The O2-sensitive brain stem, hyperoxic hyperventilation, and CNS oxygen toxicity

Central nervous system oxygen toxicity (CNS-OT) is a complex disorder that presents, initially, as a sequence of cardio-respiratory abnormalities and nonconvulsive signs and symptoms (S/Sx) of brain stem origin that culminate in generalized seizures, loss of consciousness, and postictal cardiogenic pulmonary edema. The risk of CNS-OT and its antecedent “early toxic indications” are what limits the use of hyperbaric oxygen (HBO2) in hyperbaric and undersea medicine. The purpose of this review is to illustrate, based on animal research, how the temporal pattern of abnormal brain stem responses that precedes an “oxtox hit” provides researchers a window into the early neurological events underlying seizure genesis. Specifically, we focus on the phenomenon of hyperoxic hyperventilation, and the medullary neurons presumed to contribute in large part to this paradoxical respiratory response; neurons in the caudal Solitary complex (cSC) of the dorsomedial medulla, including putative CO2 chemoreceptor neurons. The electrophysiological and redox properties of O2-/CO2-sensitive cSC neurons identified in rat brain slice experiments are summarized. Additionally, evidence is summarized that supports the working hypothesis that seizure genesis originates in subcortical areas and involves cardio-respiratory centers and cranial nerve nuclei in the hind brain (brainstem and cerebellum) based on, respectively, the complex temporal pattern of abnormal cardio-respiratory responses and various nonconvulsive S/Sx that precede seizures during exposure to HBO2.

Seizures Caused by Exposure to Hyperbaric Oxygen in Rats Can Be Predicted by Early Changes in Electrodermal Activity

Hyperbaric oxygen (HBO₂) is breathed during undersea operations and in hyperbaric medicine. However, breathing HBO₂ by divers and patients increases the risk of central nervous system oxygen toxicity (CNS-OT), which ultimately manifests as sympathetic stimulation producing tachycardia and hypertension, hyperventilation, and ultimately generalized seizures and cardiogenic pulmonary edema. In this study, we have tested the hypothesis that changes in electrodermal activity (EDA), a measure of sympathetic nervous system activation, precedes seizures in rats breathing 5 atmospheres absolute (ATA) HBO₂. Radio telemetry and a rodent tether apparatus were adapted for use inside a sealed hyperbaric chamber. The tethered rat was free to move inside a ventilated animal chamber that was flushed with air or 100% O₂. The animal chamber and hyperbaric chamber (air) were pressurized in parallel at ~1 atmosphere/min. EDA activity was recorded simultaneously with cortical electroencephalogram (EEG) activity, core body temperature, and ambient pressure. We have captured the dynamics of EDA using time-varying spectral analysis of raw EDA (TVSymp), previously developed as a tool for sympathetic tone assessment in humans, adjusted to detect the dynamic changes of EDA in rats that occur prior to onset of CNS-OT seizures. The results show that a significant increase in the amplitude of TVSymp values derived from EDA recordings occurs on average (±SD) 1.9 ± 1.6 min before HBO₂-induced seizures. These results, if corroborated in humans, support the use of changes in TVSymp activity as an early "physio-marker" of impending and potentially fatal seizures in divers and patients.

Exogenous ketone ester delays CNS oxygen toxicity without impairing cognitive and motor performance in male Sprague-Dawley rats

Hyperbaric oxygen (HBO2) is breathing >1 atmosphere absolute (ATA; 101.3 kPa) O2 and is used in HBO2 therapy and undersea medicine. What limits the use of HBO2 is the risk of developing central nervous system (CNS) oxygen toxicity (CNS-OT). A promising therapy for delaying CNS-OT is ketone metabolic therapy either through diet or exogenous ketone ester (KE) supplement. Previous studies indicate that KE induces ketosis and delays the onset of CNS-OT; however, the effects of exogeneous KE on cognition and performance are understudied. Accordingly, we tested the hypothesis that oral gavage with 7.5 g/kg induces ketosis and increases the latency time to seizure (LSz) without impairing cognition and performance. A single oral dose of 7.5 g/kg KE increases systemic β-hydroxybutyrate (BHB) levels within 0.5 h and remains elevated for 4 h. Male rats were separated into three groups: control (no gavage), water-gavage, or KE-gavage, and were subjected to behavioral testing while breathing 1 ATA (101.3 kPa) of air. Testing included the following: DigiGait (DG), light/dark (LD), open field (OF), and novel object recognition (NOR). There were no adverse effects of KE on gait or motor performance (DG), cognition (NOR), and anxiety (LD, OF). In fact, KE had an anxiolytic effect (OF, LD). The LSz during exposure to 5 ATA (506.6 kPa) O2 (≤90 min) increased 307% in KE-treated rats compared with control rats. In addition, KE prevented seizures in some animals. We conclude that 7.5 g/kg is an optimal dose of KE in the male Sprague-Dawley rat model of CNS-OT.

