. Osteopontin has value as a clinical tumor progression marker.

An osteopontin splice variant induces anchorage independence in human breast cancer cells

In malignant tumors, metastasis genes are typically deregulated by aberrant expression or splicing. Osteopontin is expressed at high levels by various cancers and contributes importantly to their invasive potential. In contrast, osteopontin derived from host cells induces cellular immunity and could bolster antitumor protection by cytotoxic T lymphocytes. Here we show that breast cancer cells express multiple splice variants of osteopontin. According to RT-PCR analysis of human breast tissue specimens, the splice variant osteopontin-c is a highly specific marker for transformed cells, which is not expressed in their surrounding normal tissue. The full-length form of osteopontin aggregates in the presence of physiologic amounts of calcium and, in this state, leads to enhanced cell adhesion. Ostensibly, this effect is inhibitory for tumor cell dissemination. The shortest splice variant, osteopontin-c, does not aggregate in the presence of calcium and enhances clone formation in soft agar. According to microarray analysis, osteopontin-c induces the expression of oxidoreductases, consistent with protection from anoikis during anchorage-independent growth. These studies define a third functional domain of osteopontin, beside the C-terminal CD44-binding site and the central integrin-binding site. They also provide evidence for a bifunctional character of osteopontin, with the soluble form supporting invasiveness and the aggregated form promoting adhesion.

The metastasis gene osteopontin: a candidate target for cancer therapy

Malignant tumors are characterized by dysregulated growth control, overcoming of replicative senescence, and metastasis formation. Current therapeutic regimens mostly exert their effects through inhibition of cell cycle progression, leaving two major components of transformation untouched. The cytokine osteopontin is essential for the dissemination of various cancers. Past research has implied several modes in which osteopontin and its main receptors on tumor cells can be suppressed. Osteopontin expression is inhibitable on the levels of gene transcription and the RNA message, and the osteopontin protein can be blocked with antibodies or synthetic peptides. The osteopontin receptor CD44 has been targeted by diverse therapeutic strategies, including cytotoxic and immunotherapeutic approaches. The receptor integrin alpha(V)beta(3) contributes not only to tumor cell dissemination, but also to angiogenesis and osteolysis in bone metastases. Small molecule inhibitors of this receptor are under study as drug candidates. Because receptors and cytokine ligands that mediate metastasis formation are sparsely expressed in the adult healthy organism and are more readily reached by pharmaceuticals than intracellular drug targets they may represent a particularly suitable focus for therapeutic intervention.

Differential roles of osteopontin/Eta-1 in early and late lpr disease

The cytokine osteopontin (Eta-1) leads to macrophage-dependent polyclonal B-cell activation and is induced early in autoimmune prone mice with the lpr mutation, suggesting a significant pathogenic role for this molecule. Indeed, C57BL/6-Fas(lpr/lpr) mice crossed with osteopontin(-/-) mice display delayed onset of polyclonal B-cell activation, as judged by serum immunoglobulin levels. In contrast, they are subject to normal onset, but late exacerbation of lymphoproliferation and evidence of kidney disease. These observations define two stages of Fas(lpr/lpr) disease with respect to osteopontin-dependent pathogenesis that should be taken into account in the design of therapeutic approaches to the clinical disease.

Stress response genes: the genes that make cancer metastasize

Cancer is characterized by dysregulated growth control, overcoming of replicative senescence, and metastasis formation. The topology of cancer spread is mediated by a set of developmentally nonessential genes which are physiologically involved in stress responses, inflammation, wound healing, and neovascularization. The function of these gene products is extensively modified posttranscriptionally. In cancer, metastasis genes are dysregulated at the levels of expression or splicing. These genes constitute a unique group of cancer-related biomolecules.

Costimulation by extracellular matrix proteins determines the response to TCR ligation

Although ligation of the T-cell antigen receptor (TCR) is central to the responsiveness and antigen specificity of T-cells, it is insufficient to elicit a response. To determine whether the need for costimulation reflects inadequate strength of signal transduction through the TCR or an absolute block of signaling in the absence of a coligand, we studied T-cell activation under serum-free conditions eliminating costimulation by various extracellular matrix proteins which otherwise have an omnipresent and frequently overlooked effect. Engagement of the TCR leads to induction of Fas, but not to measurable IL-2 secretion or apoptosis. Those activation parameters are induced by costimulation through integrin alphaVbeta3. Furthermore, T-cell survival or elimination is determined by the type of ligand binding to this coreceptor with vitronectin, fibronectin, and fibrinogen efficiently inducing apoptosis and IL-2 production while osteopontin and entactin mediate IL-2 secretion comparably without causing programmed cell death. Consistent with the cytokine properties of these ligands, differential costimulation depends on their presentation in soluble rather than immobilized form. The determination of elimination versus survival of activated T-cells by coligation of beta3-integrins may have bearing on the fundamental postthymic mechanisms that shape the T-cell repertoire.

