Salvage Stereotactic Radiosurgery for Recurrent WHO Grade 2 and 3 Meningiomas: A Multicenter Study (STORM)

PURPOSE

The role of stereotactic radiosurgery (SRS) in the management of grade 2 and 3 meningiomas is not well elucidated. Unfortunately, local recurrence rates are high, and guidelines for management of recurrent disease are lacking. To address this knowledge gap, we conducted STORM, a multicenter retrospective cohort study of patients treated with primary SRS for recurrent grade 2 and 3 meningiomas.

METHODS AND MATERIALS

Data on patients with recurrent grade 2 and 3 meningioma treated with SRS at first recurrence were retrospectively collected from eight academic centers in the United States. Patients with multiple lesions at the time of initial diagnosis or more than two lesions at the time of first recurrence were excluded from this analysis. Patient demographics and treatment parameters were extracted at time of diagnosis, first recurrence, and second recurrence. Oncologic outcomes including progression-free survival (PFS) and overall survival (OS) as well as toxicity outcomes were reported at the patient level.

RESULTS

From 2000-2022, 108 patients were identified (94% grade 2, 6.0% grade 3). 106 patients (98%) had upfront surgical resection (60% gross-total resection) with 18% receiving adjuvant radiotherapy (RT). Median time to first progression was 2.5 years (IQR 1.34-4.30). At first recurrence, patients were treated with single or fractionated SRS to a median marginal dose of 16 Gy to a maximum of two lesions (87% received single fraction SRS). Median follow-up time after SRS was 2.6 years. 1-, 2-, and 3-year PFS was 90%, 75%, and 57%, respectively after treatment with SRS. 1-, 2-, and 3-year OS was 97%, 94%, and 92%, respectively. On multivariable analysis, grade 3 disease (HR 6.80; 95% CI 1.61-28.6), male sex (HR 3.48; 95% CI 1.47-8.26), and receipt of prior RT (HR 2.69; 95% CI 1.23-5.86) were associated with worse PFS. SRS dose and tumor volume were not correlated with progression. Treatment was well-tolerated, with a 3.0% incidence of grade 2+ radiation necrosis.

CONCLUSIONS

This is the largest multi-center study to evaluate salvage SRS in recurrent grade 2 and 3 meningiomas. In this select cohort of patients with primarily grade 2 meningioma with potentially more favorable natural history of delayed, localized first recurrence amenable to salvage SRS, local control rates and toxicity profiles were favorable, warranting further prospective validation.

Spectroscopic MRI Detects Occult Glioblastoma Invasion during Chemoradiation

PURPOSE/OBJECTIVE(S)

The standard of care for glioblastoma (GBM) includes surgical resection followed by adjuvant chemoradiation (chemoRT). Treatment margins are controversial since conventional imaging does not define the extent of infiltrating tumor cells. Whole-brain spectroscopic MRI (sMRI) allows for visualization of native metabolites in normal brain and tumor cells, and the relative choline to N-acetyl-aspartate ratio greater than 2 (rChoNAA>2) strongly correlates with the presence of occult GBM cells in otherwise normal-appearing brain. With an MRI-Linac, we are performing studies of adaptive radiotherapy to measure changes in cavity size, edema, and enhancement during chemoRT. We questioned whether rChoNAA>2 would change along with anatomical changes to inform clinical target volumes for adaptive chemoRT trials.

MATERIALS/METHODS

In a prospective study, 18 patients with primary GBM underwent daily MRI-guided chemoRT with standalone 3T sMRI generation of rChoNAA>2 maps at three timepoints before, during, and after chemoradiation. Conventional treatment volumes of T1 post-contrast and cavity (GTV2, i.e., boost) with or without FLAIR hyperintensity (GTV1) were compared to rChoNAA>2 volumes. DICE similarity coefficients were calculated to assess the spatial similarity of these volumes. Hausdorff distances were calculated to identify rChoNAA>2 extending beyond GTVs throughout the course of chemoradiation.

RESULTS

The mean GTV1 was 58.1 cc (range 0-251.4 cc), the mean GTV2 was 47.9 cc (range 0-139.9 cc), and the mean rChoNAA>2 volume was 31.1 cc (range 0-103.2 cc). rChoNAA>2 volumes did not significantly change over the course of chemoRT or correlate with measurement timepoint. The mean DICE similarity coefficient between GTV1 and rChoNAA>2 volumes was 0.39 (range 0-0.80), and the mean DICE similarity coefficient between GTV2 and rChoNAA>2 volumes was 0.29 (range 0-0.77). DICE similarity coefficients were significantly different from unity indicating spatial differences between rChoNAA>2 and conventional MRI volumes. The mean Hausdorff distances of rChoNAA>2 extending beyond GTV1 was 1.3 cm (range 0.7-2.1 cm), and the mean Hausdorff distances of rChoNAA>2 extending beyond GTV2 was 1.9 cm (range 0.8-2.9 cm), suggesting high-risk disease invading beyond what is visible on conventional MRI sequences.

CONCLUSION

Whole-brain sMRI with generation of rChoNAA>2 maps suggest conventional MRI does not fully capture the extent of disease in primary GBM throughout the course of chemoradiation. rChoNAA>2 maps often extend up to approximately 2 cm beyond conventional boost radiotherapy volumes. Further studies are ongoing to determine how sMRI can be used to adapt radiation target volumes during chemoradiation and escalate dose to occult disease.

Delineation of recurrent glioblastoma by whole brain spectroscopic magnetic resonance imaging

BACKGROUND

Glioblastoma (GBM) cellularity correlates with whole brain spectroscopic MRI (sMRI) generated relative choline to N-Acetyl-Aspartate ratio (rChoNAA) mapping. In recurrent GBM (rGBM), tumor volume (TV) delineation is challenging and rChoNAA maps may assist with re-RT targeting.

METHODS

Fourteen rGBM patients underwent sMRI in a prospective study. Whole brain sMRI was performed to generate rChoNAA maps. TVs were delineated by the union of rChoNAA ratio over 2 (rChoNAA > 2) on sMRI and T1PC. rChoNAA > 2 volumes were compared with multiparametric MRI sequences including T1PC, T2/FLAIR, diffusion-restriction on apparent diffusion coefficient (ADC) maps, and perfusion relative cerebral blood volume (rCBV).

RESULTS

rChoNAA > 2 (mean 27.6 cc, range 6.6-79.1 cc) was different from other imaging modalities (P ≤ 0.05). Mean T1PC volumes were 10.7 cc (range 1.2-31.4 cc). The mean non-overlapping volume of rChoNAA > 2 and T1PC was 29.2 cm³. rChoNAA > 2 was 287% larger (range 23% smaller-873% larger) than T1PC. T2/FLAIR volumes (mean 111.7 cc, range 19.0-232.7 cc) were much larger than other modalities. rCBV volumes (mean 6.2 cc, range 0.2-19.1 cc) and ADC volumes were tiny (mean 0.8 cc, range 0-3.7 cc). Eight in-field failures were observed. Three patients failed outside T1PC but within rChoNAA > 2. No grade 3 toxicities attributable to re-RT were observed. Median progression-free and overall survival for re-RT patients were 6.5 and 7.1 months, respectively.

CONCLUSIONS

Treatment of rGBM may be optimized by sMRI, and failure patterns suggest benefit for dose-escalation within sMRI-delineated volumes. Dose-escalation and radiologic-pathologic studies are underway to confirm the utility of sMRI in rGBM.

Survival and Yield of Surveillance Imaging in Long-Term Survivors of Brain Metastasis Treated with Stereotactic Radiosurgery

OBJECTIVES

The optimal frequency of surveillance brain magnetic resonance imaging (MRI) in long-term survivors with brain metastases after stereotactic radiosurgery (SRS) is unknown. Our aim was to identify the optimal frequency of surveillance imaging in long-term survivors with brain metastases after SRS.

METHODS

Eligible patients were identified from a cohort treated with SRS definitively or postoperatively at our institution from 2014 to 2019 with no central nervous system (CNS) failure within 12 months from SRS. Time to CNS disease failure diagnosis and cost per patient were estimated using theoretical MRI schedules of 2, 3, 4, and 6 months starting 1 year after SRS until CNS failure. Time to diagnosis was calculated from the date of CNS progression to the theoretical imaging date on each schedule.

