Peri-infarct blood-brain barrier dysfunction facilitates induction of spreading depolarization associated with epileptiform discharges

Recent studies showed that spreading depolarizations (SDs) occurs abundantly in patients following ischemic stroke and experimental evidence suggests that SDs recruit tissue at risk into necrosis. We hypothesized that BBB opening with consequent alterations of the extracellular electrolyte composition and extravasation of albumin facilitates generation of SDs since albumin mediates an astrocyte transcriptional response with consequent disturbance of potassium and glutamate homeostasis. Here we show extravasation of Evans blue-albumin complex into the hippocampus following cortical photothrombotic stroke in the neighboring neocortex. Using extracellular field potential recordings and exposure to serum electrolytes we observed spontaneous SDs in 80% of hippocampal slices obtained from rats 24 h after cortical photothrombosis. Hippocampal exposure to albumin for 24 h through intraventricular application together with serum electrolytes lowered the threshold for the induction of SDs in most slices irrespective of the pathway of stimulation. Exposing acute slices from naive animals to albumin led also to a reduced SD threshold. In albumin-exposed slices the onset of SDs was usually associated with larger stimulus-induced accumulation of extracellular potassium, and preceded by epileptiform activity, which was also observed during the recovery phase of SDs. Application of ifenprodil (3 μM), an NMDA-receptor type 2 B antagonist, blocked stimulus dependent epileptiform discharges and generation of SDs in slices from animals treated with albumin in-vivo. We suggest that BBB opening facilitates the induction of peri-infarct SDs through impaired homeostasis of K+.

Abstract 1177: The mutational status of the p53 tumor suppressor gene is a determinant of GSTP1 expression and mediates GSTP1-dependent drug resistance in human glioblastoma

Mutations in the p53 tumor suppressor gene, a transcription factor activated by a variety of cellular stresses, including, those inflicted by anti-cancer agents, is a common genetic abnormality in GBMs. Although, p53 is involved in critical cellular processes, such as, cell cycle arrest, DNA repair and apoptosis, studies of p53 in tumor drug resistance and/or patient response to therapy have yielded mixed results. Thus, in gliomas and other cancers, such as, breast, bladder, and ovarian carcinomas, some studies have associated wild-type p53 with higher tumor drug resistance, while other studies indicate that mutant or functionally inactive p53, rather than wt p53, confers drug resistance. These observations indicate the significant complexity of the role of p53 in tumor response to therapy and suggest that other factors, including, downstream p53 pathways and/or regulation, may be important determinants of the p53 effects on the tumor drug resistance phenotype. We previously reported that the human GSTP1 gene, that encodes a major drug metabolizing protein, cell signaling regulator and a mediator of tumor drug resistance, is transcriptionally activated by p53 via a canonical p53 binding motif located in intron 4 of the GSTP1 gene. Our goal, in this study, is to gain further insight into the relationship between p53-dependent transcriptional control of GSTP1 in GBM and the extent to which it contributes to GSTP1 expression in primary patient tumor and, ultimately, to their response to therapy. For this, we sequenced the p53 gene across exons 2-11 in 42 primary GBM specimens quantified the level of GSTP1 gene expression by RNA-PCR and genotyped the allelic variants in them. The results showed, approx. half of the tumors to harbor wild-type p53. In those with mutant p53, the mutations spanned the entire p53 target region, the majority in the core DNA binding domain with the hot spots in codons 55, 72, 175, 245, 248, and 273. GSTP1 expression was significantly heterogeneous between the tumors, and with a few exceptions, correlated directly with the presence of wild-type p53. In representative tumors, the high GSTP1 gene expression was associated with resistance to cisplatin and temozolomide. These result suggest that, in GBM, transcriptional activation of GSTP1 by wild-type, and some mutant forms of p53, contributes to their resistance to therapy. Supported by NIH grants RO1 CA 153050, RO1CA127872, RO1 CA 112519, P50CA108786 and P30-CA14236.

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 1177. doi:1538-7445.AM2012-1177

Magnetic stimulation intensity modulates motor inhibition

Repetitive transcranial magnetic stimulation (rTMS) is a standard tool in neuroscience research and therapy. Here we study one rTMS property that has not received adequate attention, the interaction of subthreshold intensity stimulation and low frequencies. We applied 1Hz rTMS over the motor cortex at three intensities, 40%, 80% and 100% of the resting motor threshold (rMT), and measured cortical excitability before and after the stimulation sessions. When comparing motor evoked potential (MEP) measured from the abductor pollicis brevis (APB) muscle before and after rTMS stimulation, we found that low intensity (40% MT) stimulation significantly decreased MEP magnitude, some smaller (non-significant) inhibition was found for the 80% MT intensity and increased MEP was found for the high intensity (100% MT) stimulation. Our results indicate that when explaining the input-output relationship of motor cortex induced activation as an intensity-dependent function, there might be a need to split it into separate functions associated with separate processes mediated by different cell types such as interneurons, pyramidal neurons and others.

