Erlotinib Treatment in Colorectal Cancer Suppresses Autophagy Based on KRAS Mutation.

The KRAS gene is mutated in approximately 45% of colorectal cancer patients. There are currently very few targeted treatments or therapies equipped to directly inhibit KRAS due to its unusual structural intricacies. Erlotinib, an EGFR inhibitor, has previously been demonstrated to reduce cell viability by inducing autophagy in lung cancer cell lines with varying EGFR mutations. In contrast to lung cancer cells, evidence is provided herein for the first time that erlotinib treatment in colorectal cancer (CRC) cell lines reduces autophagy and still results in decreased cell viability. However, the effects of erlotinib in CRC cell lines containing a wildtype KRAS gene were different than in cells carrying a mutant KRAS gene. We show that there is significantly more downregulation of autophagy in KRAS mutant CRC cells compared to KRAS wildtype cells, both at transcriptional and translational levels, suggesting that the KRAS mutation is advantageous for cancer growth, even in the presence of erlotinib. Cell viability results determined that KRAS wildtype CRC cells had significantly more cell death compared to KRAS mutant cells. Using patient mRNA datasets, we showed that there was a significant correlation between the presence of the KRAS mutation and the expression of autophagy proteins. Additionally, through molecular dynamics simulations, we develop a blueprint for KRAS and autophagy protein interaction and the impact of the KRAS mutation on autophagy protein regulation. Overall, this is the first report of erlotinib treatment in CRC cells that assesses autophagy, and we demonstrate that autophagy activity is downregulated in these cells. This effect is not only greater in cells carrying a KRAS mutation compared to wildtype cells, but the KRAS mutant cells also have increased cell viability compared to wildtype cells. We hypothesize that the difference in cell viability and autophagy expression between KRAS mutant and KRAS wildtype cells after treatment with erlotinib can be of therapeutic value to treat CRC patients carrying KRAS mutations.

Impact of carbamazepine on SMARCA4 (BRG1) expression in colorectal cancer: modulation by KRAS mutation status.

SMARCA4 is a gene traditionally considered a tumor suppressor. Recent research has however found that SMARCA4 likely promotes cancer growth and is a good target for cancer treatment. The drug carbamazepine, an autophagy inducer, was used on colorectal cancer cell lines, HCT1116 and Hke3 (KRAS mutant and wildtype). Our study finds that Carbamazepine affects SMARCA4 levels and that this effect is different depending on the KRAS mutation status. This study analyzes the effect of carbamazepine on early-stage autophagy via ULK1 as well as simulates the docking of carbamazepine on KRAS, depending on the mutation status. Our study highlights the therapeutic uses of carbamazepine on cancer, and we propose that carbamazepine in conjunction with other chemotherapies may prove useful in targeting KRAS-mutated colorectal cancer.

BRG1: Promoter or Suppressor of Cancer? The Outcome of BRG1's Interaction with Specific Cellular Pathways.

BRG1 is one of two catalytic subunits of the SWI/SNF ATP-dependent chromatin-remodeling complex. In cancer, it has been hypothesized that BRG1 acts as a tumor suppressor. Further study has shown that, under certain circumstances, BRG1 acts as an oncogene. Targeted knockout of BRG1 has proven successful in most cancers in suppressing tumor growth and proliferation. Furthermore, BRG1 effects cancer proliferation in oncogenic KRAS mutated cancers, with varying directionality. Thus, dissecting BRG1's interaction with various cellular pathways can highlight possible intermediates that can facilitate the design of different treatment methods, including BRG1 inhibition. Autophagy and apoptosis are two important cellular responses to stress. BRG1 plays a direct role in autophagy and apoptosis and likely promotes autophagy and suppresses apoptosis, supporting unfettered cancer growth. PRMT5 inhibits transcription by interacting with ATP-dependent chromatin remodeling complexes, such as SWI/SNF. When PRMT5 associates with the SWI/SNF complex, including BRG1, it represses tumor suppressor genes. The Ras/Raf/MAPK/ERK1/2 pathway in cancers is a signal transduction pathway involved in the transcription of genes related to cancer survival. BRG1 has been shown to effect KRAS-driven cancer growth. BRG1 associates with several proteins within the signal transduction pathway. In this review, we analyze BRG1 as a promising target for cancer inhibition and possible synergy with other cancer treatments.

Structural modifications and kinetic effects of KRAS interactions with HRAS and NRAS: an in silico comparative analysis of KRAS mutants.