RESULTS

This cohort included 55 patients (median follow-up from SRS: 2.48 years). During the study period, 20.0% had CNS disease failure (median: 2.26 years from SRS treatment). In this cohort, a theoretical 2-month, 3-month, 4-month, and 6-month MRI brain surveillance schedule produced a respective estimated time to diagnosis of CNS disease failure of 1.11, 1.74, 1.65, and 3.65 months. The cost of expedited diagnosis for the cohort (dollars/month) for each theoretical imaging schedule compared with a 6-month surveillance schedule was $6600 for a 2-month protocol, $4496 for a 3-month protocol, and $2180 for a 4-month protocol.

CONCLUSIONS

Based on cost-benefit, a 4-month MRI brain schedule should be considered in patients with metastatic disease to the brain treated definitively or postoperatively with SRS without evidence of CNS recurrence at 1 year.

Modeling electrokinetic flows with the discrete ion stochastic continuum overdamped solvent algorithm

In this article we develop an algorithm for the efficient simulation of electrolytes in the presence of physical boundaries. In previous work the discrete ion stochastic continuum overdamped solvent (DISCOS) algorithm was derived for triply periodic domains, and was validated through ion-ion pair correlation functions and Debye-Hückel-Onsager theory for conductivity, including the Wien effect for strong electric fields. In extending this approach to include an accurate treatment of physical boundaries we must address several important issues. First, the modifications to the spreading and interpolation operators necessary to incorporate interactions of the ions with the boundary are described. Next we discuss the modifications to the electrostatic solver to handle the influence of charges near either a fixed potential or dielectric boundary. An additional short-ranged potential is also introduced to represent interaction of the ions with a solid wall. Finally, the dry diffusion term is modified to account for the reduced mobility of ions near a boundary, which introduces an additional stochastic drift correction. Several validation tests are presented confirming the correct equilibrium distribution of ions in a channel. Additionally, the methodology is demonstrated using electro-osmosis and induced-charge electro-osmosis, with comparison made to theory and other numerical methods. Notably, the DISCOS approach achieves greater accuracy than a continuum electrostatic simulation method. We also examine the effect of under-resolving hydrodynamic effects using a "dry diffusion" approach, and find that considerable computational speedup can be achieved with a negligible impact on accuracy.

Combined PI3Kα-mTOR Targeting of Glioma Stem Cells

Glioblastoma (GBM) is the most common and lethal primary intrinsic tumour of the adult brain and evidence indicates disease progression is driven by glioma stem cells (GSCs). Extensive advances in the molecular characterization of GBM allowed classification into proneural, mesenchymal and classical subtypes, and have raised expectations these insights may predict response to targeted therapies. We utilized GBM neurospheres that display GSC characteristics and found activation of the PI3K/AKT pathway in sphere-forming cells. The PI3Kα selective inhibitor alpelisib blocked PI3K/AKT activation and inhibited spheroid growth, suggesting an essential role for the PI3Kα catalytic isoform. p110α expression was highest in the proneural subtype and this was associated with increased phosphorylation of AKT. Further, employing the GBM BioDP, we found co-expression of PIK3CA with the neuronal stem/progenitor marker NES was associated with poor prognosis in PN GBM patients, indicating a unique role for PI3Kα in PN GSCs. Alpelisib inhibited GSC neurosphere growth and these effects were more pronounced in GSCs of the PN subtype. The antineoplastic effects of alpelisib were substantially enhanced when combined with pharmacologic mTOR inhibition. These findings identify the alpha catalytic PI3K isoform as a unique therapeutic target in proneural GBM and suggest that pharmacological mTOR inhibition may sensitize GSCs to selective PI3Kα inhibition.

Pharmacological mTOR targeting enhances the antineoplastic effects of selective PI3Kα inhibition in medulloblastoma

Despite recent advances in the treatment of medulloblastoma, patients in high-risk categories still face very poor outcomes. Evidence indicates that a subpopulation of cancer stem cells contributes to therapy resistance and tumour relapse in these patients. To prevent resistance and relapse, the development of treatment strategies tailored to target subgroup specific signalling circuits in high-risk medulloblastomas might be similarly important as targeting the cancer stem cell population. We have previously demonstrated potent antineoplastic effects for the PI3Kα selective inhibitor alpelisib in medulloblastoma. Here, we performed studies aimed to enhance the anti-medulloblastoma effects of alpelisib by simultaneous catalytic targeting of the mTOR kinase. Pharmacological mTOR inhibition potently enhanced the suppressive effects of alpelisib on cancer cell proliferation, colony formation and apoptosis and additionally blocked sphere-forming ability of medulloblastoma stem-like cancer cells in vitro. We identified the HH effector GLI1 as a target for dual PI3Kα and mTOR inhibition in SHH-type medulloblastoma and confirmed these results in HH-driven Ewing sarcoma cells. Importantly, pharmacologic mTOR inhibition greatly enhanced the inhibitory effects of alpelisib on medulloblastoma tumour growth in vivo. In summary, these findings highlight a key role for PI3K/mTOR signalling in GLI1 regulation in HH-driven cancers and suggest that combined PI3Kα/mTOR inhibition may be particularly interesting for the development of effective treatment strategies in high-risk medulloblastomas.

Potent Antineoplastic Effects of Combined PI3Kα-MNK Inhibition in Medulloblastoma

Medulloblastoma is a highly malignant pediatric brain tumor associated with poor outcome. Developing treatments that target the cancer stem cell (CSC) population in medulloblastoma are important to prevent tumor relapse and induce long-lasting clinical responses. We utilized medulloblastoma neurospheres that display CSC characteristics and found activation of the PI3K/AKT pathway in sphere-forming cells. Of all class IA PI3Ks, only the PI3Kα isoform was required for sphere formation by medulloblastoma cells. Knockdown of p110α, but not p110β or p110δ, significantly disrupted cancer stem cell frequencies as determined by extreme limiting dilution analysis (ELDA), indicating an essential role for the PI3Kα catalytic isoform in medulloblastoma CSCs. Importantly, pharmacologic inhibition of the MAPK-interacting kinase (MNK) enhanced the antineoplastic effects of targeted PI3Kα inhibition in medulloblastoma. This indicates that MNK signaling promotes survival in medulloblastoma, suggesting dual PI3Kα and MNK inhibition may provide a novel approach to target and eliminate medulloblastoma CSCs. We also observed a significant reduction in tumor formation in subcutaneous and intracranial mouse xenograft models, which further suggests that this combinatorial approach may represent an efficient therapeutic strategy for medulloblastoma. IMPLICATIONS: These findings raise the possibility of a unique therapeutic approach for medulloblastoma, involving MNK targeting to sensitize medulloblastoma CSCs to PI3Kα inhibition.

HDL nanoparticles targeting sonic hedgehog subtype medulloblastoma

Medulloblastoma is the most common paediatric malignant brain cancer and there is a need for new targeted therapeutic approaches to more effectively treat these malignant tumours, which can be divided into four molecular subtypes. Here, we focus on targeting sonic hedgehog (SHH) subtype medulloblastoma, which accounts for approximately 25% of all cases. The SHH subtype relies upon cholesterol signalling for tumour growth and maintenance of tumour-initiating cancer stem cells (CSCs). To target cholesterol signalling, we employed biomimetic high-density lipoprotein nanoparticles (HDL NPs) which bind to the HDL receptor, scavenger receptor type B-1 (SCARB1), depriving cells of natural HDL and their cholesterol cargo. We demonstrate uptake of HDL NPs in SCARB1 expressing medulloblastoma cells and depletion of cholesterol levels in cancer cells. HDL NPs potently blocked proliferation of medulloblastoma cells, as well as hedgehog-driven Ewing sarcoma cells. Furthermore, HDL NPs disrupted colony formation in medulloblastoma and depleted CSC populations in medulloblastoma and Ewing sarcoma. Altogether, our findings provide proof of principle for the development of a novel targeted approach for the treatment of medulloblastoma using HDL NPs. These findings present HDL-mimetic nanoparticles as a promising therapy for sonic hedgehog (SHH) subtype medulloblastoma and possibly other hedgehog-driven cancers.

