Iatrogenic Esophagopleural Fistula After the Management of Acute Variceal Hemorrhage With Minnesota Tube Placement.

An esophagopleural fistula (EPF) is a rare condition. EPFs are typically of spontaneous, iatrogenic, or neoplastic origin. A 50-year-old man with hepatitis C and alcoholic cirrhosis presented with a history of recurrent variceal hemorrhage requiring esophageal banding, Minnesota tube placement, and a transjugular intrahepatic portosystemic shunt. His hospital course after esophageal perforation and EPF was complicated by acute respiratory failure and empyema, necessitating intubation and thoracostomy tube placement. To the best of our knowledge, this is the first reported case of EPF secondary to Minnesota tube placement. The EPF completely healed after endoscopic repair.

Rare Variant Hirschsprung Disease Presenting as Large Bowel Obstruction in Adulthood: Hypoganglionosis in the Anorectal Canal.

Hirschsprung disease (HD) is a congenital bowel innervation disorder characterized by the absence of ganglion cells in the neural plexus of the colorectal wall. Variant HD describes a heterogeneous group of intestinal innervation disorders in which clinical presentation resembles HD despite the presence of ganglion cells seen in rectal biopsies. We present the first reported case of a rare variant HD, hypoganglionosis isolated in the anorectal canal, diagnosed in an adult who presented with a long history of constipation and treated with proctosigmoidectomy with coloanal anastomosis. Histopathology showed rare ganglion cells isolated in the anorectal canal.

Hepatic parasitic abscess resistant to traditional anthelmintics: difficulty of diagnosis and treatment of fascioliasis in the USA.

We report a case of human fascioliasis in the USA that encountered many diagnostic uncertainties. Numerous tests available for detection of fascioliasis were utilised but the diagnosis remained elusive. Confounders included three negative stool ova and parasite examinations, positive hepatitis A virus IgM antibody, cross-reactive false-positive Echinococcus IgG antibody, absence of characteristic image findings and unrevealing liver biopsy. Praziquantel was started as empiric treatment for helminth infections, but was ineffective. Due to the rarity of the disease in the USA, serologic testing and triclabendazole were only available from the Centers for Disease Control and Prevention, which led to a delay in diagnosis and treatment.

Reporting of Inferior Vena Cava Filter Complications on CT: Impact of Standardized Macros.

OBJECTIVE: The objective of our study was to report the effect of implementing standardized inferior vena cava filter (IVCF) macros on the reporting of IVCFs and filter-related complications in abdominal CT reports. MATERIALS AND METHODS: Retrospective analysis was performed of all abdominal CT reports performed between October 2014 and January 2015 before implementation of IVCF macros (n = 5143). Duplicated examinations and studies requested specifically to evaluate known IVCFs were excluded. In March 2016, normal and abnormal standardized IVCF macros were implemented. Two radiologists reviewed all CT abdominal reports using IVCF macros between March 2016 to July 2016 to assess for missed IVCF complications. RESULTS: Before the implementation of the IVCF macros, 146 of 5143 (2.8%) abdominal CT studies (89 men and 57 women; mean age, 59 years) showed an IVCF. After implementation of IVCF macros, 105 abdominal CT studies using the IVCF macros were analyzed (48 men and 57 women; mean age, 58 years), including 73 normal macros and 32 abnormal macros). The rate of reported caval penetration and filter element-organ interaction improved from 12% (9/73) to 57% (28/49) (p < 0.001) and from 0% (0/53) to 36% (9/25) (p < 0.001) before and after macro implementation, respectively. However, one filter fracture and two filter-associated thrombi were missed when using the IVCF macros. CONCLUSION: Implementation of standardized IVCF macros improves reporting of IVCFs and IVCF-associated complications in abdominal CT reports.

Concurrent Central Venous Stent and Central Venous Access Device Placement Does Not Compromise Stent Patency or Catheter Function in Patients with Malignant Central Venous Obstruction.

