Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables.

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

[Susceptibility gene to infarct: a review of the literature]. / I geni di suscettibilità all'infarto: una revisione della letteratura.

The investigation on the susceptibility genes of myocardial infarction has initiated substantially in the last 20 years. Most efforts have been mainly addressed to identify and evaluate genes involved in those systems already suspected to be implicated in the pathogenesis of coronary heart disease. Principal examples are lipid metabolism, coagulation and fibrinolytic systems, membrane receptors of platelets, levels of plasma homocysteine and vascular tone. Therefore up to now, the identification of the genetic factors of myocardial infarction has been carried out through case-control association studies employing a "candidate gene" approach. This method has often led to controversial results, usually difficult to compare. This is an attempt to provide a progress report on the principal susceptibility genes of coronary heart disease.

[PROCARDIS: A current approach to the study of the genetics of myocardial infarct]. / Il PROCARDIS: un approccio attuale allo studio della genetica dell'infarto miocardico.

Coronary artery disease is a complex and multifactorial pathology. Although the environmental component of coronary artery disease has been thoroughly investigated and is hence well known, knowledge about the genetic factors implicated in this disease is still scarce. Technological advances and the fact that the Human Genome Project has almost been completed allow the application of approaches that were not feasible few years ago to the genetic investigation of complex diseases. The aim of the PROCARDIS study is to identify new susceptibility genes of precocious coronary artery disease, through a genome-wide screen applying statistical methods of linkage analysis followed by a family-based association study. The originality of PROCARDIS lies in the fact that it is an international multicenter study. This allows recruitment of a very large number of individuals so that the population size, considered up to now unachievable, is adequate for the aims of the study.

Apoptosis by anthracyclines at therapeutic concentrations in MDR1+ human leukemic cells.

Induction of apoptosis by daunorubicin (DNR) and idarubicin (IDA) was evaluated cytofluorometrically in CEM and CEM-MDR1+ leukemic cells exposed to drug concentrations similar to peak plasma levels obtainable in vivo (DNR 200-400 ng/ml, IDA 50-100 ng/ml, 30' incubation), and differentiating apoptosis from necrosis (FITC-annexin V+/propidium iodide- and + cells, respectively). Firstly, to set experimental conditions, apoptosis was evaluated in CEM cells at 3, 6, 12, 18, 24, 48, 72, and 96 hours from end of drug incubation, the maximal increase being noted at 24-48 hours. Net apoptosis rates were determined after subtraction of the spontaneous activity observed in untreated cells. The apoptotic effect from varying drug type and concentration was compared at 24 hours in CEM-MDR1+ cells, with and without co-incubation with MDR1 functional downregulator cyclosporin A (CSA) used at therapeutic concentration (1500 ng/ml). The results indicated that, at drug concentrations likely to be approached in vivo as a short-lasting peak level (IDA 100-200 ng/ml) with increased-dose IDA (> 12-15 mg/m2), pro-apoptotic effects by IDA+CSA in CEM-MDR1+ cells were significantly greater than by DNR+CSA, and corresponded to the levels observed with IDA 50 ng/ml without CSA in control CEM cells. This in vitro study demonstrates that it is possible to determine in the same sample cell fluorescence related to anthracyclines, apoptotic cells (FITC-annexin V positive), and necrotic cells (propidium iodide positive), and confirms that cytofluorimetric evaluation of apoptosis can reliably predict the effects of anthracycines in function of drug type, concentration and, in MDR1+ cells, concurrent MDR1 inhibition. Extension of this assay to the clinical ground may be warranted.

Primary effusion lymphoma after heart transplantation: a new entity associated with human herpesvirus-8.

Deep immunosuppression and Epstein-Barr virus (EBV) infection promote the emergence of lymphoproliferative disorders in patients undergoing solid organ transplantation. In the last few years a new herpesvirus, named human herpesvirus-8 (HHV-8), has been identified in Kaposi's sarcoma and primary effusion lymphoma (PEL) developing in AIDS patients. Subsequently, the same viral DNA sequences have been identified in almost all cases of Kaposi's sarcoma emerged outside HIV infection, thus suggesting their possible pathogenetic role in this tumor. Similarly, the association between HHV-8 and PEL also emerged in cases without HIV infection, even though the total number of these patients is still limited. Here, we focus on the emergence of this unusual lymphoma in patients undergoing solid organ transplant and underline once again its association with the HHV-8. Moreover, despite the characteristic local growth of this peculiar type of lymphoma, we demonstrate at the molecular level, an early neoplastic spread to the bone marrow suggesting the need to investigate in more detail the origin of the disease, as well as the molecular mechanisms controlling its systemic dissemination.

Cellular uptake and antiproliferative effects of therapeutic concentrations of idarubicin or daunorubicin and their alcohol metabolites, with or without cyclosporin A, in MDR1+ human leukemic cells.

