Multiple pathways contribute to the hyperproliferative responses from truncated granulocyte colony-stimulating factor receptors

Mutations in the granulocyte colony-stimulating factor receptor (G-CSF-R) gene leading to a truncated protein have been identified in a cohort of neutropenia patients highly predisposed to acute myeloid leukemia. Such mutations act in a dominant manner resulting in hyperproliferation but impaired differentiation in response to G-CSF. This is due, at least in part, to defective internalization and loss of binding sites for several negative regulators, leading to sustained receptor activation. However, those signaling pathways responsible for mediating the hyperproliferative function have remained unclear. In this study, analysis of an additional G-CSF-R mutant confirmed the importance of residues downstream of Box 2 as important contributors to the sustained proliferation. However, maximal proliferation correlated with the ability to robustly activate signal transducer and activator of transcription (STAT) 5 in a sustained manner, whereas co-expression of dominant-negative STAT5, but not dominant-negative STAT3, was able to inhibit G-CSF-stimulated proliferation from a truncated receptor. Furthermore, a Janus kinase (JAK) inhibitor also strongly reduced the proliferative response, whereas inhibitors of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK) or phosphatidylinositol (PI) 3-kinase reduced proliferation to a lesser degree. These data suggest that sustained JAK2/STAT5 activation is a major contributor to the hyperproliferative function of truncated G-CSF receptors, with pathways involving MEK and PI 3-kinase playing a reduced role.

Identification of genes differentially regulated by the P210 BCR/ABL1 fusion oncogene using cDNA microarrays

Objective: The t(9;22) translocation is associated with more than 95% of cases of chronic myeloid leukemia. The resulting fusion of the BCR and ABL1 loci produces the constitutively active BCR/ABL1 tyrosine kinase. A wide range of signal transduction molecules are activated by BCR/ABL1, including MYC, PI-3 kinase, and different STAT molecules. In contrast, relatively few genes are known to be regulated by BCR/ABL1 at the level of transcription.

Materials and Methods: In an effort to better understand the transcriptional program activated by BCR/ABL1, we used cDNA microarrays to evaluate the relative expression of approximately 6450 human genes in U937 myelomonocytic cells expressing P210 BCR/ABL1 via a tetracycline-inducible promoter.

Results: We confirmed the previously reported up-regulation of the PIM1 and JUN oncogenes by BCR/ABL1. In addition, we identified 59 more genes up-regulated by BCR/ABL1. Interestingly, roughly one third of these were genes previously reported to be interferon (IFN)-responsive, including the OAS1, IFIT1, IFI16, ISGF3G, and STAT1 genes. An additional seven BCR/ABL1-regulated genes were found to be IFN-responsive in U937 cells. The expression profile also included genes encoding transcription factors, kinases, and signal transduction molecules, as well as genes regulating cell growth, differentiation, apoptosis, and cell adhesion, features previously suggested to be affected by BCR/ABL1.

Conclusion: These observations shed novel insight into the mechanism of BCR/ABL1 action and provide a range of targets for further investigation.

Stigmatization of patients with AIDS : understanding the interrelationships between Thai nurses' attitudes towards HIV/AIDS, drug use and commercial sex

There is currently a scarcity of research on the nature of HIV/AIDS stigma within the Thai health context. This is problematic given the negative role of stigma in hindering the provision of patient care and treatment. This study used a mixed-method approach to investigate the interrelationships between the stigma of HIV/AIDS and the stigmas relating to its various modes of disease transmission including injection drug use (IDU). Twenty interviews were conducted with trainees and qualified nurses from a Bangkok college. Participants were presented with vignettes describing a hypothetical person varying in disease diagnoses (AIDS, leukemia, no disease) and co-characteristics (IDU,  commercial sex (CS), blood transfusion, no co-characteristic). Using a Q-sort task, participants arranged the vignettes along a bipolar scale according to their willingness to interact with the persons, and were asked to explain their decisions. Univariate and multivariate regression analyses showed that IDU, AIDS, and CS were all individually stigmatizing. Strong interactions were found between the stigmas of HIV/AIDS, IDU, and CS. Interview data also showed clear biases toward patients according to their IDU and CS habits. The findings  suggest that addressing these co-stigmas could be vital to the success of efforts aimed at reducing the disease stigma of HIV/AIDS.

