Sunil J. Patel

Immune Checkpoint Inhibition for Hypermutant Glioblastoma Multiforme Resulting From Germline Biallelic Mismatch Repair Deficiency

PURPOSE Recurrent glioblastoma multiforme (GBM) is incurable with current therapies. Biallelic mismatch repair deficiency (bMMRD) is a highly penetrant childhood cancer syndrome often resulting in GBM characterized by a high mutational burden. Evidence suggests that high mutation and neoantigen loads are associated with response to immune checkpoint inhibition. PATIENTS AND METHODS We performed exome sequencing and neoantigen prediction on 37 bMMRD cancers and compared them with childhood and adult brain neoplasms. Neoantigen prediction bMMRD GBM was compared with responsive adult cancers from multiple tissues. Two siblings with recurrent multifocal bMMRD GBM were treated with the immune checkpoint inhibitor nivolumab. RESULTS All malignant tumors (n = 32) were hypermutant. Although bMMRD brain tumors had the highest mutational load because of secondary polymerase mutations (mean, 17,740 ± standard deviation, 7,703), all other high-grade tumors were hypermutant (mean, 1,589 ± standard deviation, 1,043), similar to other cancers that responded favorably to immune checkpoint inhibitors. bMMRD GBM had a significantly higher mutational load than sporadic pediatric and adult gliomas and all other brain tumors (P < .001). bMMRD GBM harbored mean neoantigen loads seven to 16 times higher than those in immunoresponsive melanomas, lung cancers, or microsatellite-unstable GI cancers (P < .001). On the basis of these preclinical data, we treated two bMMRD siblings with recurrent multifocal GBM with the anti-programmed death-1 inhibitor nivolumab, which resulted in clinically significant responses and a profound radiologic response. CONCLUSION This report of initial and durable responses of recurrent GBM to immune checkpoint inhibition may have implications for GBM in general and other hypermutant cancers arising from primary (genetic predisposition) or secondary MMRD.

Poor drug distribution as a possible explanation for the results of the PRECISE trial

OBJECT Convection-enhanced delivery (CED) is a novel intracerebral drug delivery technique with considerable promise for delivering therapeutic agents throughout the CNS. Despite this promise, Phase III clinical trials employing CED have failed to meet clinical end points. Although this may be due to inactive agents or a failure to rigorously validate drug targets, the authors have previously demonstrated that catheter positioning plays a major role in drug distribution using this technique. The purpose of the present work was to retrospectively analyze the expected drug distribution based on catheter positioning data available from the CED arm of the PRECISE trial. METHODS Data on catheter positioning from all patients randomized to the CED arm of the PRECISE trial were available for analyses. BrainLAB iPlan Flow software was used to estimate the expected drug distribution. RESULTS Only 49.8% of catheters met all positioning criteria. Still, catheter positioning score (hazard ratio 0.93, p = 0.043) and the number of optimally positioned catheters (hazard ratio 0.72, p = 0.038) had a significant effect on progression-free survival. Estimated coverage of relevant target volumes was low, however, with only 20.1% of the 2-cm penumbra surrounding the resection cavity covered on average. Although tumor location and resection cavity volume had no effect on coverage volume, estimations of drug delivery to relevant target volumes did correlate well with catheter score (p < 0.003), and optimally positioned catheters had larger coverage volumes (p < 0.002). Only overall survival (p = 0.006) was higher for investigators considered experienced after adjusting for patient age and Karnofsky Performance Scale score. CONCLUSIONS The potential efficacy of drugs delivered by CED may be severely constrained by ineffective delivery in many patients. Routine use of software algorithms and alternative catheter designs and infusion parameters may improve the efficacy of drugs delivered by CED.

N-Acetyl cysteine protects against injury in a rat model of focal cerebral ischemia.