Ways of restoring an altered drug sensitivity in P-170 glycoprotein (MDR1) positive leukemias are being actively sought for, mostly using MDRI negative regulators together with the MDR1-sensitive anthracycline-type drugs daunorubicin and mitoxantrone. Because idarubicin is less vulnerable to MDR1-mediated transport and could thereby represent a better companion to MDR1 inhibitors, we assessed the ability of the anti-MDR1 agent cyclosporin A to modulate this function in multidrug resistant T-lymphoblastic CEM cells challenged in vitro with either daunorubicin or idarubicin. In order to obtain information of potential interest for the design of a clinical trial, we adopted drug plus metabolite concentrations and exposure times close to the in vivo pharmacokinetics of equimyelotoxic doses of intravenous daunorubicin 45 mg/m2 or idarubicin 10-12 mg/m2, respectively, plus infusional cyclosporin A 16 mg/kg/d. Study methods were cytofluorimetry for the detection of intracellular drug uptake, retention and pro-apoptotic effects (binding of fluoresceinated annexin V), and the standard MTT assay as growth inhibition test. The results showed significantly greater drug uptake (at 30'), retention (at 12 hours), and apoptotic cell rates with idarubicin+/-idarubicinol than daunorubicin+/-daunorubicinol (p<0.05), and a further potentiation of these effects by cyclosporin A. Differing from daunorubicin, idarubicin intracellular accumulation and, by inference, related apoptotic changes were increased by cyclosporin A only in the early phase of drug-cell interaction; a potential advantage towards a reduced toxicity by CsA delivered as short rather than prolonged infusion in the in vivo setting. MTT assay results were also in favour of idarubicin but greatly influenced by cyclosporin A itself. Altogether, study results in MDR1+ cells incubated with CsA 1500 ng/ml plus idarubicin+idarubicinol 100+20 ng/ml, that are peak levels achievable in vivo with an idarubicin dose > or = 12 mg/m2 plus cyclosporin A 16 mg/kg/d, were in the range of those obtained with standard-dose daunorubicin in MDR1- cells (p=n.s.). In summary, an idarubicin plus short-course cyclosporin A combination could be considered for the management of MDR1+ leukemias, where it may represent a more effective and less toxic option than daunorubicin plus continuous infusion cyclosporin A.

Short course infusional idarubicin plus intermittent cytarabine and etoposide for refractory hematologic malignancies: clinical and preliminary pharmacological results.

BACKGROUND AND OBJECTIVE: Idarubicin (IDA) is relatively immune to the multidrug resistance P-gp mechanism that is frequently expressed in recurrent and refractory hematologic malignancies. Owing to rapid metabolism in vivo, a continuous infusion (CI) of IDA might prolong exposure time to the parent drug rather than its more P-gp susceptible alcohol metabolite. For this reason we developed a brief retreatment schedule incorporating CI IDA in order to obtain clinical as well as preliminary pharmacological data in patients with refractory leukemias and lymphomas. DESIGN AND METHODS: Eligible patients had either advanced-stage acute myeloid or lymphoid leukemias (AML, ALL) or high-grade non-Hodgkin's lymphomas (NHL) which failed curative-intent frontline or salvage regimens in use at our institution during the study period (July-October 1992). CI IDA 5 mg/m2/d was employed together with intermittent (every 8 hours) intermediate-dose cytarabine (500 mg/m2) and etoposide (200 mg/m2); all drugs were given for 2-4 days. A preliminary pharmacokinetic evaluation of CI IDA was carried out in three patients, including a comparison with bolus delivery in one. The in vitro effects of CI-type vs bolus-type IDA delivery in terms of intracellular IDA accumulation and related pro-apoptotic activity were assessed in P-gp- and P-gp+ human leukemic CEM cells by means of cytofluorimetry (IDA fluorescence intensity = FI, annexin V expression), with and without the addition of P-gp inhibitor cyclosporin A (CsA). RESULTS: Complete (2) or partial (4) responses were achieved in a total of 12 patients (17% and 33%, respectively), despite prior treatments with anthracyclines (100% of cases) and cytarabine-etoposide (33% of cases). Hematological toxicity caused the duration of treatment to be reduced from 4 days to 2 days after the first 4 patients. The procedural death rate was 42% (5/12), which was probably related in part to the sum of adverse prognostic characteristics: median patient age 55 years, two-thirds of cases having previously failed second/third-line regimens. The pharmacokinetic study showed an increased plasma AUC value with CI IDA in one patient (2.9-fold increase vs bolus delivery) due to the prolonged presence of low IDA plasma levels (10-20 ng/mL vs 50 ng/mL), as seen in two other cases as well. On the other hand, the in vitro study did not prove to be in favor of CI IDA because the FI threshold (> 1500 units) associated with increased apoptosis of P-gp+ cells (> 10%) was achieved only with bolus-type IDA exposure (50 ng/mL for 30') plus CsA. INTERPRETATION AND CONCLUSIONS: This short regimen demonstrated activity against end-stage leukemias and lymphomas and might prove to be more effective and less toxic in younger patients and in those with less advanced disease. In view of the results from plasma pharmacokinetics and in vitro intracellular IDA accumulation and apoptosis assays in lymphoblastic CEM cells, CI IDA 5 mg/m2/day may not represent a better therapeutic option than a rapid bolus injection, particularly in P-gp+ neoplasms. If obtaining an adequate intracellular drug concentration is the primary treatment goal, a higher CI IDA dosage, the addition of a P-gp down-regulator such as CsA and others, and in vivo study focusing on tumor samples from patients could all be helpful.