PURPOSE: To determine if concurrent placement of a central venous stent (CVS) and central venous access device (CVAD) compromises stent patency or catheter function in patients with malignant central venous obstruction. MATERIALS AND METHODS: CVS placement for symptomatic stenosis resulting from malignant compression was performed in 33 consecutive patients who were identified retrospectively over a 10-year period; 28 (85%) patients had superior vena cava syndrome, and 5 (15%) had arm swelling. Of patients, 11 (33%) underwent concurrent CVS and CVAD placement, exchange, or repositioning; 22 (67%) underwent CVS deployment alone and served as the control group. Types of CVADs ranged from 5-F to 9.5-F catheters. Endpoints were CVS patency as determined by clinical symptoms or CT and CVAD function, which was determined by clinical performance. RESULTS: All procedures were technically successful. There was no difference between the 2 groups in clinically symptomatic CVS occlusion (P = .2) or asymptomatic in-stent stenosis detected on CT (P = .5). None of the patients in the CVS and CVAD group had recurrent clinical symptoms, but 3 (30%) of 10 patients with imaging follow-up had asymptomatic in-stent stenosis. In the control group, 3 (14%) patients had clinically symptomatic CVS occlusion and required stent revision, whereas 4 (21%) of 19 patients with imaging follow-up had asymptomatic in-stent stenosis. During the study, 2 (20%) functional but radiographically malpositioned catheters were identified (0.66 per 1,000 catheter days). CONCLUSIONS: Presence of a CVAD through a CVS may not compromise stent patency or catheter function compared with CVS placement alone.

Significance of Echocardiographically Detected Central Venous Catheter Tip-Associated Thrombi.

PURPOSE: To explore significance, management, and outcomes of central venous catheter (CVC) tip-associated thrombi incidentally detected on echocardiography. MATERIALS AND METHODS: Echocardiogram data from all patients with CVCs from October 2009 to June 2011 were reviewed (N = 170). Patients with CVC tip-associated thrombi were selected (n = 49). Echocardiograms were reviewed for ejection fraction, presence of patent foramen ovale (PFO), presence of other intracardiac shunts, and mean thrombus size. Management decisions, thrombus extension, pulmonary embolism, paradoxical emboli, and stroke within 3 months were recorded. RESULTS: Mean thrombus size was 2.1 cm (range, 0.5-5.7 cm). Of patients with thrombi, 11 (22%) were already on anticoagulation, and there was no change in management. Anticoagulation was started without complications in 17 (35%) patients, the catheter was removed in 4 (8%) patients, and no new treatment was initiated in 17 (35%) patients. Of these 17 patients, 16 (94%) developed no complications. One (6%) patient with a PFO and right-to-left shunt experienced a stroke before PFO closure. After surgical closure of the PFO, the same patient developed catheter tip-associated thrombus without complication. There were no pulmonary emboli, strokes, or other detected embolic phenomena. CONCLUSIONS: In this sample with CVC tip-associated thrombi but without PFO or other intracardiac shunts, no embolic or other complications were detected, regardless of anticoagulation status. These data suggest a benign course for such thrombi and that anticoagulation, catheter removal, thrombectomy, and thrombolysis may be unnecessary when catheter tip-associated thrombi are incidentally detected on echocardiography.

A 16-F Sheath with Endobronchial Forceps Improves Reported Retrieval Success of Long-Dwelling "Closed Cell" Inferior Vena Cava Filter Designs.