Molecular mechanisms of tumor dissemination in primary and metastatic brain cancers

Cancer is characterized by dysregulated growth control, overcoming of replicative senescence, and metastasis formation. Tumor dissemination distinguishes malignant from benign neoplasms and is mediated by homing receptors, their ligands, and proteinases. The homing receptor CD44 is frequently expressed on primary brain tumors and brain metastases. Its engagement by osteopontin physiologically induces macrophage chemotaxis, a mechanism that may be utilized by metastatic brain tumors in the process of dissemination. In host defense, osteopontin and its receptors, CD44 and integrin alpha(V)beta(3), play key roles in mediating delayed type hypersensitivity responses by activating macrophages to induce Th1 cytokines while inhibiting Th2 cytokines. Other metastasis associated gene products similarly contribute to host defenses. Hence, cancer spread is regulated by a set of developmentally non-essential genes which physiologically mediate stress responses, inflammation, wound healing, and neovascularization. Function of the relevant gene products is extensively modified post-transcriptionally and their dysregulation in cancer occurs on the levels of expression and splicing. Consistent patterns of organ preference by malignancies of particular tissue origin suggest a necessary connection between loss of growth control and senescence genes and expression of genes mediating the dissemination of tumor cells.

Eta-1 (osteopontin): an early component of type-1 (cell-mediated) immunity

Cell-mediated (type-1) immunity is necessary for immune protection against most intracellular pathogens and, when excessive, can mediate organ-specific autoimmune destruction. Mice deficient in Eta-1 (also called osteopontin) gene expression have severely impaired type-1 immunity to viral infection [herpes simplex virus-type 1 (KOS strain)] and bacterial infection (Listeria monocytogenes) and do not develop sarcoid-type granulomas. Interleukin-12 (IL-12) and interferon-gamma production is diminished, and IL-10 production is increased. A phosphorylation-dependent interaction between the amino-terminal portion of Eta-1 and its integrin receptor stimulated IL-12 expression, whereas a phosphorylation-independent interaction with CD44 inhibited IL-10 expression. These findings identify Eta-1 as a key cytokine that sets the stage for efficient type-1 immune responses through differential regulation of macrophage IL-12 and IL-10 cytokine expression.

Final common pathways in neurodegenerative diseases: regulatory role of the glutathione cycle

Attempts to unify diverse mechanisms of neurotoxicity have led to the concept of final common pathways which characterize frequently occurring cellular responses to disruption of homeostasis. The clinical presentation and common patho-biochemistry of reactive oxygen intermediates of Guam's disease have suggested that such pathways may be operative in three major neurodegenerative disorders: Alzheimer's dementia, amyotrophic lateral sclerosis and Parkinson's disease. A candidate-signaling pathway in this regard is characterized by the cascade arachidonic acid/HPETE/*OH/cGMP followed by activation of cGMP-dependent kinase and phosphorylation of NF-kB proteins and possibly CREB. This sequence may lead to apoptosis as well as long-term potentiation and memory and constitutes a biochemical correlate to excitotoxicity. The predominant control of *OH release from HPETE, a checkpoint in this pathway, is exerted by the glutathione cycle, a central biochemical process that is also intimately associated with the synthesis of the neurotransmitters glutamate and GABA and is connected to energy metabolism. Modifications in the activity of the glutathione cycle may provide treatment options.

Inactivation of misselected CD8 T cells by CD8 gene methylation and cell death

Misselected CD8 cells that express T cell receptors (TCRs) that do not recognize class I major histocompatibility complex (MHC) protein can emerge from thymic selection. A postthymic quality control mechanism that purges these cells from the repertoire is defined here. The failure of mature CD8 cells to simultaneously engage their TCR and CD8 coreceptor triggers an activation process that begins with inhibition of CD8 gene expression through remethylation and concludes with up-regulation of surface Fas and Fas ligand and cellular apoptosis. Thus, inhibition of a death signal through continued TCR-CD8 coengagement of MHC molecules is a key checkpoint for the continued survival of correctly selected T cells. Molecular defects that prevent delivery of the death signal to mistakenly selected T cells underlie the expansion of double-negative T cells, which is the cellular signature of a subset of systemic autoimmune diseases.