The RAS genes which code for KRAS, HRAS, and NRAS are three of the most frequently mutated oncogenes responsible for cancer deaths. Tumorigenesis is one of the most significant outcomes of deregulation of RAS GTPases. Although the structures have been extensively studied, there is still more to be discovered about the actual binding conformations of the three isoforms, especially when mutated, to design an inhibitory drug. Recent studies have identified important interactions between the three isoforms that affect the oncogenic strength of the others when they are mutated. In this study, we utilize molecular dynamics simulations to examine the modifications of the structural property, mechanism, and kinetic energy of KRAS when interacting individually and with HRAS and NRAS. Notably, we found that WT-KRAS' orientation when bound to WT-HRAS vs. WT-NRAS is rotated 180°, with mutants demonstrating a similar binding pattern. The binding sites of the isoforms with KRAS share similarities with those involved in the GDP/GTP active site and site of KRAS dimerization. Thus, the isoform interaction can serve as an inhibitory method of KRAS actions. This study advances the understanding of inhibiting RAS-driven cancers through a novel isoform interaction approach only recently discovered, which has been proven to be an effective alternate therapeutic approach. We developed a blueprint of the interaction which would be beneficial in the development of KRAS mutant-specific and pan-KRAS mutant inhibitory drugs that mimic the isoform interactions. Our results support the direct interaction inhibition mechanism of mutant KRAS when bound to WT-HRAS and WT-NRAS by the isoforms' hypervariable region binding to the G-domain of KRAS. Furthermore, our results support the approach of reducing the effects of oncogenic KRAS by altering the concentration of the isoforms or a drug alternative based on the overall structural and kinetic stability, as well as the binding strength of the mutant-isoform complexes.

Neurothrombectomy devices for the treatment of acute ischemic stroke: state of the evidence.

BACKGROUND: Acute ischemic strokes are associated with poor outcomes and high health care burden. Evidence exists evaluating the use of neurothrombectomy devices in patients receiving currently recommended treatments that may have limited efficacy. PURPOSE: To describe the state of the evidence supporting use of neurothrombectomy devices in the treatment of acute ischemic stroke. DATA SOURCES: MEDLINE, SCOPUS, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and Web of Science were searched, without language restrictions, from their inception through May 2010. The MEDLINE and Cochrane Central Register of Controlled Trials searches were updated through November 2010. STUDY SELECTION: Two independent investigators screened citations for human studies of any design or case series or case reports of patients with an acute ischemic stroke that evaluated a neurothrombectomy device and reported at least 1 clinical effectiveness outcome or harm. DATA EXTRACTION: Using standardized protocols, 2 independent investigators extracted information about study characteristics and outcomes, and a third reviewer resolved disagreement. DATA SYNTHESIS: 87 articles met eligibility criteria, including 18 prospective single-group studies, 7 noncomparative retrospective studies, and 62 case series or case reports. Two U.S. Food and Drug Administration (FDA)-cleared devices, the MERCI Retriever (Concentric Medical, Mountain View, California) (40%) and the Penumbra System (Penumbra, Alameda, California) (9%), represented a large portion of the available data. All prospective and retrospective studies provided data on successful recanalization with widely varying rates (43% to 78% with the MERCI Retriever and 83% to 100% with the Penumbra System). Rates of harms, including symptomatic (16 studies; 0% to 10% with the MERCI Retriever and 0% to 11% with the Penumbra System) or asymptomatic (13 studies; 28% to 43% and 1% to 30%, respectively) intracranial hemorrhage and vessel perforation or dissection (11 studies; 0% to 7% and 0% to 5%, respectively), also varied by device. Predictors of harm included older age, history of stroke, and higher baseline stroke severity scores, whereas successful recanalization was the sole predictor of good outcomes. LIMITATIONS: Most available data are from single-group, noncomparative studies. In addition, the patient population most likely to benefit from these devices is undetermined. CONCLUSION: Currently available neurothrombectomy devices offer intriguing treatment options in patients with acute ischemic stroke. Future trials should use a randomized design, with adequate power to show equivalency or noninferiority between competing strategies or devices, and strive to identify populations that are most likely to benefit from use of neurothrombectomy devices. PRIMARY FUNDING SOURCE: Agency for Healthcare Research and Quality.

Mechanical thrombectomy for acute ischemic stroke: final results of the Multi MERCI trial.