PURPOSE: To report results of a 16-F sheath/endobronchial forceps combination in retrieval of "closed cell" inferior vena cava (IVC) filter designs with prolonged dwell times of ≥ 60 days. MATERIALS AND METHODS: Forceps retrieval of selected IVC filters using a 16-F 45-cm sheath was performed in 35 patients (25 women and 10 men). Patients presented with filters that were no longer needed without (n = 10) or with (n = 21) prior failed retrieval, caval thrombosis before lysis (n = 3), and back pain (n = 1). Filter designs included 19 Günther Tulip (54%), 10 Option (29%), and six OptEase (17%). Mean dwell time was 977 days. Imaging characteristics, technical success, fluoroscopy time, and complications were recorded. RESULTS: Filters included 20 tip-embedded, 6 tip-adherent, 4 fractured, and 6 containing thrombus. All were strut and wall-embedded. Initial snare failures occurred in 8 filters because of hook straightening (n = 4), adherent material (n = 2), snare breakage (n = 1), and filter tilt (n = 1). The 16-F sheath/forceps combination was 100% successful in removing filters. In 1 patient, 2 extravascular fragments could not be retrieved. Median fluoroscopy time, excluding 3 extended lysis procedures, was 8 minutes. Minor caval abnormalities, including caval spasm and caval defects, were noted in 17 patients, and filter fracture occurred in 2 patients. No major complications occurred. CONCLUSIONS: A high rate of retrieval for closed cell long-dwelling strut and wall-embedded filters may be achieved using a 16-F sheath/endobronchial forceps combination.

Contemporary Status of Percutaneous Ablation for the Small Renal Mass.

Renal cell carcinoma is the tenth most common malignancy in the USA, with upwards of 61,000 new cases and resulting in more than 14,000 deaths annually. Although partial nephrectomy remains the standard treatment, image-guided nephron-sparing ablative techniques including cryoablation, radiofrequency ablation, and microwave ablation have emerged as treatment options in certain patient populations. Ablative therapies have high technical successes, low tumor recurrence rates, and preserve renal parenchymal volume. The purpose of this article is to provide an update on ablation therapies for small renal masses.

Anterior cervical discectomy and fusion with a zero-profile integrated plate and spacer device: a clinical and radiological study: Clinical article.

OBJECT: Anterior cervical plating decreases the risk of pseudarthrosis following anterior cervical discectomy and fusion (ACDF). Dysphagia is a common complication of ACDF, with the anterior plate implicated as a potential contributor. A zero-profile, stand-alone polyetheretherketone (PEEK) interbody spacer has been postulated to minimize soft-tissue irritation and postoperative dysphagia, but studies are limited. The object of the present study was to determine the clinical and radiological outcomes for patients who underwent ACDF using a zero-profile integrated plate and spacer device, with a focus on the course of postoperative prevertebral soft-tissue thickness and the incidence of dysphagia. METHODS: Using a surgical database, the authors conducted a retrospective analysis of all patients who had undergone ACDF between August 2008 and October 2011. All patients received a Zero-P implant (DePuy Synthes Spine). The Neck Disability Index (NDI) and visual analog scale (VAS) scores for arm and neck pain were documented. Dysphagia was determined using the Bazaz criteria. Prevertebral soft-tissue thickness, spinal alignment, and subsidence were assessed as well. RESULTS: Twenty-two male and 19 female consecutive patients, with a mean age of 58.4 ± 14.68, underwent ACDF (66 total operated levels) in the defined study period. The mean clinical follow-up in 36 patients was 18.6 ± 9.93 months. Radiological outcome in 37 patients was assessed at a mean follow-up of 9.76 months (range 7.2-19.7 months). There were significant improvements in neck and arm VAS scores and the NDI following surgery. The neck VAS score improved from a median of 6 (range 0-10) to 0 (range 0-8; p < 0.001). The arm VAS score improved from a median of 2 (range 0-10) to 0 (range 0-7; p = 0.006). Immediate postoperative dysphagia was experienced by 58.4% of all patients. Complete resolution was demonstrated in 87.8% of affected patients at the latest follow-up. The overall median Bazaz score decreased from 1 (range 0-3) immediately postoperatively to 0 (range 0-2; p < 0.001) at the latest follow-up. Prevertebral soft-tissue thickness significantly decreased across all levels from a mean of 15.8 ± 4.38 mm to 10.1 ± 2.93 mm. Postoperative lordosis was maintained at the latest follow-up. Mean subsidence from the immediate postoperative to the latest follow-up was 4.1 ± 4.7 mm (p < 0.001). Radiographic fusion was achieved in 92.6% of implants. No correlation was found between prevertebral soft-tissue thickness and Bazaz dysphagia score. CONCLUSIONS: A zero-profile integrated plate and spacer device for ACDF surgery produces clinical and radiological outcomes that are comparable to those for nonintegrated plate and spacer constructs. Chronic dysphagia rates are comparable to or better than those for previously published case series.

