Preclinical study of CD19 detection methods post tafasitamab treatment

Introduction

Several CD19 targeted antibody-based therapeutics are currently available for patients with diffuse large B-cell lymphoma (DLBCL), including the Fc-modified antibody immunotherapy tafasitamab. This therapeutic landscape warrants the evaluation of potential sequencing approaches. Prior to a subsequent CD19-targeted therapy, CD19 expression on tafasitamab-treated patient biopsy samples may be assessed. However, no standardized methods for its detection are currently available. In this context, selecting a tafasitamab-competing CD19 detection antibody for immunohistochemistry (IHC) or flow cytometry (FC) may lead to misinterpreting epitope masking by tafasitamab as antigen loss or downregulation.

Methods

We analyzed a comprehensive panel of commercially available CD19 detection antibody clones for IHC and FC using competition assays on tafasitamab pre-treated cell lines. To remove bound tafasitamab from the cell surface, an acidic dissociation protocol was used. Antibody affinities for CD19 were measured using Surface Plasmon Resonance (SPR) or Bio-Layer Interferometry (BLI).

Results

While CD19 was successfully detected on tafasitamab pre-treated samples using all 7 tested IHC antibody clones, all 8 tested FC antibody clones were confirmed to compete with tafasitamab. An acidic dissociation was demonstrated essential to circumvent CD19 masking by tafasitamab and avoid false negative FC results.

Discussion

The current study highlights the importance of selecting appropriate CD19 detection tools and techniques for correct interpretation of CD19 expression. The findings presented herein can serve as a guideline to investigators and may help navigate treatment strategies in the clinical setting.

Pharmacokinetics (PK) and pharmacodynamics (PD) in First-MIND: A phase Ib, open-label, randomized study of tafasitamab (tafa) ± lenalidomide (LEN) in addition to R-CHOP in patients (pts) with newly diagnosed diffuse large B-cell lymphoma (DLBCL)

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Background: The combination of tafa + LEN has accelerated approval in the United States (2020) and conditional approval in Canada and Europe (2021) for R/R DLBCL in ASCT-ineligible adult pts. A tolerable safety profile for R-CHOP + tafa ± LEN in pts with newly diagnosed DLBCL in the Phase Ib First-MIND study (NCT04134936) was previously reported, with numerically superior efficacy for R-CHOP + tafa + LEN (ASH 2021; #3556). We report PK, PD, and immunogenicity of R-CHOP + tafa ± LEN in this first line setting. Methods: Eligible pts ≥18 years with treatment-naïve DLBCL, IPI 2–5, and ECOG PS 0–2 were randomized 1:1 to either six 21-day (D) cycles (C) of R-CHOP (R-CHO, D1; P, D1–5) + tafa (12 mg/kg IV, D1, 8, 15) (Arm A) or R-CHOP + tafa + LEN (25 mg orally, D1–10) (Arm B). Secondary endpoints included tafa serum conc and number and percentage of pts developing anti-tafa Abs. Exploratory endpoints included natural killer (NK) cell, T-cell, and B-cell count in peripheral blood. Results: Data cut-off: 13 March 2021 for safety analysis, incl. ≥1 month follow-up after EoT visit for all pts; 15 September 2021 for efficacy. Tafa serum conc reached steady state by C3 (geometric mean trough conc: Arm A, 186.40–216.55 µg/mL; Arm B, 171.77–201.54 µg/mL) and steadily declined after treatment completion. Anti-tafa Abs were detected in 1/65 (1.5%) pts. This pt showed pre-existing tafa Abs at baseline, which decreased during treatment. Median NK cell count decreased from baseline at C1D8 but was at baseline or higher levels by EoT visit (Arm A) and C1D15 (Arm B; Table). T-cell count decreased from baseline at C1D8 in both arms but was at baseline level or higher by C1D15 (Arm A) and EoT visit (Arm B). Median B-cell count decreased from baseline to 0 cells/μL (Arm A, C1D15; Arm B, C1D8); at 6-month follow-up after EoT visit, B-cell count had recovered to measurable levels in ̃50% of pts. Conclusions: Tafa serum conc reached and maintained a therapeutic dose level in this first-line regimen and declined in line with known tafa half-life (̃16 days) after treatment completion; tafa levels were comparable between the two treatment arms. No pt developed treatment-induced or treatment-boosted anti-tafa Abs. Median NK-cell, T-cell, and B-cell counts were comparable between treatment arms in all cycles. Clinical trial information: NCT04134936. [Table: see text]

A Phase I, Randomized, Double-Blind, Placebo-Controlled, Single-Dose and Multiple-Rising-Dose Study of the BTK Inhibitor TAK-020 in Healthy Subjects

Bruton’s tyrosine kinase (BTK) is a target for treatment of hematologic malignancies and autoimmune diseases. TAK‐020 is a highly selective covalent BTK inhibitor that inhibits both B cell receptor and fragment crystallizable receptor signaling. We assessed the safety/tolerability and pharmacokinetics/pharmacodynamics (PDs) of TAK‐020 in healthy subjects. Each cohort of the single‐rising dose (n = 72; 9 cohorts) and the multiple‐rising dose (n = 48; 6 cohorts) portions of the study comprised six TAK‐020‐treated and two placebo‐treated, subjects aged 18–55 years (inclusive). The PD effects were assessed by measuring BTK occupancy and the inhibition of fragment crystallizable epsilon receptor 1 (FcεRI)‐mediated activation of basophils. Overall, treatment‐emergent adverse events (TEAEs) were similar to placebo; there were no serious TEAEs or no TEAEs leading to discontinuation. TAK‐020 was rapidly absorbed (median time to maximum plasma concentration (T_max) 45–60 minutes) with a half‐life of ~ 3–9 hours at doses ≥ 2.5 mg. TAK‐020 exposure was generally dose proportional for single doses ≤ 70 mg and after multiple doses of ≤ 60 mg once daily. Target occupancy was dose dependent, with doses ≥ 2.5 mg yielding maximum and sustained occupancy > 70% for > 96 hours. Single doses ≥ 4.4 mg reduced FcεRI‐mediated activation of basophils by > 80% and comparable inhibition was observed with daily dosing ≥3.75 mg for 9 days. Inhibition persisted for 24–72 hours postdose and the duration generally increased with dose. TAK‐020 was generally well‐tolerated in healthy subjects after single and multiple doses and demonstrated target engagement and pathway modulation. The PD effects outlasted drug exposures, as expected for covalent inhibition of BTK.

Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo

We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5 deg2 to 20 deg2 will require at least three detectors of sensitivity within a factor of ∼ 2 of each other and with a broad frequency bandwidth. Should the third LIGO detector be relocated to India as expected, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

Abstract B1-59: Identification of key molecular characteristics for achieving increased anti-tumor activity by combined mTORC1/2 and MEK1/2 investigational agents

The development of combination therapies is important to cancer treatment due to the potential to target multiple oncogenic pathways together, which may lead to enhanced anti-tumor activity and decreased chance for resistance. The RAS/RAF/MEK/ERK (MAP kinase) and PI3K/AKT/mTOR pathways are well-known pathways driving the oncogenic process in many cancer types; therefore, the simultaneous inhibition of these pathways may produce increased anti-tumor activity. It is important to find ideal cancer indications and molecular subtypes that may be most sensitive to drug combination inhibiting these pathways; this requires understanding of the molecular and genetic underpinnings. In this study, an in-vitro cell viability assay on 240 cancer cell lines was used to reveal the synergy mechanisms of the combination of investigational agents MLN0128 (mTORC1/2 inhibitor) with TAK733 (MEK1/2 inhibitor). Cells were administered with MLN0128 and TAK733 in DMSO in ten 2-fold serial dilutions and cell viability was measured using Promega's CellTiter-GLO® assay after a 72 hour incubation period. The 100 data points (10×10) were fit to a 9-parameter model to obtain a response surface for each cell line and the effect of the combined administration was measured using a non-linear blending score. Our previous study found that genes in the MAP kinase pathway such as KRAS, NRAS, or BRAF were mutated in cell lines demonstrating synergy. In this study, a 76-gene expression signature was additionally identified using a regression-based analysis. The 76 mRNAs include some genes within the two oncogenic pathways, as well as those that regulate feedback of the MAP kinase pathway and cross-talk between the pathways. A pathway and protein-protein interaction network-based analysis of the 76-gene signature and mutated genes suggest that the activation of the MAP kinase pathway in cells originally resistant to MLN0128 may be essential for a synergistic outcome from the MLN0128 and TAK733 combination. Cell lines with activating mutations or over-expressed genes in MAP kinase pathway are generally sensitive to TAK733 administration; these cell lines also demonstrated synergy to the combination of MLN0128 and TAK733. On the other hand, cell lines with highly expressed PI3K tend to antagonistically respond to the combination. In conclusion, our study suggests the key molecular conditions of cell lines in order to achieve increased anti-tumor activity by the combination of MLN0128 and TAK733. These findings can be utilized to establish a better-differentiated strategy in terms of patient stratification for the combination therapy using MLN0128 and TAK733.

Citation Format: Hyunjin Shin, Andrew Krueger, Bin Li, Derek Blair, William L. Trepicchio, Jeffrey Ecsedy. Identification of key molecular characteristics for achieving increased anti-tumor activity by combined mTORC1/2 and MEK1/2 investigational agents. [abstract]. In: Proceedings of the AACR Special Conference on Computational and Systems Biology of Cancer; Feb 8-11 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 2):Abstract nr B1-59.

Improved upper limits on the stochastic gravitational-wave background from 2009-2010 LIGO and Virgo data

Gravitational waves from a variety of sources are predicted to superpose to create a stochastic background. This background is expected to contain unique information from throughout the history of the Universe that is unavailable through standard electromagnetic observations, making its study of fundamental importance to understanding the evolution of the Universe. We carry out a search for the stochastic background with the latest data from the LIGO and Virgo detectors. Consistent with predictions from most stochastic gravitational-wave background models, the data display no evidence of a stochastic gravitational-wave signal. Assuming a gravitational-wave spectrum of Ω_{GW}(f)=Ω_{α}(f/f_{ref})^{α}, we place 95% confidence level upper limits on the energy density of the background in each of four frequency bands spanning 41.5-1726 Hz. In the frequency band of 41.5-169.25 Hz for a spectral index of α=0, we constrain the energy density of the stochastic background to be Ω_{GW}(f)<5.6×10^{-6}. For the 600-1000 Hz band, Ω_{GW}(f)<0.14(f/900  Hz)^{3}, a factor of 2.5 lower than the best previously reported upper limits. We find Ω_{GW}(f)<1.8×10^{-4} using a spectral index of zero for 170-600 Hz and Ω_{GW}(f)<1.0(f/1300  Hz)^{3} for 1000-1726 Hz, bands in which no previous direct limits have been placed. The limits in these four bands are the lowest direct measurements to date on the stochastic background. We discuss the implications of these results in light of the recent claim by the BICEP2 experiment of the possible evidence for inflationary gravitational waves.

Abstract 698: Variability in xenograft growth rates can be explained by intra-tumor evolutionary dynamics

Growing evidence frames cancer as a disease of somatic Darwinian evolution. Recent reports establish both inter- and intra-tumor genetic heterogeneity within patients, and evolution in response to treatment. Cell lines and xenografts also display genetic heterogeneity arising from chromosomal instability, and evolve in response to experimental conditions. Although selection pressures in culture or in a mouse differ from those in a patient, studying the evolutionary process pre-clinically may yield insights useful in the design of experimental systems of cancer.

Using the soft agar colony growth assay, we previously showed that individual colonies in soft agar have widely divergent growth rates that are mostly inherited over experimental timescales. In this work we ask what the impact of that divergence is on xenograft growth kinetics, and examine the implications for the development of resistance.

First, we applied a stochastic, dynamic model of tumor kinetics to simulate clonal heterogeneity in xenograft growth rates. Each simulated “virtual tumor” consisted of a set of independently growing subclone cells, whose growth rates were bootstrapped from a distribution derived from 104 individual HCT-116 colonies in the soft agar colony growth assay. Both the sampling distribution variance and the number of subclones sampled to found each xenograft were varied to test the effect of intercell heterogeneity and starting population size on overall xenograft growth rate. We simulated tumor growth profiles over both a two-week implant and a three-week observation period to reflect experimental conditions. Three stochastic simulation scenarios were considered for possible cellular events: birth only; birth and death; and birth, death, and mutation.

We compared the simulation results to an experimentally determined distribution derived from 308 individual HCT-116 xenograft tumors. Our findings suggest the variability of whole tumors is related to the clonal growth rate diversity within the HCT-116 cell line. In particular, the observed xenograft growth rate heterogeneity can be explained entirely by a scenario where many orders of magnitude fewer cells survive to initiate each tumor than the millions of cells implanted experimentally. This finding is consistent with previously published experimental results that have been interpreted to suggest the existence of cancer stem cells. We demonstrate the small number of founder cells in each xenograft leads to evolutionary drift under treatment conditions, when a resistant mutant may come to dominate stochastically due to the small population size.We then extend this work to ask questions about experimental design - how to develop a xenograft model system that is either more reproducible (less heterogeneity) or more heterogeneous (less reproducible). The latter system may be particularly valuable in studying the emergence of resistance.

Citation Format: Christopher J. Zopf, Andrew Chen, Mayank Patel, Santhosh Palani, Syamala Bandi, Derek Blair, Wen Chyi Shyu, Arijit Chakravarty. Variability in xenograft growth rates can be explained by intra-tumor evolutionary dynamics. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 698. doi:10.1158/1538-7445.AM2014-698

Search for gravitational waves associated with γ-ray bursts detected by the interplanetary network

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M⊙c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

Search for gravitational waves associated with γ-ray bursts detected by the interplanetary network

We present the results of a search for gravitational waves associated with 223 γ-ray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 2005-2010 during LIGO's fifth and sixth science runs and Virgo's first, second, and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a well-modeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitational wave search sensitivity as compared to corresponding all-time, all-sky searches. We find no evidence of a gravitational wave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitational wave signals associated with the GRBs. For all IPN-detected GRBs, for which a sufficient duration of quality gravitational wave data are available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitational wave emission energy of 10(-2)M⊙c(2) at 150 Hz, and find a median of 13 Mpc. For the 27 short-hard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12 Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in first-generation LIGO and Virgo gravitational wave detectors and a resulting examination of prospects for the advanced gravitational wave detectors.

Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10(-8) in some regions of the cosmic string parameter space.

Abstract A282: Antitumor activity of alisertib (MLN8237), an investigational small molecule Aurora A kinase inhibitor, as a single agent and in combination with paclitaxel, in experimental models of small cell lung cancer

Alisertib (MLN8237) is a highly selective, potent small molecule inhibitor of Aurora A kinase that is being developed for the treatment of patients with advanced malignancies, including small cell lung cancer (SCLC). SCLC accounts for approximately 13-15% of all lung cancers diagnosed and represents a major unmet medical need. SCLC is an aggressive disease with a median survival of 2-4 months if left untreated. Despite SCLC often being chemosensitive initially, with response rates between 60 - 80%, relapse is almost universal. Here, we assessed the antitumor effects of alisertib in vitro in various SCLC cell lines and in vivo in primary human SCLC xenograft models. The growth inhibitory effect of alisertib was determined in a number of SCLC cell lines. The effect on growth of these lines was measured by two independent methods, after treating these cells for 96 hours with varying concentrations of alisertib. The viability assays used were CyQuant direct, which measures cell proliferation by quantifying DNA content, and PrestoBlue, which determines cell viability by measuring the ability of cells to reduce resazurin. Cell growth was inhibited by alisertib in all lines tested with concentrations producing a 50% inhibition (IC50) ranging from 9 to 34 nM and 8 to 26 nM in the CyQuant and PrestoBlue assays, respectively. The antitumor activity of alisertib as a single agent was also evaluated in a number of primary human SCLC xenografts. In all tumor models tested, alisertib resulted in significant tumor growth inhibition at 20 mg/kg, administered both QD and BID. Alisertib dosed at 20 mg/kg BID in the CTG-0198 model led to regressions in tumor size during the period of dosing. The antitumor activity of alisertib was also tested in combination with a number of standard of care agents including paclitaxel. The combination of alisertib and paclitaxel provided enhanced antitumor activity in comparison to either agent alone in a number of models. These results demonstrate that alisertib effectively inhibits growth of experimental human SCLC models in cell culture, and displays effective antitumor activity in multiple primary human SCLC xenografts, both alone and in combination with paclitaxel. This work provides preclinical support for the further clinical evaluation of alisertib in SCLC.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A282.

Citation Format: Derek Blair, Mengkun Zhang, Michael D. Smith, Carmin Szynal, Jeffrey A. Ecsedy, Huifeng Niu. Antitumor activity of alisertib (MLN8237), an investigational small molecule Aurora A kinase inhibitor, as a single agent and in combination with paclitaxel, in experimental models of small cell lung cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A282.

Abstract B28: Identification of drug-response biomarkers for combined mTORC1/2 and MEK1/2 investigational agents using a large-scale cancer cell line screen

Combination therapy in oncology drug development has the potential to overcome resistance against single agent-based therapy. In many cancers, the RAS/RAF/MEK/ERK and PI3K/AKT/mTOR pathways confer major cell growth and survival mechanisms. Therefore, a greater treatment effect may be achieved by inhibiting both pathways simultaneously through drug combination. In this study, the enhanced anti-proliferative activity of investigational drug MLN0128 (mTORC1/2 investigational agent) when combined with TAK733 (MEK1/2 investigational agent) was assessed using an in-vitro cell viability assay on 240 cancer cell lines. Cells were administered with MLN0128 and TAK-733 in DMSO in ten 2-fold serial dilutions and cell viability was measured using Promega's CellTiter-GLO® assay after a 72 hour incubation period. The data points were fit to a 9-parameter model to obtain a response surface and the effect of the combined administration for each cell line was measured using a non-linear blending score estimated from the response surface. Statistical analysis was conducted to determine if the estimated combination effect was associated with known mutated oncogenes, tumor suppressor genes, or cancer histology reports of the 240 cell lines. Interestingly, the synergy of combined agents appeared to be mainly driven by TAK733, as cell lines sensitive to TAK733 as a single agent demonstrated beneficial combination effect with the addition of MLN0128. Furthermore, cell lines with mutations in KRAS, NRAS, and BRAF showed greater synergy scores of the combination. Likewise, cell lines of colon, pancreatic, and skin origins were more sensitive to the combination. Of particular interest are cell lines with mutated KRAS/NRAS or colon origins since they were generally resistant to single agent MLN0128, but became sensitized to the combination with TAK733. In conclusion, our study of drug combination assays on a large-scale in-vitro cell line panel revealed that mutant KRAS/NRAS or colorectal cancers may be sensitive to combined MLN0128 with TAK733.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B28.

Citation Format: Hyunjin Shin, Derek Blair, Bin Li, Greg Hather, William L. Trepicchio, Jeffrey Ecsedy, Esha Gangolli. Identification of drug-response biomarkers for combined mTORC1/2 and MEK1/2 investigational agents using a large-scale cancer cell line screen. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B28.

Abstract A59: Treatment with targeted anticancer agent affects rapidly growing subclones: An integrated in vitro/in silico analysis of clonal heterogeneity in soft agar

A growing body of clinical evidence supports a view that the often observed refractory tumor rebound arises from variation in treatment response among tumor subclones already present in the tumor at the time of diagnosis. Heterogeneity within the tumor provides subpopulations of varying fitness under the selective pressure of treatment. Through evolutionary dynamics, sensitive subpopulations wither under purifying selection, while resistant subclones replenish the population.

In this report, we employ a previously developed in vitro system based on the soft agar clonogenic assay to characterize the degree of heterogeneity in cell growth rate (fitness) between subclones in a population. The system consists of high-throughput incubation and daily imaging of colonies growing in wells of titrated treatment conditions over two to three weeks, followed by automated image analysis, image registration, and colony tracking. Individual colony growth kinetics are well-described by a single-exponential model with fit growth rates uncorrelated to location within the well. Growth rate is likely inherited over the course of the experiment as seen by a strong correlation to final diameter, and further supported by Gillespie stochastic simulations showing the final, untreated population growth rate distribution could only be achieved if heritability was strong.

The methods described here are then applied to HCT-116 colonies allowed to grow for a week and then treated with targeted anticancer agents (in the PI-3K and MAP kinase pathways). This allowed direct comparison of individual colony growth rates pre- and post-treatment. We find growth rate scales down proportionally after treatment as faster growing colonies experience a greater decrease in growth rate. Comparing the post-treatment growth rates of the slowest and fastest growing colonies demonstrates the majority of projected population debulking occurs by inhibiting the fastest growing subclones. Scatter plots of post- vs. pre-treatment growth rate show the effect of treatment is somewhat stochastic: not all fast-growing colonies are affected to the same extent.

Heterogeneity in the population, then, serves to increase the likelihood of the existence of a fast-growing subclone with greater resistance to treatment. This enables the population to more rapidly and assuredly evolve through selection on pre-existing variation in subclones. Thus, natural selection in response to treatment, rather than biochemical or mutational adaptation, appears to drive the emergence of resistance in the population. Because of the high degree of heterogeneity in subclonal growth rates, this resistance can emerge rapidly in soft agar (over several days). The methodology described may be applied to gain insight into heterogeneity in cancer cell line treatment response for drugs with various mechanisms of action.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A59.

