Clinical and Operative Risk Factors Associated With Prolonged Length of Stay After Endoscopic Pituitary Adenoma Resection

BACKGROUND AND OBJECTIVES

Pituitary adenomas (PAs) are the most common intrasellar tumor. Clinically relevant adenomas have a prevalence of 1 per 1000 in the general population. Transsphenoidal surgery (TSS) is the most common surgical treatment and is the first-line management for most PAs. Most patients fare well postoperatively, but a subset of patients experience a prolonged length of stay (PLOS). In this article, we aim to identify demographic and clinical factors associated with PLOS after TSS for PA.

METHODS

Patients with sellar pathologies surgically treated at a single tertiary center from March 1, 2009, to May 31, 2020, were retrospectively reviewed. All patients older than 18 years receiving nonemergent endoscopic TSS for pituitary adenoma were included. Clinical and demographic characteristics were analyzed using χ2-tests and student t-tests. For those factors with a P-value less than .01, multivariate logistic regression and negative binomial regression models were constructed to estimate the adjusted odds of PLOS across predictive factors.

RESULTS

A total of 301 patients were included in the study. This cohort had an average age of 54.65 ± 15.06 years and an average body mass index of 29.47 ± 6.69. The median length of stay was 54.9 hours [25th-75th percentiles: 43.5-72.9]. Postoperative cerebrospinal fluid leak (P < .01), postoperative diabetes insipidus (DI) (P < .01), increased surgery duration (P = .01), and elevated maximal tumor dimension (P = .01) were predictive of PLOS in logistic regression. Increased surgery duration, previous pituitary radiation, intraoperative complications, and postoperative DI (all P < .01) were associated with increased rate of PLOS in negative binomial regression.

CONCLUSION

Patients undergoing endoscopic TSS for PA resection demonstrate prolonged lengths of stay if they have higher tumor burden, have lengthier surgeries with intraoperative complications, or develop postoperative complications such as cerebrospinal fluid leak or DI. Careful monitoring of these factors will allow for better resource optimization, reducing costs to both the hospital and the patient.

Application of the Robotic-Assisted Digital Exoscope for Resection of Posterior Fossa Tumors in Adults: A Series of 45 Cases

BACKGROUND AND OBJECTIVES

Complete safe resection is the goal when pursuing surgical treatment for posterior fossa (PF) tumors. Efforts have led to the development of the exoscope that delineates tumors from non-neoplastic brain. This investigation aims to assess patient outcomes where PF tumor resection is performed with the exoscope by a retromastoid or suboccipital approach.

METHODS

A retrospective analysis was conducted for patients with PF tumors who underwent exoscope resection from 2017 to 2022. Patient demographics, clinical, operative, and outcome findings were collected. Extent of resection studies were also performed. Associations between perioperative data, discharge disposition, progression-free survival (PFS), and overall survival (OS) were evaluated.

RESULTS

A total of 45 patients (22 male patients) with a median age of 57 years were assessed. Eighteen (40%) and 27 patients (60%) were diagnosed with malignant and benign tumors, respectively. Tumor neurovascular involvement was found in 28 patients (62%). Twenty-four (53%) and 20 (44%) tumors formed in the cerebellum and cerebellopontine angle cistern, respectively. One tumor (2%) was found in the cervicomedullary junction. The mean extent of resection was 96.7% for benign and malignant tumors. The PFS and OS rate at 6 months (PFS6, OS6) was 89.7% and 95.5%, respectively. Neurological complications included sensory loss and motor deficit, with 11 patients reporting no postoperative symptoms. Of the neurological complications, 14 were temporary and 9 were permanent.

CONCLUSION

The exoscope is an effective intraoperative visualization tool for delineating PF tumors. In our series, we achieved low postoperative tumor volumes and a high gross total resection rate.

Correlation between tumor volume and serum prolactin and its effect on surgical outcomes in a cohort of 219 prolactinoma patients

OBJECTIVE

Prolactinoma is the most common pituitary adenoma and can be managed medically or surgically. The authors assessed the correlation between tumor volume and prolactin level and its effect on surgical outcomes.