Differential Response of Glioma Stem Cells to Arsenic Trioxide Therapy Is Regulated by MNK1 and mRNA Translation

Mesenchymal (MES) and proneural (PN) are two distinct glioma stem cell (GSC) populations that drive therapeutic resistance in glioblastoma (GBM). We screened a panel of 650 small molecules against patient-derived GBM cells to discover compounds targeting specific GBM subtypes. Arsenic trioxide (ATO), an FDA-approved drug that crosses the blood-brain barrier, was identified as a potent PN-specific compound in the initial screen and follow-up validation studies. Furthermore, MES and PN GSCs exhibited differential sensitivity to ATO. As ATO has been shown to activate the MAPK-interacting kinase 1 (MNK1)-eukaryotic translation initiation factor 4E (eIF4E) pathway and subsequent mRNA translation in a negative regulatory feedback manner, the mechanistic role of ATO resistance in MES GBM was explored. In GBM cells, ATO-activated translation initiation cellular events via the MNK1-eIF4E signaling axis. Furthermore, resistance to ATO in intracranial PDX tumors correlated with high eIF4E phosphorylation. Polysomal fractionation and microarray analysis of GBM cells were performed to identify ATO's effect on mRNA translation and enrichment of anti-apoptotic mRNAs in the ATO-induced translatome was found. Additionally, it was determined that MNK inhibition sensitized MES GSCs to ATO in neurosphere and apoptosis assays. Finally, examination of the effect of ATO on patients from a phase I/II clinical trial of ATO revealed that PN GBM patients responded better to ATO than other subtypes as demonstrated by longer overall and progression-free survival.Implications: These findings raise the possibility of a unique therapeutic approach for GBM, involving MNK1 targeting to sensitize MES GSCs to drugs like arsenic trioxide. Mol Cancer Res; 16(1); 32-46. ©2017 AACR.

Abstract LB-009: Mnk targeting enhances vulnerability of medulloblastoma stem-like cancer cells to PI3K-p110alpha inhibition

Our recent work suggested that inhibition of mTORC1 activates Mnk in a PI3K-dependent manner, thereby providing a survival mechanism for medulloblastoma cells. The PI3K-Akt axis represents an important survival pathway that also confers therapy resistance to medulloblastoma stem cells, resulting in tumor recurrence. Here, we investigated a role for p110 isoforms of PI3K in medulloblastoma stem-like cancer cell biology and studied the potential of Mnk inhibition for sensitizing medulloblastoma stem-like cancer cells and orthotopic xenograft tumors to PI3K inhibition.

We used medulloblastoma cell lines Daoy and D556 grown as conventional 2-D cultures or under stem-cell conditions as 3-D neurospheres to elucidate the roles of PI3K-Akt signaling in medulloblastoma proliferation, colony formation and stem cell function. We employed extreme limiting dilution analysis (ELDA) to ask whether concomitant Mnk inhibition enhances antineoplastic effects of PI3K inhibition on cancer stem cell growth. Additionally, in a preliminary intracereballar xenograft mouse study, we investigated the effects of pharmacologic PI3K and Mnk inhibition.

We found that Akt activity greatly increased when 2-D cultures were converted into 3-D neurospheres. This Akt activation coincided with increased expression of CD133 and nestin, suggesting an important role for PI3K-Akt signaling in medulloblastoma stem cells. The p110a specific inhibitor BYL-719 blocked this Akt activation in neurospheres indicating this Akt activation is mediated by p110a. Consistently, of all class I PI3K catalytic isoforms (p110a, p110b, p110d and p110g) only knockdown of p110a disrupted stem cell frequencies in ELDA. We previously reported that mTORC1 inhibition engages Mnk signaling in a negative feedback manner to promote survival. Here we show that Mnk inhibition by CGP57380 sensitized medulloblastoma cells for pharmacologic inhibition and siRNA-mediated knockdown of p110a both in 2-D cancer cells and 3-D stem-like cancer cell cultures. After intracerebellar injection of medulloblastoma cells in nude mice, we found that combined targeting of PI3K-p110a and Mnk results in inhibition of tumor growth and increased survival.

In summary, pharmacologic inhibition of PI3K-p110a by BYL-719 showed potent activity against medulloblastoma cells and stem-like cancer cells. Knockdown of p110a disrupted cancer stem cell frequency in ELDA and this effect was greatly enhanced by pharmacologic inhibition of Mnk. Finally, in an orthotopic mouse model we found that concomitant inhibition of p110a and Mnk prolonged survival and reduced tumor size. The striking effects of concomitant Mnk inhibition on stem-like cancer cells, neurospheres and tumors is particularly interesting as it suggests enhanced vulnerability of the therapy-resistant, tumor-initiating cancer stem cell population to p110a inhibition in medulloblastoma.

Citation Format: Jonathan B. Bell, Frank Eckerdt, Quanhong Ma, Jessica R. Clymer, Stewart Goldman, Rintaro Hashizume, Leonidas C. Platanias. Mnk targeting enhances vulnerability of medulloblastoma stem-like cancer cells to PI3K-p110alpha inhibition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-009.

MNK Inhibition Disrupts Mesenchymal Glioma Stem Cells and Prolongs Survival in a Mouse Model of Glioblastoma

Glioblastoma multiforme remains the deadliest malignant brain tumor, with glioma stem cells (GSC) contributing to treatment resistance and tumor recurrence. We have identified MAPK-interacting kinases (MNK) as potential targets for the GSC population in glioblastoma multiforme. Isoform-level subtyping using The Cancer Genome Atlas revealed that both MNK genes (MKNK1 and MKNK2) are upregulated in mesenchymal glioblastoma multiforme as compared with other subtypes. Expression of MKNK1 is associated with increased glioma grade and correlated with the mesenchymal GSC marker, CD44, and coexpression of MKNK1 and CD44 predicts poor survival in glioblastoma multiforme. In established and patient-derived cell lines, pharmacologic MNK inhibition using LY2801653 (merestinib) inhibited phosphorylation of the eukaryotic translation initiation factor 4E, a crucial effector for MNK-induced mRNA translation in cancer cells and a marker of transformation. Importantly, merestinib inhibited growth of GSCs grown as neurospheres as determined by extreme limiting dilution analysis. When the effects of merestinib were assessed in vivo using an intracranial xenograft mouse model, improved overall survival was observed in merestinib-treated mice. Taken together, these data provide strong preclinical evidence that pharmacologic MNK inhibition targets mesenchymal glioblastoma multiforme and its GSC population.

IMPLICATIONS

These findings raise the possibility of MNK inhibition as a viable therapeutic approach to target the mesenchymal subtype of glioblastoma multiforme. Mol Cancer Res; 14(10); 984-93. ©2016 AACR.

Abstract B26: MAPK-interacting kinase inhibition sensitizes glioblastoma and glioma stem cells to arsenic trioxide

Glioblastoma (GBM) is the deadliest primary brain tumor with a median survival of around one year. Arsenic trioxide (ATO) is an emerging therapy for the treatment of GBM and other malignant brain tumors. The cytotoxic effects of ATO are mainly mediated by the production of reactive oxygen species and induction of cell death pathways. However, glioma stem cells in heterogeneous GBM tumors impart resistance by activation of survival pathways, thereby preventing therapeutic responses to cytotoxic agents such as ATO. We have previously shown that ATO responses in leukemia are antagonized by the MAPK-interacting kinases (MNKs), which activate protein translation and survival pathways including the eukaryotic translation initiation factor 4E (eIF4E) in response to ATO treatment. Yet, the role of MNK signaling in GBM and glioma stem cells and the potential of using MNK inhibitors to sensitize GBM to ATO has not been explored. In this study, we sought to determine the mechanisms by which MNK signaling regulates arsenic trioxide responses in GBM and glioma stem cells.

GBM cell lines were treated with ATO in the presence or absence of MNK inhibitors or siRNA against MNK isoforms. Western blots of treated samples were analyzed with antibodies against phosphorylated eIF4E, the key downstream effector of the MNKs. Following treatment with ATO and MNK inhibitors, proliferation rate and apoptosis were determined by WST-1 assay and Annexin V-FITC/PI staining. GBM cell lines were grown under stem cell conditions and subjected to qPCR and flow cytometry to monitor CD44 expression and aldehyde dehydrogenase (ALDH) activity, both markers of stemness. Patient-derived glioma stem cell lines displaying mesenchymal-like phenotype were treated with ATO and MNK inhibitors and analyzed by neurosphere formation assay.

Treatment of GBM cell lines with ATO resulted in MNK activation and induction of eIF4E phosphorylation in a MNK1-depedent manner. Furthermore, MNK inhibition sensitized GBM cells to the anti-proliferative and pro-apoptotic effects of ATO. Knockdown of MNK1 in GBM cell lines grown under stem cell conditions decreased neurosphere formation. Finally, pharmacological MNK inhibition sensitized mesenchymal-like glioma stem cells to ATO. Our results suggest ATO in combination with MNK inhibition might represent a new approach for the treatment of GBM, in particular the therapy-resistant glioma stem cell subpopulation.