Citation Format: Christopher J. Zopf, Carmin Szynal, Santhosh Palani, Doug Bowman, John Bradley, Jerome Mettetal, Jeffrey Ecsedy, Andy Dorner, Wen Chyi Shyu, Keisuke Kuida, Derek Blair, Arijit Chakravarty. Treatment with targeted anticancer agent affects rapidly growing subclones: An integrated in vitro/in silico analysis of clonal heterogeneity in soft agar. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A59.

Abstract B214: Application of an evolutionary model of cancer cell response to dose-response viability curves to assess the potential for pre-existing resistance

In recent years, tumor progression in the clinic has been demonstrated to be polyclonal. A single tumor contains diverse subpopulations of cancer cells which under the selective pressure of drug treatment evolve to produce drug resistance. As well, clonal diversity and genomic instability exist in tissue culture cancer cell lines. In this work, we determine the levels of pre-existing resistant subpopulations in cancer cell lines through the application of an evolutionary model of cancer cell response to an in vitro time-course of dose-response viability curves.

Methods: We simulated dose response curves versus exposure time for a range of heterogeneous (varying fractions of sensitive and resistance cells) populations of cancer cells with predefined PD parameters. We added Gaussian noise to our estimates and fitted the time-course dose response data with both a single population model and with a dual population model and compared the goodness of the fit, PD parameter and residual variability levels for each of the heterogeneous populations. Model fitting and simulations were performed using NONMEM. Cancer cells were assumed to grow exponentially and the drug effect was modeled as a sigmoidal Emax function. An analytical solution was derived to estimate the population fractions from the plateau levels of the dose response curves. We validated the model predictions against a previously published dataset (Sci. Transl. Med. 3, 90ra59, 2011) where the baseline fraction of sensitive and resistant cells was varied in a controlled manner. Finally, the model was used to predict the percentage of resistant cells in a pre-existing population in response to treatment with signal transduction inhibitors. These predictions were then validated directly using time-lapse microscopy on cells grown in plastic and on soft agar.

Results: From the simulations, we determined the study design necessary for modeling dose response relationship for heterogeneous populations to be a time course (0, 24, 48, 72h) viability assay with a range of concentrations spanning low to saturable effect. The dual population model accurately fitted the dose response curves simulated from heterogeneous populations, whereas the single population model showed poor predictability and exhibited large unexplained residual variability. The dual population model also predicted well the PD parameters and growth kinetics of the sensitive and resistance populations when applied to the published dataset with single time course (72h) viability measurement performed on heterogeneous populations with varying levels of resistance sub-fractions. When applied to a prospective in vitro study, the dual population model adequately predicted the fraction of resistance populations preexisting in the cell line tested.

Conclusion: Taken together, the modeling approach described here provides a novel evolutionary approach to the assessment of pre-existing resistance to drug treatment that can be rapidly applied for mechanistic investigations of single-agent and combination cancer therapeutics.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B214.

Citation Format: Snehal Samant, Derek Blair, Andrew Chen, Jerome Mettetal, Wen Chyi Shyu, Mark Hixon, Jeffrey Ecsedy, Santhosh Palani, Arijit Chakravarty. Application of an evolutionary model of cancer cell response to dose-response viability curves to assess the potential for pre-existing resistance. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B214.

Abstract 5229: An integrated in vitro/in silico platform to study the evolutionary dynamics of resistance to cancer therapy

Emerging clinical evidence suggests that tumor response to treatment occurs along stochastic, evolutionary trajectories, with the amplification of pre-existing clones of resistant cells being shown to be responsible for treatment failure in a number of cases. In this evolutionary view of cancer, pre-existing tumor heterogeneity forms a pool of candidate mutations for selection to act on. Thus, a clearer picture of the heterogeneity in cancer cell lines will facilitate a mechanistic understanding of the dynamics of resistance evolution.

In this report, we describe the development of an in vitro system based on the soft agar clonogenic assay, to characterize the degree of heterogeneity in net growth rate (fitness) and the effects of this variation in fitness on the population-level response to drug treatment.

The in vitro system was developed as a 24-well soft agar clonogenic assay, with sequential images of the growing colonies taken every day, over a period of two weeks. An automated system for plate preparation, imaging, and plate transfer from incubator to imager was developed to increase assay throughput. A modified greedy algorithm was developed in MATLAB to reliably track colonies as they grow and shift in the image frame from day to day. The individual growth rates of colonies in the pre-treatment colonies followed an exponential model, indicative of a clonal origin for the individual colonies, which was confirmed by microscopy.

Next, we developed an in silico platform (based on a Monte Carlo stochastic simulation) to study this heterogeneity in growth rates, and derive insights that are relevant to the planning of therapeutic interventions. This simulation was also used to optimize the design of the experimental system and can provide guidance on the optimal seeding density to avoid merging colonies. We are now using this simulation platform to explore the impact of heterogeneity on population fitness and on drug resistance. This platform can also be extended to examine the individual colonies derived from drug treatment, and provides a rapid and simple means of isolation of resistant subclones for further study.

Taken together, the combined in vitro/in silico platform presented here forms the basis of a Systems Biology approach for assessing the role of cancer cell heterogeneity in the evolution of resistance in response to treatment

Citation Format: Keisuke Kuida, Carl Boand, John Bradley, Jean Courtemanche, John Donovan, Doanh Mai, Jerome Mettetal, Santhosh Palani, Derek Blair, Jeffrey Ecsedy, Andy Dorner, Wen Chyi Shyu, Joe Bolen, Doug Bowman, Arijit Chakravarty. An integrated in vitro/in silico platform to study the evolutionary dynamics of resistance to cancer therapy . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5229. doi:10.1158/1538-7445.AM2013-5229

Abstract 3411: Mathematical model of the cell cycle to determine mechanism of action and optimize dosing schedule

A mechanistic understanding of a drug's biological effect can have significant implications for selection of clinical dosing schedule, combination partners, as well as biomarker selection. In this context, a question often faced from target validation to the end of Phase I is how much of a drug's antitumor effect is through altering cell-cycle progression or through the induction of cell death. Here we demonstrate the utility of a mathematical model of the cell-cycle for determining the effect of a drug on cell-cycle kinetics, as an objective and quantiative interpretation of DNA flow cytometry and cellular growth rate data. The model uses periodic measurement of DNA content as analyzed by flow cytometry to determine the percentage of cells in G0/G1, S, and G2/M phases of the cell cycle, as well as continuous readouts of cell confluence over the course of treatment to assess growth rates. The model is then fitted to the data to extract effective cell cycle transition rates demonstrating the effect of the drug on cell cycle progression.

To demonstrate of the approach, we applied the model to data acquired during treatment of A375 melanoma cells with the investigational drug TAK-733, an allosteric MEK 1/2 inhibitor hypothesized to cause a G1 arrest. Rather than an arrest at G1, the model predicted that the G1-to-S transition rate was reduced, and that much of the change in cell cycle data was due to an increase in the S-to-G2/M and G2/M-to-G0/G1 transition rates. These model predictions were then tested with video microscopy and both predictions (increased time spent in G0/G1 as well as reduced time spent in mitosis) were supported by experimental data.

