Faculty Bibliography

The transsphenoidal corridor for pituitary adenoma surgery was established as early as 1906 by Schloffer and was subsequently refined by Cushing throughout the early 20thcentury [1]. The use of intraoperative magnetic resonance imaging (iMRI) in endoscopic endonasal transsphenoidal resections, however, is a relatively contemporary addition to the surgical treatment of pituitary tumors. The morbidity of these cases has decreased over the years in light of advances in intraoperative navigation as well as improvements in endoscope dynamics and surgical instruments. Despite such improvements, a substantial number of patients require repeat surgeries or subsequent radiotherapy for residual and/or recurrent disease. This can be largely attributed to cavernous sinus invasion or suprasellar extension, which pose technical challenges to achieving gross total resections (GTRs). The rate of GTR for pituitary tumors cited in the literature varies from 59-88%.[2-3] The advantage of iMRI is that it provides the surgeon with immediate feedback regarding their progress and ability to safely achieve GTR which, in pituitary surgery, is critical for long term cure. Additionally, although there is concern for increased risk of postoperative endocrine dysfunction, Zhibin et al prove that this is not necessarily the case. In their series, 133 patients who underwent iMRI had higher rates of GTR and did not have a significant difference in postoperative hypopituitarism. [4] This study includes a combined retrospective and prospective comparative analysis of 238 patients who underwent transsphenoidal resection of a pituitary tumor from January 2013 until May 2019. All patients were operated on by one of four experienced neurosurgeons and one of three experienced otolaryngologists. There were 203 patients who did not undergo iMRI and 25 patients who did. A 3 tesla MRI magnet was used in all cases. All intraoperative images were read and interpreted by a senior neuroradiologist at our institution. Amongst the two groups, there was no statistically significant difference in patient age (p = 0.488), tumor size (microadenoma versus macroadenoma, p = 0.878), and primary versus recurrent tumor (p = 0.837). The use of iMRI did not yield a decrease in the length of stay (4.84 days in the no iMRI group and 5 in the iMRI group, p = 0.777). There were zero cases of a return to the OR for residual tumor in the intraoperative MRI group versus the non-MRI group. However, this did not reach statistical significance. This study did not yield a statistically significant difference in GTR (p = 0.75), near total resection (NTR, p = 0.167), or subtotal resection (p = 0.083). This is likely secondary to a low sample size and therefore power in the iMRI group. Finally, there was no significant difference in the number of patients requiring postoperative DDAVP (p = 0.099) or hydrocortisone (p = 0.873) after discharge. Preliminary results reveal a potential benefit of iMRI use to assess for residual disease which can be addressed immediately during the initial operation, thus decreasing the need for re-operations. Furthermore, the ability to correlate intraoperative findings with an intraoperative structure may lead to more precise identification and preservation of normal gland, which can possibly decrease the incidence of postoperative endocrine dysfunction

Direct access through the sinuses and nasopharyngeal mucosa in the endoscopic endonasal approach (EEA) raises concern for a contaminated operative environment and subsequent infection. The reported rate of meningitis in endoscopic endonasal skull base surgery in the literature ranges from 0.7 to 3.0% [1, 2]. The only factor identified as being independently associated with meningitis in a statistically significant manner is cerebrospinal fluid (CSF) leak [1-5]. However, many centers performing high volume of EEAs use postoperative antibiotic coverage independent of the presence intraoperative or postoperative CSF leak. Furthermore, while meningitis remains a severe concern, most centers use postoperative gram-positive coverage to prevent toxic shock syndrome caused by Staphylococcus aureus infection in the setting of prolonged nasal packing. There are currently a multitude of approaches regarding perioperative antibiotic coverage in EEAs [1-4]. Given the lack of consensus in the literature and our experience regarding the benefit of discontinuation of prolonged prophylactic antibiotics throughout the breadth of neurosurgical procedures, we sought to analyze the need for postoperative antibiotics in EEAs further. As such, we performed a prospective analysis compared with a retrospective cohort to delineate whether discontinuation of postoperative antibiotics leads to a change in the rate of postoperative infections. The retrospective cohort consisted of patients who underwent an EEA from January 1, 2013 to May 31, 2019. These patients all received postoperative antibiotics while nasal packing was in place (median 7 days). Starting on April 1, 2019 until August 1, 2019, we discontinued postoperative antibiotic use. Patients from this group made up the prospective cohort. The retrospective cohort had 315 patients (66% pituitary macroadenomas vs. 7% microadenomas, 4% meningiomas, 4% craniopharyngiomas, 4% chordomas, and 15% others) while the prospective group had 23 patients (57% pituitary macroadenomas, 30% craniopharyngiomas, 8% meningiomas/chordomas, and 5% others). The primary endpoint was rate of postoperative infections and specifically, meningitis and multidrug resistant organism (MDRO) infections. There was no statistically significant difference in the use of nasal packing (p = 0.085), intraoperative CSF leak (p = 0.133), and postoperative CSF leak (p = 0.507) between the two groups. There was also no significant difference in the number of patients with positive preoperative MSSA and MRSA nasal swabs (p = 0.622). There was a significant decrease in the number of patients discharged with antibiotics (55.1% in the retrospective and 4.5% in the prospective group, p = 0.000). The number of patients with positive blood cultures (p = 0.701) and positive urine cultures (p = 0.691) did not differ significantly between the two groups. Finally, there was no statistically significant difference in postoperative CSF infections (p = 0.34) or MDRO infections (0.786) between the two groups. We describe promising preliminary results that demonstrate that discontinuation of postoperative antibiotics in EEAs do not lead to a statistically significant increase in the rate of postoperative CSF or MDRO infections. The previous algorithm for postoperative antibiotic coverage in our center, like many centers, called for gram-positive coverage, which may have contributed to the overall preponderance of gram-negative meningitis cases in this cohort