Low-dose intrathecal fluorescein and etiology-based graft choice in endoscopic endonasal closure of CSF leaks.

OBJECTIVE: Skull base cerebrospinal fluid (CSF) leaks of various etiologies are increasingly repaired through the natural corridor using an endoscopic endonasal approach. Characteristics of the skull base defect significantly correlate with etiology, which should be ascertained to guide surgical management. The objectives of this study were to assess the long-term outcomes of patients that underwent endoscopic endonasal repair of CSF leak using low-dose intrathecal fluorescein (ITF) and an etiology-based algorithm for multi-layer graft closure. METHODS: Patients were divided into 4 groups: A--congenital, B--post-traumatic, C--post-endonasal surgery, D--post-craniotomy. Low-dose ITF was utilized in all case series. Long-term clinical follow-up data, including perioperative complications associated with the use of intrathecal fluorescein and leak closure rates, were obtained retrospectively. Endoscopic visualization of fluorescein-stained CSF as well as the method of skull base closure and graft material is detailed. RESULTS: We identified a total of 41 patients (N=24 in Group A, N=4 in Group B, N=12 in Group C and N=1 in Group D) that underwent 50 CSF leak repairs using the endoscopic endonasal approach with an average follow-up of 31.6 months. Nine patients (21.9%) had undergone a previous attempt at CSF leak repair. Lumbar drain was used intraoperatively in 26 patients (63.4%) and kept in place for an average duration of 3.25 days. ITF successfully identified the site of leak in 80.5% of cases regardless of etiology. Leaks were successfully closed in 92% of patients. One patient (2.4%) experienced transient leg weakness following lumbar drain placement. Another patient (2.4%) developed hydrocephalus requiring a ventriculoperitoneal shunt. CONCLUSION: Low-dose ITF is a safe and useful adjunct to endoscopic endonasal repair of CSF leaks with minimal complications and successful localization of the leak in approximately 80%. An etiology-based approach to graft choice and duration of lumbar drain placement in CSF leak repair may optimize closure rates.

Navigated guide tube for the placement of mini-open pedicle screws using stereotactic 3D navigation without the use of K-wires: technical note.

OBJECT: Three-dimensional spinal navigation increases screw accuracy, but its implementation in clinical practice has been difficult, mainly because of surgeons' concerns about increased operative times, disturbance of workflow, and safety. The authors present a custom-designed navigated guide that addresses some of these concerns by allowing for drilling, tapping, and placing the final screw via a minimally invasive approach without the need for K-wires. In this paper, the authors' goal was to describe the technical aspects of the navigated guide tube as well as pedicle screw accuracy. METHODS: The authors present the technical details of a navigated guide that allows drilling, tapping, and the placement of the final screw without the need for K-wires. The first 10 patients who received minimally invasive mini-open spinal pedicle screws are presented. The case series focuses on the immediate postoperative outcomes, pedicle screw accuracy, and pedicle screw-related complications. An independent board-certified neuroradiologist determined pedicle screw accuracy according to a 4-tiered grading system. RESULTS: The navigated guide allowed successful placement of mini-open pedicle screws as part of posterior fixation from L-1 to S-1 without the use of K-wires. Only 7-mm-diameter screws were placed, and 72% of screws were completely contained within the pedicle. Breaches less than 2 mm were seen in 23% of cases, and these were all lateral except for one screw. Breaches were related to the lateral to medial trajectory chosen to avoid the superior facet joint. There were no complications related to pedicle screw insertion. CONCLUSIONS: A novel customized navigated guide tube is presented that facilitates the workflow and allows accurate placement of mini-open pedicle screws without the need for K-wires.