Activation of T cells by superantigen: cytokine production but not apoptosis depends on MEK-1 activity

Engagement of the TCR may result in proliferation and cytokine release or programmed cell death. These two outcomes may be the consequence of distinct T cell receptor-coupled signal transduction pathways or may reflect quantitative differences in signaling strength via a single pathway. Here we show that genetic inhibition of MAP kinase kinase (MEK) by a dominant negative mutant or through chemical inhibition by PD98059 inhibits IL-2 secretion but not programmed cell death after TCR ligation by superantigen. This supports the hypothesis that T cell cytokine release and apoptosis result from signaling through distinct pathways and implies that the molecular signaling mechanisms regulating apoptosis of mature T cells and negative selection of thymocytes may be similar.

Localization and treatment of an oxidation-sensitive defect within the TCR-coupled signalling pathway that is associated with normal and premature immunologic aging

The age-dependent decline in the ability of T-cells to mount a proliferative response both to mitogens and to receptor ligation is due to an age-related defect in signal transduction, since functional expression of receptors displayed by aged T-cells is not reduced. We show here that, although turnover of phosphatidylinositol is not diminished, total inositol-trisphosphate generation decreases after T-cell receptor (TCR) ligation, resulting in reduced flux of calcium. Defective inositol-trisphosphate generation may result from impaired activation of phospholipase C due to decreased tyrosine phosphorylation of this enzyme after ligation of CD3 in aged cells. Proliferation of aged T-cells, which is normally 10-30% of the level of young controls, was enhanced almost tenfold by glutathione or its precursor N-acetyl L-cysteine (NAC), reached levels of young controls and was accompanied by restoration of normal inositol-trisphosphate generation and calcium flux. These findings suggest that the T-cell antigen receptor is associated with at least two types of signal transduction modules. The first depends on synthesis and phosphorylation of phosphatidylinositol that is independent of sulphydryl groups and is not affected by senescence. The second transduction module includes tyrosine phosphorylation and activation of phospholipase C. This module is regulated by glutathione levels and is diminished in aged T-cells, that are deficient in reducing equivalents which support the PLC gamma-dependent generation of inositol-trisphosphate from phosphatidylinositol derivatives. This underlying biochemical defect also occurs earlier in strains which display premature aging due to differences in the H-2 region of MHC I.

Quality of care, process, and outcomes in elderly patients with pneumonia

CONTEXT

Pneumonia is a frequent cause of hospitalization and death among elderly patients, but the relationships between processes of care for pneumonia and outcomes are uncertain, making quality improvement a challenge.

OBJECTIVES

To assess quality of care for Medicare patients hospitalized with pneumonia and to determine whether process of care performance is associated with lower 30-day mortality.

DESIGN

Multicenter retrospective cohort study with medical record review.

SETTING

A total of 3555 acute care hospitals throughout the United States.

PATIENTS

A total of 14069 patients at least 65 years old hospitalized with pneumonia.

MAIN OUTCOME MEASURES

Four processes of care: time from hospital arrival to initial antibiotic administration; blood culture collection before initial hospital antibiotics; blood culture collection within 24 hours of hospital arrival; and oxygenation assessment within 24 hours of hospital arrival. Associations between processes of care and 30-day mortality were determined with logistic regression analysis.

RESULTS

National estimates of process-of-care performance were antibiotic administration within 8 hours of hospital arrival, 75.5% (95% confidence interval [CI], 73.1-77.9); blood cultures before antibiotics, 57.3% (95% CI, 54.5-60.1); initial blood culture collection, 68.7% (95% CI, 66.2-71.2); and initial oxygenation assessment, 89.3% (95% CI, 87.5-90.9). Lower 30-day mortality was associated with antibiotic administration within 8 hours of hospital arrival (odds ratio [OR], 0.85; 95% CI, 0.75-0.96) and blood culture collection within 24 hours of arrival (OR, 0.90; 95% CI, 0.81-1.00). State and territory performance estimates varied from 49.0% to 89.7% for antibiotics given within 8 hours and from 45.6% to 82.6% for blood cultures drawn within 24 hours.

CONCLUSIONS

Administering antibiotics within 8 hours of hospital arrival and collecting blood cultures within 24 hours were associated with improved survival. The fact that states varied widely in the performance of these measures suggests that opportunities exist to improve hospital care of elderly patients with pneumonia.

A novel Bcl-x isoform connected to the T cell receptor regulates apoptosis in T cells

We define a novel Bcl-x isoform, Bcl-x gamma, that is generated by alternative splicing and characterized by a unique 47 amino acid C-terminus. Bcl-x gamma is expressed primarily in thymocytes, where it may depend on an interaction between the TCR and host MHC products, and in mature T cells, where its expression is associated with ligation of the T cell receptor. Overexpression of Bcl-x gamma in T cells inhibits activation-induced apoptosis; inhibition of Bcl-x gamma, after stable expression of Bcl-x gamma antisense cDNA, enhances activation-induced apoptosis. In contrast to other Bcl-x isoforms, cells that fail to express Bcl-x gamma after CD3 ligation undergo programmed cell death, while activated T cells that express Bcl-x gamma are spared. Identification of Bcl-x gamma helps provide a molecular explanation of T cell activation and death after antigen engagement.