Background/UNASSIGNED:Glioma is a family of primary brain malignancies with limited treatment options and in need of novel therapies. We previously demonstrated that the adhesion G protein-coupled receptor GPR133 (ADGRD1) is necessary for tumor growth in adult glioblastoma, the most advanced malignancy within the glioma family. However, the expression pattern of GPR133 in other types of adult glioma is unknown. Methods/UNASSIGNED:We used immunohistochemistry in tumor specimens and non-neoplastic cadaveric brain tissue to profile GPR133 expression in adult gliomas. Results/UNASSIGNED:We show that GPR133 expression increases as a function of WHO grade and peaks in glioblastoma, where all tumors ubiquitously express it. Importantly, GPR133 is expressed within the tumor bulk, as well as in the brain-infiltrating tumor margin. Furthermore, GPR133 is expressed in both isocitrate dehydrogenase (IDH) wild-type and mutant gliomas, albeit at higher levels in IDH wild-type tumors. Conclusion/UNASSIGNED:The fact that GPR133 is absent from non-neoplastic brain tissue but de novo expressed in glioma suggests that it may be exploited therapeutically.

A 66-year-old woman with a history of stage IA mixed endometrioid and serous endometrial cancer presented to our centre with 2 weeks of worsening headaches nearly 4 years after her initial surgery. At admission, she manifested bitemporal hemianopsia, difficulty walking and clinical and laboratory findings of panhypopituitarism, including diabetes insipidus. Magnetic resonance imaging of the brain revealed a 2.7 cm sellar/suprasellar mass compressing the optic chiasm and infiltrating the pituitary stalk. Computerised tomography documented mediastinal, lung, adrenal and liver involvement, including a 2.5 cm palpable left supraclavicular node that on excisional biopsy demonstrated metastatic endometrial adenocarcinoma. Due to the advanced stage of her cancer as well as the presence of multiple metastases, including lung and hepatic metastases causing post-obstructive pneumonia and coagulopathy, the sellar/suprasellar mass was treated with fractionated radiosurgery rather than surgical excision.

Neurologic manifestations of the novel coronavirus SARS-CoV-2 infection have received wide attention, but the mechanisms remain uncertain. Here, we describe computational data from public domain RNA-seq datasets and cerebrospinal fluid data from adult patients with severe COVID-19 pneumonia that suggest that SARS-CoV-2 infection of the central nervous system is unlikely. We found that the mRNAs encoding the ACE2 receptor and the TMPRSS2 transmembrane serine protease, both of which are required for viral entry into host cells, are minimally expressed in the major cell types of the brain. In addition, CSF samples from 13 adult encephalopathic COVID-19 patients diagnosed with the viral infection via nasopharyngeal swab RT-PCR did not show evidence for the virus. This particular finding is robust for two reasons. First, the RT-PCR diagnostic was validated for CSF studies using stringent criteria; and second, 61% of these patients had CSF testing within 1 week of a positive nasopharyngeal diagnostic test. We propose that neurologic sequelae of COVID-19 are not due to SARS-CoV-2 meningoencephalitis and that other etiologies are more likely mechanisms.

IDH1/2 mutations are early drivers present in diverse human cancer types arising in various tissue sites. IDH1/2 mutation is known to induce a global hypermethylator phenotype. However, the effects on DNA methylation across IDH mutant cancers and functionally different genome regions, remain unknown. We analyzed DNA methylation data from IDH1/2 mutant acute myeloid leukemia, oligodendroglioma, astrocytoma, solid papillary breast carcinoma with reverse polarity, sinonasal undifferentiated carcinoma and cholangiocarcinoma, which clustered by their embryonal origin. Hypermethylated common probes affect predominantly gene bodies while promoters in IDH1/2 mutant cancers remain unmethylated. Enhancers showed global hypermethylation, however commonly hypomethylated enhancers were associated with tissue differentiation and cell fate determination. We demonstrate that some chromosomes, chromosomal arms and chromosomal regions are more affected by IDH1/2 mutations while others remain resistant to IDH1/2 mutation induced methylation changes. Therefore IDH1/2 mutations have different methylation effect on different parts of the genome, which may be regulated by different mechanisms.