Citation Format: Jonathan B. Bell, Frank Eckerdt, Ahmet Dirim Arslan, Asneha Iqbal, Angel A. Alvarez, Shi-Yuan Cheng, Ichiro Nakano, Leonidas C. Platanias. MAPK-interacting kinase inhibition sensitizes glioblastoma and glioma stem cells to arsenic trioxide. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr B26.

Numerical simulation of a laboratory-scale turbulent V-flame

We present a three-dimensional, time-dependent simulation of a laboratory-scale rod-stabilized premixed turbulent V-flame. The experimental parameters correspond to a turbulent Reynolds number, Re(t) = 40, and to a Damköhler number, D(a) = 6. The simulations are performed using an adaptive time-dependent low-Mach-number model with detailed chemical kinetics and a mixture model for differential species diffusion. The algorithm is based on a second-order projection formulation and does not require an explicit subgrid model for turbulence or turbulence/chemistry interaction. Adaptive mesh refinement is used to dynamically resolve the flame and turbulent structures. Here, we briefly discuss the numerical procedure and present detailed comparisons with experimental measurements showing that the computation is able to accurately capture the basic flame morphology and associated mean velocity field. Finally, we discuss key issues that arise in performing these types of simulations and the implications of these issues for using computation to form a bridge between turbulent flame experiments and basic combustion chemistry.

Herpes simplex encephalitis. A study of seven patients and their immunological response prior to routine acyclovir treatment

OBJECTIVES

A retrospective study on cerebrospinal fluid (CSF) samples was made possible by access to a large CSF bank, which has been supplemented by the well characterised prior collection of CSF from patients with Herpes simplex encephalitis (including serial samples from some patients and kindly donated by Professor Maurice Longson, Manchester). These samples are of particular interest because they were collected prior to the routine administration of acyclovir.

METHODS

Although an earlier study had shown that there was indeed a correlation between higher titres of antibody and a better outcome, the data did not emerge with statistical significance. The current study was based upon an improved method, which demonstrates the antigen-specific clonality of the immune response.

RESULTS

The primitive polyclonal anamnestic response was contrasted with the strong antigen-specific response, which was manifested by a monoclonal pattern in some patients. A clear distinction emerged between two sub-groups of patients on the basis of these findings, which showed a statistically significant (P<0.03) correlation with outcome.

CONCLUSIONS

This has allowed us to further support the hypothesis that a strong immunological response has positive prognostic value during the course of the disease.

The drosophila aeroplane mutant is caused by an I-element insertion into a tissue-specific teashirt enhancer motif

In Drosophila melanogaster, aeroplane (ae) is a regulatory allele of teashirt (tsh), and the mutant wing posture phenotype of homozygous ae flies is caused by a defect in the hinge region of the wing, whereby the base of the wing at the proximal ventral radius is fused to the thorax in the region of the pleural wing process. The apparent paralysis of the wings and the drooping halteres are caused by an I-element insertion into a 3' noncoding sequence of tsh. The cis-acting regulatory element interrupted by the I element is required, to drive tsh expression in the regions of the developing adult that give rise to proximal wing and haltere tissues. Loss of this expression results in the fusion of the proximal structures of the wing and halteres to the thoracic cuticle. Further characterization of this tsh regulatory motif has now identified an additional enhancer activity directing tsh expression in tissues forming portions of the midgut. Subdivision of this midgut enhancer activity has identified putative negatively acting motifs.

Identification of a regulatory allele of teashirt (tsh) in Drosophila melanogaster that affects wing hinge development. An adult-specific tsh enhancer in Drosophila

A cis-acting regulatory element defined herein is required to drive teashirt (tsh) expression in the regions of the developing adult that give rise to proximal wing and haltere tissues. Loss of this expression results in the fusion of the proximal structures of the wing and halteres to the thoracic cuticle. This represents the first description of a viable adult-specific regulatory allele of tsh with a visible phenotype, and it enlarges our understanding of the expression of tsh and its function during the development of the adult.

Rediscovery and further characterization of the aeroplane (ae) wing posture mutation in Drosophila melanogaster

In 1931, Theodore Quelprud characterized a novel spontaneous mutation in Drosophila melanogaster, which was named aeroplane (ae) based on its abnormal wing posture. Although the characterization of the original ae locus was minimal, it is very likely that another allele of this extinct mutation has now been identified. aeroplane-like (ae-l) was isolated as a by-product of a transformation experiment. The apparent wing paralysis is not caused by any obvious abnormalities in the thorax, wing, indirect flight muscles or direct flight muscles. Classical genetic complementation analyses of ae-l with other genes in the region suggest that it represents an allele of a novel locus. Unexpectedly, a molecular examination revealed that the physical lesion identified in the ae-l mutant is exceptionally close to the homeotic gene teashirt (tsh) and, indeed, may represent an unusual allele of teashirt.

Molecular interactions between Vestigial and Scalloped promote wing formation in Drosophila

Scalloped (Sd) and Vestigial (Vg) are each needed for Drosophila wing development. We show that Sd is required for Vg function and that altering their relative cellular levels inhibits wing formation. In vitro, Vg binds directly to both Sd and its human homolog, Transcription Enhancer Factor-1. The interaction domains map to a small region of Vg that is essential for Vg-mediated gene activation and to the carboxy-terminal half of Sd. Our observations indicate that Vg and Sd function coordinately to control the expression of genes required for wing development, which implies that Vg is a tissue-specific transcriptional intermediary factor of Sd.

The thermal explosion revisited

The classical problem of the thermal explosion in a long cylindrical vessel is modified so that only a fraction alpha of its wall is ideally thermally conducting while the remaining fraction 1-alpha is thermally isolated. Partial isolation of the wall naturally reduces the critical radius of the vessel. Most interesting is the case when the structure of the boundary is a periodic one, so that the alternating conductive alpha and isolated 1-alpha parts of the boundary occupy together the segments 2pi/N (N is the number of segments) of the boundary. A numerical investigation is performed. It is shown that at small alpha and large N, the critical radius obeys a scaling law with the coefficients depending on N. For large N, the result is obtained that in the central core of the vessel the temperature distribution is axisymmetric. In the boundary layer near the wall having the thickness approximately 2pir0/N (r0 is the radius of the vessel), the temperature distribution varies sharply in the peripheral direction. The temperature distribution in the axisymmetric core at the critical value of the vessel radius is subcritical.

A genetic and molecular analysis of an invectedDominant mutation in Drosophila melanogaster

The invected gene of Drosophila melanogaster is a homeobox-containing gene that is closely related to engrailed. A dominant gain of function allele, invectedDominant, was derived from mutagenesis of a dominant allele of vestigial, In(2R)vgW. A careful analysis of the phenotype of invectedDominant shows that it is associated with a transformation of the anterior compartment of the wing to a posterior fate. This transformation is normally limited to the wing blade itself and does not involve the remaining tissues derived from the wing imaginal disc, including the wing hinge and dorsal thorax of the fly. The ectopic expression of invected protein associated with invectedDominant correlates spatially with the normal expression pattern of vestigial in the wing imaginal disc, suggesting that control elements of vestigial are driving ectopic invected expression. This was confirmed by sequence analysis that shows that the dominant vestigial activity was eliminated by a deletion that removes the 3' portion of the vestigial coding region. This leaves a gene fusion wherein the vestigial enhancer elements are still juxtaposed immediately 5' to the invected transcriptional start site, but with the vg sequences harboring an additional lesion. Unlike recessive invected alleles, the invectedDominant allele produces an observable phenotype, and as such should prove useful in determining the role of invected in patterning the wing imaginal disc. Genetic analysis has shown that mutations of polyhomeotic, a gene involved in regulating engrailed expression, cause a reproducible alteration in the invectedDominant phenotype. Finally, the invectedDominant allele should prove valuable for identifying and characterizing genes that are activated within the posterior compartment. A screen using various lacZ lines that are asymmetrically expressed in an anterior-posterior manner in the wing imaginal disc isolated one line that shows posterior-specific expression within the transformed anterior compartment.