The model was then used to test whether the cell cycle activity of the compound has any implications for optimization of dosing schedule. By varying the schedule of drug treatment in the simulation, we find that for the biologically relevant concentration range the compound is schedule independent (i.e. effect is proportional to AUC). This finding suggests that there is no need to maintain constant pathway inhibition to see efficacy in tumor volume reduction. To test this prediction, we compare the results with the outcome of experiments in an A375 xenograft model with different dosing schedules and verify directly that AUC was indeed a better predictor of efficacy than Cmin.

With this example, we demonstrate that mathematical modeling can be used to aid in interpretation of cell cycle data, often generated to describe the cell killing activity of oncology compounds. In addition, the model provides a method of interpreting the mechanism of action for early development decision making around schedule selection. This work demonstrates an approach that can be extended to other compounds to provide an integrated measure of the total contribution of cell death and/or cell cycle arrest, to help provide a mechanistic rationale for schedule selection with single agent and combination therapies.

Citation Format: Jerome Mettetal, Derek Blair, Esha Gangoli, Patrick Vincent, Jeff Ecsedy, Wen Chyi Shyu, Arijit Chakravarty. Mathematical model of the cell cycle to determine mechanism of action and optimize dosing schedule. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3411. doi:10.1158/1538-7445.AM2013-3411

Immune complex-mediated co-ligation of the BCR with FcγRIIB results in homeostatic apoptosis of B cells involving Fas signalling that is defective in the MRL/Lpr model of systemic lupus erythematosus

Negative regulation of B cell activation by cognate immune complexes plays an important homeostatic role in suppressing B cell hyperactivity and preventing consequent autoimmunity. Immune complexes co-ligate the BCR and FcγRIIB resulting in both growth arrest and apoptosis. We now show that such apoptotic signalling involves induction and activation of p53 and its target genes, the pro-apoptotic Bcl-2 family members, Bad and Bid, as well as nuclear export of p53. Collectively, these events result in destabilisation of the mitochondrial and lysosomal compartments with consequent activation and interplay of executioner caspases and endosomal-derived proteases. In addition, the upregulation of Fas and FasL with consequent activation of caspase 8-dependent death receptor signalling is required to facilitate efficient apoptosis of B cells. Consistent with this role for Fas death receptor signalling, apoptosis resulting from co-ligation of the BCR and FcγRIIB is defective in B cells from Fas-deficient MRL/MpJ-Fas(lpr) mice. As these mice develop spontaneous, immune complex-driven lupus-like glomerulonephritis, targeting this FcγRIIB-mediated apoptotic pathway may therefore have novel therapeutic implications for systemic autoimmune disease.

Abstract 3738: A rationale for combining the targeted investigational agents TAK-733, a MEK1/2 inhibitor, with alisertib (MLN8237), an Aurora A kinase inhibitor, for cancer therapy

MEK1/2 kinases have diverse functions in cell proliferation and survival, including the regulation of cell cycle transitions between the G1, S, and G2 phases and mediation of DNA damage response pathways. Therefore, inhibition of MEK1/2 may facilitate the antiproliferative effects of other therapies that disrupt cell cycle progression leading to DNA damage, including antimitotic therapies. AAK is a serine/threonine protein kinase essential for normal mitotic progression. Inhibition of AAK leads to inappropriate progression through mitosis in the presence of misaligned chromosomes resulting in aneuploidy and DNA damage, which leads to apoptosis or senescence. Here, we evaluated the combination of the allosteric MEK1/2 inhibitor TAK-733 with alisertib, the selective AAK inhibitor. Proliferation assays in multiple tumor cell lines showed a concentration-dependent decrease in the IC50 of TAK-733 and alisertib with increasing concentrations of the second agent, suggesting increased anti-proliferative activity of these agents when combined. This result was corroborated by measuring changes in cell confluence over time, a surrogate for proliferation rate, using an IncuCyte live-cell imaging system. The decreased proliferation rate of the combination was due in part to induction of apoptosis, as demonstrated by Annexin V and sub-diploid DNA content analysis. Cell cycle progression differences of the TAK-733/alisertib combination relative to the single agents were assessed using time-lapse video microscopy by measuring the time to the first mitotic event after drug addition, time spent in mitosis, and time between mitotic events. Of these, the only observed difference in cell-cycle progression time in the A2780 ovarian carcinoma cell line was the time between mitotic events, which was 10 hours longer for the combination relative to single agent alisertib. Moreover, the combination of TAK-733 and alisertib significantly reduced the ability of the cells to re-enter the cell cycle after one mitosis compared to either single agent; 30% for the combination, compared to 90% for TAK-733 and 76% for alisertib. Flow cytometry DNA content analysis showed that TAK-733 suppressed the formation of &gt;4N/tetraploid cells induced by alisertib alone in multiple cell lines. This observed decrease in the proportion of &gt;4N cells is greater than the decrease that could be extrapolated solely from the cell cycle-slowing effect of the combination, suggesting that TAK-733 reduces the proliferative potential of the alisertib-generated aneuploid cells via cell-cycle arrest and apoptosis. Collectively, these findings demonstrate an added benefit of TAK-733 over alisertib alone and provide a pre-clinical rationale for further investigation of the combination of TAK-733 and alisertib for cancer therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3738. doi:1538-7445.AM2012-3738

Directional limits on persistent gravitational waves using LIGO S5 science data

The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.L.) upper-limit maps of GW strain power with typical values between 2-20×10(-50)  strain(2) Hz(-1) and 5-35×10(-49)  strain(2) Hz(-1) sr(-1) for pointlike and extended sources, respectively. The latter result is the first of its kind. We also set 90% C.L. limits on the narrow-band root-mean-square GW strain from interesting targets including Sco X-1, SN 1987A and the Galactic center as low as ≈7×10(-25) in the most sensitive frequency range near 160 Hz.

Abstract B136: Application of a mathematical model to understand the cell cycle progression effects of MEK1/2 kinase inhibition using the investigational small-molecule allosteric inhibitor TAK-733

In order to more precisely understand the effects of MEK1/2 inhibition on cell cycle progression, cellular imaging and biochemical assays were coupled with mathematical modeling.

The MEK/ERK signaling cascade modulates multiple outcomes relevant to cancer therapy including cell growth, proliferation, differentiation and apoptosis. Moreover, MEK/ERK signaling regulates transitions between the G1, S and G2 cell cycle phases, and mediates the response to DNA damage induced by a wide variety of DNA damaging agents. Inhibition of the MEK/ERK pathway represents a promising approach for the treatment of cancer. A number of small-molecule inhibitors are currently in clinical trials, including TAK-733, a novel, investigational, selective, non ATP competitive, allosteric inhibitor of MAP kinase-ERK kinase (MEK) activity.

