Efficacy of the investigational mTOR kinase inhibitor MLN0128/INK128 in models of B-cell acute lymphoblastic leukemia.

The mechanistic target of rapamycin (mTOR) is a serine/threonine kinase whose activity contributes to leukemia proliferation and survival. Compounds targeting the mTOR active site inhibit rapamycin-resistant functions and have enhanced anticancer activity in mouse models. MLN0128 (formerly known as INK128) is a novel, orally active mTOR kinase inhibitor currently in clinical development. Here, we evaluated MLN0128 in preclinical models of B-cell acute lymphoblastic leukemia (B-ALL). MLN0128 suppressed proliferation of B-ALL cell lines in vitro and reduced colony formation by primary human leukemia cells from adult and pediatric B-ALL patients. MLN0128 also boosted the efficacy of dasatinib (DA) in Philadelphia Chromosome-positive (Ph+) specimens. In a syngeneic mouse model of lymphoid BCR-ABL+ disease, daily oral dosing of MLN0128 rapidly cleared leukemic outgrowth. In primary xenografts of Ph+ B-ALL specimens, MLN0128 significantly enhanced the efficacy of DA. In non-Ph B-ALL xenografts, single agent MLN0128 had a cytostatic effect that was most pronounced in mice with low disease burden. In all in vivo models, MLN0128 was well tolerated and did not suppress endogenous bone marrow proliferation. These findings support the rationale for clinical testing of MLN0128 in both adult and pediatric B-ALL and provide insight towards optimizing therapeutic efficacy of mTOR kinase inhibitors.

Mycotoxin-contaminated diets and deactivating compound in laying hens: 1. effects on performance characteristics and relative organ weight.

The current experiment was conducted to determine the effect of mycotoxin-contaminated diets with aflatoxin (AFLA) and deoxynivalenol (DON) and dietary inclusion of deactivation compound on layer hen performance during a 10-wk trial. The experimental design consisted of a 4 × 2 factorial with 4 toxin levels: control, low (0.5 mg/kg AFLA + 1.0 mg/kg DON), medium (1.5 mg/kg AFLA + 1.5 mg/kg DON), and high (2.0 mg/kg AFLA + 2.0 mg/kg DON) with or without the inclusion of deactivation compound. Three hundred eighty-four 25-wk-old laying hens were randomly assigned to 1 of the 8 treatment groups. Birds were fed contaminated diets for a 6-wk phase of toxin administration followed by a 4-wk recovery phase, when all birds were fed mycotoxin-free diets. Twelve hens from each treatment were subjected to necropsy following each phase. Relative liver and kidney weights were increased (P < 0.05) at the medium and high toxin levels following the toxin phase, but the deactivation compound reduced (P < 0.05) relative liver and kidney weights following the recovery period. The high toxin level decreased (P < 0.05) feed consumption and egg production during the toxin period, whereas the deactivation compound increased (P < 0.05) egg production during the first 2 wk of the toxin phase. Egg weights were reduced (P < 0.05) in hens fed medium and high levels of toxin. An interaction existed between toxin level and deactivation compound inclusion with regard to feed conversion (g of feed/g of egg). High inclusion level of toxins increased feed conversion compared with the control diet, whereas deactivation compound inclusion reduced feed conversion to a level comparable with the control. These data indicate that deactivation compound can reduce or eliminate adverse effects of mycotoxicoses in peak-performing laying hens.

Effects of mycotoxin-contaminated diets and deactivating compound in laying hens: 2. effects on white shell egg quality and characteristics.

An experiment was conducted to determine the effect of dietary inclusion of Mycofix Select (Biomin GmbH, Herzogenburg, Austria) on discrete egg parameters and quality characteristics of hens fed mycotoxin-contaminated diets (aflatoxin; AFLA) and deoxynivalenol (DON)) during a 10-wk trial. A 4 × 2 factorial design was used with 4 contamination levels: control, low (0.5 mg/kg of AFLA + 1.0 mg/kg of DON), medium (1.5 mg/kg of AFLA + 1.5 mg/kg of DON), and high (2.0 mg/kg of AFLA + 2.0 mg/kg of DON) with or without the inclusion of mycotoxin deactivating compound. Three hundred and eighty-four 25-wk-old laying hens were housed 3 per cage. Birds were fed contaminated diets for a 6-wk phase of toxin administration followed by a 4-wk recovery phase, when all birds were fed mycotoxin-free diets. Parameters evaluated included egg weight, Haugh unit value, specific gravity, eggshell thickness, egg shape index, and relative albumen and yolk weights. Albumen height and Haugh unit value were depressed (P < 0.05) at the high mycotoxin level 2 wk postinclusion. Egg weight was significantly reduced (P < 0.05) with the high toxins level by the third week of toxin administration and remained throughout the study during toxin administration. Egg shape index indicated a variation (P < 0.05) in shape with all toxin levels compared with the control. Relative yolk weight was decreased (P < 0.05) by the high toxin level. An interaction existed between the deactivating compound inclusion and toxins level with regard to specific gravity. Following the toxin phase, the deactivating compound inclusion increased (P < 0.05) egg specific gravity in the control and low toxin groups whereas a decrease (P < 0.05) was observed at the high toxin level. These data indicate that mycotoxins present in feed can reduce egg quality, size, yolk weight, and alter egg shape and that inclusion of a mycotoxin deactivating compound can ameliorate some of the negative effects of mycotoxin consumption.