Stigmatization of AIDS patients : disentangling Thai nursing students' attitudes towards HIV/AIDS, drug use and commercial sex

This paper analyzes the interrelationships between the stigma of HIV/AIDS stigma and the co-stigmas of commercial sex (CS) and injecting drug use (IDU). Students of a Bangkok nursing college (N = 144) were presented with vignettes describing a person varying in the disease diagnoses (AIDS, leukemia, no disease) and co-characteristics (IDU, CS, blood transfusion, no co-characteristic). For each vignette, participants completed a social distance measure assessing their attitudes towards the hypothetical person portrayed. Multivariate analyses showed strong interactions between the stigmas of AIDS and IDU but not between AIDS and CS. Although AIDS was shown to be stigmatizing in and of itself, it was significantly less stigmatizing than IDU. The findings highlight the need to consider the non-disease-related stigmas associated with HIV as well as the actual stigma of HIV/AIDS in treatment and care settings. Methodological strengths and limitations were evaluated and implications for future research discussed.

Hybrid methods to select informative gene sets in microarray data classification

One of the key applications of microarray studies is to select and classify gene expression profiles of cancer and normal subjects. In this study, two hybrid approaches–genetic algorithm with decision tree (GADT) and genetic algorithm with neural network (GANN)–are utilized to select optimal gene sets which contribute to the highest classification accuracy. Two benchmark microarray datasets were tested, and the most significant disease related genes have been identified. Furthermore, the selected gene sets achieved comparably high sample classification accuracy (96.79% and 94.92% in colon cancer dataset, 98.67% and 98.05% in leukemia dataset) compared with those obtained by mRMR algorithm. The study results indicate that these two hybrid methods are able to select disease related genes and improve classification accuracy.

Design of new oxazaphosphorine anticancer drugs

The oxazaphosphorines including cyclophosphamide (CPA, Cytoxan, or Neosar), ifosfamide (IFO, Ifex) and trofosfamide (Ixoten) represent an important group of therapeutic agents due to their substantial antitumor and immunomodulating activity. However, several intrinsic limitations have been uncounted during the clinical use of these oxazaphosphorines, including substantial pharmacokinetic variability, resistance and severe host toxicity. To circumvent these problems, new oxazaphosphorines derivatives have been designed and evaluated with an attempt to improve the selectivity and response with reduced host toxicity. These include mafosfamide (NSC 345842), glufosfamide (D19575, β-Dglucosylisophosphoramide mustard), S-(-)-bromofosfamide (CBM-11), NSC 612567 (aldophosphamide perhydrothiazine) and NSC 613060 (aldophosphamide thiazolidine). Mafosfamide is an oxazaphosphorine analog that is a chemically stable 4-thioethane sulfonic acid salt of 4-hydroxy-CPA. Glufosfamide is IFO derivative in which the isophosphoramide mustard, the alkylating metabolite of IFO, is glycosidically linked to a β-D-glucose molecule. Phase II studies of glufosfamide in the treatment of pancreatic cancer, non-small cell lung cancer (NCSLC), and recurrent glioblastoma multiform (GBM) have recently completed and Phase III trials are ongoing, while Phase I studies of intrathecal mafosfamide have recently completed for the treatment of meningeal malignancy secondary to leukemia, lymphoma, or solid tumors. S-(-)- bromofosfamide is a bromine-substituted IFO analog being evaluated in a few Phase I clinical trials. The synthesis and development of novel oxazaphosphorine analogs with favourable pharmacokinetic and pharmacodynamic properties still constitutes a great challenge for medicinal chemists and cancer pharmacologists.

The role of the granulocyte colony-stimulating factor receptor (G-CSF-R) in disease

Granulocyte colony-stimulating factor (G-CSF) is a key regulator of granulopoiesis via stimulation of a specific cell-surface receptor, the G-CSF-R, found on hematopoietic progenitor cells as well as neutrophilic granulocytes. It is perhaps not surprising, therefore, that mutations of the G-CSF-R has been implicated in several clinical settings that affect granulocytic differentiation, particularly severe congenital neutropenia, myelodysplastic syndrome and acute myeloid leukemia. However, other studies suggest that signalling via the G-CSF-R is also involved in a range of other malignancies. This review focuses on the molecular mechanisms through which the G-CSF-R contributes to disease.