CNS function and dysfunction during exposure to hyperbaric oxygen in operational and clinical settings

Hyperbaric oxygen (HBO2) is breathed during hyperbaric oxygen therapy and during certain undersea pursuits in diving and submarine operations. What limits exposure to HBO2 in these situations is the acute onset of central nervous system oxygen toxicity (CNS-OT) following a latent period of safe oxygen breathing. CNS-OT presents as various non-convulsive signs and symptoms, many of which appear to be of brainstem origin involving cranial nerve nuclei and autonomic and cardiorespiratory centers, which ultimately spread to higher cortical centers and terminate as generalized tonic-clonic seizures. The initial safe latent period makes the use of HBO2 practical in hyperbaric and undersea medicine; however, the latent period is highly variable between individuals and within the same individual on different days, making it difficult to predict onset of toxic indications. Consequently, currently accepted guidelines for safe HBO2 exposure are highly conservative. This review examines the disorder of CNS-OT and summarizes current ideas on its underlying pathophysiology, including specific areas of the CNS and fundamental neural and redox signaling mechanisms that are thought to be involved in seizure genesis and propagation. In addition, conditions that accelerate the onset of seizures are discussed, as are current mitigation strategies under investigation for neuroprotection against redox stress while breathing HBO2 that extend the latent period, thus enabling safer and longer exposures for diving and medical therapies.

A Prospective Cohort Study Comparing Colorimetric and Fluorescent Imaging for Sentinel Lymph Node Mapping in Endometrial Cancer

BACKGROUND

This prospective cohort study aimed to assess sentinel lymph node (SLN) mapping using isosulfan blue (ISB) compared with ISB plus indocyanine green (ICG) and near-infrared imaging (NIR) for patients with endometrial cancer.

METHODS

In this study, 200 patients with endometrial cancer underwent SLN assessments and were randomized to ISB + ICG (n = 180) or ISB alone (n = 20). Blue dye determinations were recorded for all 200 cases followed by NIR imaging of ICG for 180 randomized subjects. All the patients underwent robotically assisted hysterectomy with pelvic ± aortic lymphadenectomy.

RESULTS

The mean age of the patients was 64.5 ± 8.4 years, and the mean body mass index (BMI) was 33 ± 7.6 kg/m². The histologies were endometrioid G1 (43%), G2 (30%), G3 (7%), and type 2 (20%). The mean time from dye injection to initiation of mapping was 13.4 ± 6.2 min, and the time to removal of SLN was 17.4 ± 11.2 min. Detection of SLN for the 20 ISB control cases did not differ from that for the 180 ISB + ICG cases (p > 0.05). The rates of SLN detection for ISB + ICG/NIR (n = 180) versus ISB (n = 200) were as follows: bilateral (83.9 vs. 40%), unilateral (12.2 vs. 36%), and none (3.9 vs. 24%) (p < 0.001). The median SLN per case was 2 (range 0-4). Positive SLNs were found in 21.1% (n = 38) of the ISB + ICG cases compared with 13.5% (n = 27) of the ISB cases (p = 0.056). The false-negative rate for SLN biopsy was 2.5% (95% confidence interval, 0.1-14.7%). In 61% (25/41) of the node-positive cases, SLN was the only positive lymph node (LN). Isolated tumor cells were found in 39.5% (15/38) of the SLN metastasis cases compared with 26.7% (4/15) of the non-SLN metastasis cases (p = 0.528).