METHODS

The authors reviewed 219 patients who underwent transsphenoidal prolactinoma resection at a single institution from 2012 to 2019. Outcomes were compared between patients with and without biochemical remission. Tumor volumes were quantified with BrainLab Smartbrush. Correlation analysis and linear regression were used to examine the association between tumor volume and serum prolactin level. Volume-adjusted prolactin level was defined as serum prolactin level divided by tumor volume. The authors utilized receiver operating characteristic (ROC) curve analysis to determine the thresholds for predicting biochemical remission status.

RESULTS

The mean tumor volume was 5.66 cm3, and the mean preoperative prolactin level was 752.3 µg/L. Men had larger prolactinomas than women (mean volume 11.32 vs 2.54 cm3; p < 0.001), and women had a greater volume-adjusted prolactin level (mean 412.5 vs 175.9 µg/L/cm3, p < 0.001). In total, 66.7% of surgical patients achieved biochemical remission 6 weeks after surgery, whereas a similar cohort of medically treated patients during the same time frame demonstrated a 69.4% remission rate. Pearson correlation and linear regression analysis revealed a strong association between preoperative tumor volume and prolactin levels, with an increase in serum prolactin level of 101.31 µg/L per 1-cm3 increase in tumor volume (p < 0.001). This held true for men (R = 0.601, p < 0.001) and women (R = 0.935, p < 0.001), with women demonstrating a greater increase in prolactin level per 1-cm3 increase in volume (185.70 vs 79.77 µg/L, p < 0.001). Patients who achieved remission exhibited a 66.08-µg/L increase in preoperative prolactin level per 1 cm3 of preoperative tumor volume (p < 0.001), which was less than the 111.46-µg/L increase per 1 cm3 in patients without remission (p < 0.001). Patients who failed to achieve remission had residual tumors with a 77.77-µg/L increase in prolactin per 1 cm3 of remaining tumor volume after resection (p < 0.001). ROC curve analysis revealed significant thresholds that optimally predicted lack of postoperative remission on the basis of preoperative prolactin and tumor volume. These thresholds were rendered nonsignificant in patients with documented Knosp grade ≥ 3.

CONCLUSIONS

Although the authors found a correlation between prolactinoma volume and serum prolactin level, patients without remission had a greater increase in serum prolactin level per increase in preoperative tumor volume than those who achieved remission, suggesting unique tumor composition. The authors also identified prolactin and tumor volume thresholds that optimally predicted biochemical remission status. The authors hope that their results can be used to identify prolactinomas for which surgery could achieve remission as an alternative to medical management.

Single-cell RNA sequencing and spatial transcriptomics reveal cancer-associated fibroblasts in glioblastoma with protumoral effects

Cancer-associated fibroblasts (CAFs) were presumed absent in glioblastoma given the lack of brain fibroblasts. Serial trypsinization of glioblastoma specimens yielded cells with CAF morphology and single-cell transcriptomic profiles based on their lack of copy number variations (CNVs) and elevated individual cell CAF probability scores derived from the expression of 9 CAF markers and absence of 5 markers from non-CAF stromal cells sharing features with CAFs. Cells without CNVs and with high CAF probability scores were identified in single-cell RNA-Seq of 12 patient glioblastomas. Pseudotime reconstruction revealed that immature CAFs evolved into subtypes, with mature CAFs expressing actin alpha 2, smooth muscle (ACTA2). Spatial transcriptomics from 16 patient glioblastomas confirmed CAF proximity to mesenchymal glioblastoma stem cells (GSCs), endothelial cells, and M2 macrophages. CAFs were chemotactically attracted to GSCs, and CAFs enriched GSCs. We created a resource of inferred crosstalk by mapping expression of receptors to their cognate ligands, identifying PDGF and TGF-β as mediators of GSC effects on CAFs and osteopontin and HGF as mediators of CAF-induced GSC enrichment. CAFs induced M2 macrophage polarization by producing the extra domain A (EDA) fibronectin variant that binds macrophage TLR4. Supplementing GSC-derived xenografts with CAFs enhanced in vivo tumor growth. These findings are among the first to identify glioblastoma CAFs and their GSC interactions, making them an intriguing target.