Ischemic cerebrovascular disease (stroke) is one of the leading causes of death and long-time disability. Ischemia/reperfusion to any organ triggers a complex series of biochemical events, which affect the structure and function of every organelle and subcellular system of the affected cells. The purpose of this study was to investigate the therapeutic efficacy of N-acetyl cysteine (NAC), a precursor of glutathione and a potent antioxidant, to attenuate ischemia/reperfusion injury to brain tissue caused by a focal cerebral ischemia model in rats. A total of 27 male Sprague-Dawley rats weighing 250-300 g were used in this study. Focal cerebral ischemia (45 min) was induced in anesthetized rats by occluding the middle cerebral artery (MCA) with an intra-luminal suture through the internal carotid artery. The rats were scored post-reperfusion for neurological deficits. They were then sacrificed after 24 h of reperfusion and infarct volume in the brain was assessed by 2,3,5-triphenyl tetrazolium chloride (TTC). Brain sections were immunostained for tumor necrosis factor (TNF-alpha) and inducible nitric oxide synthase (iNOS). Animals treated with NAC showed a 49.7% (S.E.M.=1.25) reduction in brain infarct volume and 50% (S.E.M.=0.48) reduction in the neurological evaluation score as compared to the untreated animals. NAC treatment also blocked the ischemia/reperfusion-induced expression of tumor necrosis factor and inducible nitric oxide synthase. The data suggest that pre-administration of NAC attenuates cerebral ischemia and reperfusion injury in this brain ischemia model. This protective effect may be as a result of suppression of TNF-alpha and iNOS.

Safety and Feasibility of Convection-enhanced Delivery of Cotara for the Treatment of Malignant Glioma: Initial Experience in 51 Patients

OBJECTIVE: We report the safety and feasibility of using convection-enhanced delivery to administer Cotara (Peregrine Pharmaceuticals, Inc., Tustin, CA), a novel radioimmunotherapeutic agent, to patients with malignant glioma. METHODS: Between April 1998 and November 2002, 51 patients with histologically confirmed malignant glioma received Cotara by convection-enhanced delivery. Most patients (88%) were treated with Cotara targeting tumor volume-dependent, single or multiple administrations of activity ranging from 0.5 to 3.0 mCi/cm3 of baseline clinical target volume. Two weeks after infusion, single-photon emission computed tomographic imaging determined the spatial distribution of Cotara. Patients were followed for as long as 41 months (average follow-up, 5 mo). Safety was evaluated on the basis of incidence of procedure-related, neurological, and systemic adverse events. Feasibility was evaluated in a subset of patients on the basis of the correlation between the prescribed activity and the actual activity administered to the targeted region. RESULTS: Fifty-one patients, 37 with recurrent glioblastoma multiforme, 8 with newly diagnosed glioblastoma multiforme, and 6 with recurrent anaplastic astrocytomas, were treated. Average tumor volume was 36 ± 27.6 cm3 (range, 5–168 cm3). Of the 67 infusions, 13 (19%), 52 (78%), and 2 (3%) delivered less than 90%, 100 ± 10%, and more than 110%, respectively, of the prescribed administered activity to the targeted region. Treatment-emergent, drug-related central nervous system adverse events included brain edema (16%), hemiparesis (14%), and headache (14%). Systemic adverse events were mild. Several patients had objective responses to Cotara. CONCLUSION: The majority of Cotara infusions delivered between 90 and 110% of the prescribed administered activity to the targeted region. This method of administration has an acceptable safety profile compared with literature reports of other therapeutics delivered by convection-enhanced delivery.

Drug resistance in glioblastoma: a mini review.

Glioblastoma multiforme (GBM) is recognized as the most common and lethal form of central nervous system cancer. Currently used surgical techniques, chemotherapeutic agents, and radiotherapy strategies have done very little in extending the life expectancies of patients diagnosed with GBM. The difficulty in treating this malignant disease lies both in its inherent complexity and numerous mechanisms of drug resistance. In this review, we summarize several of the primary mechanisms of drug resistance. We reviewed available published literature in the English language regarding drug resistance in glioblastoma. The reasons for drug resistance in glioblastoma include drug efflux, hypoxic areas of tumor cells, cancer stem cells, DNA damage repair, and miRNAs. Many potential therapies target these mechanisms, including a series of investigated alternative and plant-derived agents. Future research and clinical trials in glioblastoma patients should pursue combination of therapies to help combat drug resistance. The emerging new data on the potential of plant-derived therapeutics should also be closely considered and further investigated.