MEK inhibition is often described to invoke a complete arrest at the G1-S cell cycle transition leading to a rapid cessation of cell growth. In order to assess this, the kinetics of cell cycle progression using continuous quantitative techniques in several different cell types was examined. Time-lapse microscopy studies and confluence analyses using an IncuCyte system demonstrated that cells treated with TAK-733 continue to divide over a period of five days, albeit at a slower rate than the DMSO treated cells. These observations were corroborated with flow cytometry using CFSE, a fluorescent cytoplasmic dye whose rate of decay is a measure of the cell division rate, and with immunofluorescence microscopy using the G2/M marker cyclin B. This continued cell cycling in the presence of TAK-733 was demonstrated to occur with abnormal cell cycle progression times and abnormal DNA content profiles, suggesting altered rates of passage through S and G2/M phase.

A mathematical model was constructed to quantitatively describe how MEK inhibition is affecting the passage of the cell population through the cell cycle. When the model is fitted to the experimentally observed data, it inferred the rate of entrance and exit from each phase of the cell cycle under both control and treatment conditions. The model simultaneously captured both the observed accumulation in G0/G1 as well as the observed progression through the cell cycle during treatment. Interestingly, it was able to explain both of these results without invoking a complete G1 arrest. Instead it showed that the rate of exit from G1 is reduced upon inhibition. These findings were supported by time-lapse microscopy observations which were not used in fitting the model.

This reassessment of the canonical view of cell-cycle progression defects following MEK1/2 inhibition by means of the mathematical modeling approach described here may provide key differentiation opportunities in the rational development of TAK-733 and other MEK1/2 inhibitors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B136.

Effect of regional climate warming on the phenology of butterflies in boreal forests in Manitoba, Canada

We examined the effect of regional climate warming on the phenology of butterfly species in boreal forest ecosystems in Manitoba, Canada. For the period 1971-2004, the mean monthly temperatures in January, September, and December increased significantly, as did the mean temperatures for several concurrent monthly periods. The mean annual temperature increased ≈ 0.05°C/yr over the study period. The annual number of frost-free days and degree-day accumulations increased as well. We measured the response of 19 common butterfly species to these temperature changes with the date of first appearance, week of peak abundance, and the length of flight period over the 33-yr period of 1972-2004. Although adult butterfly response was variable for spring and summer months, 13 of 19 species showed a significant (P < 0.05) increase in flight period extending longer into the autumn. Flight period extensions increased by 31.5 ± 13.9 (SD) d over the study period for 13 butterfly species significantly affected by the warming trend. The early autumn and winter months warmed significantly, and butterflies seem to be responding to this warming trend with a change in the length of certain life stages. Two species, Junonia coenia and Euphydryas phaeton, increased their northerly ranges by ≈ 150 and 70 km, respectively. Warmer autumns and winters may be providing opportunities for range extensions of more southerly butterfly species held at bay by past climatic conditions.

The Geneva prognostic score and mortality in patients diagnosed with pulmonary embolism by CT pulmonary angiogram

This study prospectively evaluates whether a previously established adverse outcome score (the Geneva prognostic score) predicts 3 and 12-month overall mortality among the patients diagnosed with pulmonary embolism (PE) by a CT pulmonary angiogram (CTPA). Five hundred twenty-three consecutive patients who had CTPA for suspected PE were recruited prospectively from March 2003 to October 2004. The Geneva prognostic score was calculated for all patients. Twelve-month follow up was completed in all patients in December 2005. There were 105 patients diagnosed with PE. The mean score was 2.71 (standard deviation (SD) 1.25) for those patients who had died (n = 7) and 1.14 (SD 1.19) for those patients who were alive (n = 98) at 3-month follow up (P < 0.001). The mean scores were 2.69 (SD 0.95) for those who had died (n = 13) and 1.04 (SD 1.15) for those patients who were alive (n = 92) at 12-month follow up (P < 0.001). At 3-month follow up, among the 88 patients with a score of 2 or less, three patients (3.4%) died and among 17 patients with a score of greater than 2, four patients (23.5%) died (P = 0.01). At 12-month follow up, five patients (5.7%) with a score of 2 or less died and eight patients (47.1%) with a score of three or more died (P < 0.0001). The Geneva prognostic score stratifies patients with low and high risk for overall mortality at 3 and 12 months among patients diagnosed with PE by CTPA.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

All-sky LIGO search for periodic gravitational waves in the early fifth-science-run data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50-1100 Hz and with the frequency's time derivative in the range -5 x 10{-9}-0 Hz s{-1}. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10{-24} are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 10{-6}, the search is sensitive to distances as great as 500 pc.

Search for gravitational-wave bursts from soft gamma repeaters

We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star f modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant flare from SGR 1806-20 and 190 lesser events from SGR 1806-20 and SGR 1900+14. The unprecedented sensitivity of the detectors allows us to set the most stringent limits on transient GW amplitudes published to date. We find upper limit estimates on the model-dependent isotropic GW emission energies (at a nominal distance of 10 kpc) between 3x10;{45} and 9x10;{52} erg depending on waveform type, detector antenna factors and noise characteristics at the time of the burst. These upper limits are within the theoretically predicted range of some SGR models.

Interaction between carbon nanotubes and mammalian cells: characterization by flow cytometry and application

We show herein that CNT-cell complexes are formed in the presence of a magnetic field. The complexes were analyzed by flow cytometry as a quantitative method for monitoring the physical interactions between CNTs and cells. We observed an increase in side scattering signals, where the amplitude was proportional to the amount of CNTs that are associated with cells. Even after the formation of CNT-cell complexes, cell viability was not significantly decreased. The association between CNTs and cells was strong enough to be used for manipulating the complexes and thereby conducting cell separation with magnetic force. In addition, the CNT-cell complexes were also utilized to facilitate electroporation. We observed a time constant from CNT-cell complexes but not from cells alone, indicating a high level of pore formation in cell membranes. Experimentally, we achieved the expression of enhanced green fluorescence protein by using a low electroporation voltage after the formation of CNT-cell complexes. These results suggest that higher transfection efficiency, lower electroporation voltage, and miniaturized setup dimension of electroporation may be accomplished through the CNT strategy outlined herein.

Insights into the structural specificity of the cytotoxicity of 3-deoxyphosphatidylinositols

D-3-deoxyphosphatidylinositol (D-3-deoxy-PI) derivatives have cytotoxic activity against various human cancer cell lines. These phosphatidylinositols have a potentially wide array of targets in the phosphatidylinositol-3-kinase (PI3K)/Akt signaling network. To explore the specificity of these types of molecules, we have synthesized D-3-deoxydioctanoylphosphatidylinositol (D-3-deoxy-diC8PI), D-3,5-dideoxy-diC8PI, and D-3-deoxy-diC8PI-5-phosphate and their enantiomers, characterized their aggregate formation by novel high-resolution field cycling (31)P NMR, and examined their susceptibility to phospholipase C (PLC), their effects on the catalytic activities of PI3K and PTEN against diC8PI and diC8PI-3-phosphate substrates, respectively, and their ability to induce the death of U937 human leukemic monocyte lymphoma cells. Of these molecules, only D-3-deoxy-diC8PI was able to promote cell death; it did so with a median inhibitory concentration of 40 microM, which is much less than the critical micelle concentration of 0.4 mM. Under these conditions, little inhibition of PI3K or PTEN was observed in assays of recombinant enzymes, although the complete series of deoxy-PI compounds did provide insights into ligand binding by PTEN. D-3-deoxy-diC8PI was a poor substrate and not an inhibitor of the PLC enzymes. The in vivo results are consistent with the current thought that the PI analogue acts on Akt1, since the transcription initiation factor eIF4e, which is a downstream signaling target of the PI3K/Akt pathway, exhibited reduced phosphorylation on Ser209. Phosphorylation of Akt1 on Ser473 but not Thr308 was reduced. Since the potent cytotoxicity for U937 cells was completely lost when L-3-deoxy-diC8PI was used as well as when the hydroxyl group at the inositol C5 in D-3-deoxy-diC8PI was modified (by either replacing this group with a hydrogen or phosphorylating it), both the chirality of the phosphatidylinositol moiety and the hydroxyl group at C5 are major determinants of the binding of 3-deoxy-PI to its target in cells.