Central venous catheter tip malposition

Central venous catheters are commonly utilised to gain vascular access for varied clinical indications. Successful central venous catheter placement requires not only technical expertise, but also awareness of the potential complications. This article reviews the major procedural and post-procedural complications resulting from central venous catheter tip malposition.

Abstract 5611: Interleukin-2 receptor α (IL-2R α/CD25)-specific antibodies eliminate regulatory T-cells (TRegs) and enhance tumor-specific immune responses

Interleukin-2 Receptor α (IL-2R α / CD25)-specific Antibodies Eliminate Regulatory T-cells (TRegs) and enhance Tumor-specific Immune Responses

Duke University Medical Center, Durham, NC, USA

Introduction: Immunotherapy is an attractive therapeutic alternative for glioblastoma (GBM), but is limited by the lack of frequent and homogeneously-expressed tumor-specific antigens. The nearly universal presence and homogeneous expression of antigens derived from Cytomegalovirus (CMV) in GBM, but not normal brain, has now been well-established and may provide ideal antigens for tumor-specific immunotherapy. Despite the potential immunogenicity of CMV antigens, CMV immune responses in patients with GBM are blunted which may be a result of immunosuppressive regulatory T cells (TRegs) which are present at high levels in patients with GBM. Monoclonal antibodies (MAbs) that block IL-2Rα have been shown to abrogate TReg function in animal models, but also inhibit effective antitumor immune responses in the context of established tumors and attenuate immune responses in humans with autoimmune disorders or allogeneic organ transplants.

Material and Methods: The interleukin-2 receptor α (IL-2R α)-specific MAbs, PC61 (250 µg/mouse) and daclizumab (1 mg/kg), were administered during the recovery from TMZ-induced lymphopenia in mice and humans with GBM, respectively, concurrent with tumor-specific vaccination targeting the model antigen OVA or CMV pp65.

Results: As expected, in normal mice, anti-IL2Rα MAb treatment depletes and functionally impairs TRegs, but it also abrogates vaccine-induced immune responses. However, in direct contrast, when IL-2Rα-specific MAbs are administered during recovery from temozolomide (TMZ)-induced lymphopenia, anti-IL2Rα MAb administration depletes TRegs while simultaneously augmenting vaccine-induced effector T-cell responses and antitumor efficacy. Similarly, in a randomized Phase II trial, administration of the humanized IL-2Rα-specific MAb daclizumab after therapeutic TMZ dramatically reduces TReg levels (73.9% + 8.2 S.D.) and increases pp65-specific CD8+ T-cell responses (4.3 fold) in response to vaccination with CMV pp65 mRNA transfected DCs. Time-to-progression in the cohort of patients treated with daclizumab exceeds 24 months with a likelihood of 2 year progression-free survival of 66.7% (CI95 19.5%, 90.4%).

Conclusions: Therapeutic TMZ-induced lymphopenia provides a unique window of opportunity in which the presence of anti-IL-2Rα antibodies selectively inhibits TRegs, but potentiates ongoing anti-tumor effector T cell responses.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5611.

The effects of EPA, DHA, and aspirin ingestion on plasma lysophospholipids and autotaxin

Lysophophatidylcholine (LPC) and lysophosphatidic acid (LPA) are potent lysolipid mediators increasingly linked with atherosclerosis and inflammation. A current model proposing that plasma LPA is produced when LPC is hydrolyzed by the enzyme autotaxin has not been rigorously investigated in human subjects. We conducted a clinical trial of eicosapentaenoic acid/docosahexaenoic acid (EPA/DHA) and aspirin ingestion in normal volunteers. Fasting blood samples were drawn at baseline and after 4-week supplementation with EPA/DHA (3.4 g/d) with and without aspirin (650 mg). Plasma LPC and LPA species and autotaxin activity were measured. EPA-LPC and DHA-LPC concentrations increased significantly with EPA/DHA supplementation whereas EPA- and DHA-LPA did not. Autotaxin activity was unaffected by any treatment, and aspirin had no effect on any endpoint. Taken together, our data demonstrate that plasma LPC, but not LPA, species can be dynamically regulated by dietary supplementation, and argue against a simple model of LPA generation via LPC hydrolysis.