Metabolism and transport of oxazphosphorines and the clinical implications

The oxazaphosphorines including cyclophosphamide (CPA), ifosfamide (IFO), and trofosfamide represent an important group of therapeutic agents due to their substantial antitumor and immuno-modulating activity. CPA is widely used as an anticancer drug, an immunosuppressant, and for the mobilization of hematopoetic progenitor cells from the bone marrow into peripheral blood prior to bone marrow transplantation for aplastic anemia, leukemia, and other malignancies. New oxazaphosphorines derivatives have been developed in an attempt to improve selectivity and response with reduced toxicity. These derivatives include mafosfamide (NSC 345842), glufosfamide (D19575, β-D-glucosylisophosphoramide mustard), NSC 612567 (aldophosphamide perhydrothiazine), and NSC 613060 (aldophosphamide thiazolidine). This review highlights the metabolism and transport of these oxazaphosphorines (mainly CPA and IFO, as these two oxazaphosphorine drugs are the most widely used alkylating agents) and the clinical implications. Both CPA and IFO are prodrugs that require activation by hepatic cytochrome P450 (CYP)-catalyzed 4-hydroxylation, yielding cytotoxic nitrogen mustards capable of reacting with DNA molecules to form crosslinks and lead to cell apoptosis and/or necrosis. Such prodrug activation can be enhanced within tumor cells by the CYP-based gene directed-enzyme prodrug therapy (GDEPT) approach. However, those newly synthesized oxazaphosphorine derivatives such as glufosfamide, NSC 612567 and NSC 613060, do not need hepatic activation. They are activated through other enzymatic and/or non-enzymatic pathways. For example, both NSC 612567 and NSC 613060 can be activated by plain phosphodiesterase (PDEs) in plasma and other tissues or by the high-affinity nuclear 3'-5' exonucleases associated with DNA polymerases, such as DNA polymerases and ε. The alternative CYP-catalyzed inactivation pathway by N-dechloroethylation generates the neurotoxic and nephrotoxic byproduct chloroacetaldehyde (CAA). Various aldehyde dehydrogenases (ALDHs) and glutathione S-transferases (GSTs) are involved in the detoxification of oxazaphosphorine metabolites. The metabolism of oxazaphosphorines is auto-inducible, with the activation of the orphan nuclear receptor pregnane X receptor (PXR) being the major mechanism. Oxazaphosphorine metabolism is affected by a number of factors associated with the drugs (e.g., dosage, route of administration, chirality, and drug combination) and patients (e.g., age, gender, renal and hepatic function). Several drug transporters, such as breast cancer resistance protein (BCRP), multidrug resistance associated proteins (MRP1, MRP2, and MRP4) are involved in the active uptake and efflux of parental oxazaphosphorines, their cytotoxic mustards and conjugates in hepatocytes and tumor cells. Oxazaphosphorine metabolism and transport have a major impact on pharmacokinetic variability, pharmacokinetic-pharmacodynamic relationship, toxicity, resistance, and drug interactions since the drug-metabolizing enzymes and drug transporters involved are key determinants of the pharmacokinetics and pharmacodynamics of oxazaphosphorines. A better understanding of the factors that affect the metabolism and transport of oxazaphosphorines is important for their optional use in cancer chemotherapy.

Somatostatin modulates G-CSF-induced but not interleukin-3-induced proliferative responses in myeloid 32D cells via activation of somatostatin receptor subtype 2

Somatostatin, originally identified as a peptide involved in neurotransmission, functions as an inhibitor of multiple cellular responses, including hormonal secretion and proliferation. Somatostatin acts through activation of G-protein-coupled receptors of which five subtypes have been identified. We have recently established that human CD34/c-kit expressing hematopoietic progenitors and acute myeloid leukemia (AML) cells exclusively express SSTR2. A major mechanism implicated in the antiproliferative action of somatostatin involves activation of the SH2 domain-containing protein tyrosine phosphatase SHP-1. While 0.1-1 x 10(-9) M of somatostatin, or its synthetic stable analog octreotide, can inhibit G-CSF-induced proliferation of AML cells, little or no effects are seen on GM-CSF- or IL-3-induced responses.
MATERIALS AND METHODS: To study the mechanisms underlying the antiproliferative responses of myeloblasts to somatostatin, clones of the IL-3-dependent murine cell line 32D that stably express SSTR2 and G-CSF receptors were generated. RESULTS: Similar to AML cells, octreotide inhibited G-CSF-induced but not IL-3-induced proliferative responses of 32D[G-CSF-R/SSTR2] cells. Somatostatin induced SHP-1 activity and inhibited G-CSF-induced, but not IL-3-induced, activation of the signal transducer and activator of transcription proteins STAT3 and STAT5.
CONCLUSION: Based on these data and previous results, we propose a model in which recruitment and activation of the tyrosine phosphatase SHP-1 by SSTR2 is involved in the selective negative action of somatostatin on G-CSF-R signaling.

