Predicting hematological toxicity (myelosuppression) of cytotoxic drug therapy from in vitro tests

Several clinical oncology units are studying the roles of in vitro hematotoxicology in phase I evaluations. At the same time, the European Center for the Validation of Alternative Methods (ECVAM) is supporting a validation study of the CFU-GM assay [13]. It is important that these activities be coordinated so that high-performance, optimized technical protocols are used for prospective and retrospective clinical evaluations. The EORTC, the NCI, and ECVAM could provide support for these coordinated efforts. There is an opportunity for medical oncologists involved in early clinical trials to participate in the evaluation of in vitro tests and their clinical application. Fundamental to acceptance of these assays by oncologists and regulatory scientists, they must predict clinical outcome for myelosuppressive agents and then improve phase I design and performance. These achievements would justify more aggressive dose escalation schemes using guidance from in vitro studies without compromising patient safety. Success in predicting neutropenia might also stimulate the research required to understand how to predict other hematologic toxicities, such as thrombocytopenia.The complexity of a validation study in hematotoxicology is that it seeks to predict the level of exposure that causes neutropenia, in contrast to other validation studies that have sought to classify a xenobiotic as toxic or not. It may be that the clinical relevance of a new assay is not just a yes–no answer. This important distinction came from the realization that the xenobiotic tolerance in other organ systems of the body must be the same or greater than marrow in order for myelosuppression to be a clinical consequence of exposure. Pharmacological principles of systemic exposure and toxicity that are integrated into the prediction model provide the links to clinical oncology.It is also important to anticipate future applications of in vitro hematotoxicology. If the maximum tolerated level of drug exposure for human hematopoietic cells can be predicted, then in vitro hematotoxicology could play an important role in new drug discovery. One concept involves screening for compounds that show efficacy at the IC level that predicts maximum tolerated exposure levels in the human [12, 22]. 'Therapeutic index-based' drug discovery has been applied to the tallimustine family with some success [21].     

Schizencephaly: diagnosis and progression in utero

Schizencephaly is an unusual condition of obscure etiology. Most theories of pathogenesis postulate an in utero insult leading to maldevelopment rather than destruction of brain. The cause has most often been described as vascular or idiopathic dysgenesis. The authors report a case in which two in utero ultrasound (US) examinations performed at 31 and 36 menstrual weeks demonstrated progressive deterioration of the relatively narrow, symmetrical clefts connecting the lateral ventricles with the subarachnoid space into broad defects that corresponded to the entire distribution of the middle cerebral arteries. The findings in this case document progressive destruction of brain tissue in utero and are consistent with a vascular cause rather than a failure of formation of portions of the cerebral mantle.     

Akt1/protein kinase Balpha is critical for ischemic and VEGF-mediated angiogenesis

Akt, or protein kinase B, is a multifunctional serine-threonine protein kinase implicated in a diverse range of cellular functions including cell metabolism, survival, migration, and gene expression. However, the in vivo roles and effectors of individual Akt isoforms in signaling are not explicitly clear. Here we show that the genetic loss of Akt1, but not Akt2, in mice results in defective ischemia and VEGF-induced angiogenesis as well as severe peripheral vascular disease. Akt1 knockout (Akt1-/-) mice also have reduced endothelial progenitor cell (EPC) mobilization in response to ischemia, and reintroduction of WT EPCs, but not EPCs isolated from Akt1-/- mice, into WT mice improves limb blood flow after ischemia. Mechanistically, the loss of Akt1 reduces the basal phosphorylation of several Akt substrates, the migration of fibroblasts and ECs, and NO release. Reconstitution of Akt1-/- ECs with Akt1 rescues the defects in substrate phosphorylation, cell migration, and NO release. Thus, the Akt1 isoform exerts an essential role in blood flow control, cellular migration, and NO synthesis during postnatal angiogenesis.     