Base miscoding and strand misalignment errors by mutator Klenow polymerases with amino acid substitutions at tyrosine 766 in the O helix of the fingers subdomain

A mutant derivative of Klenow fragment DNA polymerase containing serine substituted for tyrosine at residue 766 has been shown by kinetic analysis to have an increased misinsertion rate relative to wild-type Klenow fragment, but a decreased rate of extension from the resulting mispairs (Carroll, S. S., Cowart, M., and Benkovic, S. J. (1991) Biochemistry 30, 804-813). In the present study we use an M13mp2-based fidelity assay to study the error specificity of this mutator polymerase. Despite its compromised ability to extend mispairs, the Y766S polymerase and a Y766A mutant both have elevated base substitution error rates. The magnitude of the mutator effect is mispair-specific, from no effect for some mispairs to rates elevated by 60-fold for misincorporation of TMP opposite template G. The results with the Y766S mutant are remarkably consistent with the earlier kinetic analysis of misinsertion, demonstrating that either approach can be used to identify and characterize mutator polymerases. Both the Y766S and Y766A mutant polymerases are also frameshift mutators, having elevated rates for two-base deletions and a 276-base deletion between a direct repeat sequence. However, neither mutant polymerase has an increased error rate for single-base frameshifts in repetitive sequences. This error specificity suggests that the deletions generated by the mutator polymerases are initiated by misinsertion rather than by strand slippage. When considered with recent structure-function studies of other polymerases, the data indicate that the nucleotide misinsertion and strand-slippage mechanisms for polymerization infidelity are differentially affected by changes in distinct structural elements of DNA polymerases that share similar subdomain structures.

Role of CD34+ cells in engraftment after high-dose melphalan in multiple myeloma patients given peripheral blood stem cell rescue

During the period December 1992 to June 1995, 95 patients were treated with high-dose melphalan (HDM) with peripheral blood stem cell rescue (PBSCR). Sixty-five had received previous treatment and 28 had relapsed. Among patients who had relapsed 21/28 had received HDM previously including one who received HDM twice during the course of the study. Seventy-five patients were given HDM/PBSCR for the first time. Comparisons have been made between engraftment times for platelets and neutrophils among patients who received less than or greater than 2 x 10(6) CD34+ cells at rescue. Analyses have also been done to evaluate the effect of previous HDM on recovery. Mobilization of progenitor cells was done with granulocyte colony-stimulating factor (G-CSF). Patients received only PBSCR. No growth factors were given to the PBSCR recipients during the recovery period. The percentage of patients from whom the number of CD34+ cells mobilized was > 2 x 10(6)/kg was similar in patients who received HDM for the first time (23%) compared with those who had had it previously (19%). The yield of CD34+ cells correlated with the number of granulocyte-macrophage colony forming units (CFU-GM). Although the number of CD34+ cells infused was < 2 x 10(6)/kg in 77% of patients, all engrafted for neutrophils to > 0.5 x 10(9)/l. This was delayed in patients who had had previous HDM (P < 0.02). Platelet recovery to > 25, 50 and 100 x 10(9)/l was delayed in all patients who received < 2 x 10(6) CD34+ cells/kg infused (P < 0.02). In patients who had had previous HDM both neutrophil (P < 0.05) and platelet recovery (P < 0.007) were delayed compared with recovery in patients who had not had HDM. In patients who had had previous HDM and received < 2 x 10(6) CD34+ cells/kg infused only 3/17 regained platelets to > 100 x 10(9)/l compared with 3/4 who had > 2 x 10(6) CD34+ cells/kg infused (P < 0.05 Fisher's exact test). There was no evidence that low numbers of CD34+ cells in the PBSCR were associated with early death. The data show that previous treatment with HDM had adverse effects on the subsequent engraftment of platelets among patients given HDM/PBSCR. The data suggest that additional measures are needed to achieve platelet reconstitution in these heavily pre-treated patients.

Lymphocyte recovery and clinical response in multiple myeloma patients receiving interferon alpha 2 beta after intensive therapy

The recovery of immunoregulatory cells in the peripheral blood of patients with multiple myeloma receiving maintenance therapy with interferon alpha 2 beta (IFN-alpha 2 beta) after intensive therapy with high-dose melphalan and autologous bone marrow or peripheral blood stem cell rescue was studied. IFN-alpha 2 beta significantly inhibited the recovery of CD3+, CD4+, CD8+, CD56+/CD3- and CD16+/CD3- lymphocytes compared with numbers found in patients who had no further post-transplant treatment, but had no effect on the recovery of CD19+ cells. Among patients who did not receive IFN-alpha 2 beta, the number of CD8+, CD56+/CD3- and CD16+CD3- lymphocytes recovered to values similar to normal volunteers with increasing time after intensive therapy, however the number of CD4+ cells remained significantly below levels found in normal volunteers. Although CD16+/CD3- and CD56+/CD3- cell numbers were reduced in patients receiving IFN-alpha 2 beta, natural killer (NK) activity was not affected. The levels of soluble interleukin 2 receptor (sIL-2R) were similar in all patients and IL-2 was not detected in any patient. At the time of writing, of the total of 69 patients, seven have relapsed, of whom three were receiving IFN-alpha 2 beta, however there was no correlation between the absolute numbers of any lymphocyte subset with imminent relapse. The data suggest that the recovery of a specific lymphocyte subset(s) in peripheral blood is unlikely to be associated with the maintenance of response after intensive therapy.

2',5'-Oligoadenylate synthetase levels in patients with multiple myeloma receiving maintenance therapy with interferon alpha 2b do not correlate with clinical response

In clinical trials with interferon alpha 2b (IFN-alpha 2b) as maintenance therapy for multiple myeloma, the therapeutic benefit is inconclusive. Although the mechanism(s) by which IFN-alpha 2b prolongs remission in some patients is unknown, 2',5'-oligoadenylate synthetase (2,5-A synthetase) has been used as an objective indicator that IFN-alpha 2b is active in vivo. The enzyme was assayed in cytosol preparations of peripheral blood mononuclear cells (MNCs) from 111 patients who were receiving IFN-alpha 2b and 54 patients who were not, using an assay which measures the conversion of [alpha-32P]ATP to triphospho(adenylyl 2',5')adenosine. 2,5-A synthetase activity was compared with response to intensive therapy and with duration of maintenance therapy. Seventy-three per cent of patients had measurable amounts of 2,5-A synthetase during the first 6 months of maintenance therapy. This percentage decreased with longer follow-up but not significantly. There was no difference between the magnitude of enzyme induction amongst patients who were in complete remission, partial response or who had no change in disease status following intensive therapy. Peripheral blood T cells were a major source of 2,5-A synthetase activity in patients receiving the cytokine. However, both T and B cells produced the enzyme following exposure to IFN-alpha in vitro. The data show that the level of 2,5-A synthetase in patients with multiple myeloma is not indicative of clinical response to IFN-alpha 2b.

Distinguishable functions for engrailed and invected in anterior-posterior patterning in the Drosophila wing

Subdivision of the limb primordia into compartments initiates pattern formation in the developing limbs. Interaction between distinctly specific cells in adjacent compartments leads to localized expression of the secreted signalling molecules Wingless (Wg) or Decapentaplegic (Dpp), which in turn organize pattern and control growth of the limbs. The homeobox gene engrailed has been implicated in specification of posterior cell fate, whereas the LIM/homeobox gene, apterous, specifies dorsal fate. Removing apterous activity causes a complete transformation from dorsal to ventral fate and leads to the formation of an ectopic dorsal-ventral boundary organizer. By contrast, removing engrailed activity causes incomplete morphological transformation from posterior to anterior fate in the wing, and fails to produce an ectopic anterior-posterior organizer (reviewed in ref.2). Complete transformation can only be effected by simultaneously eliminating activity of engrailed and its homologue invected. Here we show that invected functions principally to specify posterior cell fate. Thus establishment of the anterior-posterior organizer and control of compartment identity are genetically distinguishable, and invected may perform a discrete subset of functions previously ascribed to engrailed.