Health watch exposure estimates:do they underestimate benzene exposure

A nested case–control study found that the excess of leukemia, identified among the male members of the Health Watch cohort, was associated with benzene exposure. Exposure had been retrospectively estimated for each individual occupational history using an algorithm in a relational database. Benzene exposure measurements, supplied by Australian petroleum companies, were used to estimate exposure for specific tasks. The tasks carried out within each job, the products handled, and the technology used, were identified from structured interviews with contemporary colleagues. More than half of the subjects started work after 1965 and had an average exposure period of 20 years. Exposure was low; nearly 85% of the cumulative exposure estimates were at or below 10 ppm-years. Matched analyses showed that leukemia risk increased with increasing cumulative benzene exposures and with increasing exposure intensity of the highest-exposed job. Non-Hodgkin lymphoma and multiple myeloma were not associated with benzene exposure. A reanalysis reported here, showed that for the 7 leukemia case-sets with greater than 16 ppm-years cumulative exposure, the odds ratio was 51.9 (5.6–477) when compared to the 2 lowest exposed categories combined to form a new reference category. The addition of occasional high exposures, e.g. as a result of spillages, increased exposure for 25% of subjects but for most, the increase was less than 5% of total exposure. The addition of these exposures reduced the odds ratios. Cumulative exposures did not range as high as those in comparable studies; however, the recent nature of the cohort and local handling practices can explain these differences.

The Jak-Stat pathway in Hematopoiesis and Disease

This book for the first time comprehensively surveys the research investigating the Jak-Stat pathway and its role in normal blood development as well as its perturbation in disease. It draws on the expertise of world-renowned medical researchers to take the reader from basic biology through to recent therapeutic advances.

Granulocyte colony-stimulating factor receptor: stimulating granulopoiesis and much more

The granulocyte colony-stimulating factor receptor (G-CSFR) plays an important role in the production, survival and activation of neutrophilic granulocytes during both normal and emergency hematopoiesis. The G-CSFR also participates in the development of other myeloid lineages, the mobilization of hematopoietic stem cells and myeloid cell migration. This has lead to several important clinical applications for its ligand, G-CSF. More recently, additional important roles for G-CSFR have emerged outside the hematopoietic system, such as in the protection and repair of a diverse range of tissues, including muscle, liver and neural tissue, providing further scope for developing G-CSF as a therapeutic agent. The G-CSFR has also been implicated in the etiology of disease, with mutations/variants of G-CSFR implicated in neutropenia, myelodysplasia and leukemia. Additionally, autocrine/paracrine stimulation of G-CSFR may be important in the biology of solid tumors, including metastasis.

Microarray classification using statistical learning and decision tree algorithms

This considers the challenging task of cancer prediction based on microarray data for the medical community. The research was conducted on mostly common cancers (breast, colon, long, prostate and leukemia) microarray data analysis, and suggests the use of modern machine learning techniques to predict cancer.

Study of myeloid leukemogenesis in Zebrafish

In this study zebrafish were used to identify, characterize and study leukemic "cancer"-genes as well as to investigate their role in normal development, particularly blood cell development. The experiments demonstrated that zebrafish represent an excellent tool for studying leukemogenesis, the genes involved in this process and for testing anti-cancer therapeutics.

Rhotekin 2, a novel GTPase effector involved in resistance to apoptosis

This thesis describes the discovery, characterization, and function of a new protein, Rhotekin 2. It is a signaling protein with a significant role in resistance to cell death in human lymphocytes and therefore may be a potential new target in future treatments of immune diseases such a HIV and leukemia.