Abstract B009: Sub-oxidant ascorbate sensitizes glioblastoma stem cells to DNA damaging agents by inducing DNA de-methylation and altering the chromatin landscape

Gliomas are the most common primary brain cancer and glioblastoma (GBM) represents the most aggressive and lethal subtype. The high GBM morbidity and mortality are due to profound genetic, epigenetic, and phenotypic heterogeneity within the tumor that contributes to an almost guaranteed development of therapeutic resistance and tumor recurrence. GBM stem-like cells (GSCs) are tumor cell sub-populations that disproportionately drive tumor propagation, therapy resistance, and tumor recurrence. Epigenetic deregulation is thought to play a fundamental role in the formation and expansion of GSCs and their contributions to oncogenesis. However, the epigenetic reprogramming events that contribute to GSC tumor propagation and therapy resistance remain elusive. DNA methylation (5mC) can be modified to generate hydroxymethylation (5hmC) or reversed through enzymatic reactions coordinated by the Ten-Eleven Translocation (TET) enzymes. Multiple studies show a decrease in both 5hmC levels and TET expression in gliomas and a correlation between loss of 5hmC and increasing glioma grade and poor prognosis. These observations suggest that re-establishing TET activity and 5hmC levels in tumor cells will have tumor suppressive effects. Ascorbate (vitamin C) has gained pre-clinical interest as an attractive antitumor agent for GBM due to its ability to regulate redox status, cross the blood-brain barrier, and enhance TET enzymatic activity; therefore, providing an innovative potential epigenetic therapeutic for GBM. We show that low-dose ascorbate (i.e. sub-pro-oxidant concentrations) enhances TET activity and elevates global 5hmC levels concurrent with decreases in 5mC in GSCs. These changes in DNA methylation correlate with a decrease in self-renewal capacity and increased tumor cell death induced by temozolomide (TMZ) and ionizing radiation (IR). We also present a novel mechanism whereby ascorbate increases the histone mark H3K36me3 by upregulating GSC expression of the histone methyltransferase NSD1 via demethylation of the gene promoter region. We propose that the enhanced susceptibility of ascorbate-treated tumor cells to DNA damage therapies results from increased H3K36me3-induced euchromatin states that increases genomic susceptibility to DNA damage. These findings support the need to better understand the epigenetic, transcriptomic, and chromatin architectural effects of ascorbate in cancer. These results also strongly indicate that ascorbate could serve as an adjunct to standard-of-care GBM treatment by restoring TET tumor-suppressor activity and re-sensitizing GSCs to conventional radio- and chemotherapeutics.

Citation Format: Maureen Malloy, Sweta Sudhir, Harmon Khela, Maria Fagundo-Lugo, Bachchu Lal, Joseph Bressler, John Laterra, Hernando Lopez Bertoni. Sub-oxidant ascorbate sensitizes glioblastoma stem cells to DNA damaging agents by inducing DNA de-methylation and altering the chromatin landscape. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Epigenomics; 2022 Oct 6-8; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_2):Abstract nr B009.

CSIG-18. ANTI-TUMOR EFFECTS OF VERTEPORFIN AND PHOTODYNAMIC THERAPY IN COMBINATION WITH STANDARD OF CARE ON PATIENT-DERIVED GBM CELL LINES

Glioblastoma (GBM) is the most common and aggressive primary brain tumor with a median survival of approximately 15 months. GBM tumorigenicity frequently arises from aberrant signaling transduction pathways involving receptor tyrosine kinases (RTKs), such as EGFR and PI3K. Amplification of the Epidermal Growth Factor Receptor (EGFR) gene upregulates Hippo pathway transcription factors YAP1 and TAZ, leading to tumor cell proliferation, radiation resistance, and poor survival. Verteporfin (VP), also known as Visudyne, is an FDA-approved macular degeneration photosensitizer that has photodynamic effects when combined with 489 nm of light. Additionally, VP is a small-molecule inhibitor of the YAP/TAZ/TEAD complex that has been shown to reduce tumor migration and is in phase I clinical trial as a chemotherapeutic for patients with recurrent GBM. We now investigate if VP is an effective photosensitizer for PDT in GBM and if it enhances the effects of TMZ and RT. Compared to VP alone, VP+PDT reduced the IC50 of VP treatment in GBM cells +/- EGFR amplification. Light activation of VP has a significant antitumor effect as observed with cytotoxicity in comparison to vehicle and VP treated cells (p&lt; 0.01). Compared to control, VP, VP+PDT+TMZ, and CRT show significantly less intravasation (p&lt; 0.01). Furthermore, Western blot analysis shows differential expression of YAP, TAZ and TEAD compared to Control and VP after treatment with VP+PDT. Differential YAP signaling is observed via IF staining in EGFR+ GBM cells treat with VP+PDT. Our research supports the use of VP as a photosensitizer in GBM cells. We found downregulation of the hippo pathway and decrease tumorigenicity of GBM cells. Application of VP-PDT treatment in combination with standard of care may be proven beneficial in GBM patients. We plan to further explore these in vitro findings in mice models and investigate other pathways including immune response with NanoString analysis.