We previously found GPR133 (ADGRD1), an orphan adhesion GPCR, is De novo expressed in glioblastoma (GBM) and enriched in patient-derived glioblastoma stem cells (GSCs). Knockdown of GPR133 reduces GBM cell proliferation and tumorsphere formation, and abolishes orthotopic tumor initiation in vivo in mice. Analysis of TCGA data indicates that increased GPR133 transcription inversely correlates with patient survival in GBM. While these findings underscore the importance of GPR133 in GBM and suggest an essential role in tumor growth, its ligand and mechanism of activation remain unknown. Toward identifying GPR133 ligands, we used GPR133's N-terminal ectodomain as bait and performed affinity co-immunoprecipitation (CoIP) followed by mass spectrometry as an unbiased screening approach. We identified 490 extracellular proteins with enriched binding to GPR133 compared to control. Reverse CoIP using the 15 most abundant candidate ligands as bait to purify the receptor confirmed this interaction reproducibly in 4 candidates. Despite this binding, overexpression of these candidate ligands, or addition of purified recombinant protein, is not sufficient to increase receptor signaling as assessed by cAMP levels in HEK293 cells. This suggests that ligand binding to the GPR133 ectodomain may not be sufficient by itself to induce receptor activation. We hypothesize receptor activation requires mechanical forces in addition to ligand binding. Consistent with this hypothesis, the GPR133 binding proteins we have identified may be anchored to the extracellular matrix, mediating such mechanical force. To test whether mechanical shearing of the extracellular domain is sufficient for receptor activation, we used Dynabeads coupled to antibody against GPR133's N-terminal ectodomain, and indeed observed receptor activation leading to elevated cAMP levels. No activation was observed when Dynabeads devoid of antibody were used. This mode of GPR133 activation might indicate a role in sensing mechanical/viscoelastic properties of GBM extracellular matrix, which may be relevant to tumor cell migration and invasion

Neomorphic mutations in isocitrate dehydrogenase I (IDH1) result in the formation of the oncometabolite 2-hydroxyglutarate (2HG) in a significant subset of gliomas and other tumors including acute myeloid leukemias. Preclinical evidence suggests that gliomas harboring IDH1 mutations undergo widespread, long-lasting modifications to the epigenome that persist following inhibition of 2HG production. However, the exact mechanism underlying gliomagenesis remains unclear. To address difficulties in growing these tumors in culture, our group generated a model of low-grade astrocytoma in human neural stem cells (NSCs). This model, referred to as 3-Hit NSCs, suggested a block in differentiation potential underlies gliomagenesis at the cellular level. This block is rescued by restoration of expression of the transcription factor (sex determining region Y)-box 2 (SOX2), which is transcriptionally downregulated during IDH mutant gliomagenesis. We believe that these changes occur secondary to profound alterations in 3-dimensional chromatin organization around the SOX2 genomic locus. Our preliminary data suggest SOX2 expression in control NSCs depends on 3-dimensional association of its promoter to an uncharacterized, distal enhancer located 600 kb telomeric to the SOX2 gene. We believe this association is disrupted in 3-Hit NSCs due to eviction of chromatin organizer CTCF from its motifs in the SOX2 topologically associating domain (TAD). To test this hypothesis, we used CRISPR-Cas9 technology to excise CTCF motifs immediately upstream of the SOX2 promoter and in the region of the putative enhancer in control NSCs. Excision of such motifs significantly reduced SOX2 mRNA levels and impaired growth of control NSCs. We are currently working on characterizing this novel SOX2-enhancer interaction in native stem cells, as well as tumors that depend on SOX2 expression. This works aims to elucidate the core epigenetic mechanisms underlying IDH mutant gliomagenesis. Our findings will be used to improve therapy in IDH-mutant glioma

BACKGROUND:Chromosomal instability is associated with earlier progression in isocitrate dehydrogenase (IDH)-mutated astrocytomas. Here we evaluated the prognostic significance of polysomy in gliomas tested for 1p19q status. METHODS:We analyzed 412 histologic oligodendroglial tumors with use of 1p19q testing at 8 institutions from 1996 to 2013; fluorescence in situ hybridization (FISH) for 1p19q was performed. Polysomy was defined as >2 1q and 19p signals in cells. Tumors were divided into groups on the basis of their 1p19q status and polysomy and were compared for progression-free survival (PFS) and overall survival (OS). RESULTS:In our cohort, 333 tumors (81%) had 1p19q loss; of these, 195 (59%) had concurrent polysomy and 138 (41%) lacked polysomy, 79 (19%) had 1p19q maintenance; of these, 30 (38%) had concurrent polysomy and 49 (62%) lacked polysomy. In agreement with prior studies, the group with 1p19q loss had significantly better PFS and OS than did the group with 1p19q maintenance (p < 0.0001 each). Patients with 1p19q loss and polysomy showed significantly shorter PFS survival than patients with 1p19q co-deletion only (p-<0.0001), but longer PFS and OS than patients with 1p19q maintenance (p < 0.01 and p<0.0001). There was no difference in survival between tumors with >30% polysomic cells and those with <30% of polysomic cells. Polysomy had no prognostic significance on progression-free or overall survival in patients with 1p19q maintenance. CONCLUSIONS:The presence of polysomy in oligodendroglial tumors with co-deletion of 1p19q predicts early recurrence and short survival in patients with 1p19q co-deleted tumors.