Measurement of apoptosis in heterogenous cell populations

The increasing interest in programmed cell death has created the need to measure apoptosis in complex cell systems. We have combined the use of fluorescent antibodies with the Hoechst 33342/propidium iodide system in order to quantitate programmed cell death in fractions of heterogenous cell populations. Here we describe the analysis of T-cell apoptosis after ligation of the T-cell antigen receptor by superantigen in vitro and ex vivo. This technique can separate cells according to seven parameters, fluorescence caused by FITC, PE, allophycocyanin, incorporation of Hoechst 33342, PI, forward scatter, and side scatter, and it allows determination of elevated Hoechst 33342 uptake in less than 10% of the cell population.

Interaction between CD44 and osteopontin as a potential basis for metastasis formation

Malignant growth has been associated with oncogene activation, telomerase activity, and expression of CD44 splice variants on the cell surface. Though dysregulation of growth control due to expression of oncogene products is fairly well understood, the mechanism of CD44-mediated homing and colony formation in specific tissues has remained cryptic. We have identified the cytokine osteopontin as a ligand for CD44. Osteopontin binds to naturally expressed and stably transfected CD44 in a manner that is specific, dose-dependent, inhibitable by anti-CD44 antibodies, insensitive to competition by Gly-Arg-Gly-Asp-Ser, and sensitive to competition by hyaluronate. The receptor-ligand interaction mediates chemotaxis or attachment, depending on presentation of osteopontin in soluble or immobilized form. In contrast, binding of CD44 to hyaluronate mediates aggregation or attachment but not chemotaxis. We found that two events occurring in malignancy-secretion of osteopontin and expression of CD44v-are linked in such a way that they may cause migration of tumor cells to specific sites of metastasis formation.

The immunology of Eta-1/osteopontin

The cytokine Eta-1/osteopontin is secreted by activated macrophages and may constitute the most abundant molecule secreted by activated T-lymphocytes. It causes macrophages to migrate and suppress production of reactive oxygen species. It enhances generation of immunoglobulins or proliferation of B-lymphocytes. Its biochemical characteristics suggest that Eta-1/osteopontin may be the T-lymphocyte suppressor factor. The apparently conflicting effects on individual immune functions may reflect homeostatic mechanisms.

Receptor-ligand interaction between CD44 and osteopontin (Eta-1)

The CD44 family of surface receptors regulates adhesion, movement, and activation of normal and neoplastic cells. The cytokine osteopontin (Eta-1), which regulates similar cellular functions, was found to be a protein ligand of CD44. Osteopontin induces cellular chemotaxis but not homotypic aggregation, whereas the inverse is true for the interaction between CD44 and a carbohydrate ligand, hyaluronate. The different responses of cells after CD44 ligation by either osteopontin or hyaluronate may account for the independent effects of CD44 on cell migration and growth. This mechanism may also be exploited by tumor cells to promote metastasis formation.

A signaling pathway coupled to T cell receptor ligation by MMTV superantigen leading to transient activation and programmed cell death

Stimulation of T cells by retroviral and bacterial super-antigens is followed by specific T cell elimination, in contrast with stimulation of T cells by peptide, which is usually associated with clonal expansion. We show here that this differential response phenotype is apparent at the level of individual T cell clones following TCR ligation with peptide or MTV antigen. We exploited selective coupling of apoptosis to TCR ligation by MTV7 to examine some of the intracellular biochemical events that underlie this response. MTV-dependent activation resulting in apoptosis was associated with activation of phospholipase A2 and the generation of reactive oxygen intermediates. Inhibition of these biochemical events prevented both MTV-dependent activation and apoptosis without affecting the peptide-dependent response of the same T cell clones. These results indicate that clonal expansion or programmed cell death following TCR ligation may be consequences of distinct TCR-coupled signaling pathways.

The pathophysiology of reactive oxygen intermediates in the central nervous system

Current evidence for the participation of free radicals in diseases of the central nervous system is reviewed. We conclude that the pathogenesis is based on a uniform mechanism: free radicals preferentially attack myelin, which contains easily peroxidizable phospholipids. The basal ganglia seem to be a brain area that is especially susceptible to radical damage which is possibly related to the synthesis of neurotransmitters. The clinical picture of the resulting cell death is dominated by convulsions and retardation in childhood and by psychomotoric disability and dementia in adulthood.