G-CSF is a major component of colony-stimulating activity (CSA) in the plasma of patients with multiple myeloma after treatment with high-dose melphalan (HDM)

Colony-stimulating activity (CSA) was measured by the production of granulocyte-macrophage colony-forming units (GM-CFU) from normal donor bone marrow in the plasma of 29 patients with multiple myeloma (MM) after intensive treatment with high-dose melphalan (HDM) with or without autologous bone marrow rescue (ABMR). Although patients who received ABMR had an earlier recovery of circulating neutrophils compared with those who received HDM alone, the time at which CSA reached a maximum was similar in both groups (10 to 11 days) after therapy. The decline in CSA correlated with the recovery of the neutrophil count. In plasma from patients who received recombinant human granulocyte colony-stimulating factor (rhG-CSF), in addition to an autograft, CSA reached a maximum earlier (7 days). Furthermore, neutrophil recovery was earlier in these patients. Platelet recovery was not increased by rhG-CSF. The time at which CSA was maximum in four patients who were undergoing intensive therapy for the second time occurred 9 days after treatment with HDM. Although the period without neutrophils was longer in three (of four) patients who survived long term, one patient who received rhG-CSF had a shorter period of neutropenia than the two who had not had the cytokine. G-CSF was detected in plasma from seven of seven patients but not at all times after treatment. In plasma samples that contained G-CSF, colony numbers were increased by recombinant interleukin-4 (rIL-4) in vitro. Neither IL-3 nor GM-CSF was detected in plasma; however, antibody to GM-CSF reduced CSA in all samples after intensive therapy. The data suggest that CSA is a consistent physiologic response to intensive therapy, even in previously treated patients, but that hematologic recovery is dependent on the availability of viable progenitor cells.

Protected P-element termini suggest a role for inverted-repeat-binding protein in transposase-induced gap repair in Drosophila melanogaster

P-element transposition is thought to occur by a cut-and paste mechanism that generates a double-strand break at the donor site, the repair of which can lead to internally deleted elements. We have generated a series of both phenotypically stronger and weaker allelic derivatives of vg21, a vestigial mutant caused by a P-element insertion in the 5' region of the gene. Virtually all of the new alleles arose by internal deletion of the parental element in vg21, and we have characterized a number of these internally deleted P elements. Depending upon the selection scheme used, we see a very different spectrum of amount and source of P-element sequences in the resultant derivatives. Strikingly, most of the breakpoints occur within the inverted-repeats such that the last 15-17 bp of the termini are retained. This sequence is known to bind the inverted-repeat-binding protein (IRBP). We propose that the IRBP may act to preserve the P-element ends when transposition produces a double-strand gap. This allows the terminus to serve as a template upon which DNA synthesis can act to repair the gap. Filler sequences found at the breakpoints of the internally deleted P elements resemble short stretches, often in tandem arrays, of these terminal sequences. The structure of the filler sequences suggests replication slippage may occur during the process of gap repair.

The proliferation of multiple myeloma colonies (MY-CFUc) in vitro is independent of prognosis and is not associated with mutated N- or K-ras alleles in human bone marrow aspirates

During the period September 1987 to March 1993 the proliferation of myeloma cells as colonies (MY-CFUc) in vitro was examined in bone marrow aspirates from 43 patients with multiple myeloma and two patients with Waldenström's macroglobulinaemia. Twenty-four samples from 45 patients, of whom three were at presentation, four were in complete remission (CR), six had achieved a partial response (PR) and 11 had progressive disease (PD), produced MY-CFUc in vitro. The same bone marrow aspirates or one taken within 2 months of that assessed for MY-CFUc were used in the polymerase chain reaction (PCR). Genomic DNA was analysed for mutations in N- and K-ras by slot blotting of the amplified products from the PCR with 32P-labelled probes and by direct sequencing. No mutations were detected in N- or K-ras proto-oncogenes at codons 12, 13 or 61 in any sample. Eleven of the patients from whom MY-CFUc were produced remain alive with a median survival of 73 months (range 15-75 months). MY-CFUc have been cultured from 19 of these 24 patients on subsequent occasions, of whom nine remain alive. Among patients whose cells did not produce MY-CFUc in vitro at the time of sampling for mutated ras alleles, biopsy samples from four patients have produced MY-CFUc in vitro on subsequent occasions, of whom one patient remains alive. The data show that the proliferation of MY-CFUc in vitro occurred independently of disease status and was not indicative of prognosis. The failure to detect mutated N- or K-ras alleles in any sample suggests that if such mutations were present in the cells which form colonies in vitro they represented less than 0.1% of the tumour burden and did not affect the survival of this group of patients.

Neutralising antibodies in patients with multiple myeloma receiving maintenance therapy with interferon alpha 2b

In a study of 29 patients who were receiving or had received interferon alpha 2b (IFN-alpha 2b) as maintenance therapy for multiple myeloma, antibodies were detected in 58% (17/29) of patients measured by a solid-phase enzyme-linked immunosorbent assay (ELISA). Only 7/17 patients who were positive for antibody in the ELISA had neutralising antibody to IFN-alpha 2b, measured by virus growth inhibition. These patients comprised six who were receiving IFN-alpha 2b at the time of assessment and one who had finished treatment. Among patients who were receiving the cytokine, four had progressive disease, one was in complete remission and one in partial remission. Neutralising activity was also detected to natural human leucocyte IFN-alpha in the same patients. Two patients who were positive for neutralising antibody remain in remission and are continuing to receive IFN-alpha 2b. These two patients have since lost their neutralising titre. No neutralising antibody to IFN-alpha 2b or natural human leucocyte IFN-alpha was detected in serum from six normal donors. The data suggest that neutralising antibody formation in patients with multiple myeloma is not responsible for relapse in patients receiving IFN-alpha 2b. The transient nature of neutralising antibody production in patients who remain in remission suggests that this response to IFN-alpha 2b is not associated with memory B cells.

Targeting of an enhancer trap to vestigial

The vestigial gene (vg+) is required for normal wing development and is expressed in a spatially distinct pattern in imaginal discs. We have exploited a general property of P element alleles to target an enhancer trap to the 5' region of the gene. By replacing the P element resident at this site in vg21 with a P element carrying a lacZ reporter gene, the vglacZ1 allele was selected on the basis of its increased mutant phenotype. In contrast to vg+ expression, which occurs primarily in the presumptive wing margin and hinge, beta-galactosidase expression in vglacZ1 wing discs is localized to the dorsal wing surface and displays homologous haltere expression. The targeting of P element enhancer traps could be readily extended to other genes with low rates of primary P element insertion.

TGF beta 1 and IL-4 have opposing effects on the proliferation of chronic phase chronic myeloid leukaemic cells stimulated by G-CSF in vitro

The effects of transforming growth factor beta 1 (TGF beta 1) have been studied in vitro on the clonogenicity of haemopoietic progenitor cells (CFU-CML) from 14 patients with chronic myeloid leukaemia (CML) in chronic phase and 13 normal donors. In 14/14 patients with CML, 5 ng of TGF beta 1/dish decreased CFU-CML-formation in cultures stimulated with 15 ng of granulocyte colony-stimulating factor (G-CSF)/dish (p < 0.0005) and in 13/14 patients TGF beta 1 reduced CFU-CML-formation induced by G-CSF in combination with 5 ng of recombinant human interleukin-4 (rhIL-4)/dish (p < 0.005). In 10/14 samples the number of CFU-CML were reduced to levels lower than in cultures containing G-CSF alone (p < 0.01). In contrast, TGF beta 1 had no significant inhibitory effect on the G-CSF-directed proliferation of normal donor mononuclear cells (MNC) either alone or in combination with rhIL-4. RhIL-4 increased G-CSF-induced colony formation in 13/14 CML samples (p < 0.001), but did not have the same effect in the normal donor samples. The in vitro clonogenicity of CML peripheral blood MNC stimulated with 15 ng of G-CSF could not be correlated with the white cell count or the percentage of CD34+ cells at diagnosis.

The functional analysis of nonsense suppressors derived from in vitro engineered Saccharomyces cerevisiae tRNA(Trp) genes

Nonsense suppressors derived from Saccharomyces cerevisiae tRNA(Trp) genes have not been identified by classical genetic screens, although one can construct efficient amber (am) suppressors from them by making the appropriate anticodon mutation in vitro. Herein, a series of in vitro constructed putative suppressor genes was produced to test if pre-tRNA(Trp) processing difficulties could help to explain the lack of classical tRNA(Trp)-based suppressors. It is clear that inefficient processing of introns from precursor tRNA(Trp), or inaccurate overall processing, may explain why some of these constructs fail to promote nonsense suppression in vivo. However, deficient processing must be only one of the reasons why classical tRNA(Trp)-based suppressors have not been characterized, as suppression may still be extremely weak or absent in instances where the in vitro construct can lead to an accumulation of mature tRNA(Trp). Furthermore, suppression is also very weak in strains transformed with an intronless derivative of a putative tRNA(Trp) ochre (oc) suppressor gene, wherein intron removal cannot pose a problem.