Differential effects of energy stress on AMPK phosphorylation and apoptosis in experimental brain tumor and normal brain

Background

AMP-activated protein kinase (AMPK) is a known physiological cellular energy sensor and becomes phosphorylated at Thr-172 in response to changes in cellular ATP levels. Activated AMPK acts as either an inducer or suppressor of apoptosis depending on the severity of energy stress and the presence or absence of certain functional tumor suppressor genes.

Results

Here we show that energy stress differentially affects AMPK phosphorylation and cell-death in brain tumor tissue and in tissue from contra-lateral normal brain. We compared TSC2 deficient CT-2A mouse astrocytoma cells with syngeneic normal astrocytes that were grown under identical condition in vitro. Energy stress induced by glucose withdrawal or addition of 2-deoxyglucose caused more ATP depletion, AMPK phosphorylation and apoptosis in CT-2A cells than in the normal astrocytes. Under normal energy conditions pharmacological stimulation of AMPK caused apoptosis in CT-2A cells but not in astrocytes. TSC2 siRNA treated astrocytes are hypersensitive to apoptosis induced by energy stress compared to control cells. AMPK phosphorylation and apoptosis were also greater in the CT-2A tumor tissue than in the normal brain tissue following implementation of dietary energy restriction. Inefficient mTOR and TSC2 signaling, downstream of AMPK, is responsible for CT-2A cell-death, while functional LKB1 may protect normal brain cells under energy stress.

Conclusion

Together these data demonstrates that AMPK phosphorylation induces apoptosis in mouse astrocytoma but may protect normal brain cells from apoptosis under similar energy stress condition. Therefore, using activator of AMPK along with glycolysis inhibitor could be a potential therapeutic approach for TSC2 deficient human malignant astrocytoma.

Cutting edge: IL-4-mediated protection of primary B lymphocytes from apoptosis via Stat6-dependent regulation of glycolytic metabolism

IL-4 prevents the death of naive B lymphocytes through the up-regulation of antiapoptotic proteins such as Bcl-x(L). Despite studies implicating glucose utilization in growth factor-dependent survival of hemopoietic cells, the role of glucose energy metabolism in maintaining B cell viability by IL-4 is unknown. We show that IL-4 triggers glucose uptake, Glut1 expression, and glycolysis in splenic B cells; this is accompanied by increased cellular ATP. Glycolysis inhibition results in apoptosis, even in the presence of IL-4. IL-4-induced glycolysis occurs normally in B cells deficient in insulin receptor substrate-2 or the p85alpha subunit of PI3K and is not affected by pretreatment with PI3K or MAPK pathway inhibitors. Stat6-deficient B cells exhibit impaired IL-4-induced glycolysis. Cell-permeable, constitutively active Stat6 is effective in restoring IL-4-induced glycolysis in Stat6-deficient B cells. Therefore, besides controlling antiapoptotic proteins, IL-4 mediates B cell survival by regulating glucose energy metabolism via a Stat6-dependent pathway.

Deconvolution of the cellular oxidative stress response with organelle-specific Peptide conjugates

Oxidative stress is a deleterious force that must be combated relentlessly by aerobic organisms and is known to underlie many human diseases including atherosclerosis, Parkinson's disease, and Alzheimer's disease. Information available about the oxidative stress response has come primarily from studies using reactive oxygen species (ROS) with ill-defined locations within the cell. Thus, existing models do not account for possible differences between stress originating within particular regions of the cell. Here, oxidative stress is studied at the subcellular level using ROS-generating compounds localizing within two different organelles: the nucleus and the mitochondrion. Differences in cytotoxicity, gene expression, and survival pathway activation are detected as a function of the subcellular origin of oxidative stress, indicating that independent mechanisms are used to cope with oxidative stress arising in different cellular compartments. These comparative studies, enabled by the development of organelle-specific oxidants, examine the cellular responses to site-specific oxidative stress with heightened precision.

Withholding anticoagulation after a negative computed tomography pulmonary angiogram as a stand-alone imaging investigation: a prospective management study

BACKGROUND

Accurate diagnosis of pulmonary embolism (PE) is essential and it is not clear whether a computed tomography pulmonary angiogram (CTPA) could be used as a stand-alone imaging investigation. The aim of the study was to test the accuracy of the clinical outcome of a negative CTPA as a stand-alone imaging investigation to exclude PE.

METHODS

Five hundred and thirty-four consecutive patients who had a CTPA for diagnosis or exclusion of PE were recruited from March 2003 to October 2004. Four hundred and ninety-four patients had a helical CTPA as a stand-alone imaging investigation for diagnosis or exclusion of PE. A 3-month post-CTPA follow up was carried out in all patients to establish the clinical outcome accuracy of a negative CTPA as a stand-alone imaging investigation.

RESULTS

There were 387 (78.3%) negative and 107 (21.7%) positive CTPA examinations. The average age of the patients was 57.16 years (standard deviation 18.57). Among those with a negative CTPA who survived, one patient had deep vein thrombosis and 342 patients had no evidence of an episode of venous thromboembolism or PE at the 3-month follow up. Thirty-eight patients died within the 3-month follow-up period and one patient's death was attributed to suspected PE. The negative predictive value of a CTPA is 99.5% (95% confidence interval 98.1-99.9%).

CONCLUSION

Helical negative CTPA examination excludes clinically significant PE as a stand-alone imaging investigation. Where concurrent deep vein thrombosis is suspected, lower limb needs to be imaged by ultrasound if the CTPA is negative.

Cutting Edge: B Cell Receptor (BCR) Cross-Talk: The IL-4-Induced Alternate Pathway for BCR Signaling Operates in Parallel with the Classical Pathway, Is Sensitive to Rottlerin, and Depends on Lyn

B cell exposure to IL-4 alters subsequent BCR signaling such that ERK phosphorylation becomes signalosome-independent; however, the nature of this new, alternate signaling pathway and its relationship to the classical, signalosome-dependent signaling pathway are not known. In this study, we report that the alternate and classical pathways for BCR signaling are differentially affected by rottlerin, and by Go6976 or LY294002, respectively. Furthermore, in B cells lacking protein kinase C (PKC)beta, the classical pathway for BCR signaling is blocked, whereas the alternate pathway is little affected. Conversely, in B cells lacking Lyn, the alternate pathway for BCR signaling is blocked, whereas the classical pathway is little affected. The rottlerin-sensitive element is not PKCdelta, inasmuch as the alternate pathway is not blocked in PKCdelta-deficient B cells. These results indicate that the rottlerin-sensitive, Lyn-dependent alternate pathway, and the classical pathway, for BCR signaling operate in parallel when BCR engagement follows IL-4 exposure.