Phosphatidylinositol synthesis is a proximal event in intracellular signaling coupled to T cell receptor ligation. Differential induction by conventional antigen and retroviral superantigen

There is increasing evidence that at least two functionally distinct signal transduction pathways may be coupled to the TCR complex. A conventional signal transduction pathway coupled to TCR ligation by peptide/MHC complexes includes increased [Ca2+]i, phosphatidylinositol (PI) hydrolysis, and cytokine expression. TCR ligation by MIs-1a/MTV superantigens may be coupled to an alternative signal transduction pathway without increased [Ca2+]i or detectable PI hydrolysis. We asked whether early events in the PI hydrolytic pathway might account for differential levels of PI breakdown after TCR ligation by conventional Ag and superantigen. We show that TCR ligation by conventional peptide Ag is coupled to a burst of PI synthesis in nontransformed T cells, which may represent a rate-limiting step for downstream PI hydrolysis. Incorporation of radiolabeled glucose by newly synthesized PI as well as inositol-1,4,5-trisphosphate provided direct evidence that this intracellular pool of PI represents an important substrate for this signaling pathway. By contrast, TCR ligation of the same T cell clone by retroviral superantigen leads to similar levels of T cell proliferation without detectable PI synthesis. Increased levels of radiolabeled intracellular PI reflected de novo synthesis of PI from glucose-6-phosphate rather than recycling of inositol phosphates because labeled phosphate and glucose were incorporated into PI but extracellular [3H]inositol was not. These findings suggest that differential PI synthesis represents an early biochemical event that distinguishes two functionally distinct signaling pathways coupled to TCR ligation by peptide Ag and retroviral superantigen.

Phosphatidylinositol synthesis is a proximal event in intracellular signaling coupled to T cell receptor ligation. Differential induction by conventional antigen and retroviral superantigen

There is increasing evidence that at least two functionally distinct signal transduction pathways may be coupled to the TCR complex. A conventional signal transduction pathway coupled to TCR ligation by peptide/MHC complexes includes increased [Ca2+]i, phosphatidylinositol (PI) hydrolysis, and cytokine expression. TCR ligation by MIs-1a/MTV superantigens may be coupled to an alternative signal transduction pathway without increased [Ca2+]i or detectable PI hydrolysis. We asked whether early events in the PI hydrolytic pathway might account for differential levels of PI breakdown after TCR ligation by conventional Ag and superantigen. We show that TCR ligation by conventional peptide Ag is coupled to a burst of PI synthesis in nontransformed T cells, which may represent a rate-limiting step for downstream PI hydrolysis. Incorporation of radiolabeled glucose by newly synthesized PI as well as inositol-1,4,5-trisphosphate provided direct evidence that this intracellular pool of PI represents an important substrate for this signaling pathway. By contrast, TCR ligation of the same T cell clone by retroviral superantigen leads to similar levels of T cell proliferation without detectable PI synthesis. Increased levels of radiolabeled intracellular PI reflected de novo synthesis of PI from glucose-6-phosphate rather than recycling of inositol phosphates because labeled phosphate and glucose were incorporated into PI but extracellular [3H]inositol was not. These findings suggest that differential PI synthesis represents an early biochemical event that distinguishes two functionally distinct signaling pathways coupled to TCR ligation by peptide Ag and retroviral superantigen.

Differential activation of cyclophosphamide and ifosphamide by cytochromes P-450 2B and 3A in human liver microsomes

The present study identifies the specific human cytochrome P-450 (CYP) enzymes involved in hydroxylation leading to activation of the anticancer drug cyclophosphamide and its isomeric analogue, ifosphamide. Substantial interindividual variation (4-9-fold) was observed in the hydroxylation of these oxazaphosphorines by a panel of 12 human liver microsomes, and a significant correlation was obtained between these 2 activities (r = 0.85, P < 0.001). Enzyme kinetic analyses revealed that human liver microsomal cyclophosphamide 4-hydroxylation and ifosphamide 4-hydroxylation are best described by a 2-component Michaelis-Menten model composed of both low Km and high Km P-450 4-hydroxylases. To ascertain whether one or more human P-450 enzymes are catalytically competent in activating these oxazaphosphorines, microsomal fractions prepared from a panel of human B-lymphoblastoid cell lines stably transformed with individual P-450 complementary DNAs were assayed in vitro for oxazaphosphorine activation. Expressed CYP2A6, -2B6, -2C8, -2C9, and -3A4 were catalytically competent in hydroxylating cyclophosphamide and ifosphamide. Whereas CYP2C8 and CYP2C9 have the characteristics of low Km oxazaphosphorine 4-hydroxylases, CYP2A6, -2B6, and -3A4 are high Km forms. In contrast, CYP1A1, -1A2, -2D6, and -2E1 did not produce detectable activities. Furthermore, growth of cultured CYP2A6- and CYP2B6-expressing B-lymphoblastoid cells, but not of CYP-negative control cells, was inhibited by cyclophosphamide and ifosphamide as a consequence of prodrug activation to cytotoxic metabolites. Experiments with P-450 form-selective chemical inhibitors and inhibitory anti-P-450 antibodies were then performed to determine the contributions of individual P-450s to the activation of these drugs in human liver microsomes. Orphenadrine (a CYP2B6 inhibitor) and anti-CYP2B IgG inhibited microsomal cyclophosphamide hydroxylation to a greater extent than ifosphamide hydroxylation, consistent with the 8-fold higher activity of complementary DNA-expressed CYP2B6 with cyclophosphamide. In contrast, troleandomycin, a selective inhibitor of CYP3A3 and -3A4, and anti-CYP3A IgG substantially inhibited microsomal ifosphamide hydroxylation but had little or no effect on microsomal cyclophosphamide hydroxylation. By contrast, the CYP2D6-selective inhibitor quinidine did not affect either microsomal activity, while anti-CYP2A antibodies had only a modest inhibitory effect. Overall, the present study establishes that liver microsomal CYP2B and CYP3A preferentially catalyze cyclophosphamide and ifosphamide 4-hydroxylation, respectively, suggesting that liver P-450-inducing agents targeted at these enzymes might be used in cancer patients to enhance drug activation and therapeutic efficacy.