CONCLUSIONS

In this prospective study, ISB + ICG and NIR detected more SLNs and more LN metastases than ISB alone. Assessment of SLN with ICG + ISB/NIR imaging had excellent sensitivity for detection of metastasis and no safety issues.

Robot-assisted versus open radical hysterectomy: A multi-institutional experience for early-stage cervical cancer

OBJECTIVE

To compare perioperative and clinico-pathological outcomes of patients with early-stage cervical cancer who underwent robot-assisted radical hysterectomy (RRH) and open radical hysterectomy (ORH).

METHODS

This retrospective multi-center study abstracted demographic, clinico-pathological and perioperative outcomes data from medical records of 491 cervical cancer patients treated with RRH (n = 259) ORH (n = 232) between 2005 and 2011 at two American and one Norwegian University Cancer Centres.

RESULTS

Mean estimated blood loss (EBL) and transfusion rates were less for RRH than for ORH (97 vs. 49 mL, p < 0.001, and 3% vs. 7%, p = 0.018, respectively). Mean length of hospital stay (LOS) was significantly shorter in RRH versus ORH (1.8 vs. 5.1 days, p < 0.001). Mean operative time was longer for RRH than ORH (220 vs. 156 min, p < 0.001). Although overall complications were similar (p = 0.49), intra-operative complications were less common in the RRH group than ORH (4% vs. 10%, p = 0.004). In multivariate regression analyses longer operative time, less EBL and intra-operative complications, shorter LOS, and more pre-operative cone were significantly associated with RRH versus ORH. Recurrence and death rates were not statistically different for the two groups at a mean follow-up time of 39 months (p = 1.00 and p = 0.48, respectively).

CONCLUSIONS

RRH had improved clinical outcomes compared to ORH in the treatment of early-stage cervical cancer in terms of EBL, intra-operative complications, transfusion rates, LOS, and pre-operative cone. Disease recurrence and survival were comparable for the two procedures.

Cellular therapy in combination with cytokines improves survival in a xenograft mouse model of ovarian cancer

Studies have shown enhanced survival of ovarian cancer patients in which the tumors are infiltrated with tumor infiltrating lymphocytes and natural killer cells showing the importance of immune surveillance and recognition in ovarian cancer. Therefore, in this study, we tested cellular immunotherapy and varying combinations of cytokines (IL-2 and/or pegylated-IFNα-2b) in a xenograft mouse model of ovarian cancer. SKOV3-AF2 ovarian cancer cells were injected intra-peritoneally (IP) into athymic nude mice. On day 7 post-tumor cell injection, mice were injected IP with peripheral blood mononuclear cells (PBMC; 5 × 10(6) PBMC) and cytokine combinations [IL-2 ± pegylated-IFNα-2b (IFN)]. Cytokine injections were continued weekly for IFN (12,000 U/injection) and thrice weekly for IL-2 (4000 U/injection). Mice were euthanized when they became moribund due to tumor burden at which time tumor and ascitic fluid were measured and collected. Treatment efficacy was measured by improved survival at 8 weeks and overall survival by Kaplan-Meier analysis. We observed that the mice tolerated all treatment combinations without significant weight loss or other apparent illness. Mice receiving PBMC plus IL-2 showed improved median survival (7.3 weeks) compared to mice with no treatment (4.2 weeks), IL-2 (3.5 weeks), PBMC (4.0 weeks), or PBMC plus IL-2 and IFN (4.3 weeks), although PBMC plus IL-2 was not statistically different than PBMC plus IFN (5.5 weeks, p > 0.05). We demonstrate that cytokine-stimulated cellular immune therapy with PBMC and IL-2 was well tolerated and resulted in survival advantage compared to untreated controls and other cytokine combinations in the nude-mouse model.

Robotic transperitoneal infra-renal aortic lymphadenectomy in early-stage endometrial cancer

OBJECTIVES

To assess the clinical performance of robotic-assisted infra-renal aortic lymphadenectomy (IRL) using a single center-docked approach for patients with endometrial cancer.

METHODS

Robotic-assisted hysterectomy with pelvic and aortic lymphadenectomy was performed in 97 clinical stage I endometrial cancer (EC) patients with the intent to remove infra-renal aortic lymph nodes. Peri-operative data was contemporaneously accessioned and a retrospective database analysis was performed to examine clinical outcomes.

