The novel BH-3 mimetic apogossypolone induces Beclin-1- and ROS-mediated autophagy in human hepatocellular carcinoma [corrected] cells

Apogossypolone (ApoG2), a novel derivative of gossypol, exhibits superior antitumor activity in Bcl-2 transgenic mice, and induces autophagy in several cancer cells. However, the detailed mechanisms are not well known. In the present study, we showed that ApoG2 induced autophagy through Beclin-1- and reactive oxygen species (ROS)-dependent manners in human hepatocellular carcinoma (HCC) cells. Incubating the HCC cell with ApoG2 abrogated the interaction of Beclin-1 and Bcl-2/xL, stimulated ROS generation, increased phosphorylation of ERK and JNK, and HMGB1 translocation from the nucleus to cytoplasm while suppressing mTOR. Moreover, inhibition of the ROS-mediated autophagy by antioxidant N-acetyl-cysteine (NAC) potentiates ApoG2-induced apoptosis and cell killing. Our results show that ApoG2 induced protective autophagy in HCC cells, partly due to ROS generation, suggesting that antioxidant may serve as a potential chemosensitizer to enhance cancer cell death through blocking ApoG2-stimulated autophagy. Our novel insights may facilitate the rational design of clinical trials for Bcl-2-targeted cancer therapy.

SU-E-T-603: Influence of PTV Delineation at Air Cavity Interface on Tomotherapy Plan Quality

PURPOSE

To determine if different ways in PTV delineation at an air cavity interface yield differences in overall plan quality and treatment efficiency Methods: Three different PTVs were used for treating a patient whose CTV surrounded a large air cavity created by a resected hard palate. The CTV lined the surface of the air cavity while PTV1 included the entire air cavity, PTV2 extended 4mm from the surface of the cavity into air, and PTV3 was reduced 4mm within the surface of the cavity. Tomotherapy plans were generated for all three PTVs. During each planning, all constraints to target and normal structures were kept constant along with the number of optimizations. Same planning process was repeated on a head and neck digital phantom with mock target, normal structures and cavity.

RESULTS

Three treatment planning approaches showed no significantly different target coverage in terms of minimum or maximum dose to their respective PTVs. All plans attained 95% coverage of the CTV and PTV by 100% of the prescription. The conformity index (CI) of the plans delivered to PTV1, PTV2, and PTV3 were 1.09, 1.11, and 1.18, respectively. The skin, optic nerves, brainstem and spinal cord all received similar maximum dose to their respective volumes for each plan within 1Gy. The monitor units required for each treatment plan were all within 6% of one another with PTV1 having the highest. For head and neck phantom, the CIs of three plans were 1.05, 1.21, and 1.18, respectively. The coverage of the phantom CTV and sparing of normal structures were nearly equivalent. The total treatment times were identical.

CONCLUSIONS

Tomotherapy planning is able to deliver dose to a head and neck PTV containing a large air cavity without compromising target coverage, sparing of normal tissues, or delivery time.

Intermediate-conductance Ca(2+) -activated potassium and volume-sensitive chloride channels in endothelial progenitor cells from rat bone marrow mononuclear cells

AIM

Bone marrow endothelial progenitor cells (BMEPCs) are believed to be a promising cell source for regenerative medicine; however, their electrophysiology properties have not been fully clarified, which is important to the clinical application of BMEPCs. The current study was designed to determine the transmembrane ion currents and mRNA expression levels of related ion channel subunits in rat BMEPCs.

METHODS

Bone marrow mononuclear cells were isolated by density gradient separation and cultured in EPC medium. The transmembrane ion currents were determined using whole-cell patch-voltage clamp technique, and the levels of mRNA and protein expressions of functional ionic channels were measured using RT-PCR and western immunoblot analysis.

RESULTS

We observed two types of ionic currents in undifferentiated rat BMEPCs. One was Ca(2+) -activated potassium current (I(kca) ), which was seen in approx. 90% of cells when 1 μm Ca(2+) was employed in pipette solution, and it was predominantly inhibited by intermediate-conductance I(kca) inhibitor clotrimazole. The other one was volume-sensitive chloride current (I(cl) ), which was detected in 85.7% of cells when BMEPCs were subjected to K(+) -free hypotonic extracellular solution, whose currents could be inhibited by 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB). The corresponding ion channel genes and proteins, KCNN4 for I(kca) and Clcn3 for I(cl) , were confirmed by RT-PCR and western immunoblot analysis of BMEPCs.

CONCLUSION

Our results demonstrated for the first time that rat BMEPCs expressed intermediate-conductance Ca(2+) -activated potassium currents and volume-sensitive chloride currents, and corresponding genes and proteins of these two channels are KCNN4 and Clcn3 respectively.