Orthotopic glioblastoma stem-like cell xenograft model in mice to evaluate intra-arterial delivery of bevacizumab: from bedside to bench.

Bevacizumab (BV), a humanized monocolonal antibody directed against vascular endothelial growth factor (VEGF), is a standard intravenous (IV) treatment for recurrent glioblastoma multiforme (GBM), that has been introduced recently as an intra-arterial (IA) treatment modality in humans. Since preclinical models have not been reported, we sought to develop a tumor stem cell (TSC) xenograft model to investigate IA BV delivery in vivo. Firefly luciferase transduced patient TSC were injected into the cortex of 35 nude mice. Tumor growth was monitored weekly using bioluminescence imaging. Mice were treated with either intraperitoneal (IP) or IA BV, with or without blood-brain barrier disruption (BBBD), or with IP saline injection (controls). Tumor tissue was analyzed using immunohistochemistry and western blot techniques. Tumor formation occurred in 31 of 35 (89%) mice with a significant signal increase over time (p=0.018). Post mortem histology revealed an infiltrative growth of TSC xenografts in a similar pattern compared to the primary human GBM. Tumor tissue analyzed at 24 hours after treatment revealed that IA BV treatment with BBBD led to a significantly higher intratumoral BV concentration compared to IA BV alone, IP BV or controls (p<0.05). Thus, we have developed a TSC-based xenograft mouse model that allows us to study IA chemotherapy. However, further studies are needed to analyze the treatment effects after IA BV to assess tumor progression and overall animal survival.

Intra-arterial bevacizumab with blood brain barrier disruption in a glioblastoma xenograft model.

PURPOSE: In this study we investigated the treatment response and survival of intra-arterial (IA) compared to intra-peritoneal (IP) delivery of bevacizumab (BV) in a glioblastoma (GBM) xenograft mouse model. METHODS: 3x10(5) U87-Luc cells were stereotactically implanted into the cortex of 35 nude mice and grouped for treatment (n = 7 in each group): IP saline (group 1), single IP BV (group 2), biweekly IP BV for 3 weeks (group 3), single intra-arterial (IA) BV alone (group 4) and single IA BV with blood brain barrier disruption (BBBD) (group 5). Tumor growth was monitored every 3 to 4 days using bioluminescence imaging (BLI) and survival was analyzed by the Kaplan Meier method. Tumor tissue was analyzed using H&E staining and immunohistochemistry. RESULTS: Based on BLI, BV treated mice showed a delayed tumor growth over time compared to control. Kaplan Meier analysis demonstrated a median survival time of 28 days for group 1,31 days for group 2, 34 days for group 3, 36 days for group 4 and 36 days for group 5 (p < 0.0001). Mice treated with repeated IP BV (p = 0.003) or single IA BV with (p = 0.015) or without (p = 0.005) BBBD showed a significant survival benefit compared to single IP BV treated mice. Post mortem analysis revealed a histological pattern with a more discontinuous border between tumor and mouse brain in the repeated IP BV and single IA BV with or without BBBD treated mice compared to the sharply defined edges of single IP BV treated and control mice. CONCLUSIONS: In this study we showed a significant survival benefit of repeated IP BV and single IA BV with or without BBBD treated mice compared to single IP BV treated and control mice in a U87 xenograft model.

Pedicle screw navigation: a systematic review and meta-analysis of perforation risk for computer-navigated versus freehand insertion.