RESULTS

IRL versus infra-mesenteric artery (IMA) dissections were accomplished in 88 (90.7%) and nine (9.3%) cases, respectively. There were no laparotomy conversions. Histology included 20.6% G1, 41.2% G2, and 38.1% G3 (endometrioid and Type II histologies). Forty-four (45.4%) cases had >50% depth-of-invasion and 43 (44.3%) cases had lymphovascular space invasion. Lymph node metastases were detected in 39 (40.2%) cases [37 (38.1%) pelvic, 16 (16.5%) pelvic+aortic, two (2.1%) isolated aortic lymph nodes]. Aortic metastasis was identified in 16/37 (43.2%) pelvic node positive cases, and 6/34 (17.7%) IRL cases with positive pelvic nodes had infra-renal metastasis, yet normal aortic nodes below the IMA. Harvested aortic lymph nodes for IRL exceeded IMA cases (15.9±6.3 vs. 8.9±4.6; p<0.01). Mean BMI for IMA cases exceeded IRL cases (37.4±3.3 vs. 31.4±7.1kg/m(2); p<0.001). Twenty-five (81%) patients with BMI >35kg/m(2) underwent successful IRL (range 36-47kg/m(2)) compared to 95% of cases <35kg/m(2) (p=0.03).

CONCLUSIONS

IRL was accomplished in 95% of EC patients with BMI <35kg/m(2) and 81% with BMI >35kg/m(2) using a single center-docked approach. A strict 35kg/m(2) BMI cut-off for avoiding IRL is therefore not advised.

Abstract 4743: Ex vivo expanded cytokine-induced killer cells maintain cytotoxic activity against ovarian cancer in an in vivo model

Introduction: Ovarian cancer (OC) is the leading cause of death among gynecological malignancies and thus there is a compelling need to develop novel treatment protocols. The study aim was to asses the anti-tumor efficacy of ex vivo expanded cytokine-induced killer cells (CIK) against OC using in vitro and in vivo models.

Methods: CIK were expanded from peripheral blood mononuclear cells (PBMC) isolated from OC patients (n=21) and healthy donors (HD; n=11), in a cocktail of IL-2, IL-12, and anti-CD3 antibody ± IL-7 (10 ng/ml). Cell populations present were determined by flow cytometry. CIK cytotoxicity was assessed against an OC cell line (SKOV3-AF2) in presence of IL-2 and IFNα-2b. To determine in vivo activity, OC cells (1x106) were injected intraperitoneally (IP) into female athymic nude mice (n=100). Day-7 post-OC cell injection, mice were injected IP with treatment cells [CIK (5x106) from OC patient or PBMC (5x106) from HD]. Also on day-7, IL-2 treatment was initiated (4,000 U/IP-injection) and continued thrice weekly. Control mice with and without treatment cells or IL-2 were also included. Mice were sacrificed when they became moribund due to tumor burden at which time solid tumor and ascitic fluid were measured and collected. Cell and cytokine treatment efficacy was measured by overall survival of the mice.

Results: CIK expanded exponentially from both HD (149-fold) and OC patients (139-fold) over 3-weeks; expansion cultures consisted primarily of T-cells (&gt;98%) by days 7-8. However, CIK expansion was doubled in the presence of IL-7 (159 vs. 81-fold; p&lt;0.05). CIK from OC patients and HD elicited a significant cytotoxic response against OC cells (26.8% and 24.8%, respectively) compared to negative controls lacking CIK (0.4%; p&lt;0.01). In the in vivo experiments, mice tolerated all CIK, PBMC and cytokine dosages tested as evidenced by no significant weight loss (&lt;10%) or treatment-associated morbidity (100% survival, post-treatment cell injection). Mice that received CIK + IL-2 (expanded in the absence of IL-7) or PBMC + IL-2 demonstrated a survival advantage at 9-weeks (50% and 55%, respectively) compared to untreated mice (9%), treated with IL-2 alone (13%) or PBMC alone (14%). There was no significant difference in average tumor weight or ascitic fluid between treatment groups, probably due to mice being sacrificed when they were moribund due to tumor burden (not a specific time post-tumor cell injection).