Denitrosation of the anti-cancer drug 1,3-bis(2-chloroethyl)-1-nitrosourea catalyzed by microsomal glutathione S-transferase and cytochrome P450 monooxygenases

The alkylating agent BCNU [1,3-bis(2-chloroethyl)-1-nitrosourea] can be inactivated through denitrosation reactions catalyzed by both cytosolic and microsomal enzymes. While previous studies have identified a class mu glutathione S-transferase [rat transferase 4-4 (Yb2)] as a major catalyst of the cytosolic denitrosation reaction, the enzymatic catalysts of BCNU denitrosation in microsomal membranes have not been identified. In the present study, both NADPH and glutathione (GSH) were found to support BCNU denitrosation catalyzed by isolated rat liver microsomes. Treatment of rats with the microsomal enzyme inducers phenobarbital and dexamethasone increased NADPH-dependent liver microsomal BCNU denitrosation up to fivefold without major effect on the GSH-dependent denitrosation activity. Although the NADPH-dependent activity was fully inhibited by antibody to NADPH-P450 reductase, purified NADPH-P450 reductase catalyzed BCNU denitrosation at rates that could only account for approximately 2-3% of the microsomal activity. Other experiments, including selective inhibition of NADPH-dependent microsomal BCNU denitrosation by chemical and antibody inhibitors of cytochrome P450, competitive inhibition of P450-catalyzed cyclophosphamide and ifosfamide activation by BCNU, and reconstitution of the denitrosation reaction by purified P450 enzyme 2B1 (major phenobarbital-inducible P450 form), established an important role for cytochrome P450 in BCNU denitrosation. By contrast, GSH-dependent microsomal BCNU denitrosation was unaffected by cytochrome P450 inhibitors, but was inhibited, with varying degrees of selectivity, by the microsomal glutathione S-transferase inhibitors ethacrynic acid, bromosulfophthalein, and indomethacin. These studies establish that BCNU inactivation can be catalyzed by two independent microsomal enzyme systems and suggest that therapeutically useful improvements in BCNU antitumor activity might be achieved through differential inhibition of these enzyme systems in tumor as compared to extratumoral sites.

HIV glycoprotein as a superantigen. A mechanism of autoimmunity and implications for a vaccination strategy

The pathogenic effects of HIV may reflect mimicry of several key immunological molecules. The surface glycoprotein of HIV has superantigenic properties responsible for the sequential deletion of T-cell clones. In addition, the glycoprotein has several regions sharing homology with class II MHC products. It can elicit cross-reactive antibodies which block replenishment of these T-cells in the thymus. The usefulness of conventional vaccination strategies in the fight against AIDS has been subject to debate. Based on these considerations, we argue that effective vaccines should avoid viral sequences homologous to class II MHC proteins which might exacerbate this process.