OBJECT: In this paper the authors' goal was to compare the accuracy of computer-navigated pedicle screw insertion with nonnavigated techniques in the published literature. METHODS: The authors performed a systematic literature review using the National Center for Biotechnology Information Database (PubMed/MEDLINE) using the Medical Subject Headings (MeSH) terms "Neuronavigation," "Therapy, computer assisted," and "Stereotaxic techniques," and the text word "pedicle." Included in the meta-analysis were randomized control trials or patient cohort series, all of which compared computer-navigated spine surgery (CNSS) and nonassisted pedicle screw insertions. The primary end point was pedicle perforation, while the secondary end points were operative time, blood loss, and complications. RESULTS: Twenty studies were included for analysis; of which there were 18 cohort studies and 2 randomized controlled trials published between 2000 and 2011. Foreign-language papers were translated. The total number of screws included was 8539 (4814 navigated and 3725 nonnavigated). The most common indications for surgery were degenerative disease, spinal deformity, myelopathy, tumor, and trauma. Navigational methods were primarily based on CT imaging. All regions of the spine were represented. The relative risk for pedicle screw perforation was determined to be 0.39 (p < 0.001), favoring navigation. The overall pedicle screw perforation risk for navigation was 6%, while the overall pedicle screw perforation risk was 15% for conventional insertion. No related neurological complications were reported with navigated insertion (4814 screws total); there were 3 neurological complications in the nonnavigated group (3725 screws total). Furthermore, the meta-analysis did not reveal a significant difference in total operative time and estimated blood loss when comparing the 2 modalities. CONCLUSIONS: There is a significantly lower risk of pedicle perforation for navigated screw insertion compared with nonnavigated insertion for all spinal regions.

Silicate-substituted calcium phosphate ceramic bone graft replacement for spinal fusion procedures.

STUDY DESIGN: Retrospective study. OBJECTIVE: To assess the clinical and radiographical outcomes in spinal fusion procedures using silicate-substituted calcium phosphate (Si-CaP). SUMMARY OF BACKGROUND DATA: Si-CaP is a newer-generation synthetic ceramic designed to maximize osteoinduction and osteoconduction. METHODS: This is a retrospective analysis of a prospectively collected patient database including 108 patients (204 individual spinal levels). Different surgical procedures performed included 25 anterior cervical discectomy and fusions, 17 posterior cervical fusions, 7 combined anterior and posterior cervical fusions, 10 thoracic fusion surgeries, 18 transforaminal lumbar interbody fusions with 12 axial lumbar interbody fusions, 11 transpsoas discectomy and fusions, and 8 combined thoracolumbar fusion procedures. Si-CaP was used as bone extender without any additional graft material, bone marrow aspirate, or bone morphogenetic protein. Clinical outcomes were assessed using the visual analogue scale (VAS), Oswestry Disability Index, and Neck Disability Index. Fusion was determined by the presence of bony bridging on 2 consecutive sections in at least 2 planes on computed tomographic imaging. RESULTS: At a follow-up of 12 (± 4.7) months, 90% of all patients demonstrated radiographical fusion. Fusion rates were highest in the cervical spine (97%) followed by thoracic and lumbar spines (86% and 81%, respectively). There were significant improvements in all clinical outcome measures-Oswestry Disability Index, 11.1 (± 10.2) and Neck Disability Index, 9.0 (± 11.4); VAS-back, 3.1(± 3.0); VAS-leg, 3.5 (± 3.6); VAS-neck, 3.7 (± 2.5); and VAS-arm 4.0 (± 3.2). There was no radiographical loosening of instrumentation due to infection or nonunion in this series, and no subsequent revisions for nonunion were required. CONCLUSION: Si-CaP is an alternative to autogenous bone graft in spinal arthrodesis procedures. At 12-month follow-up, we detected high levels of bony fusion using Si-CaP in combination with various surgical spinal techniques.

Intra-arterial delivery of bevacizumab after blood-brain barrier disruption for the treatment of recurrent glioblastoma: progression-free survival and overall survival.

