Emerging applications of hypomethylating agents in the treatment of glioblastoma (Review).

DNA hypomethylating agents (HMAs) such as decitabine and 5-azacytidine have established roles in the treatment paradigms for myelodysplastic syndrome and acute myelogenous leukemia, where they are considered to exert their anticancer effects by restoring the expression of tumor suppressor genes. Due to their relatively favorable adverse effect profile and known ability to pass through the blood-brain barrier, applications in the treatment of glioblastoma (GBM) and other central nervous system malignancies are under active investigation. The present review examines the types of HMAs currently available, their known and less-understood antineoplastic mechanisms, and the evidence to date of their preclinical and clinical efficacy in glioblastoma and other solid malignancies. The present review discusses the potential synergies HMAs may have with established and emerging GBM treatments, including temozolomide, immune checkpoint inhibitors and cancer vaccines. Recent successes and setbacks in clinical trials for newly diagnosed and recurrent GBM are summarized in order to highlight opportunities for HMAs to improve therapeutic responses. Challenges for future clinical trials are also assessed.

The role of venous anatomy in guiding treatment approach for dural arteriovenous fistulas of the craniocervical junction; case series & systematic review.

BACKGROUND: Dural arteriovenous fistulas (DAVF) of the craniocervical junction (CCF) are an uncommon entity with the following venous drainage pattern: inferior, superior and mixed. Patients may present with subarachnoid hemorrhage, myelopathy or brainstem dysfunction. CCJ DAVF can be treated with microsurgery or with transarterial and transvenous embolization, depending on the venous drainage pattern. We present our institutional experience of treating CCJ DAVFs along with a systematic review of the literature. METHODS: Six patients with CCJ DAVF were treated at our institution over five years. Data was collected using electronic medical record review. Systematic review was performed on CCJ DAVF using the PubMed database from 1990 to 2021. We characterized venous drainage patterns, treatment choices, and outcomes to create a classification system. RESULTS: 50 case reports, consisting of 115 patients, were included in our review. 61 (53.0 %) patients had inferior drainage while 32 (27.8 %) patients had superior drainage and 22 (19.2 %) patients had mixed venous drainage. Patients with inferior drainage had the fistulous connection at the foramen magnum while patients with superior drainage had a fistulous connection at C1-C2 (p value = 0.026). Patients with inferior drainage were more likely to present with myelopathy while patients with superior drainage presented with hemorrhage (p value = 0.000). CONCLUSIONS: Classifying the venous drainage pattern is essential in making treatment decision. Transvenous embolization works best with large superior venous drainage. If endovascular treatment is not an option, then surgical clipping can achieve successful cure. Transarterial embolization is a reasonable option in cases with a large arterial feeder.

Thromboelastography (TEG) results are predictive of ischemic and hemorrhagic complications in patients with unruptured intracranial aneurysms treated with flow diversion.

INTRODUCTION: Flow diversion is an effective treatment modality for intracranial aneurysms but is associated with ischemic and hemorrhagic complications. Patients treated with flow diversion require dual antiplatelet therapy and subsequent platelet function tests. At our institution, Thromboelastography with Platelet Mapping (TEG-PM) is the test of choice. The primary objective of this study was to identify TEG parameters that are predictive of postoperative complications in patients treated with elective flow diversion. METHODS: This was a retrospective study of 118 patients with unruptured intracranial aneurysms treated with flow diversion. Data was collected via chart review. Bivariate analyses were performed to identify significant variables in patients who suffered an ischemic stroke or a groin hematoma. ROC curves were constructed for the TEG parameters with statistical significance. Bivariate analyses were repeated using dichotomized TEG results. RESULTS: Patients who experienced a symptomatic ischemic stroke had a history of stroke (p value = 0.007), larger aneurysm neck width (p value = 0.017), and a higher alpha angle (p value = 0.013). Cut off point for ischemic complication is 63° on ROC curve with a sensitivity of 100% and specificity of 65%. Patients who experienced a groin hematoma were no different from their healthy peers but had a lower alpha angle (p value = 0.033). Cut off point for hemorrhagic complication is 53.3° with a sensitivity of 82% and specificity of 67%. CONCLUSION: The Alpha Angle parameter of TEG-PM has a sizeable predictive ability for both ischemic complications of the central nervous system and hemorrhagic complications of the access site after elective flow diversion.