The quality criteria concept: an introduction and overview.

The Quality Criteria concept has been developed over the past decade in Europe and applied with success for conventional X ray examinations of adult and paediatric patients. This concept has recently been extended to computed tomography, and will also be available for digital radiography in the near future. The aim of the Quality Criteria for diagnostic images is to define a level of performance considered necessary to produce images of standard quality for a particular anatomical region and which could address any clinical indication. The image criteria include anatomical criteria, which relate to the visualisation or critical reproduction of anatomical features and also physical criteria measurable by objective means. The diagnostic reference doses introduced by ICRP 73 are an essential element of the Quality Criteria concept given for examinations on standard-sized patients. The Quality Criteria should provide a logical framework for radiation protection initiatives which links the desired or acceptable outcome, in terms of image quality, of a radiological examination, to the radiographic technique required to produce this outcome and the patient dose which should be achievable.

Retinol binding protein expression is induced in HepG2 cells by zinc deficiency.

Zinc (Zn) deficiency is often associated with low plasma vitamin A (retinol) concentrations. It has been suggested that the reduction in plasma retinol is secondary to reduced liver retinol binding protein (RBP) synthesis. In the present study, RBP expression was determined in HepG2 cells cultured in either Zn adequate media or chelated media containing varying concentrations of Zn. Levels of RBP mRNA increased in a time- and Zn concentration-dependent manner such that 0.5 microM Zn-treated cells exhibited a >7.5-fold increase while cells treated with 15 microM Zn were increased 2.9-fold at 72 h compared to controls. RBP protein also progressively increased by 72 h to levels >8-fold and 3-fold higher than controls, in 0.5 microM and 15 microM Zn-treated cells, respectively. The increase in RBP occurred without any change in DNA concentration between groups through 72 h. The Zn deficiency-induced elevations in RBP transcript levels could be reversed within 24-48 h of repletion in Zn adequate media. Thus, the reductions in plasma retinol observed in Zn deficiency are in part a direct consequence of the deficiency.

Mouse retinol binding protein gene: cloning, expression and regulation by retinoic acid.

A full-length cDNA clone encoding the retinol binding protein (RBP) was isolated from a mouse liver cDNA library by hybridization screening. The nucleotide sequence of murine RBP is 85 and 95% homologous to that of human and rat RBP, respectively, with a deduced amino acid sequence > or = 83% homologous to both species. Analysis of the tissue expression pattern of RBP mRNA in the female mouse indicated relatively abundant expression in the liver, with lesser amounts in extrahepatic tissues including adipose, kidney, spleen and uterus, suggesting that these tissues may have a significant role in retinol homeostasis. Mouse liver cell RBP regulation by retinoids was also investigated. Both all-trans retinoic acid (AT-RA) and 9-cis retinoic acid (9c-RA) induced RBP mRNA expression in a dose- and time-dependent manner. Maximal levels (up to 4-fold above controls) were observed at > or = 48 h following treatment of both mouse hepatoma cells in vitro and in vivo in mice receiving a single, oral dose of either retinoid. Interestingly, 9c-RA was more potent at RBP induction in both in vivo and in vitro systems. Given the extent and temporal pattern of RBP induction, we suggest that the RA-mediated increase in liver RBP is part of a cellular protection mechanism. Increased levels of RBP would facilitate sequestration and possibly cellular export of RA in cells receiving prolonged exposure to high levels of RA, thus minimizing toxicity.

Dosimetry for optimisation of patient protection in computed tomography.

The complex conditions of irradiation in computed tomography (CT), involving highly-collimated X-ray beams, necessitate the use of specially-defined dose descriptors such as the computed tomography dose index (CTDI). When used in a weighted form (CTDIW), this concept can describe the absorbed dose from a single slice in standard head and body phantoms. The model can easily be extended to characterise patient exposure for a complete examination by means of the reference dose quantity dose-length product (DLP). Effective dose can also be estimated from DLP, when required.

Induction of mouse retinol binding protein gene expression by cyclic AMP in Hepa 1-6 cells.