Sequential arousal and airway-defensive behavior of infants in asphyxial sleep environments.

Infants are prone to accidental asphyxiation. Therefore, we studied airway-defensive behaviors and their relationship to spontaneous arousal behavior in 41 healthy sleeping infants (2-26 wk old), using two protocols: 1) infant was rebreathing expired air, face covered by bedding material; and 2) infant was exposed to hypercarbia, face uncovered. Multiple measurements of respiratory and motor activities were recorded (video, polygraph). The infants' response to increasing hypercarbia consisted of four highly stereotyped behaviors: sighs (augmented breaths), startles, thrashing limb movements, and full arousal (eyes open, cry). These behaviors occurred abruptly in self-limited clusters of activity and always in the same sequence: first a sigh coupled with a startle, then thrashing, then full arousal. Incomplete sequences (initial behaviors only) occurred far more frequently than the complete sequence and were variably effective in removing the bedding covering the airway. In both protocols, as inspired CO2 increased, incomplete arousal sequences recurred periodically and with increasing frequency and complexity until the infant either succeeded in clearing his/her airway or was completely aroused. Spontaneous arousal sequences, identical to those occurring during hypercarbia, occurred periodically during sleep. This observation suggests that the infant's airway-defensive responses to hypercarbia consist of an increase in the frequency and complexity of an endogenously regulated, periodically occurring sequence of arousal behaviors.

The role of idarubicin in adult acute lymphoblastic leukaemia: from drug resistance studies to clinical application.

Idarubicin (4-demethoxydaunorubicin) is more potent and less cardiotoxic than daunorubicin or doxorubicin. These properties suggested a role in acute myelogenous leukaemia, that was confirmed by prospective randomized trials. In acute lymphoblastic leukaemia of adults, on the contrary, there is very little information regarding idarubicin. We have used idarubicin since 1991 and found, in a retrospective comparison with a doxorubicin regimen, a decreased incidence of primarily refractory disease. The role of idarubicin in the postremission phase could not be assessed in detail but an early intensive use of anthracyclines, either idarubicin or doxorubicin, was associated with an improved outcome in early-B CD10+ and t(9;22)/BCR-leukaemias. Concurrent in vitro studies demonstrated that idarubicin, at pharmacologically relevant concentrations, was less sensitive to P-glycoprotein-mediated drug efflux than daunorubicin and was a more effective agent to use with cyclosporin-A to circumvent this drug resistance mechanism. Idarubicin is a very effective drug for the early management of adult acute lymphoblastic leukaemia and may be presently considered (along with cyclosporin-A or other modulator) as the reference anthracycline for cases overexpressing the P-glycoprotein drug resistance mechanism.

Impaired ventilation in infants sleeping facedown: potential significance for sudden infant death syndrome.

Although accidental suffocation has been suggested as a cause of sudden infant death syndrome in infants who are found prone with their faces straight down, the occurrence and effects on breathing of this position in living infants are unknown. We studied prone sleeping infants to see whether they will sleep with their faces straight down; whether they can spontaneously change from this position; the way that thermal stimuli or bedding softness influences this change; and whether rebreathing or airway obstruction occurs. We studied 11 healthy infants, aged 0.2 to 6 months, while they slept on soft and on firm bedding. Most infants slept facedown spontaneously or when turned to this position. All could turn their heads readily but slept facedown for variable periods. All infants put their faces straight down more often after cold than after warm stimuli. Obstructive apnea occurred only once, but rebreathing occurred in all subjects. When the infants were in the facedown position, inspired carbon dioxide was three times greater on soft than on hard bedding. End-tidal carbon dioxide partial pressure rose in all subjects while they were in the facedown position; in one infant, high end-tidal carbon dioxide partial pressure and desaturation occurred without signs of arousal. We conclude that infants sleeping facedown may occasionally have significant asphyxia; this sleep position may have a role in some infant deaths diagnosed as sudden infant death syndrome.