BACKGROUND AND PURPOSE: Endovascular mechanical thrombectomy may be used during acute ischemic stroke due to large vessel intracranial occlusion. First-generation MERCI devices achieved recanalization rates of 48% and, when coupled with intraarterial thrombolytic drugs, recanalization rates of 60% have been reported. Enhancements in embolectomy device design may improve recanalization rates. METHODS: Multi MERCI was an international, multicenter, prospective, single-arm trial of thrombectomy in patients with large vessel stroke treated within 8 hours of symptom onset. Patients with persistent large vessel occlusion after IV tissue plasminogen activator treatment were included. Once the newer generation (L5 Retriever) device became available, investigators were instructed to use the L5 Retriever to open vessels and could subsequently use older generation devices and/or intraarterial tissue plasminogen activator. Primary outcome was recanalization of the target vessel. RESULTS: One hundred sixty-four patients received thrombectomy and 131 were initially treated with the L5 Retriever. Mean age+/-SD was 68+/-16 years, and baseline median (interquartile range) National Institutes of Health Stroke Scale score was 19 (15 to 23). Treatment with the L5 Retriever resulted in successful recanalization in 75 of 131 (57.3%) treatable vessels and in 91 of 131 (69.5%) after adjunctive therapy (intraarterial tissue plasminogen activator, mechanical). Overall, favorable clinical outcomes (modified Rankin Scale 0 to 2) occurred in 36% and mortality was 34%; both outcomes were significantly related to vascular recanalization. Symptomatic intracerebral hemorrhage occurred in 16 patients (9.8%); 4 (2.4%) of these were parenchymal hematoma type II. Clinically significant procedural complications occurred in 9 (5.5%) patients. CONCLUSIONS: Higher rates of recanalization were associated with a newer generation thrombectomy device compared with first-generation devices, but these differences did not achieve statistical significance. Mortality trended lower and the proportion of good clinical outcomes trended higher, consistent with better recanalization.

Safety and efficacy of mechanical embolectomy in acute ischemic stroke: results of the MERCI trial.

BACKGROUND AND PURPOSE: The only Food and Drug Administration (FDA)-approved treatment for acute ischemic stroke is tissue plasminogen activator (tPA) given intravenously within 3 hours of symptom onset. An alternative strategy for opening intracranial vessels during stroke is mechanical embolectomy, especially for patients ineligible for intravenous tPA. METHODS: We investigated the safety and efficacy of a novel embolectomy device (Merci Retriever) to open occluded intracranial large vessels within 8 hours of the onset of stroke symptoms in a prospective, nonrandomized, multicenter trial. All patients were ineligible for intravenous tPA. Primary outcomes were recanalization and safety, and secondary outcomes were neurological outcome at 90 days in recanalized versus nonrecanalized patients. RESULTS: Recanalization was achieved in 46% (69/151) of patients on intention to treat analysis, and in 48% (68/141) of patients in whom the device was deployed. This rate is significantly higher than that expected using an historical control of 18% (P<0.0001). Clinically significant procedural complications occurred in 10 of 141 (7.1%) patients. Symptomatic intracranial hemorrhages was observed in 11 of 141 (7.8%) patients. Good neurological outcomes (modified Rankin score < or =2) were more frequent at 90 days in patients with successful recanalization compared with patients with unsuccessful recanalization (46% versus 10%; relative risk [RR], 4.4; 95% CI, 2.1 to 9.3; P<0.0001), and mortality was less (32% versus 54%; RR, 0.59; 95% CI, 0.39 to 0.89; P=0.01). CONCLUSIONS: A novel endovascular embolectomy device can significantly restore vascular patency during acute ischemic stroke within 8 hours of stroke symptom onset and provides an alternative intervention for patients who are otherwise ineligible for thrombolytics.

The "drip-and-ship" approach: starting IV t-PA for acute ischemic stroke at outside hospitals prior to transfer to a regional stroke center.

PURPOSE: Acute stroke therapy with intravenous (IV) tissue plasminogen activator (t-PA) is vastly underutilized. Increasingly, patients are being started on IV t-PA and being transferred to regional Stroke Center programs, where additional therapies can be offered in a multimodal format. We describe our experience at the Stroke Center at Hartford Hospital with interhospital patient transfers who received IV t-PA prior to transfer to our medical center. METHODS: A retrospective analysis of our Acute Stroke Therapies database was undertaken, encompassing the intial four-year period of our Stroke Center program (May 1, 2001 to April 30, 2005). We evaluated the patient characteristics, clinical outcomes, and adjunctive therapies of patients who were started on IV t-PA at referring hospitals prior to their emergent transfer to our Stroke Center. RESULTS: From a total of 229 patients who received IV and/or IA thrombolysis and newer catheter-delivered devices or clinical trials at our Stroke Center, a total of 33 (14.4%) were started on IV t-PA at an outside hospital prior to transfer. Symptomatic hemorrhage occurred in one of the 33 patients (3.0%), and in-hospital mortality rate for these patients was 6.1%. A total of 26 patients (78.8%) had a positive outcome in that they were discharged either to home or to acute rehabilitation. CONCLUSIONS: Use of IV t-PA in a "drip-and-ship" approach is growing at the regional Stroke Center at Hartford Hospital. This protocol is safe and offers several advances for the care of patients with AIS: (a) empowering emergency physicians and neurologists at outside hospitals, via access to a 24/7 Acute Stroke Hotline, to treat patients with AIS; (b) facilitating the early initiation of IV t-PA; and (c) offering adjunctive therapeutic approaches, following arrival at our facility, for patients not sufficiently improving with IV t-PA alone.