Activation of the anti-cancer drug ifosphamide by rat liver microsomal P450 enzymes

The NADPH-dependent metabolism of ifosphamide catalyzed by rat liver microsomes was investigated in order to identify individual P450 enzymes that activate this anti-cancer drug and to ascertain their relationship to the P450 enzymes that activate the isomeric drug cyclophosphamide. Pretreatment of rats with phenobarbital or clofibrate increased by up to 8-fold the activation of both ifosphamide and cyclophosphamide catalyzed by isolated liver microsomes. Studies using P450 form-selective inhibitory antibodies demonstrated that constitutively expressed P450s belonging to subfamily 2C (forms 2C11/2C6) make significant contributions to the activation of both oxazaphosphorines in uninduced male rat liver microsomes, while the phenobarbital-inducible P450 2B1 was shown to be a major catalyst of these activations in phenobarbital-induced microsomes. Pretreatment of rats with dexamethasone increased liver microsomal activation of ifosphamide approximately 6-fold without a corresponding effect on cyclophosphamide activation rates. Ifosphamide activation catalyzed by dexamethasone-induced liver microsomes was minimally inhibited by anti-P450 2B or anti-P450 2C antibodies, but was selectively inhibited by anti-P450 3A antibodies. Selective inhibition of liver microsomal ifosphamide activation was also effected by the macrolide antibiotic triacetyloleandomycin, an inhibitor of several dexamethasone-inducible 3A P450s. These studies establish that a dexamethasone-inducible family 3A P450 can make an important contribution to rat liver microsomal ifosphamide activation, and suggest that dexamethasone pretreatment might provide a useful approach for modulation of ifosphamide metabolism in order to improve its therapeutic efficacy in cancer patients.

Platinum anticancer drugs modulate P-450 mRNA levels and differentially alter hepatic drug and steroid hormone metabolism in male and female rats

Treatment of male rats with the anticancer drug cisplatin leads to feminization of the profile of cytochrome P-450 and other microsomal enzymes involved in steroid hormone and drug metabolism (G.A. LeBlanc, and D.J. Waxman, J. Biol. Chem., 263: 15732-15739, 1988). The present study uses the rat model to evaluate the differential effects of cisplatin treatment on liver microsomal enzymes between genders, and also examines whether the modulation of enzyme activities by cisplatin and its analogues involves changes in P-450 gene expression. While cisplatin treatment of male rats caused a severalfold increase in female-predominant hepatic enzymes, including testosterone 5 alpha-reductase and testosterone 7 alpha-hydroxylase (P-450 form 2A1), it partially decreased the expression of these enzymes in females. The reduced expression of these estrogen-dependent enzymes in females may derive from the loss of circulating estradiol that was shown to occur in response to cisplatin treatment. Analysis of mRNA levels of individual P-450 forms revealed that the effects of cisplatin on P-450-catalyzed steroid hydroxylase activities in both male and female rats are primarily operative through the drug's effects on P-450 mRNA expression. P-450-dependent cyclophosphamide activation was significantly compromised in male rats after cisplatin administration; however, this activity was not altered in cisplatin-treated females. This sex-dependent effect of cisplatin was due to its suppression of P-450 form 2C11, a male-specific P-450 that is a major contributor to microsomal cyclophosphamide bioactivation in male rat liver. The clinically active cisplatin analogue iproplatin elicited effects very similar to those of cisplatin, while carboplatin and transplatin did not have significant effects on hepatic P-450 expression. Together, these findings demonstrate that the response of rat liver to cisplatin-induced changes in hepatic P-450 enzyme profiles and cyclophosphamide bioactivation capacity differs between the sexes, and in addition, these effects can be minimized by use of carboplatin in place of cisplatin.

Inhibition of the neutrophil NADPH oxidase by folic acid and antagonists of the folic acid metabolism

The influence of folic acid and several antagonists of the folic acid metabolism on neutrophil superoxide generation was investigated with the cytochrome c reduction assay. The compounds were found to be partial competitive inhibitors of the NADPH oxidase, their activity apparently increasing with larger substituents at the 10 position. There is evidence that compounds with a 4-oxo substituent are taken up more slowly by neutrophils than those with a 4-amino functionality. Scavenging properties could be excluded from control measurements with the xanthine/xanthine oxidase assay.

Glutathione peroxidase deficiency and childhood seizures

4 children with intractable seizures, repeated infections, and intolerance to anticonvulsants had evidence of glutathione peroxidase deficiency. 2 had low intracellular enzyme activity but normal blood selenium and high plasma glutathione peroxidase concentrations. The other 2 had low intracellular glutathione peroxidase activity with low circulating glutathione peroxidase and selenium concentrations. The clinical state of the children improved after discontinuation of anticonvulsant medication and selenium substitution.

The antifolate 10-deazaaminopterin inhibits neutrophil chemotaxis and superoxide generation

The effect of the dihydrofolate reductase inhibitor 10-deazaaminopterin on several neutrophil functions was tested in vitro. At 100 uM it inhibited chemotaxis by 50% and reduced the generation of superoxide by 30%. It had no influence on phagocytosis and did not significantly change the secretion of beta-D-glucuronidase, a marker enzyme of degranulation. After preincubation of white cells with various concentrations of 10-deazaaminopterin, followed by resuspension in drug-free medium, no inhibition of chemotaxis or superoxide generation was seen. Therefore, the effects on chemotaxis and NADPH oxidase appear to be reversible and not due to metabolic transformation of the dihydrofolate reductase inhibitor.