SU-E-T-635: Effect of Planning Parameters on Tomotherapy Dosimetric Quality and Treatment Efficiency

PURPOSE

To investigate how the setting of optimization parameters, fractional dose and tuning structure in tomotherapy treatment planning affects plan dosimetric quality and treatment efficiency.

METHODS

A digital phantom to simulate head and neck radiotherapy was constructed for this study. Tumor was 10cm long C-shaped with two surrounding parallel normal structures (P-NS) and one serial normal structure (S-NS). Dose prescription was 54 Gy in total. Fourteen treatment plans were generated with varied parameters in five categories: a) jaw size (1 to 5cm), b) pitch (0.215 to 0.43), c) modulation factor (1.5 to 4), d) dose per fraction (100 to 600cGy) and e) whether to use tuning structure. Plans were compared with multiple dosimetric endpoints including target minimum/maximum/mean dose, V100%, conformity, heterogeneity, S-NS maximum dose, P-NS and body mean dose, and treatment times. The reference plan was defined for the plan with conventional parameters: jaw 2.5cm, pitch 0.287, modulation factor 3.0, 200cGy per fraction and use of a 2cm ring structure in optimization.

RESULTS

Compared with 2.5cm jaw reference plan, 1cm jaw plan decreased the mean body dose 10.7% while 5 cm jaw plan increased the dose 17.9%. Smaller pitch (p=0.215) made the plan more conform than reference plan, and bigger pitch (p=0.43) had opposite effect. A small modulation factor (M=1.5) failed to spare critical structures. A medium modulation factor (M=2) resulted in similar plan to the reference but with 29% less treatment time. A low fractional dose (100 cGy) planned with similar parameter as reference had much inferior target coverage (V100%=85.6% vs V100%=96.4). Lastly, the use of tuning structure improved the conformity of target.

CONCLUSIONS

Selection of optimization parameters in tomotherapy treatment planning affects target coverage, critical structure sparing, body dose, and treatment time. Target coverage is compromised if fractional dose is low to the range of 100 cGy.

P4-07-02: Detection, Enrichment, Characterization and Propagation of Circulating Tumour Cells from Patients with Advanced Metastatic Breast Cancer

Background: Circulating tumour cells (CTCs) have attracted much attention lately due to their potential utility in diagnostic, therapeutic and prognostic applications. Characterization of these cells may indeed permit more targeted and individualized therapeutic approaches, as well as provide a means to monitor treatment response. Although detection of CTCs in peripheral blood (PB) is relatively easy using current methodologies, characterization of the CTC pool has proven more challenging due to their low abundance. Furthermore, in-vitro expansion of this elusive cell pool in mammosphere cultures has not yet been reported. In order to achieve a more complete characterization of CTCs and attempt to obtain live cells in sufficient quantity for in vitro expansion, we have used aphaeresis as a means to collect a large initial cell fraction from which to enrich CTCs from peripheral blood.

Methods: A cohort (n=17) of late stage breast cancer patients were first screened using 10ml PB. Peripheral blood mononuclear cells (PBMCs) were isolated using a Ficoll gradient and then enriched for CTCs by anti-CD45 negative selection using an automated system (RoboSep) based on magnetic bead separation. CTCs were detected by immunocytochemistry (ICC) for cytokeratin expression and patients classified as CTC-positive were selected for the aphaeresis procedure. Following collection of aphaeresis material (APM), PBMCs were isolated using a Ficoll gradient, enriched by automated anti-CD45 negative selection and characterized for a variety of markers by ICC, immunofluorescence and flow cytometry. CTCs were then cultured in serum-free medium as monolayers and suspensions. Recovery at the various steps of the isolation process was determined using PB from healthy subjects spiked with MCF-7 breast cancer cells and processed using the same approach.

Results: Recovery of spiked MCF-7 cells was about 40% after Ficoll and magnetic bead separation. Using this negative selection procedure 17/17 (100%) of subjects tested were positive at screening. Most patients (14/17) underwent aphaeresis and a large number (9,600 to 108,000) of enriched CTCs was recovered from APM in all patients tested, either as individual cells or as CTC clusters. Using dual immunofluorescence labelling, co-localization of the epithelial cell marker CK8 and the chemokine receptor CXCR4 was observed within CTCs. Furthermore, over 20% of CTCs were positive for both CK8 and ALDH1, indicative of a stem-like phenotype. APM-derived CTCs from all patients (14/14) could be propagated, both as attached cells and in suspension culture. They formed colonies in monolayer culture, and clusters in mammosphere culture, indicating stem cell-like properties. They replicated for at least three passages in mammosphere culture.

Conclusion: Our CTC detection and enrichment method using negative selection offers a distinct advantage over current methodologies, including collection of clusters, and the ability to grow and expand CTCs in serum-free culture conditions. Furthermore, these cells demonstrate breast cancer stem cell-like characteristics, the ability to replicate for multiple passages as mammospheres in suspensions and a metastatic signature.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-07-02.