The incidence of venous thromboembolism following surgical resection of intracranial and intraspinal meningioma. A systematic review and retrospective study.

INTRODUCTION: Historically, the development of venous thromboembolism (VTE) including deep venous thrombosis (DVT) and pulmonary thromboembolism (PE) was cited as a higher post-operative risk for patients harboring meningiomas. However, recent literature has suggested that there may be no elevated risk for VTE among these patients. The authors perform both a retrospective review of their own cases as well as a systematic review of the literature in order to determine the frequency of the VTE and rate of post-operative hemorrhage in this patient population. METHODOLOGY: Patients undergoing surgery for intracranial and spinal meningioma from 2012 to 2019 were retrospectively reviewed for patient demographics, clinical characteristics, and post-operative complications. Logistic regression was used to determine risk factors for the development of VTE. Additionally, a PubMed search was performed to identify patients addressing this topic. RESULTS: Our retrospective review included 189 patients who underwent 197 operations. The rate of VTE for patients receiving LMWH was 3.55 % vs. 4.06 % for those not receiving LMWH. There were no observed hemorrhages after initiation of LMWH. Multivariate analysis found tumor volume, history of DVT, and length of hospital stay as independent risk factors for VTE. In the systematic review, 11 papers describing 28,954 patients were included. The risk of developing a VTE with or without LMWH was 2.71 % versus 4.07 %, respectively. The hemorrhage risk was 2.23 % on LMWH versus 4.20 % not on LMWH. DISCUSSION: In several heterogeneous series of all types of neurosurgical procedures, the reported rate of VTE was 11.1 %. In our review of the literature, the VTE rate of 2.71 % was similar to our cohort's rate of 3.55 %, for patients administered LMWH postoperatively. Higher rates of VTE with meningiomas may not be the case as once thought. Regular use of LMWH appears to be a safe, but it also did not necessarily lower the rates of VTE in our cohort. The use of routine lower-extremity duplex ultrasound, mechanical prophylaxis, and early mobilization, may have contributed to these lower rates of VTEs in patients with meningiomas.

COVID-19 Infection Among Healthcare Workers: Serological Findings Supporting Routine Testing.

A growing body of evidence demonstrates that asymptomatic and pre-symptomatic transmission of SARS-CoV-2 is a major contributor to the COVID-19 pandemic. Frontline healthcare workers in COVID-19 hotspots have faced numerous challenges, including shortages of personal protective equipment (PPE) and difficulties acquiring clinical testing. The magnitude of the exposure of healthcare workers and the potential for asymptomatic transmission makes it critical to understand the incidence of infection in this population. To determine the prevalence of asymptomatic SARS-CoV-2 infection amongst healthcare workers, we studied frontline staff working in the Montefiore Health System in New York City. All participants were asymptomatic at the time of testing and were tested by RT-qPCR and for anti-SARS-CoV-2 antibodies. The medical, occupational, and COVID-19 exposure histories of participants were recorded via questionnaires. Of the 98 asymptomatic healthcare workers tested, 19 (19.4%) tested positive by RT-qPCR and/or ELISA. Within this group, four (4.1%) were RT-qPCR positive, and four (4.1%) were PCR and IgG positive. Notably, an additional 11 (11.2%) individuals were IgG positive without a positive PCR. Two PCR positive individuals subsequently developed COVID-19 symptoms, while all others remained asymptomatic at 2-week follow-up. These results indicate that there is considerable asymptomatic infection with SARS-CoV-2 within the healthcare workforce, despite current mitigation policies. Furthermore, presuming that asymptomatic staff are not carrying SARS-CoV-2 is inconsistent with our results, and this could result in amplified transmission within healthcare settings. Consequently, aggressive testing regiments, such as testing frontline healthcare workers on a regular, multi-modal basis, may be required to prevent further spread within the workforce and to patients.

Epigenetic preconditioning with decitabine sensitizes glioblastoma to temozolomide via induction of MLH1.