Conclusions: Ex vivo expanded CIK demonstrated an anti-OC effect both in vitro and in a xenograft model. CIK expanded from HD and OC patients elicited a significant cytotoxicity against OC cells in vitro. In addition, OC bearing mice treated with CIK + IL-2 or PBMC + IL-2 showed improved survival. Additional mouse studies are underway to test the efficacy of CIK, PBMC, and their combination. Data generated will provide the basis for development of an immunotherapy-based Phase I trial for OC.

Citation Format: Susan Blaydes Ingersoll, Milan Srivastava, Sarfraz Ahmad, Nicole M. Stavitzski, Jeremiah L. Oyer, Ghazanfar Ali, Robert K. Banks, Neil J. Finkler, John R. Edwards, Robert W. Holloway. Ex vivo expanded cytokine-induced killer cells maintain cytotoxic activity against ovarian cancer in an in vivo model. [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 4743. doi:10.1158/1538-7445.AM2013-4743

Abstract 2159: Expression of Sp1 and survivin in ovarian cancer specimens: potential novel therapeutic targets in disease treatment

Ovarian cancer (OC) is one of the most common female cancers and is the leading cause of death from gynecologic malignancies. Although, cisplatin is the front-line chemotherapeutic option for OC, its success is compromised due to dose-limiting toxicity and acquired resistance by tumor cells. Specificity protein 1 (Sp1) is a transcription factor that is over-expressed in several cancers and is inversely associated with survival. Survivin, a member of IAP family, is known to cause resistance to chemo- and radiation therapy. Studies from our laboratories have shown that the NSAID, tolfenamic acid (TA), targets Sp1 protein and inhibits expression of survivin in various cancer models. Our primary objective was to evaluate the expression of Sp1 and survivin in OC patients’ specimens and target these candidates using TA for enhancing the cisplatin response. Expression of Sp1 and survivin in clinical specimens was determined by qPCR and Western blots. qPCR showed increased expression of survivin (∼5-fold) and Sp1 (∼2-fold) in tumor samples. Western blot also revealed over-expression of both Sp1 (&gt;2.6-fold) and survivin (&gt;100-fold). OC cell lines (ES2, OVCAR-3) were used to determine the anti-proliferative response to cisplatin and TA. TA and cisplatin showed a dose- and time-dependent inhibition of cell viability in OC cell lines [TA (50 ÂμM) caused 50% (ES2) and 40% (OVCAR-3) growth inhibition and cisplatin (5 ÂμM) caused 60% and 40% inhibition at 48 h post-treatment]. Combination treatment using optimized doses of TA (50 ÂμM) and cisplatin (5 ÂμM) resulted in a synergistic response and caused stronger inhibition (ES2: ∼80%, OVCAR-3: &gt;60) compared to single-agent. Increased inhibition of proliferation by the combination of TA and cisplatin was accompanied by cell-cycle arrest, predominantly in the G2/M phase. A significant increase in apoptosis, as determined by Caspase 3/7 activity, annexin-V staining, and PARP cleavage, was also observed in the combination treatment. Cell invasion and migration was assessed using matrigel coated transwell chambers. Compared to TA or cisplatin treatment alone, their combination significantly inhibited ES2 cell invasion. Analysis of ES2 cells by global proteomic profiling indicated that the combination treatment upregulated proteins associated with oxidative phosphorylation, apoptosis, and electron transport chain; and down-regulated cytoplasmic ribosomal proteins, translational factors, and proteins involved in DNA damage response, and cell cycle. In conclusion, elevated expression of Sp1 and survivin confirmed their association in OC and demonstrated the relevance of targeting these candidates, which may render the OC cells more sensitive to chemotherapy and offer therapeutic potential. Further studies to delineate underlying mechanism(s) of action possibly involving signaling pathways and reactive oxygen species are currently underway.

Citation Format: Umesh T. Sankpal, Susan B. Ingersoll, Mohammed I. Shukoor, Chris M. Lee, Nicole M. Stavitzski, Vadiraja B. Bhat, Sarfraz Ahmad, Robert W. Holloway, Liz Abraham, Riyaz Basha. Expression of Sp1 and survivin in ovarian cancer specimens: potential novel therapeutic targets in disease treatment. [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 2159. doi:10.1158/1538-7445.AM2013-2159