Poststroke seizures.

Stroke is the most common cause of seizures in the elderly, and seizures are among the most common neurologic sequelae of stroke. About 10% of all stroke patients experience seizures, from stroke onset until several years later. This review discusses current understanding of the epidemiology, pathogenesis, classification, clinical manifestations, diagnostic studies, differential diagnosis, and management issues of seizures associated with various cerebrovascular lesions, with a focus on anticonvulsant use in the elderly.

Expanding the range of therapies for acute ischemic stroke: the early experience of the Regional Stroke Center at Hartford Hospital.

PURPOSE: Three to four percent of all patients with acute ischemic stroke (AIS) receive the only FDA-approved therapy, intravenous tissue plasminogen activator. We sought to assess the impact of a regional stroke program, the Stroke Center at Hartford Hospital, in facilitating various therapies for patients with AIS, and their early outcomes. METHODS: For a 34-month period (May 2001 to February, 2004), 113 patients received either i.v. and/or intra-arterial thrombolysis, or an experimental protocol as a therapy for AIS. The Hartford Hospital and Stroke Center databases were queried for the diagnosis of AIS using ICD-9 codes, site of patient presentation, transportation modality, stroke severity, and clinical outcome. RESULTS: The percentage of patients with AIS treated has increased each of the past five fiscal years, to 15.4% for fiscal year 2004 to date. This growth is paralleled by increases in mean annual stroke severity of all stroke patients admitted to Hartford Hospital and in the numbers of patients transferred with AIS from other hospitals in southern New England. Symptomatic hemorrhage rate for the 113 patients was 5.3%. In-hospital mortality rate was 25.7%. Most patients (56.6%) were discharged from Hartford Hospital either to home or to acute rehabilitation. CONCLUSIONS: A regional stroke program greatly facilitated acute stroke treatment interventions. We attribute this growth to widespread educational programming, an Acute Stroke Team, catheter-based therapies with a dedicated Interventional Neuroradiology service, a 1800 Acute Stroke Hotline, and clinical trials.

Initial experience with a transcatheter septal closure system for secondary stroke prevention in patients with interatrial septal defects.

BACKGROUND: Percutaneous transcatheter closure of a patent foramen ovale (PFO) has been utilized over the last several years to prevent thromboembolic events in selected patients with a prior cryptogenic stroke. We describe our initial experience at Hartford Hospital with a transcatheter PFO closure system and our multidisciplinary approach. METHODS: From March to November 2002, we performed percutaneous transcatheter closure of a PFO in 16 patients with a prior history of cryptogenic stroke(s) and/or transient ischemic attack using the CardioSEAL Septal Occluder system. All 16 patients had a PFO visualized on their transesophageal echocardiogram (TEE) study, and 15 patients also had an atrial septal aneurysm. PFO closure was performed with a CardioSEAL Septal Occluder in the cardiac catheterization laboratory under general anesthesia with TEE guidance. Following device placement, all patients were discharged on a regimen of aspirin and clopidigrel, with follow-up in the Stroke Clinic. RESULTS: Successful deployment of the septal occluder and effective PFO closure was achieved in all 16 patients with no major procedural or in-hospital complications. Short-term clinical follow-up has demonstrated no recurrent neurologic thromboembolic events, but one patient was rehospitalized for de novo atrial fibrillation. Follow-up transthoracic echocardiographic assessment at three to six months postprocedure, obtained in eight patients thus far, has demonstrated no residual interatrial shunting. CONCLUSION: Our early results suggest that percutaneous PFO closure with the CardioSEAL Septal Occluder system is a safe option for secondary stroke prevention in carefully selected patients with interatrial septal defects and a history of cryptogenic stroke or TIA. Patient selection and the long-term effectiveness and safety of this approach require further assessment.

Determinants and clinical significance of persistent residual shunting in patients with percutaneous patent foramen ovale closure devices.