BACKGROUND: This prospective, single-center study assesses progression-free survival (PFS) and overall survival (OS) in patients with recurrent glioblastoma multiforme (GBM) treated with a single dose of superselective intra-arterial cerebral infusion (SIACI) of bevacizumab (BV) after blood-brain barrier disruption (BBBD). Patients were initially enrolled in our phase I study, for which the primary end point was to determine the safety and maximum tolerated dose of SIACI BV. METHODS: Fourteen patients with recurrent GBM were recruited between August 2009 and November 2010 after failing the standard treatment with radiation therapy and temozolomide. None of these patients were previously treated with BV. After receiving a single dose of IA BV (2 to 15 mg/kg), standard IV BV chemotherapy was continued in 12 of 14 patients (86%). The recently updated Response Assessment in Neuro-Oncology Working Group (RANO) criteria were used to evaluate PFS, and the Kaplan-Meier estimator was used to evaluate PFS and OS. RESULTS: Using RANO criteria, the median PFS in these patients was 10 months. The median OS estimation for this cohort was 8.8 months. The OS was less than the PFS because 4 patients died without progressing. Toxicity attributed to the IA BV treatment was present in 2 patients (wound dehiscence and rash). Another patient suffered from seizures 1 week after the SIACI procedure; however, this patient had epilepsy before and seizure type/frequency were similar before and after therapy. CONCLUSIONS: Our study shows that for patients naïve to BV, a single dose of SIACI BV after BBBD followed by IV BV offers an encouraging outcome in terms of PFS when compared with previous trials using IV BV with and without concomitant irinotecan (CPT-11). Larger phase II trials are warranted to determine whether repeated IA BV alone is superior to IV BV for recurrent GBM.

Superselective intra-arterial cerebral infusion of novel agents after blood-brain disruption for the treatment of recurrent glioblastoma multiforme: a technical case series.

Glioblastoma multiforme constitutes the most common primary brain tumor and carries a grim prognosis for patients treated with conventional therapy including surgery, radiation therapy, and chemotherapy. There has been a recent revival of selective intra-arterial delivery of targeted agents for the treatment of glioblastoma multiforme. Because these agents are less toxic and their delivery leads to a higher tumor-drug concentration, this combination may provide a better outcome in patients with high-grade glioma. This article discusses early experiences in patients who received superselective intra-arterial cerebral infusion of bevacizumab, cetuximab, and temozolamide after blood-brain barrier disruption with mannitol.

Protein phosphatase 2A mediates dormancy of glioblastoma multiforme-derived tumor stem-like cells during hypoxia.

PURPOSE: The hypoxic microenvironment of glioblastoma multiforme (GBM) is thought to increase resistance to cancer therapies. Recent evidence suggests that hypoxia induces protein phosphatase 2A (PP2A), a regulator of cell cycle and cell death. The effects of PP2A on GBM tumor cell proliferation and survival during hypoxic conditions have not been studied. EXPERIMENTAL DESIGN: Expression of PP2A subunits and HIF-α proteins was measured in 65 high-grade astrocytoma and 18 non-neoplastic surgical brain specimens by western blotting. PP2A activity was measured by an immunoprecipitation assay. For in vitro experiments, GBM-derived tumor stem cell-like cells (TSCs) were exposed to severe hypoxia produced by either CoCl2 or 1% O2. PP2A activity was inhibited either by okadaic acid or by shRNA depletion of the PP2A C subunit. Effects of PP2A activity on cell cycle progression and cell survival during hypoxic conditions were assessed using flow cytometry. RESULTS: In our patient cohort, PP2A activity was positively correlated with HIF-1∝ protein expression (P = 0.002). Patients with PP2A activity levels above 160 pMP had significantly worse survival compared to patients with levels below this threshold (P = 0.002). PP2A activity was an independent predictor of survival on multivariable analysis (P = 0.009). In our in vitro experiments, we confirmed that severe hypoxia induces PP2A activity in TSCs 6 hours after onset of exposure. PP2A activity mediated G1/S phase growth inhibition and reduced cellular ATP consumption in hypoxic TSCs. Conversely, inhibition of PP2A activity led to increased cell proliferation, exhaustion of intracellular ATP, and accelerated P53-independent cell death of hypoxic TSCs. CONCLUSIONS: Our results suggest that PP2A activity predicts poor survival in GBM. PP2A appears to reduce the metabolic demand of hypoxic TSCs and enhances tumor cell survival. Modulation of PP2A may be a potential target for cancer therapy.