Identifying risk factors for postoperative diabetes insipidus in more than 2500 patients undergoing transsphenoidal surgery: a single-institution experience

OBJECTIVE

Diabetes insipidus (DI) following transsphenoidal surgery can adversely impact quality of life and be difficult to manage. This study sought to characterize pre- and perioperative risk factors that may predispose patients to DI after pituitary surgery.

METHODS

A retrospective review of patients treated at a single institution from 2007 to 2019 was conducted. DI was defined as postoperative sodium > 145 mEq/L and urine output > 300 ml/hr and/or postoperative desmopressin (ddAVP) use. DI was further characterized as transient or permanent. Uni- and multivariate analyses were performed to determine variables associated with postoperative DI.

RESULTS

The authors identified 2529 patients who underwent transsphenoidal surgery at their institution. Overall, DI was observed in 270 (10.7%) of the 2529 patients, with 114 (4.5%) having permanent DI and 156 (6.2%) with transient symptoms. By pathology type, DI occurred in 31 (46.3%) of 67 craniopharyngiomas, 10 (14.3%) of 70 apoplexies, 46 (14.3%) of 322 Rathke's cleft cysts, 77 (7.7%) of 1004 nonfunctioning pituitary adenomas (NFPAs), and 62 (7.6%) of 811 functioning pituitary adenomas (FPAs). Final lesion pathology significantly affected DI rates (p < 0.001). Multivariate analysis across pathologies showed that younger age (odds ratio [OR] 0.97, p < 0.001), intraoperative CSF encounter (OR 2.74, p < 0.001), craniopharyngioma diagnosis (OR 8.22, p = 0.007), and postoperative hyponatremia (OR 1.50, p = 0.049) increased the risk of DI. Because surgery for each pathology created specific risk factors for DI, the analysis was then limited to the 1815 pituitary adenomas (PAs) in the series, comprising 1004 NFPAs and 811 FPAs. For PAs, younger age (PA: OR 0.97, p < 0.001; NFPA: OR 0.97, p < 0.001; FPA: OR 0.97, p = 0.028) and intraoperative CSF encounter (PA: OR 2.99, p < 0.001; NFPA: OR 2.93, p < 0.001; FPA: OR 3.06, p < 0.001) increased DI rates in multivariate analysis. Among all PAs, patients with DI experienced peak sodium levels later than those without DI (postoperative day 11 vs 2). Increasing tumor diameter increased the risk of DI in FPAs (OR 1.52, p = 0.008), but not in NFPAs (p = 0.564).

CONCLUSIONS

In more than 2500 patients treated at a single institution, intraoperative CSF encounter, craniopharyngioma diagnosis, and young age all increased the risk of postoperative DI. Patients with postoperative hyponatremia exhibited higher rates of DI, suggesting possible bi- or triphasic patterns to DI. Greater vigilance should be maintained in patients meeting these criteria following transsphenoidal surgery to ensure early recognition and treatment of DI.