Interleukin-4-mediated protection of primary B lymphocytes from apoptosis through Stat6-dependent up-regulation of glycolytic metabolism (94.16)

Lymphocytes require extrinsic signals to maintain viability and this occurs, in part, through the up-regulation of anti-apoptotic proteins. Several recent studies have implicated cellular energy metabolism as an important component in preventing cell death following growth factor withdrawal. Interleukin 4 (IL-4) prevents death by neglect of naïve B lymphocytes; however, it is not known whether cellular glucose metabolism is crucial for survival by IL-4. We show herein that IL-4 triggers increased glucose uptake, glucose transporter (Glut1) expression, and glycolysis in splenic B lymphocytes. Inhibition of glycolysis results in apoptosis, despite the presence of IL-4. We demonstrate that insulin receptor substrate-2 and phosphatidylinositol 3-kinase activity are dispensable for IL-4-induced glucose utilization. By contrast, Stat6-deficient B cells exhibit impaired induction of Glut1 and glycolysis by IL-4. These findings establish that a key feature of IL-4 prevention of apoptosis in B cells is to promote glucose utilization via a Stat6-dependent pathway.

This work was supported by USPHS grant AI-49994.

B Cell Receptor Crosstalk: The IL-4-induced Alternate Pathway for BCR Signaling Operates in Parallel with the Classical Pathway, Is Sensitive to Rottlerin, and Depends on Lyn (86.14)

B cell exposure to IL-4 alters subsequent B cell receptor signaling such that ERK phosphorylation becomes signalosome-independent; however, the nature of this new, alternate signaling pathway and its relationship to the classical, signalosome-dependent signaling pathway, are not known. Here we report that the alternate and classical pathways for BCR signaling are differentially affected by rottlerin, and by Go6976 or LY294002, respectively. Further, in B cells lacking PKCâ, the classical pathway for BCR signaling is blocked, whereas the alternate pathway is little affected. Conversely, in B cells lacking Lyn, the alternate pathway for BCR signaling is blocked, whereas the classical pathway is little affected. The rottlerin-sensitive element is not PKCä, inasmuch as the alternate pathway as not blocked in PKCä-deficient B cells. These results indicate that the rottlerin-sensitive, Lyn-dependent alternate pathway, and the classical pathway, for BCR signaling operate in parallel when BCR engagement follows IL-4 exposure.

D-3-deoxy-dioctanoyl-PI induces cell death in the human leukemic monocyte lymphoma cell line U-937 by disruption of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway (89.33)

D-3-deoxy-phosphatidylinositol derivatives have a potentially wide array of targets in the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway. As such, these phosphatidylinositol molecules have been shown to have cytotoxic activity against a variety of human cancer cell lines. Here, we demonstrate that the D-3-deoxy-dioctanoyl-PI (D-diC8PI), but not the L-isomer or D-3,5-dideoxy-diC8PI, is able to induce the death of the U-937 human leukemic monocyte lymphoma cell line, even at low concentrations (&lt;50 μM). In order to further investigate the mechanism of the cytotoxicity of D-3-deoxy-diC8PI we examined its effect on the activity of various molecules in the PI3K/Akt pathway. In vitro, low concentrations (&lt;50 μM) of D-3-deoxy-diC8PI have no significant effect on the activity of PI3K or PTEN. However, incubation of U-937 cells with D-3-deoxy-diC8PI at these concentrations results in significant decreases in phosphorylation of key components of the PI3K/Akt signalling pathway, including the transcription initiation factor eIF4e and the translation factor S6 ribosomal protein. These data further delineate the mechanism of action of such cytotoxic D-3-deoxy-PI compounds.

Inhibition of phosphatidylinositol 3-kinase-mediated glucose metabolism coincides with resveratrol-induced cell cycle arrest in human diffuse large B-cell lymphomas

An abnormally high rate of aerobic glycolysis is characteristic of many transformed cells. Here we report the polyphenolic compound, resveratrol, inhibited phosphatidylinositol 3-kinase (PI-3K) signaling and glucose metabolism, coinciding with cell-cycle arrest, in germinal center (GC)-like LY1 and LY18 human diffuse large B-cell lymphomas (DLBCLs). Specifically, resveratrol inhibited the phosphorylation of Akt, p70 S6K, and S6 ribosomal protein on activation residues. Biochemical analyses and nuclear magnetic resonance spectroscopy identified glycolysis as the primary glucose catabolic pathway in LY18 cells. Treatment with the glycolytic inhibitor 2-deoxy-D-glucose, resulted in accumulation of LY18 cells in G0/G1 -phase, underscoring the biological significance of glycolysis in growth. Glycolytic flux was inhibited by the PI-3K inhibitor LY294002, suggesting a requirement for PI-3K activity in glucose catabolism. Importantly, resveratrol treatment resulted in inhibition of glycolysis. Decreased glycolytic flux corresponded to a parallel reduction in the expression of several mRNAs encoding rate-limiting glycolytic enzymes. These results are the first to identify as a mechanism underlying resveratrol-induced growth arrest, the inhibition of glucose catabolism by the glycolytic pathway. Taken together, these results raise the possibility that inhibition of signaling and metabolic pathways that control glycolysis might be effective in therapy of DLBCLs.

Computed tomography pulmonary angiogram diagnosis of pulmonary embolism

Over the last decade, contrast-enhanced spiral CT has been established as a non-invasive alternative to catheter angiography and is now regarded as the first-line imaging investigation for the diagnosis of pulmonary embolism (PE). The reported sensitivities for the diagnosis of PE of spiral CT vary from 45 to 100% and the specificities vary from 78 to 100%. Prospective outcome studies have shown a high negative predictive value for a single-detector spiral CT for PE. Patients' outcomes were not adversely affected in these studies when anticoagulation was withheld after a negative CT pulmonary angiogram. The main limitation of single-detector spiral CT has been its limited ability to detect isolated subsegmental PE. However, multidetector spiral CT allows evaluation of pulmonary vessels down to sixth-order branches and significantly increases the rate of detection of PE in segmental and subsegmental levels. The interobserver correlations for diagnosis of subsegmental PE with multidetector spiral CT exceed the reproducibility of selective pulmonary angiography. If appropriate equipment is available (multidetector CT), then CT pulmonary angiogram is safe to be used as the first-line imaging investigation for the diagnosis of PE.

Otitis media and a neck lump--current diagnostic challenges for Paragonimus-like trematode infections

A 29 year-old Nigerian studying in the UK presented with a neck lump and otitis media. Paragonimus-like trematode eggs were found in the neck lump aspirate. Morphologically these eggs resembled Paragonimus uterobilateralis or Achillurbainia congolensis. We favoured the diagnosis of achillurbainiasis over extrapulmonary paragonimiasis on the basis of clinical features and because we could not amplify DNA sequences using PCR primers specific for Paragonimus species. We discuss current diagnostic challenges for this rare parasitic infection.