Curcumin activated both receptor-mediated and mitochondria-mediated proteolytic pathways for apoptosis in human glioblastoma T98G cells.

The therapeutic effect of curcumin (CCM), a polyphenolic compound from the rhizome of Curcuma longa, has not yet been examined in glioblastoma. We used human glioblastoma T98G cells to explore the efficacy of CCM for inducing apoptosis and identifying proteolytic mechanisms involved in this process. Trypan blue dye exclusion test showed decrease in cell viability with increasing dose of CCM. Wright staining and ApopTag assay showed, respectively, morphological and biochemical features of apoptosis in T98G cells exposed to 25 microM and 50 microM of CCM for 24 h. Treatment with CCM activated receptor-mediated pathway of apoptosis as Western blotting showed activation of caspase-8 and cleavage of Bid to tBid. Besides, CCM caused an increase in Bax:Bcl-2 ratio, and mitochondrial release of cytochrome c, Second mitochondrial activator of caspases/Direct IAP binding protein with low pI (Smac/Diablo), and apoptosis-inducing-factor (AIF) indicating involvement of mitochondria-mediated pathway as well. Down regulation of the nuclear factor kappa B (NFkappaB), increased expression of inhibitor of nuclear factor kappa B alpha (IkappaB alpha), and decreased expression of inhibitor-of-apoptosis proteins (IAPs) such as c-IAP1 and c-IAP2 in T98G cells following CCM treatment suggested suppression of survival signal. Activation of caspase-9 and caspase-3 was detected in generation of 35 kD and 20 kD active fragments, respectively. Calpain and caspase-3 activities cleaved 270 kD alpha-spectrin at specific sites to generate 145 kD spectrin break down product (SBDP) and 120 kD SBDP, respectively. Our results strongly suggest that CCM induced both receptor-mediated and mitochondria-mediated proteolytic mechanisms for induction of apoptosis in T98G cells.

Dexamethasone protected human glioblastoma U87MG cells from temozolomide induced apoptosis by maintaining Bax:Bcl-2 ratio and preventing proteolytic activities.

BackgroundGlioblastoma is the deadliest and most prevalent brain tumor. Dexamethasone (DXM) is a commonly used steroid for treating glioblastoma patients for alleviation of vasogenic edema and pain prior to treatment with chemotherapeutic drugs. Temozolomide (TMZ), an alkylating agent, has recently been introduced in clinical trials for treating glioblastoma. Here, we evaluated the modulatory effect of DXM on TMZ induced apoptosis in human glioblastoma U87MG cells.ResultsFreshly grown cells were treated with different doses of DXM or TMZ for 6 h followed by incubation in a drug-free medium for 48 h. Wright staining and ApopTag assay showed no apoptosis in cells treated with 40 μM DXM but considerable amounts of apoptosis in cells treated with 100 μM TMZ. Apoptosis in TMZ treated cells was associated with an increase in intracellular free [Ca2+], as determined by fura-2 assay. Western blot analyses showed alternations in the levels of Bax (pro-apoptotic) and Bcl-2 (anti-apoptotic) proteins resulting in increased Bax:Bcl-2 ratio in TMZ treated cells. Western blot analyses also detected overexpression of calpain and caspase-3, which cleaved 270 kD α-spectrin at specific sites for generation of 145 and 120 kD spectrin break down products (SBDPs), respectively. However, 1-h pretreatment of cells with 40 μM DXM dramatically decreased TMZ induced apoptosis, decreasing Bax:Bcl-2 ratio and SBDPs.ConclusionOur results revealed an antagonistic effect of DXM on TMZ induced apoptosis in human glioblastoma U87MG cells, implying that treatment of glioblastoma patients with DXM prior to chemotherapy with TMZ might result in an undesirable clinical outcome.

Comparison of techniques for transsphenoidal pituitary surgery.