EXTH-04. ELUCIDATING THE PLEIOTROPIC EFFECTS OF VERTEPORFIN PHOTODYNAMIC THERAPY IN PRECLINICAL GLIOBLASTOMA MODELS

Glioblastoma (GBM) has the highest mortality rate, incidence, and therapy resistance of all primary brain tumors. Deregulation of the epidermal growth factor receptor (EGFR) has been implicated in GBM tumorigenesis. The expression of EGFR has been linked to hippo pathway transcriptional co-activators YAP and TAZ that bind to TEAD co-factors to drive the transcription of target genes. The convergence of EGFR signaling and the hippo pathway regulates stem cell programs, including proliferation, survival, and self-renewal. Verteporfin (VP), is an FDA-approved drug for photodynamic therapy (PDT) of macular degeneration. VP has been shown to have antitumor effects both in vitro and in vivo in GBM preclinical models. As a porphyrin derivative, VP can also exert therapeutic and photodynamic effects in the presence of 689 nm light; however, the efficacy of VP-PDT has not been explored in GBM. Our results indicate for the first time that VP-PDT reduces GBM cell viability to a greater extent than VP treatment alone (viability — 0.7 uM VP: 97%, 0.7 uM VP-PDT: 46%). The antitumor effects of VP-PDT are two pronged involving 1) inhibition of live cell dynamics, including migration and intravasation, by downregulating hippo pathway constituents YAP, TAZ and TEAD and transcriptional target EGFR and 2) induction of programmed cell death by reactive oxygen species. Our results suggest that VP-PDT can be a potential avenue for treating these incurable tumors.

ITVT-02. Elucidating the pleiotropic effects of verteporfin photodynamic therapy in preclinical glioblastoma models

Glioblastoma (GBM) ranks the highest in mortality rate, incidence, and aggressiveness of primary brain tumor types. The highly malignant nature of GBM makes it difficult for mainstay treatments to have an effect beyond stabilizing the disease. Deregulation of receptor tyrosine kinase (RTKs), such as EGFR and PI3K, have been implicated in GBM tumorigenesis. The expression of EGFR has been linked to hippo pathway transcriptional co-activators YAP and TAZ that bind to TEAD co-factors to drive the transcription of target genes. The convergence of EGFR signaling and the hippo pathway regulates stem cell programs, including proliferation, survival, and self-renewal. Verteporfin (VP), an FDA-approved macular degeneration therapy, has antitumor effects in in vitro and in vivo GBM preclinical models and phase I/II clinical trials for patients with EGFR mutated/amplified GBM by abrogating YAP/TAZ-TEAD interactions. As a porphyrin derivative, VP can exert therapeutic and photodynamic effects in the presence of 689 nm light; however, the efficacy of VP-PDT has not been explored in GBM. Our results indicate that VP-PDT reduces cell viability to a greater extent than solitary VP treatment (viability — 0.7 uM VP: 97%, 0.7 uM VP-PDT: 46%). The antitumor effects of VP-PDT are two pronged involving 1) inhibition of live cell dynamics, including migration and intravasation, by downregulating hippo pathway constituents YAP, TAZ and TEAD and transcriptional target EGFR and 2) induction of programmed cell death by reactive oxygen species. Our results suggest that VP-PDT can be a potential avenue for treating these incurable tumors.

ATRX regulates glial identity and the tumor microenvironment in IDH-mutant glioma

BACKGROUND

Recent single-cell transcriptomic studies report that IDH-mutant gliomas share a common hierarchy of cellular phenotypes, independent of genetic subtype. However, the genetic differences between IDH-mutant glioma subtypes are prognostic, predictive of response to chemotherapy, and correlate with distinct tumor microenvironments.

RESULTS

To reconcile these findings, we profile 22 human IDH-mutant gliomas using scATAC-seq and scRNA-seq. We determine the cell-type-specific differences in transcription factor expression and associated regulatory grammars between IDH-mutant glioma subtypes. We find that while IDH-mutant gliomas do share a common distribution of cell types, there are significant differences in the expression and targeting of transcription factors that regulate glial identity and cytokine elaboration. We knock out the chromatin remodeler ATRX, which suffers loss-of-function alterations in most IDH-mutant astrocytomas, in an IDH-mutant immunocompetent intracranial murine model. We find that both human ATRX-mutant gliomas and murine ATRX-knockout gliomas are more heavily infiltrated by immunosuppressive monocytic-lineage cells derived from circulation than ATRX-intact gliomas, in an IDH-mutant background. ATRX knockout in murine glioma recapitulates gene expression and open chromatin signatures that are specific to human ATRX-mutant astrocytomas, including drivers of astrocytic lineage and immune-cell chemotaxis. Through single-cell cleavage under targets and tagmentation assays and meta-analysis of public data, we show that ATRX loss leads to a global depletion in CCCTC-binding factor association with DNA, gene dysregulation along associated chromatin loops, and protection from therapy-induced senescence.

CONCLUSIONS

These studies explain how IDH-mutant gliomas from different subtypes maintain distinct phenotypes and tumor microenvironments despite a common lineage hierarchy.