BACKGROUND: Percutaneous patent foramen closure has emerged as a dynamic therapy for stroke prevention secondary to paradoxical embolism. Recent reports, however, have documented uncertain clinical efficacy and patients with incomplete PFO closure may remain at risk of recurrent events. We sought to identify echocardiographic determinants and the clinical significance of persistent residual shunting after percutaneous PFO closure. METHODS: From 2002 to 2008, 51 consecutive patients with recurrent stroke (n=46) or transient ischemic attack (TIA) (n=5) underwent percutaneous PFO closure at a tertiary care hospital. PFO size, degree of shunt, tunnel length, and atrial septal aneurysm geometry were documented at the time of device implantation. All patients received follow-up with transesophageal (n=43) or transthoracic (n=8) echocardiography 6.7+/-2 months post procedure and presence of residual shunting and recurrent stroke/TIA were recorded. RESULTS: All patients underwent percutaneous PFO closure without complication. Ten patients (20%) demonstrated residual right-to-left shunting at the time of follow-up: color Doppler (2), mild (n=3), moderate (n=2) and severe (n=3). Univariate analysis revealed larger PFO size (F=4.71, p=0.036) as the only independent predictor of residual shunting after PFO closure. Ninety six percent of patients remained stroke and TIA free 3 years+/-8 months post closure, with no clinical differences between the two groups. CONCLUSIONS: In patients undergoing percutaneous PFO closure for stroke or TIA, a larger PFO size predisposes to residual shunting approximately 6 months post PFO closure, but with no short term increased risk of recurrent thromboembolic events.

Acute stroke management in the elderly.

BACKGROUND AND PURPOSE: Though the proportion of elderly stroke patients is increasing, patients >80 years are often excluded from clinical stroke trials. We reviewed the management of older patients presenting with acute ischemic stroke (AIS) and assessed the safety and efficacy of recombinant tissue plasminogen activator (rtPA) administration in a community-based setting. METHODS: A retrospective review of patients >80 years (n = 341) admitted to a community stroke center with AIS were compared to their younger counterparts (n = 690) using the stroke center database from April 2003 to December 2005. Parameters that were measured included admission and discharge NIH Stroke Scale (NIHSS), rate of thrombolytic treatment, the frequency and etiology of thrombolytic exclusion criteria and complications from rtPA for the different aged populations. Additional data were collected for Barthel Index at 12 months. RESULTS: A total of 166 patients underwent thrombolysis. Older patients were not delayed in reaching the hospital within 3 h of stroke onset (182/690, 26%, in the <80 cohort vs. 98/341, 29%, in the > or = 80 cohort). Although the overall rates of tPA use were similar in both the young and aged cohort, older patients were less likely to be treated with rtPA because of reasons not listed as exclusion criteria (17% in the <80 cohort vs. 32% in the > or = 80 cohort). The older group did not have an excess risk of intracranial hemorrhage following rtPA infusion despite equivalent NIHSS on admission (13.5 in the <80 cohort vs. 12.4 in the > or = 80 cohort). Both groups showed improvement in NIHSS following thrombolytic treatment with a drop of 7.7 points in the younger age group and 5.6 points in the older group. Elderly patients treated with rtPA had a comparable 12-month modified Barthel Index score to younger cohorts. CONCLUSIONS: Early treatment with rtPA in patients >80 years appears to be both safe and efficacious. Treated patients showed improvements both acutely (a decrease in NIHSS at 72 h) and chronically, as shown by a sustained improvement in the Barthel Index. A large number of elderly patients were excluded from rtPA treatment despite arriving within the time frame of treatment for reasons not considered as traditional exclusion criteria. Older patients with AIS can be treated safely with thrombolytic therapy in a community setting. This therapy should not be withheld on the basis of age.

Cerebral edema during treatment of diabetic ketoacidosis in an adult with new onset diabetes.

INTRODUCTION: Diabetic ketoacidosis (DKA) continues to be a medical emergency, in part because of a rare and devastating complication associated with its treatment, cerebral edema. In children, cerebral edema is the principal cause of mortality, but clinically significant cerebral edema in adults is rare. METHODS AND RESULTS: We report the case of a 27-year-old male (not previously known to be diabetic) who presented with a first episode of DKA complicated by the development of fatal cerebral edema despite medical treatment. CONCLUSION: The pathophysiological mechanisms for cerebral edema associated with DKA occurring in children and adults are believed to be similar and are discussed in this report. However, patients who develop cerebral edema may deteriorate rapidly, and experience with successful treatment has been limited.