Ultralight metallic microlattices

Ultralight (<10 milligrams per cubic centimeter) cellular materials are desirable for thermal insulation; battery electrodes; catalyst supports; and acoustic, vibration, or shock energy damping. We present ultralight materials based on periodic hollow-tube microlattices. These materials are fabricated by starting with a template formed by self-propagating photopolymer waveguide prototyping, coating the template by electroless nickel plating, and subsequently etching away the template. The resulting metallic microlattices exhibit densities ρ ≥ 0.9 milligram per cubic centimeter, complete recovery after compression exceeding 50% strain, and energy absorption similar to elastomers. Young's modulus E scales with density as E ~ ρ(2), in contrast to the E ~ ρ(3) scaling observed for ultralight aerogels and carbon nanotube foams with stochastic architecture. We attribute these properties to structural hierarchy at the nanometer, micrometer, and millimeter scales.

Correlation of Formation Enthalpies with Critical Amorphization Temperature for Pyrochlore and Monazite

Systematic studies of a series of RE-titanate pyrochlore single crystals determined the formation enthalpies, ΔH0f-ox, and the critical amorphization temperature, Tc, the temperature above which the crystal can no longer be amorphized. A negative linear correlation was observed between ΔH0f-ox and Tc. In general as the cation radius ratio, RA/RB, decreases the formation enthalpy becomes less exothermic, i.e. the pyrochlore structure becomes less thermodynamically stable while the susceptibilty to ion beam-induced amorphization decreases. The opposite relation, i.e. a positive linear correlation between ΔH0f-ox and Tc was observed for a series of REPO4 single crystals with both the monazite and xenotime structures. Both relations can be understood in terms of pyrochlore and orthophosphate crystal chemistry, their formation of point defects, and the role of ion-irradiation induced phase transformations.

Ion Beam-Induced Amorphization of the Pyrochlore Structure-Type: A Review

This paper reviews the recent developments in the understanding of the radiation-damage processes in A2B2O7 (Fd3m; Z=8) pyrochlore-structure compounds. Pyrochlore structure compounds display a wide range of behaviors in response to ion beam irradiation. Some compositions, such as Gd2Ti2O7, are amorphized at relatively low doses (∼0.2 dpa at room temperature) while other compositions, such as Gd2Zr2O7, do not amorphize (even at doses of 36 dpa at 25 K) and instead disorder to a defect fluorite structure. The response to ion beam irradiation is highly dependent on compositional changes that affect both the structural distortion from the ideal fluorite structure and the associated energetics of the disordering process. Generally, the ionic size of the cations plays a dominant role in determining the radiation response of different pyrochlore compositions. However, the cation ionic radius ratio criteria cannot be applied all-inclusively in predicting the radiation “tolerance” of a pyrochlore. Systematic irradiation studies of the radiation response of rare-earth (A-site) pyrochlores in which B = Ti, Zr, and Sn have shown that the behavior of the pyrochlore also depends on the cation electronic structure, i.e., the type of bonding, which is closely related to the polyhedral distortion and structural deviation from the ideal fluorite structure. These structural changes affect the dynamic defect recovery process directly linked to the material's response to and recovery from irradiation.

Infrequent recovery of HIV from but robust exogenous infection of activated CD4(+) T cells in HIV elite controllers

BACKGROUND. Human immunodeficiency virus (HIV) elite controllers are able to control infection with HIV-1 spontaneously to undetectable levels in the absence of antiretroviral therapy, but the mechanisms leading to this phenotype are poorly understood. Although low frequencies of HIV-infected peripheral CD4(+) T cells have been reported in this group, it remains unclear to what extent these are due to viral attenuation, active immune containment, or intracellular host factors that restrict virus replication. METHODS. We assessed proviral DNA levels, autologous viral growth from and infectability of in vitro activated, CD8(+) T cell-depleted CD4(+) T cells from HIV elite controllers (mean viral load, <50 copies/mL), viremic controllers (mean viral load, <2000 copies/mL), chronic progressors, and individuals receiving highly active antiretroviral therapy. RESULTS. Although we successfully detected autologous virus production in ex vivo activated CD4(+) T cells from all chronic progressors and from most of the viremic controllers, we were able to measure robust autologous viral replication in only 2 of 14 elite controllers subjected to the same protocol. In vitro activated autologous CD4(+) T cells from elite controllers, however, supported infection with both X4 and R5 tropic HIV strains at comparable levels to those in CD4(+) T cells from HIV-uninfected subjects. Proviral DNA levels were the lowest in elite controllers, suggesting that extremely low frequencies of infected cells contribute to difficulty in isolation of virus. CONCLUSIONS. These data indicate that elite control is not due to inability of activated CD4(+) T cells to support HIV infection, but the relative contributions of host and viral factors that account for maintenance of low-level infection remain to be determined.