MenaINV Isoform Expression in Human Invasive Ductal Carcinomas of the Breast Correlates with Tumor Microenvironment of Metastatsis (TMEM) Score; a Pilot Study Indicating the Potential Use of MenaINV/11a Ratio as a Predictor of Distant Metastases

Background: Primary mammary carcinomas in rodents contain a subpopulation of invasive tumor cells that move towards perivascular macrophages and intravasate. An isoform of actin regulatory protein Mena, MenaINV is up-regulated in these invasive cells, while isoform Mena 11a is down regulated (Goswami et al 2009). The direct apposition of Mena positive tumor cells to endothelial cells and perivascular macrophages has been described as Tumor Microenvironment of Metastasis (TMEM) and its density is shown to be a predictor of metastatic outcome in human invasive ductal carcinomas of the breast (Robinson et al 2009). We questioned if MenaINV and Mena 11a isoform expression correlates with the invasiveness of breast lesions in Polyoma Middle T antigen (PyMT) mouse mammary tumors and human invasive ductal carcinomas (IDC), as well as if increased MenaINV expression is associated with high TMEM counts in human IDCs.Materials and Methods: We analyzed MenaINV and Mena 11a expression in fine needle aspiration biopsy (FNA) samples from 18 mice with PyMT mammary tumors, 3 human IDCs and 1 fibroadenoma (FA) by qRT-PCR. The expression of Mena isoforms from in situ PyMT lesions was compared with metastatic PyMT tumors and expressed as fold change. Mena isoform levels from IDC were compared to that in FA and expressed as fold change. Representative sections from IDCs were triple immunostained with anti-Mena, anti-CD 68 and anti-CD34 and independently analyzed for TMEM counts on ten x400 fields by two pathologists.Results: We observed a 7.5 fold increase in MenaINV expression and a 3 fold decrease of Mena 11a in metastatic PyMT tumors when compared to in situ lesions. The results from human samples are shown in Figure 1. The top panel shows MenaINV and Mena 11a fold change in IDCs compared to FA. The bottom panel shows TMEM counts for each IDC and MenaINV/11a ratios. Both, MenaINV expression and TMEM count varied significantly, whereas Mena 11a was exceedingly low in IDCs. In all 3 IDCs the levels of MenaINV correlated with TMEM counts.Discussion: This pilot study indicates for the first time that the expression of MenaINV and Mena 11a can be successfully analyzed in FNA biopsy samples from human breast lesions. In combination with the TMEM count, Mena isoforms can potentially become useful markers for predicting the metastatic potential of an individual breast lesion. A larger study is underway to develop a scoring system combining Mena isoform expression with the TMEM count.Figure 1: Top panel: qRT-PCR assessment of Mena splice variant expression in FNA samples from human breast lesions. Levels of MenaINV and Mena 11a in 3 IDCs were compared to those in FA. The result is expressed as fold change. Bottom panel: TMEMs on tissue sections from IDC with TMEM counts and MenaINV/11a ratios. Circles represent TMEMs.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2140.

Quantitative assessment of cardiorespiratory fitness, skeletal muscle function, and body composition in adults with primary malignant glioma

e13002

Background: The neuropsychological impact of malignant glioma is well documented; the physiological and functional effects are not known. We conducted a pilot study to quantitatively assess cardiorespiratiory fitness, skeletal muscle function, and body composition of patients with primary malignant glioma. Methods: Using a cross-sectional design, patients with clinically stable postsurgical (10 ± 7 days post surgery) high-grade glioma (HGG; n=25) and low-grade glioma (LGG) were studied. Participants performed a cardiopulmonary exercise test (CPET) with expired gas analysis to assess peak exercise capacity (VO2peak) and other parameters of cardiovascular function. Other physiological outcomes included skeletal muscle cross-sectional area (CSA; magnetic resonance imaging), isokinetic muscle strength (isokinetic dynamometer), and body composition (air displacement plethysmography). QOL was assessed by the Functional Assessment of Cancer Therapy-Brain scale (FACT-BR). Results: CPET was a feasible and safe procedure for malignant glioma patients with no serious adverse events. Peak VO2 indexed to total body weight and lean body mass for both groups was 13.0 mL.min-1 and 19 mL.min-1; the equivalent to 59% and 38% below age and sex-predicted normative values, respectively. Skeletal muscle isokinetic strength was significantly lower in HGG relative to LGG patients (83 vs. 125 Nm, p=.025) and predicted peak VO2 (r = 0.44, p<0.05). In patients with HGG, only self-reported exercise behavior was correlated with QOL (r = 0.42; p=.046) while sex (male) (r = 0.44; p=.037), lean mass (r = -0.41; p=.049), and VO2peak (r = -0.40; p=.052) were associated with fatigue. Conclusions: CPET is a safe and feasible tool to evaluate physical functioning in select patients with malignant glioma. Postsurgical glioma patients have markedly reduced exercise capacity, isokinetic strength and CSA. Muscle strength is an important contributor to poor VO2peak in this population. Prospective studies are now required to determine whether such abnormalities influence prognosis as well as test the effect of appropriately selected interventions to prevent and/or mitigate dysfunction.

No significant financial relationships to disclose.