Background The aim of this study was to compare three different techniques for transsphenoidal pituitary surgery: (1) sublabial transseptal approach with microscopic resection, (2) transnasal transseptal approach with endoscopic resection, and (3) endoscopic approach with endoscopic resection. Methods We performed a retrospective review of 50 pituitary surgeries performed by the same neurosurgeon. Demographic, radiographic, and clinical data were collected. Results Fifteen patients underwent sublabial approach with microscopic tumor resection, 21 patients underwent the transnasal approach with endoscopic resection, and 14 patients underwent the completely endoscopic technique. There were a total of 20 complications in the sublabial group, 13 transnasal complications, and 6 endoscopic complications. Cerebrospinal fluid leak incidence was 53% in the sublabial approaches, 47% transnasal, and 28% in the endoscopic patients. Diabetes insipidus was encountered in 33% of sublabial approaches, 5% of transnasal approaches, and 7% of endoscopic approaches. Lumbar drains were required in 40% of sublabial approaches, 38% of transnasal approaches, and 7% of endoscopic approaches. Nasal packing was used in 100% of sublabial and transnasal approaches and 0% of endoscopic approaches. Mean recurrence rate and follow-up was sublabial in 6.6% (50 months), transnasal in 9.5% (11 months), and endoscopic in 0% (7 months). Average hospital stay for sublabial approaches, transnasal approaches, and endoscopic approaches was 8.3, 6.2, and 3.4 days, respectively (p < 0.05). Conclusion Transsphenoidal pituitary surgery has evolved over the past several decades, because advances in technology have been the catalyst for minimally invasive surgeries. Less invasive approaches, such as the transnasal approach with endoscopic resection of tumor and the completely endoscopic technique have less morbidity and a shorter hospital stay than traditional sublabial approaches. Continued follow-up is needed to confirm long-term benefits and similar recurrence rates.

Closure of large skull base defects after endoscopic transnasal craniotomy. Clinical article.

OBJECT The authors describe the utility of and outcomes after endoscopic transnasal craniotomy and skull reconstruction in the management of skull base pathologies. METHODS The authors conducted a observational study of patients undergoing totally endoscopic, transnasal, transdural surgery. The patients included in the study underwent treatment over a 12-month period at 2 tertiary medical centers. The pathological entity, region of the ventral skull base resected, and size of the dural defect were recorded. Approach-related complications were documented, as well as CSF leaks, infections, bleeding-related complications, and any minor complications. RESULTS Thirty consecutive patients were assessed during the study period. The patients had a mean age of 45.5 +/- 20.2 years and a mean follow-up period of 182.4 +/- 97.5 days. The dural defects reconstructed were as large as 5.5 cm (mean 2.49 +/- 1.36 cm). One patient (3.3%) had a CSF leak that was managed endoscopically. Two patients had epistaxis that required further care, but there were no complications related to intracranial infections or bleeding. Some minor sinonasal complications occurred. CONCLUSIONS Skull base endoscopic reconstructive techniques have significantly advanced in the past decade. The use of pedicled mucosal flaps in the reconstruction of large dural defects resulting from an endoscopic transnasal craniotomy permits a robust repair. The CSF leak rate in this study is comparable to that achieved in open approaches. The ability to manage the skull base defects successfully with this approach greatly increases the utility of transnasal endoscopic surgery.

Meningiomas: Correlation between MRI characteristics and operative findings including consistency

SummaryThe findings on magnetic resonance imaging (MRI) in 73 surgically verified intracranial meningiomas were correlated with their histology and consistency during resection.T 1-weighted imaging was least useful since most of the tumours were iso-intense, similar to cortical grey matter regardless of histology or tumour consistency. The signal intensity on T 2-weighted images was found to best correlate with both the histology and consistency of the meningioma. Generally, the low intensity portion of the tumour on T 2-weighted images indicated a more fibrous and harder character, while the higher intensity portions indicated a more soft character. Most of the fibroblastic meningiomas showed the features of a hard tumour while angioblastic tumours showed the features of soft tumours.Tumours predicted to be harder on MR imaging generally took longer to resect than softer ones, and this relationship was shown best for the larger tumours. Using linear regression analysis, it appears that operative time for soft tumours is more affected by factors other than tumour consistency. Blood loss during surgery was also unrelated to the consistency of the tumour.These results suggest that the histology and consistency of meningiomas may be predictable from findings on T 2-weighted imaging, and this may also predict the difficulty and time required for resection.