Abstract 2124: Vitamin C enhances H3K36me3 via NSD1 promoter demethylation and sensitizes GBM stem cells to DNA damaging agents

Primary brain tumors are among the most devastating forms of cancer. Due to profound genetic, epigenetic, and morphologic heterogeneity, GBM represents the most aggressive and lethal form of the disease. GBM exhibits aberrant patterns of DNA methylation, resulting in a highly distorted epigenome, yet the molecular circuits responsible for this epigenetic dysregulation remain unknown. Glioma stem cells (GSCs) are critical modulators of tumor propagation and therapeutic resistance in GBM, and epigenetic deregulation within this cell subpopulation is thought to play fundamental roles in GSC and GBM biology. Understanding and overcoming these tumorigenic epigenetic mechanisms in GSCs is crucial to developing more effective treatment protocols and improving clinical survival. DNA methylation is a reversible process involving the addition of methyl groups, typically, at cytosine residues and demethylation is catalyzed, in part, by the ten-eleven translocation (TET) family of enzymes. These enzymes function as deoxygenases that convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Multiple studies show negative correlations between 5hmC levels and glioma grade, and loss of 5hmC correlates with poor prognosis of GBM patients. These observations suggest that understanding the mechanisms of 5hmC deregulation in GBM and developing innovative ways to re-establish 5hmC levels in tumors can impact patient outcome. Ascorbate (Vitamin C) is a TET enzyme cofactor that has gained pre-clinical interest as an attractive antitumor agent for GBM due to its ability to regulate redox status, function as potent demethylating agent, and efficiently penetrate the blood-brain barrier. We show through various molecular and biochemical endpoints, that low-dose Vitamin C significantly replenishes 5hmC and decreases stemness in GSCs. We found that, in addition to increasing global levels of 5hmC, low-dose Vitamin C acts synergistically with temozolomide (TMZ) and irradiation to induce cell death in GSCs. We also present a novel mechanism whereby Vitamin C regulates promoter demethylation of the histone methyltransferase NSD1 resulting in an increase in H3K36me3 in GSCs. We propose the increase in H3K36me3 results in euchromatin states that are more susceptible to DNA damage therapies. Our findings strongly indicate that Vitamin C can undo tumor-promoting DNA hypermethylation and sensitize GSCs to conventional radio- and chemotherapeutics and suggest it might serve as an adjunct to standard-of-care GBM treatment.

Citation Format: Harmon Khela, Sweta Sudhir, Maria Fagundo-Lugo, Bachchu Lal, John Laterra, Hernando Lopez-Bertoni. Vitamin C enhances H3K36me3 via NSD1 promoter demethylation and sensitizes GBM stem cells to DNA damaging agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2124.

Role of c-Met/β1 integrin complex in the metastatic cascade in breast cancer

Metastases cause 90% of human cancer deaths. The metastatic cascade involves local invasion, intravasation, extravasation, metastatic site colonization, and proliferation. Although individual mediators of these processes have been investigated, interactions between these mediators remain less well defined. We previously identified a complex between receptor tyrosine kinase c-Met and β1 integrin in metastases. Using cell culture and in vivo assays, we found that c-Met/β1 complex induction promoted intravasation and vessel wall adhesion in triple-negative breast cancer cells, but did not increase extravasation. These effects may have been driven by the ability of the c-Met/β1 complex to increase mesenchymal and stem cell characteristics. Multiplex transcriptomic analysis revealed upregulated Wnt and hedgehog pathways after c-Met/β1 complex induction. A β1 integrin point mutation that prevented binding to c-Met reduced intravasation. OS2966, a therapeutic antibody disrupting c-Met/β1 binding, decreased breast cancer cell invasion and mesenchymal gene expression. Bone-seeking breast cancer cells exhibited higher levels of c-Met/β1 complex than parental controls and preferentially adhered to tissue-specific matrix. Patient bone metastases demonstrated higher c-Met/β1 complex than brain metastases. Thus, the c-Met/β1 complex drove intravasation of triple-negative breast cancer cells and preferential affinity for bone-specific matrix. Pharmacological targeting of the complex may have prevented metastases, particularly osseous metastases.