Expression of a Drosophila melanogaster amber suppressor tRNA(Ser) in Caenorhabditis elegans

The purpose of this study was to test a cloned amber-suppressing tRNA(Ser) gene derived from Drosophila melanogaster for its ability to produce amber suppression in the nematode Caenorhabditis elegans. To date, all characterized nonsense suppressors in C. elegans have been derived from tRNA(Trp) genes. Suppression was assayed by monitoring the reversal of a mutant tra-3 phenotype among individuals transformed with the cloned Drosophila suppressor gene. An amber allele of tra-3 results in masculinization of XX animals with accompanying sterility. Complete suppression was observed among the transformants. The presence of the heterologous transgene, in both suppressed experimental animals and controls injected with a non-suppressing wild-type Drosophila tRNA(Ser) gene, was verified by PCR amplification of DNA from single worms using primers flanking the tRNA(Ser) gene. Suppression by the heterologous transgene was comparable in quality to that produced by endogenous C. elegans suppressors, and, in frequency as well as quality, to that produced by a transgenic C. elegans tRNA(Trp)-derived suppressors. Thus, a heterologous suppressor gene will function in C. elegans, and it need not be based on tRNA(Trp).

Characterization of the tRNA(Trp) genes of Saccharomyces cerevisiae

The purpose of this work was to examine the tRNA(Trp)-encoding genes (tRNA(Trp)) of Saccharomyces cerevisiae to gain insight as to why tRNA(Trp) amber suppressors, isolated by conventional genetic techniques, have not been reported. The results herein indicate that the haploid yeast genome contains six tRNA(Trp) genes which map to five or six chromosomes. Not only do the six genes have identical coding sequences but their introns are also identical. Gene replacement experiments indicate that five copies of tRNA(Trp) are sufficient for cell viability. Thus, mutation of one tRNA(Trp) gene to a suppressor in vivo, lowering the functional number of tRNA(Trp) genes, would not be expected to be lethal.

A P element chimera containing captured genomic sequences was recovered at the vestigial locus in Drosophila following targeted transposition

A P element carrying the Dopa decarboxylase gene, P[Ddc], was targeted into vg21, a cryptic P element induced mutant allele of the vestigial (vg) locus. The resulting allele, vg28w, contained the expected P[Ddc] plus an additional 9.5 kb of DNA, captured from elsewhere on chromosome II. Reversion of the vg28w mutant allele demonstrated that the entire insert can excise but cannot reinsert at an appreciable frequency. We explain the targeted transposition as the repair of a double stranded gap, created by the excision of the P element at vg21, and suggest that the formation of chimeric elements may be an important component of P element dependent genomic instability.

Colony-stimulating activity in the serum of patients with hemopoietic malignancies after intensive chemotherapy/radiotherapy: its augmentation by GM-CSF in vivo and interleukin 4 in vitro

Colony-stimulating activity (CSA) in the serum of patients with hematological malignancies increased substantially after intensive therapy with cyclophosphamide/busulfan, cyclophosphamide/total body irradiation, or melphalan/total body irradiation. This was not dependent on patients receiving allogeneic bone marrow transplantation (ABMT) or autologous bone marrow rescue (ABMR). In 44 of 62 patients CSA was maximum approximately 7 days after chemotherapy/radiotherapy, whereas in 18 of 62 patients CSA was maximum between 9 and 20 days after therapy and decreased thereafter. The time course of CSA was not dependent on disease and was not affected by recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) given as a continuous infusion for 14 days after therapy; however, serum from patients receiving rhGM-CSF produced significantly more colonies from donor bone marrow than serum from patients who did not receive the cytokine (p = 0.013). Despite the early peak in CSA in the majority of patients, there was no correlation between the time at which CSA was maximum and the return of patients' neutrophils to 500/microliters. Recombinant human interleukin 4 (IL-4) increased the number of granulocyte-macrophage colony-forming unit colonies, principally granulocyte colony-forming unit colonies, from normal bone marrow exposed to patients' serum after intensive therapy and antibody to GM-CSF reduced colony numbers. The results suggest that after intensive therapy granulocyte colony-stimulating factor (G-CSF) as well as GM-CSF is released into the serum and, in addition to acting directly with G-CSF, IL-4 may stimulate mononuclear cells to produce and/or release G-CSF.

Control of Drosophila wing and haltere development by the nuclear vestigial gene product

The Dipteran flight appendages, the wings and halteres, develop from larval imaginal discs that also produce other sections of the second and third thoracic adult body segments. Loss of vestigial (vg) function in Drosophila selectively eliminates wing and haltere formation. Here, we show that vg expression is spatially restricted to the presumptive wing and haltere regions of these imaginal discs. An intronic regulatory element mediates this restriction and may elaborate upon cues that activate vg expression in the embryonic disc primordia. The nuclear vg protein lacks any recognized nucleic acid-binding motif but is comprised of two putative functional domains, one of which bears similarity to part of the Deformed homeotic protein and may mediate protein-protein interactions. These results suggest that vg is directly involved in determining which thoracic imaginal disc cells will form wings and halteres, perhaps by interacting with other nuclear regulatory proteins.

Comparison of interleukin-6 levels in the bone marrow of multiple myeloma patients with disease severity and clonogenicity in vitro

Fifteen of 25 bone marrow aspirates from 23 patients who presented or had been treated for multiple myeloma at the Royal Marsden Hospital produced myeloma colonies (MY-CFUc) in vitro. There was no correlation between disease severity and the level of interleukin-6 (IL-6) in bone marrow plasma nor was there any evidence that the level of IL-6 was higher in bone marrow aspirates from patients whose tumour produced MY-CFUc in vitro compared with those who did not. The mean level of IL-6 in the whole group of patients was 0.41 ng/ml (range 0.1-0.66 ng/ml), a value similar to that found in plasma from normal donor bone marrow, 0.42 ng/ml (range 0.14-0.62 ng/ml). Separation of peripheral blood cells from serum 24 h after collection, compared with 2 h after collection, resulted in a substantial increase of IL-6 in the serum. The results suggest that levels of IL-6 in bone marrow plasma is not a monitor of disease severity in multiple myeloma (MM) and that the collection and separation of blood and/or bone marrow samples into the cellular and aqueous components should be performed using standardized conditions to minimize inter-sample variation resulting from the release of IL-6 from the cellular components.

Eukaryotic DNA polymerase amino acid sequence required for 3'----5' exonuclease activity

We have identified an amino-proximal sequence motif, Phe-Asp-Ile-Glu-Thr, in Saccharomyces cerevisiae DNA polymerase II that is almost identical to a sequence comprising part of the 3'----5' exonuclease active site of Escherichia coli DNA polymerase I. Similar motifs were identified by amino acid sequence alignment in related, aphidicolin-sensitive DNA polymerases possessing 3'----5' proofreading exonuclease activity. Substitution of Ala for the Asp and Glu residues in the motif reduced the exonuclease activity of partially purified DNA polymerase II at least 100-fold while preserving the polymerase activity. Yeast strains expressing the exonuclease-deficient DNA polymerase II had on average about a 22-fold increase in spontaneous mutation rate, consistent with a presumed proofreading role in vivo. In multiple amino acid sequence alignments of this and two other conserved motifs described previously, five residues of the 3'----5' exonuclease active site of E. coli DNA polymerase I appeared to be invariant in aphidicolin-sensitive DNA polymerases known to possess 3'----5' proofreading exonuclease activity. None of these residues, however, appeared to be identifiable in the catalytic subunits of human, yeast, or Drosophila alpha DNA polymerases.