Retinol binding protein (RBP) is the primary circulating transport molecule for retinol, facilitating its transport to target tissues and influencing target cell uptake. Specific signals and molecular mechanisms that regulate RBP gene expression are poorly understood. Using the mouse hepatoma cell line (Hepa 1-6), we examined the role of cAMP in the molecular regulation of RBP. Dibutyryl cAMP (dbcAMP) or the adenylate cyclase activator, forskolin, increased RBP mRNA levels >6-fold at 24 h. Increases in RBP mRNA were dose dependent over the range of 10 microM-1 mM for dbcAMP and 0.5-10 microM for forskolin. 8-Bromo cAMP, a nonhydrolyzable analog, over the range of 0.01-0.5 mM, increased RBP mRNA levels 9.2-fold at 24 h. Induction of RBP transcripts by analogs also resulted in a comparable increase in intracellular RBP protein. Cycloheximide (10 microgram/ml) did not prevent cAMP-mediated induction of RBP mRNA, indicating that de novo protein synthesis is not required for cAMP-mediated induction of RBP transcription. These studies demonstrate that cAMP, or agents which elevate intracellular cAMP, increase RBP transcript levels. The time course and extent of RBP mRNA induction and the resultant increase in RBP protein support the concept that cAMP regulation of RBP gene expression may be physiologically relevent. Given the ubiquitous nature of cAMP as a second messenger, and the several mechanisms by which cAMP regulates gene expression, studies are in progress to define molecular mechanisms by which cAMP regulates RBP gene expression.

Image quality and dose in computed tomography.

Radiation exposure to the patient during CT is relatively high, and it is therefore important to optimize the dose so that it is as low as possible but still consistent with required diagnostic image quality. There is no established method for measuring diagnostic image quality; therefore, a set of image quality criteria which must be fulfilled for optimal image quality was defined for the retroperitoneal space and the mediastinum. The use of these criteria for assessment of image quality was tested based on 113 retroperitoneal and 68 mediastinal examinations performed in seven different CT units. All the criteria, except one, were found to be usable for measuring diagnostic image quality. The fulfillment of criteria was related to the radiation dose given in the different departments. By examination of the retroperitoneal space the effective dose varied between 5.1 and 20.0 mSv (milli Sievert), and there was a slight correlation between dose and high percent of "yes" score for the image quality criteria. For examination of the mediastinum the dose range was 4.4-26.5 mSv, and there was no significant increment of image quality at high doses. The great variation of dose at different CT units was due partly to differences regarding the examination procedure, especially the number of slices and the mAs (milli ampere second), but inherent dose variation between different scanners also played a part.

Quality assurance in radiotherapy: the importance of medical physics staffing levels. Recommendations from an ESTRO/EFOMP joint task group.

The safe application of ionising radiation for diagnosis and therapy requires a high level of knowledge of the underlying processes and of quality assurance. Sophisticated modern equipment can be used effectively for complicated diagnostic and therapeutic techniques only with adequate physics support. In the light of recent analyses and recommendations by national and international societies a joint working group of representatives from ESTRO (European Society for Therapeutic Radiology and Oncology) and from EFOMP (European Federation of Organisations for Medical Physics) was set up to assess the necessary staffing levels for physics support to radiotherapy. The method used to assess the staffing levels, the resulting recommendations and examples of their practical application are described.

Cancer risk among staff at two radiotherapy departments in Denmark.

In comparison with the general Danish population, the relative risk (RR) for cancer among staff members employed in two radiotherapy departments in Denmark during 1954-1982 and alive on 1 April 1968 was assessed by linkage to the Danish Cancer Registry. All staff had been monitored with film dosimeters for exposure to radiation. The study cohort consisted of 4151 persons, accruing 49553 person-years at risk. The collective radiation dose was 76.54 manSv and the mean dose 18.4 mSv. A total of 163 cancer cases were observed with 152.3 expected. The risks for cancers usually considered to be radiogenic were not elevated. A significant excess of prostatic cancer was observed (five cases, relative risk, 6.02; 95% confidence interval, 1.94-14.06); this is likely to be a chance finding. No relation was observed between radiation dose or years of exposure and cancer risk, but a weak non-significant increase in risk with time since first exposure was seen.

Impact of CT-based treatment planning on radiation therapy of carcinoma of the bladder.

Computed tomography (CT) has been an integrated step in the treatment planning of radiation therapy of carcinoma of the bladder in stages T1-T3 in 49 consecutive patients referred to Radiumstationen in Aarhus. The introduction of this technique has led to a considerable increase (26 +/- 4%) in the mean effective target volume of these patients compared with that of 51 conventionally simulated patients. The largest field expansions have been performed in the cranial and ventral directions. The field margins to the bladder have been correlated with the position of the tumour mass. The findings are compared with previously published results on CT-based treatment planning of patients with bladder carcinoma.

Measurements of single event spectra with a wall-less proportional counter in low LET radiation fields.

Measurements have been made on 60Co gamma rays from a point source and on 6 MV roentgen rays from a linear accelerator with a wall-less proportional counter. Single event spectra have been measured in sites of 0.5-2 mum in diameters stimulated with a tissue equivalent gas. Calculations of the relative variance in LET are performed and compared with the relative variance of the measured distributions for estimates about the straggling contribution.

Spectral measurements and Monte Carlo calculations of scattered radiation from therapeutic radiation sources.

Spectral measurements have been made on scattered radiation in a perspex phantom in various depths from a kilocurie 60Co unit and a 6 MeV linear accelerator using a NaI crystal spectrometer. The measurements are compared to Monte Carlo calculations and a good agreement is obtained. The measured total photon distributions make the basis for calculations of absorbed dose and track length distributions in LET and their average values for the different depths and fields.