INTRODUCTION: To improve the standard treatment paradigm for glioblastoma (GBM), efforts have been made to explore the efficacy of epigenetic agents as chemosensitizers. Recent data suggest possible synergy between decitabine (DAC), a DNA hypomethylating agent, and temozolomide (TMZ) in GBM, but the mechanism remains unclear. The objective of this study was to determine the effects of DAC on TMZ sensitization in a consecutively derived set of primary GBM cultures, with a focus on mismatch repair (MMR) proteins. METHODS: Half maximal inhibitory concentrations (IC50) of TMZ were calculated in eleven consecutive patient-derived GBM cell lines before and after preconditioning with DAC. MMR protein expression changes were determined by quantitative immunoblots and qPCR arrays. Single-molecule real-time (SMRT) sequencing of bisulfite (BS)-converted PCR amplicons of the MLH1 promoter was performed to determine methylation status. RESULTS: TMZ IC50 significantly changed in 6 of 11 GBM lines of varying MGMT promoter methylation status in response to DAC preconditioning. Knockdown of MLH1 after preconditioning reversed TMZ sensitization. SMRT-BS sequencing of the MLH1 promoter region revealed higher levels of baseline methylation at proximal CpGs in desensitized lines compared to sensitized lines. CONCLUSIONS: DAC enhances TMZ cytotoxicity in a subset of GBM cell lines, comprising lines both MGMT methylated and unmethylated tumors. This effect may be driven by levels of MLH1 via E2F1 transcription factor binding. Using unbiased long-range next-generation bisulfite-sequencing, we identified a region of the proximal MLH1 promoter with differential methylation patterns that has potential utility as a clinical biomarker for TMZ sensitization.

Isolation of Glioblastoma Stem Cells with Flow Cytometry.

This chapter describes a straightforward method for isolating glioblastoma stem cells (GSCs) from in vitro tissue cultures via fluorescence-activated cell sorting (FACS) using CD133 as a surface marker. The use of a directly conjugated antibody to an APC fluorophore against the CD133 molecule provides sufficient and clear detection of positive cells from the rest of the population. This strategy avoids an unnecessary secondary antibody incubation step thereby minimizing loss and increasing yield. The same protocol can be applied to other GSC surface markers. The described method allows for quick and efficient purification of GSCs, which can then be used in several downstream applications.

Lentiviral Transduction of Primary Human Glioblastoma Cultures.

This chapter provides detailed step-by-step instructions for the production of lentiviral particles and the transduction of primary human glioblastoma cultures. Lentiviruses stably transduce both dividing and non-dividing cells, such as quiescent cancer stem cell populations. The viral envelope is pseudotyped with the vesicular stomatitis virus envelope glycoprotein G (VSV-G), which renders the lentiviral particles pantropic, so that they can infect theoretically all cell types. The third generation packaging system used in this protocol produces lentiviruses with important safety features, including replication incompetence and self-inactivation (SIN). The protocol we describe here leads to transduction of primary human glioblastoma cultures with efficiencies of up to 90%.

Postnatal and adult consequences of loss of huntingtin during development: Implications for Huntington's disease.

The mutation in huntingtin (mHtt) leads to a spectrum of impairments in the developing forebrain of Huntington's disease (HD) mouse models. Whether these developmental alterations are due to loss- or gain-of-function mechanisms and contribute to HD pathogenesis is unknown. We examined the role of selective loss of huntingtin (Htt) function during development on postnatal vulnerability to cell death. We employed mice expressing very low levels of Htt throughout embryonic life to postnatal day 21 (Hdhd•hyp). We demonstrated that Hdhd•hyp mice exhibit: (1) late-life striatal and cortical neuronal degeneration; (2) neurological and skeletal muscle alterations; and (3) white matter tract impairments and axonal degeneration. Hdhd•hyp embryos also exhibited subpallial heterotopias, aberrant striatal maturation and deregulation of gliogenesis. These results indicate that developmental deficits associated with Htt functions render cells present at discrete neural foci increasingly susceptible to cell death, thus implying the potential existence of a loss-of-function developmental component to HD pathogenesis.

Killing by bactericidal antibiotics does not depend on reactive oxygen species.

Bactericidal antibiotics kill by modulating their respective targets. This traditional view has been challenged by studies that propose an alternative, unified mechanism of killing, whereby toxic reactive oxygen species (ROS) are produced in the presence of antibiotics. We found no correlation between an individual cell's probability of survival in the presence of antibiotic and its level of ROS. An ROS quencher, thiourea, protected cells from antibiotics present at low concentrations, but the effect was observed under anaerobic conditions as well. There was essentially no difference in survival of bacteria treated with various antibiotics under aerobic or anaerobic conditions. This suggests that ROS do not play a role in killing of bacterial pathogens by antibiotics.