Purification and characterization of yeast orotidine 5'-monophosphate decarboxylase overexpressed from plasmid PGU2

Orotidine 5'-monophosphate decarboxylase (ODCase) has been overexpressed in yeast 15C cells transformed with a plasmid carrying the URA3 gene that encodes ODCase. Twenty g of cells having ODCase activity equal to 30 mg of pure enzyme per liter of cell culture were obtained after 9 h of galactose induction. To remove yeast proteases, a 60-90% ammonium sulfate fractionation step plus the addition of EDTA as an inhibitor of metallopeptidases was necessary. The purification protocol yielded ODCase that was protease-free and stable to storage at 4 degrees C for 16 months. The pure enzyme had a specific activity of 40 units/mg in 50 mM phosphate buffer, pH 6, and could be stored at -20 degrees C in 20% glycerol with retention of full activity for more than 2 years. The enzyme had a Km for orotidine 5'-monophosphate of 0.7 microM at pH 6 and 25 degrees C. The molecular weight of the plasmid-derived ODCase monomer determined by electrophoresis on denaturing polyacrylamide gels was 29,500. ODCase sedimented through sucrose density gradients as a monomer of about 30 kDa at low protein concentration and in the absence of ligands that bind at the catalytic site. An increase in the sedimentation rate could be induced by increasing the ODCase concentration or by adding ligands that are competitive inhibitors. ODCase sedimented in a single band typical of a protein of 46 kDa at the highest protein concentration studied or in the presence of 50 mM phosphate or 933 microM substrate (orotidine 5'-monophosphate) or product (UMP). A dimer sedimenting as a protein of about 64 kDa occurred in the presence of 50 microM 6-azauridine 5'-monophosphate or 2 microM 1-(5'-phospho-beta-D-ribofuranosyl) barbituric acid, competitive inhibitors of ODCase. These results resemble the ligand-induced subunit association of the ODCase domain of bifunctional UMP synthase and support the use of yeast ODCase as a model for ODCases from other species.

Investigation of the enzymatic mechanism of yeast orotidine-5'-monophosphate decarboxylase using 13C kinetic isotope effects

Orotidine-5'-monophosphate decarboxylase (ODCase) from Saccharomyces cerevisiae displays an observed 13C kinetic isotope effect of 1.0247 +/- 0.0008 at 25 degrees C, pH 6.8. The observed isotope effect is sensitive to changes in the reaction medium, such as pH, temperature, or glycerol content. The value of 1.0494 +/- 0.0006 measured at pH 4.0, 25 degrees C, is not altered significantly by temperature or glycerol, and thus the intrinsic isotope effect for the reaction is apparently being observed under these conditions and decarboxylation is almost entirely rate-determining. These data require a catalytic mechanism with freely reversible binding and one in which a very limited contribution to the overall rate is made by chemical steps preceding decarboxylation; the zwitterion mechanism of Beak and Siegel [Beak, P. & Siegel, B. (1976) J. Am. Chem. Soc. 98, 3601-3606], which involves only protonation of the pyrimidine ring, is such a mechanism. With use of an intrinsic isotope effect of 1.05, a partitioning factor of less than unity is calculated for ODCase at pH 6.0, 25 degrees C. A quantitative kinetic analysis using this result excludes the possibility of an enzymatic mechanism involving covalent attachment of an enzyme nucleophile to C-5 of the pyrimidine ring. The observed isotope effect does not rise to the intrinsic value above pH 8.5; instead, the observed isotope effects at 25 degrees C plotted against pH yield an asymmetric curve that at high pH plateaus at about 1.035. These data, in conjunction with the pH profile of Vmax/km, fit a kinetic model in which an enzyme proton necessary for catalysis is titrated at high pH, thus providing evidence for the catalytic mechanism of Beak and Siegel (1976).

Crystallization of yeast orotidine 5'-monophosphate decarboxylase complexed with 1-(5'-phospho-beta-D-ribofuranosyl) barbituric acid

Using an incomplete factorial experimental design, we have identified conditions for crystallization of yeast orotidine 5'-monophosphate decarboxylase (ODCase) in an unliganded state and complexed separately to two inhibitors: 6-azauridine 5'-monophosphate (aza-UMP) and 1-(5'-phospho-beta-D-ribofuranosyl) barbituric acid (BMP). Crystals of X-ray diffraction quality have been obtained of yeast ODCase complexed with BMP, a putative transition state analog inhibitor (Ki = 8.8 x 10(-12) M). ODCase:BMP complex crystals with a hexagonal rod habit were grown from a solution initially containing 12 mg/ml ODCase (205 microM dimer) plus 450 microM BMP by microdialysis at 4 degrees C against a mother liquor which consisted of 0.1 M Na-PIPES-acetate (pH 6.4), 37.5 microM BMP, 5 mM mercaptoethanol, 1% polyethylene glycol 400, and 2.3 M ammonium sulfate. Crystals were analyzed using precession photography and were assigned to trigonal space group R32 with unit cell dimensions a = b = 115 A, c = 385 A. The crystal density is 1.245 g/cm3 indicating the presence of two ODCase: BMP complex dimers (118 kDa each) per asymmetric unit with a packing density of 2.08 A3/Da and 41% solvent content. The morphological habit of crystals of the ODCase:BMP complex changed when the initial ammonium sulfate concentration was increased in 0.05 M steps from 2.3 to 2.45 M. All of these crystals diffracted to at least 3.0 A resolution over a period of several weeks at room temperature and are isomorphous.

Suppression of carbamazepine-induced rash with prednisone

We report our experience with 20 patients who developed a rash shortly after the introduction of carbamazepine and were treated with prednisone and an antihistamine. Sixteen patients were successfully continued on carbamazepine while 4 had to discontinue the drug.

Interleukin-6 is a cofactor for the growth of myeloid cells from human bone marrow aspirates but does not affect the clonogenicity of myeloma cells in vitro

Several groups have claimed that IL-6 is a growth factor for human myeloma cells in vitro. Bone marrow aspirates from 30 patients at different stages of treatment with VAMP/high dose melphalan, were examined for myeloma colony formation (MY-CFUc) using a clonogenic assay in vitro. Myeloma cells from 16/30 patients produced MY-CFUc in our assay system, which uses heavily irradiated HL60 cells as an underlay in soft agar. These heavily irradiated cells were shown to be essential for the inhibition of granulocyte-macrophage colonies (GM-CFUc). The addition of recombinant human IL-6 (10 ng/plate) reduced the number of bone marrow samples which produced MY-CFUc from 16 to six. Furthermore, the addition of antibody to IL-6 (1 microgram/plate) failed to inhibit MY-CFUc from 6/7 samples. Conditioned medium from human peripheral blood mononuclear cells (PBMC-CM) contains approximately 2 ng/ml IL-6 and can be used to stimulate the growth and maintenance of the B9 murine IL-6 dependent hybridoma cell line. Recombinant human IL-6 supported the growth of B9 cells in a clonogenic assay and growth was inhibited by anti-IL-6 in the presence of rhIL-6 or PBMC-CM. Mononuclear cells from a second group of myeloma patients were cultured in soft agar in a mixture of PBMC-CM and fresh growth medium. Nine of the 10 samples produced myeloid colonies which consisted of granulocytes, monocytes and macrophages and the number of colonies was reduced by at least 50% in 6/8 samples when anti-IL-6 was added to the cultures. In no instance were MY-CFUc produced. Also, conditioned medium from the bladder carcinoma cell line 5637, which is used routinely as a source of granulocyte-macrophage colony stimulating factor (GM-CSF), contains approximately 4 ng/ml IL-6. Although rhIL-6 failed to stimulate GM-CFUc in the absence of other growth factors, addition of anti-IL-6 to cultures containing a suboptimal amount of 5637-CM reduced the number of colonies by 50%. These data provide evidence that IL-6 is a cofactor for the growth of myeloid precursors but does not affect the proliferation of human myeloma cells in vitro.

Decrease in clonogenic tumour cells in bone marrow aspirates from multiple myeloma patients due to the incorporation of cyclophosphamide into treatment with vincristine, adriamycin and methyl prednisolone

A study of 32 patients receiving cyclophosphamide (CY) and verapamil (VER) in addition to the drug combination vincristine, adriamycin and methyl prednisolone (VAMP) was made in which the clinical response and growth of clonogenic myeloma cells (MY-CFUc) from bone marrow aspirates were compared. At presentation, MY-CFUc were grown from 72 per cent (23/32) of the patients. After treatment with CY-VAMP or VERCY-VAMP, MY-CFUc were grown from 25 per cent (8/32) of patients of whom only 50 per cent responded clinically. The overall clinical response rate for patients receiving CY-VAMP and VERCY-VAMP was 64 per cent (9/14) and 72 per cent (13/18) respectively of whom 14 per cent in each group achieved complete remission. There was no concomitant increase in normal tissue toxicity as measured by granulocyte-macrophage colony (GM-CFUc) formation. Comparison of these data with our previous study of patients receiving VAMP alone, suggests that the addition of CY to the regimen may increase the tumour cell kill. Further clinical studies will determine whether there is a significant increase in the complete remission rate.