Richard A. Wells

Practical recommendations on the use of lenalidomide in the management of myelodysplastic syndromes

Lenalidomide, an oral immunomodulatory agent, has received approval in the USA from the Food and Drug Administration (FDA) for the management of myelodysplastic syndromes (MDS) classified by the International Prognostic Scoring System (IPSS) as low risk or intermediate-1 risk and with a deletion 5q (del(5q)) cytogenetic abnormality. Although some patients with del(5q) have a relatively good prognosis, all del(5q) patients will become transfusion-dependent at some point during the course of their disease. The results of two clinical trials in more than 160 patients with MDS have demonstrated clear therapeutic benefits of lenalidomide, with >60% of patients achieving independence from transfusion during therapy, irrespective of age, prior therapy, sex, or disease-risk assessment. The recommendations presented in this review will aid the safe administration of lenalidomide for the treatment of patients with low-risk or intermediate-1-risk MDS and a del(5q) cytogenetic abnormality, and they will help physicians avoid unnecessary dose reduction or interruption, thus assuring the best efficacy for patients.

First among equals: The cancer cell hierarchy

Primary cancer cells exhibit heterogeneity in their proliferative ability. The cancer stem cell (CSC) model accounts for this heterogeneity by proposing that each cancer consists of a small population of CSCs that are capable of unlimited growth and self-renewal and a much larger population of cells, descendants of the CSCs, that have lost self-renewal capacity. The CSC model has important implications for cancer therapy. Eradication of CSCs, the cells responsible for maintenance of the neoplasm, would be necessary and sufficient to achieve cure. By extension, both the frequency of stem cells in a tumor and their propensity to undergo self-renewal (Psr) would have a direct impact on the curability of that tumor. The Psr is a critical biological characteristic of CSCs—small differences in Psr have enormous impact on the probability of success in cancer therapy. Differentiation therapy, defined as treatment that reduces the Psr of CSCs, is one approach to targeting CSCs.

5-Azacytidine in myelodysplastic syndromes: A clinical practice guideline

BACKGROUND Myelodysplastic syndrome (MDS) is a clonal disorder of hematopoiesis that results in peripheral blood cytopenias and a marked propensity to progress to acute myelogenous leukemia. With 40,000-76,000 new cases per year in the USA, MDS is the commonest of the hematological malignancies and represents a significant burden of morbidity and premature death. Although supportive or palliative measures such as blood transfusion have long been the mainstay of management of MDS, disease-modifying medical therapies have recently become available. The most extensively characterized of these is 5-azacytidine (5-Aza); however, no consensus exists on how this agent should be deployed in MDS. METHODS An overarching search of the literature identified 7019 citations investigating the treatment or management of MDS. Of those, six clinical articles of prospective phase 2-3 study design or meta-analyses were selected for inclusion in a systematic review of the evidence. CONCLUSIONS The Canadian Consortium on Evidence-Based Care in MDS recommends 5-Aza as first line therapy in all MDS patients with IPSS high-intermediate and high risk scores including WHO-defined AML (20-30% blasts) who cannot proceed immediately to allogeneic stem cell transplant. 5-Aza is not recommended as first line therapy with MDS patients with IPSS Low and Low-intermediate risk scores as there is no evidence that it alters the natural history of the disease nor is superior to standard therapy. The MDS consortium does not recommend combining 5-Aza with other agents at this time outside the context of a clinical trial.

Generation of high-titer viral preparations by concentration using successive rounds of ultracentrifugation

BackgroundViral vectors provide a method of stably introducing exogenous DNA into cells that are not easily transfectable allowing for the ectopic expression or silencing of genes for therapeutic or experimental purposes. However, some cell types, in particular bone marrow cells, dendritic cells and neurons are difficult to transduce with viral vectors. Successful transduction of such cells requires preparation of highly concentrated viral stocks, which permit a high virus concentration and multiplicity of infection (MOI) during transduction. Pseudotyping with the vesicular stomatitis virus G (VSV-G) envelope protein is common practice for both lentiviral and retroviral vectors. The VSV-G glycoprotein adds physical stability to retroviral particles, allowing concentration of virus by high-speed ultracentrifugation. Here we describe a method report for concentration of virus from large volumes of culture supernatant by means of successive rounds of ultracentrifugation into the same ultracentrifuge tube.MethodStable retrovirus producer cell lines were generated and large volumes of virus-containing supernatant were produced. We then tested the transduction ability of virus following varying rounds of concentration by ultra-centrifugation. In a second series of experiments lentivirus-containing supernatant was produced by transient transfection of 297T/17 cells and again we tested the transduction ability of virus following multiple rounds of ultra-centrifugation.ResultsWe report being able to centrifuge VSV-G coated retrovirus for as many as four rounds of ultracentrifugation while observing an additive increase in viral titer. Even after four rounds of ultracentrifugation we did not reach a plateau in viral titer relative to viral supernatant concentrated to indicate that we had reached the maximum tolerated centrifugation time, implying that it may be possible to centrifuge VSV-G coated retrovirus even further should it be necessary to achieve yet higher titers for specific applications. We further report that VSV-G coated lentiviral particles may also be concentrated by successive rounds of ultracentrifugation (in this case four rounds) with minimal loss of transduction efficiency.ConclusionThis method of concentrating virus has allowed us to generate virus of sufficient titers to transduce bone marrow cells with both retrovirus and lentivirus, including virus carrying shRNA constructs.

Correlation among nuclear localization of NuMA-RARα, deregulation of gene expression and leukemic phenotype of hCG-NuMA-RARα transgenic mice.

Acute promyelocytic leukemia (APL) is a model system of aberrant transcription in cancer. We sought to elucidate the mechanism of action of the variant fusion NuMA-RARα in APL, using the hCG-NuMA-RARα transgenic model. We report that subcellular localization of NuMA-RARα in transgenic mice is dependent upon its protein expression and transgene dosage. Subcellular localization of the fusion is inversely correlated with extent of gene deregulation at the mRNA level for Cebpα, Cebpɛ and Pu.1. Finally, we report that phenotype onset is correlated with NuMA-RARα copy number; mice with higher copy number developing disease later than those with lower copy number.