Clinical characteristics and outcomes of null-cell versus silent gonadotroph adenomas in a series of 1166 pituitary adenomas from a single institution

OBJECTIVE

Nonfunctioning pituitary adenomas present without biochemical or clinical signs of hormone excess and are the second most common type of pituitary adenomas. The 2017 WHO classification scheme of pituitary adenomas differentiates null-cell adenomas (NCAs) and silent gonadotroph adenomas (SGAs). The present study sought to highlight the differences in patient characteristics and clinical outcomes between NCAs and SGAs.

METHODS

The records of 1166 patients who underwent transsphenoidal surgery for pituitary adenoma between 2012 and 2019 at a single institution were retrospectively reviewed. Patient demographics and clinical outcomes were collected.

RESULTS

Of the overall pituitary adenoma cohort, 12.8% (n = 149) were SGAs and 9.2% (n = 107) NCAs. NCAs were significantly more common in female patients than SGAs (61.7% vs 26.8%, p < 0.001). There were no differences in patient demographics, initial tumor size, or perioperative and short-term clinical outcomes. There was no significant difference in the amount of follow-up between patients with NCAs and those with SGAs (33.8 months vs 29.1 months, p = 0.237). Patients with NCAs had significantly higher recurrence (p = 0.021), adjuvant radiation therapy usage (p = 0.002), and postoperative diabetes insipidus (p = 0.028). NCA pathology was independently associated with tumor recurrence (HR 3.64, 95% CI 1.07-12.30; p = 0.038), as were cavernous sinus invasion (HR 3.97, 95% CI 1.04-15.14; p = 0.043) and anteroposterior dimension of the tumor (HR 2.23, 95% CI 1.09-4.59; p = 0.030).

CONCLUSIONS

This study supports the definition of NCAs and SGAs as separate subgroups of nonfunctioning pituitary adenomas, and it highlights significant differences in long-term clinical outcomes, including tumor recurrence and the associated need for adjuvant radiation therapy, as well as postoperative diabetes insipidus. The authors also provide insight into independent risk factors for these outcomes in the adenoma population studied, providing clinicians with additional predictors of patient outcomes. Follow-up studies will hopefully uncover mechanisms of biological aggressiveness in NCAs and associated molecular targets.

Plurihormonal PIT-1-Positive Pituitary Adenomas: A Systematic Review and Single-Center Series

OBJECTIVE

The 2017 World Health Organization classification of pituitary adenomas identified the plurihormonal PIT-1-positive (PP1) adenoma as a distinct subtype. The reported data suggest that PP1 adenomas encompass the former class of silent subtype 3 (SS3) adenomas and might have an aggressive phenotype. In the present study, we summarized the current clinical data on PP1 and SS3 adenomas and compared the reported data with the data from a single institutional cohort.

METHODS

Medline and Google Scholar were searched from 1990 to 2020 for clinical series of PP1 and SS3 adenomas in accordance with the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. Studies were included if they had reported pituitary pathology as PP1 or SS3 adenomas and had reported the clinical outcomes after surgical intervention. To better define the PP1 phenotype compared with non-PP1 adenomas, we also reviewed the adenomas treated surgically at our institution from 2012 to 2019.

RESULTS

Of all the tumors reported in the studies as PP1 or SS3, 99% were macroadenomas and 18% were giant adenomas (>4 cm). Of the reported patients, 31.8% had received radiotherapy, and 22.9% had undergone multiple surgeries for their pituitary tumor. In our single-center experience, 20 patients had an adenoma that met the criteria for a PP1 adenoma. Compared with the 1146 non-PP1 tumors, the PP1 tumors did not show statistically significant differences in the extent of resection, size, number of previous surgeries, future reoperations, rate of radiotherapy, p53 staining, or MIB-1 labeling index.

CONCLUSIONS

The findings from the present large, single-center study comparing PP1 and non-PP1 adenomas do not suggest that PP1 tumors are more aggressive. Further work is warranted to identify the pathologic subtypes of pituitary adenomas that are consistently more clinically aggressive.