MyD88-dependent, superoxide-initiated inflammation is necessary for flow-mediated inward remodeling of conduit arteries

Vascular remodeling normalizes abnormal hemodynamic stresses through structural changes affecting vessel size and wall thickness. We investigated the role of inflammation in flow-mediated vascular remodeling using a murine model of partial outflow reduction without flow cessation or neointima formation. Common carotid arteries decreased in size after ipsilateral external carotid artery ligation in wild-type mice, but not in myeloid differentiation protein-88 (MyD88)–deficient mice. Inward remodeling was associated with MyD88-dependent and superoxide-initiated cytokine and chemokine production, as well as transient adventitial macrophage accumulation and activation. Macrophage depletion prevented flow-mediated inward vascular remodeling. Expression of MyD88 by intrinsic vascular cells was necessary for cytokine and chemokine production and changes in vessel size, whereas MyD88 expression by bone marrow–derived cells was obligatory for changes in vessel size. We conclude that there are at least two distinct roles for MyD88 in flow-mediated inward remodeling of conduit arteries. Our findings suggest that inflammation is necessary for vascular adaptation to changes in hemodynamic forces.     

Low-Dose Anti-T Lymphoglobulin as Prophylaxis for Graft-versus-Host Disease in Unrelated Donor Transplantations for Acute Leukemias and Myelodysplastic Syndromes

Chronic graft-versus-host disease (cGVHD) is a major complication after stem cell transplantation (HSCT). Several randomized studies already demonstrated that anti-T lymphoglobulin (ATLG) is effective in preventing GVHD after myeloablative unrelated and HLA-identical sibling transplants. However, the issue of doses and the potential increase of relapses still remain unsolved. Here we report data on 190 patients with acute leukemia and myelodysplastic syndrome who underwent an unrelated HSCT with low-dose ATLG (15 to 30 mg/kg) given at an earlier timing (days –6 to –2). HSCT was performed from HLA 10/10 (n?=?62, 33%), 9/10 (n?=?91, 48%), 8/10 (n?=?30, 16%), and <8/10 (n?=?7, 4%) identical unrelated donor. Peripheral blood was the stem cell source in 42% (n?=?80). Median follow-up was 51 months. Grades II to IV and III to IV acute GVHD were 26% and 9%, respectively, and 2-year overall and moderate to severe cGVHD were 23% and 14%, respectively. The 3-year incidences of relapse and nonrelapse mortality were 26% and 18%, respectively. The rates of 3-year overall survival (OS), disease-free survival (DFS), and GVHD-free and relapse-free survival (GRFS) were 60%, 56% and 44%, respectively. Factors such as younger donor, good performance status, and early disease were associated with better outcome in terms of OS, DFS, and GRFS. Our data indicate that doses of ATLG lower that those used in randomized clinical trials can be used for GVHD prevention, even in the adult setting, without clear increases in relapse and infections; these findings need to be further validated by a prospective randomized study.     

Entry screening to delay local transmission of 2009 pandemic influenza A (H1N1)

Background  

After the WHO issued the global alert for 2009 pandemic influenza A (H1N1), many national health agencies began to screen travelers on entry in airports, ports and border crossings to try to delay local transmission.     

Characterization of new arylsulfatase A gene mutations reinforces genotype‐phenotype correlation in metachromatic leukodystrophy

Metachromatic Leukodystrophy (MLD) is a rare inherited lysosomal storage disorder caused by the deficiency of Arylsulfatase A (ARSA). The disease manifests itself with a broad spectrum of clinical variants, all characterized by progressive neurodegeneration in the central and peripheral nervous systems. The correlation between mutations in the ARSA gene, residual enzymatic activity associated with the mutated alleles and patients' phenotype, which has been extensively drawn for common ARSA mutations, has recently been expanded to rare ones. In this context, functional studies on the rare allelic variances acquire particular relevance for patients' prognostic evaluation. Here we have characterized eight newly identified ARSA mutations, through lentiviral vector‐based expression studies on cell lines and ARSA defective murine fibroblasts. In each case, the residual activity associated with the new mutant allele correlates well with the patient's phenotype. Therefore, our results confirm the importance of functional characterization of mutant alleles for a precise genotype‐based classification and definition of prognosis in MLD patients, which is particularly relevant for pre‐symptomatic diagnosis. © 2009 Wiley‐Liss, Inc.