The measurement of oxygen-derived free radicals and related substances in medicine

Due to the high reactivity of the chemical species and the presence of multiple potentially interfering substances, the measurement of oxygen-derived free radicals in biological material requires highly developed techniques. The currently employed methods are reviewed according to the reactions upon which they are based, the assays, possible interferences and their use in medical research. Detection of the emission of light is a very popular method. Although it is in principle unspecific, there are modifications to measure individual radical species. The only direct way to detect radicals is electron spin resonance spectroscopy. Among the specific assays for O2- the reductions of nitroblue tetrazolium or cytochrome c are predominant. For the detection of H2O2 different techniques are employed for either intracellular or extracellular determination. An array of substances has been used for the measurement of OH. Which of them is the most useful depends on the question to be answered. There are also indirect methods that determine free radicals based on chemical modifications caused by them; the most important assays of this kind quantify lipid peroxides. In addition, assays for thiobarbituric acid-reactive substances and DNA strand breaks and interstrand crosslinks are used.

Galactosyltransferase variant in pleural effusion

In measuring total galactosyltransferase activity in the pleural effusions from patients with benign or malignant diseases, we found no significant difference between the two groups (p greater than 0.05). However, a small amount of a galactosyltransferase variant, GT(l), could be separated from other galactosyltransferase enzymes in malignant pleural effusions by anion-exchange chromatography (DEAE-cellulose) with a buffer of low ionic strength. Other galactosyltransferases were eluted from the column with buffer of higher ionic strength. Using a mini-column method, we detected GT(l) enzyme in 19 of 26 specimens fro cancer patients, as compared with eight of 25 specimens from patients with benign disorders. The appearance of GT(l) enzyme in pleural effusion may be a tumor-associated phenomenon.

Galactosyltransferase variant in pleural effusion

In measuring total galactosyltransferase activity in the pleural effusions from patients with benign or malignant diseases, we found no significant difference between the two groups (p greater than 0.05). However, a small amount of a galactosyltransferase variant, GT(l), could be separated from other galactosyltransferase enzymes in malignant pleural effusions by anion-exchange chromatography (DEAE-cellulose) with a buffer of low ionic strength. Other galactosyltransferases were eluted from the column with buffer of higher ionic strength. Using a mini-column method, we detected GT(l) enzyme in 19 of 26 specimens fro cancer patients, as compared with eight of 25 specimens from patients with benign disorders. The appearance of GT(l) enzyme in pleural effusion may be a tumor-associated phenomenon.

Extraction of human plasma or sera by heat treatment for a solid-phase radioimmunoassay of carcinoembryonic antigen

Heat treatment and a solid-phase radioimmunoassay are combined to give a relatively simple and rapid procedure for assay of carcinoembryonic antigen in plasma or serum. The new way we describe to extract this antigen is an alternative to the conventional method of extraction with perchloric acid. Heating plasma or serum samples in acetate buffer (0.16 mol/L, pH 5.0) at 70 degrees C for 15 min precipitates out most of the heat-labile, nonspecific plasma proteins, but leaves most of the antigen in solution, with its immunochemical properties apparently unaffected. Comparison between the heat treatment and the perchloric acid extraction yielded comparable values when tested either by solid-phase radioimmunoassay or by the zirconyl phosphate precipitation method. An added advantage of our method is that it gives the same assay values for both plasma and serum. Results for a group of pathological plasma samples, assayed by both our method and the perchloric acid-zirconyl phosphate precipitation method, gave a correlation coefficient of 0.90.

Nature of human serum blood group T antibodies

Antibodies against blood group substance T in normal human sera consist of two types, depending upon whether or not the molecules remain immunochemically active at 37 degrees C. The two agglutinins were isolated by means of T antigen-coupled Sepharose 48 affinity chromatography. Temperature-sensitive agglutinin was eluted from the affinity column at 37 degrees C, while temperature-independent agglutinin remained bound to the antigen. Subsequently, the latter was dissociated from the column in the presence of 2.5 M MgCl2. Examination of six normal sera revealed that the levels of temperature-independent agglutinin was about twice that of temperature-sensitive agglutinin. More than 90% of anti-T agglutinins in normal sera were of the IgM class, in 8 of 11 samples studied. No direct relationship appeared to exist between anti-T titers and blood type. Thermal effects on hemagglutination, at least for anti-T agglutinin interacting with T antigen bearing red cells, is primarily due to the molecular characteristics of the agglutinin and not to the conformational change of the red cell membranes.