MLL-AF9 and FLT3 cooperation in acute myelogenous leukemia: development of a model for rapid therapeutic assessment.

Human leukemias harboring chromosomal translocations involving the mixed lineage leukemia (MLL, HRX, ALL-1) gene possess high-level expression, and frequent activating mutations of the receptor tyrosine kinase FLT3. We used a murine bone marrow transplant model to assess cooperation between MLL translocation and FLT3 activation. We demonstrate that MLL-AF9 expression induces acute myelogenous leukemia (AML) in approximately 70 days, whereas the combination of MLL-AF9 and FLT3-ITD does so in less than 30 days. Secondary transplantation of splenic cells from diseased mice established that leukemia stem cells are present at a very high frequency of approximately 1:100 in both diseases. Importantly, prospectively isolated granulocyte macrophage progenitors (GMPs) coinfected with MLL-AF9 and FLT3-ITD give rise to a similar AML, with shorter latency than from GMP transduced with MLL-AF9 alone. Cooperation between MLL-AF9 and FLT3-ITD was further verified by real-time assessment of leukemogenesis using noninvasive bioluminescence imaging. We used this model to demonstrate that MLL-AF9/FLT3-ITD-induced leukemias are sensitive to FLT3 inhibition in a 2-3 week in vivo assay. These data show that activated FLT3 cooperates with MLL-AF9 to accelerate onset of an AML from whole bone marrow as well as a committed hematopoietic progenitor, and provide a new genetically defined model system that should prove useful for rapid assessment of potential therapeutics in vivo.

Learning to network and networking to learn: facilitating the process of adaptive management in a local response to the UK's National Air Quality Strategy.

The adaptive management leitmotiv of "learning to manage and managing to learn" sets out an attractive agenda for dealing with the overwhelming complexity of environmental phenomena that humans have problematized. To ensure that this rallying cry translates into effective action, it is important to give consideration to structures and procedures for facilitating the efforts of those willing or able to respond to the adaptive management call. To date, calls to establish the right organization to coordinate multiagency responses have tended to emphasize the noun, or bounded-entity, sense of the word organization. We believe that this is at the expense of its other, verb or process, connotation. In this paper, rather than searching for the perfect organization structure that mandates mutual trust and collective action shaped by all relevant parties' perspectives and possible contributions, we direct attention towards the process of nurturing integrated adaptive responses among individuals who have diverse organizational allegiances. By shifting the balance towards the process connotation of the right organization, we hope that a new mindscape can be discerned for those interested in putting adaptive management principles into practice. We seek to conjure up an image of this mindscape through the phrase "learning to network and networking to learn," and set out to strengthen this by demonstrating how adaptive response networks can arise from the mutually defining relationship between stakeholders and issues. This is demonstrated through a local response to the United Kingdom's National Air Quality Strategy.

An assessment of artefacts in localized and non-localized 31P MRS studies of phosphate metabolites and pH in rat tumours.

UA hepatomas, GH3 prolactinomas and N-methyl-N-nitrosourea-induced mammary tumours, which were subcutaneously grown in rats, have been studied by 31P MRS using non-localized pulse-acquire, image selected in vivo spectroscopy (ISIS) and one-dimensional chemical shift imaging (1-D CSI) techniques. Comparisons have been made with measurements from acid extracts of these tumour types and surrounding tissues (i.e., muscle and skin). Since muscle containing high concentrations of phosphocreatine (PCr) is often found adjacent to the tumour, we have compared the ratio of the PCr to gamma-NTP peaks in the spectra with the same ratio calculated from the acid extract data, and have used deviations between the two sets of data to assess the discrimination of the MRS localization technique to signals from the tissue surrounding the tumour. Extract data showed an average NTP content of 1.25 mumol/g wet wt for all three tumour types. PCr (at 0.42 mumol/g wet wt), was significant only in the GH3 prolactinoma whereas it was negligible in the other tumour types (< 0.1 mumol/g wet wt). There was good agreement between the ISIS PCr/gamma-NTP ratio and the extract data for all tumours. However, the 1-D CSI data showed an unexpectedly large contamination of the tumour spectrum with PCr signals from the skin which was shown by subsequent phantom experiments to be due to the curved geometry of tumour and skin rather than Fourier bleed. In pH measurements by MRS it was found that biological variability was greater than the effects of artefacts (due to either the chemical shift artefact in the ISIS technique or partial volume effects) in the localization technique. An average pH of 7.2 was observed for all tumours. By initially comparing data from different localization schemes with that from chemical extracts potential sources of error have been highlighted and show that phantom studies alone are not sufficient to fully assess the accuracy of localized MRS data.

An assessment of 31P MRS as a method of measuring pH in rat tumours.

The contribution of extracellular components to the measurement of pHMRS of a variety of rat tumours (nitrosomethyl urea induced mammary tumours, GH3 prolactinomas, Hepatoma 9618a, UA hepatomas and Walker sarcomas) has been assessed. Acid extractable P(i) was between 2.6 and 12.5 mumol/G wet wt depending on tumour type, and of this 53 +/- 4.8% (mean +/- SEM) was MRS-visible. The P(i) content of tumour exudate was 2-3 mM, of interstitial fluid (sampled from a micropore chamber incorporated within a tumour) 1.7 mM, and of blood plasma 1.95 mM. The mean extracellular volumes of the tumours, measured by distribution of 3H2O and [14C]inulin, were 49-55% depending on tumour type and were at least twice that found in normal liver. Calculations suggested that for most tumours with an extracellular volume not exceeding 55%, at least 65% of the P(i)(MRS) signal was derived from intracellular P(i), and thus that pH(MRS) is a measure of pHi. For each tumour type, pHMRS was measured both in 'pulse-acquire' mode at 1.9 T which may include signals from surrounding tissue, and in localized mode at 4.7 T where the signal came uniquely from tumour tissue. The steady state pHMRS was either neutral or on the alkaline side of neutrality (pH range 7.04-7.37). Raised lactate content and decreased buffering capacity (compared to normal tissues) accompanied these neutral to alkaline pH values.(ABSTRACT TRUNCATED AT 250 WORDS)