The Role of Cancer-Associated Fibroblasts in Tumor Progression

In the era of genomic medicine, cancer treatment has become more personalized as novel therapeutic targets and pathways are identified. Research over the past decade has shown the increasing importance of how the tumor microenvironment (TME) and the extracellular matrix (ECM), which is a major structural component of the TME, regulate oncogenic functions including tumor progression, metastasis, angiogenesis, therapy resistance, and immune cell modulation, amongst others. Within the TME, cancer-associated fibroblasts (CAFs) have been identified in several systemic cancers as critical regulators of the malignant cancer phenotype. This review of the literature comprehensively profiles the roles of CAFs implicated in gastrointestinal, endocrine, head and neck, skin, genitourinary, lung, and breast cancers. The ubiquitous presence of CAFs highlights their significance as modulators of cancer progression and has led to the subsequent characterization of potential therapeutic targets, which may help advance the cancer treatment paradigm to determine the next generation of cancer therapy. The aim of this review is to provide a detailed overview of the key roles that CAFs play in the scope of systemic disease, the mechanisms by which they enhance protumoral effects, and the primary CAF-related markers that may offer potential targets for novel therapeutics.

NCOG-51. CORRELATION BETWEEN TUMOR VOLUME AND SERUM PROLACTIN AND IMPACT OF TUMOR CELLULAR DENSITY ON PROLACTINOMA SURGICAL OUTCOMES IN A COHORT OF 181 PATIENTS

INTRODUCTION

Prolactinomas are common pituitary adenomas managed medically or surgically.

METHODS

Reviewed 181 prolactinomas resected transsphenoidally 2012-2019. Tumor volumes were quantified using BrainLab Smartbrush. Pearson correlation analysis and linear regression were used to identify associations between tumor volumes and serum prolactin. Tumor density was defined as serum prolactin divided by tumor volume.

RESULTS

Mean tumor volume was 6.33cm3 and mean pre-op prolactin was 803.4ug/L, with men having larger (12.11 vs 2.93cm3;p&lt; 0.001) and women having denser (173.9 vs 107.6ug/L/cm3;p=0.011) prolactinomas. Pearson correlation (R=0.688;p&lt; 0.001) and linear regression revealed a strong association between pre-op volume and prolactin levels, with 96.9g/L increase in prolactin/cm3 increase in volume (p&lt; 0.001); this holds true for men (R=0.584;p&lt; 0.001) and women (R=0.939;p&lt; 0.001), with women demonstrating greater prolactin/cm3 tumor density (186.5 vs 75.0ug/L;p&lt; 0.001). MiB index did not correlate with pre-op volume (p=0.449) or pre-op prolactin (p=0.452). Logistic regression showed decreased biochemical remission with increasing pre-op volume (OR=0.891;p&lt; 0.001). Increased MiB index (p=0.971) and p53 (p=0.525) staining did not affect remission rates. Positive PIT-1 staining was associated with higher remission rates (OR=2.508;p=0.005). Patients without remission had denser tumors (149.9 vs. 100.6ug/L/cm3;p=0.013), with Pearson correlation yielding R=0.736 between pre-op volume and pre-op prolactin (p&lt; 0.001), and R=0.476 between residual volume and post-op prolactin (p&lt; 0.001). Patients without remission exhibited 142.9ug/L increase in prolactin/cm3 of pre-op volume (p&lt; 0.001), higher than the 58.9ug/L increase in prolactin/cm3 in patients with remission (p&lt; 0.001). Patients without remission had residual tumors with 68.4ug/L increase in prolactin/cm3 of remaining volume after resection (p&lt; 0.001).

CONCLUSION

Our analysis revealed significant correlation between prolactinoma volume and serum prolactin levels. Patients without remission had greater tumor cellular density than those with remission. The volume-prolactin correlation persisted post-operatively, although surgery reduced tumor density. These results could identify prolactinomas for which surgery could achieve biochemical remission.

EPCO-17. A SINGLE-CELL ATLAS OF GLIOBLASTOMA EVOLUTION UNDER THERAPY

Most clinical trials for glioblastoma (GBM) enroll patients at recurrence. However, most pre-clinical animal models are of primary disease. Most studies have used tissues from primary tumors. Knowledge of GBM cellular composition at recurrence is limited. We profiled 80 human IDH-wild-type GBM specimens via single-nucleus RNA sequencing, 40 primary tumors and 40 patient-matched recurrent tumors. Select cohorts were also profiled via single-cell assay for transposase-accessible chromatin, single-cell digital-spatial, and single-cell spatial-transcriptomic assays. All patients were treated only with standard-of-care therapy: temozolomide, radiation and surgical resection. The cohort had a 1.2 male/female ratio, ages 35–76. We found a significant increase at recurrence in cells with the Verhaak mesenchymal phenotype and fewer proneural cells. Although there was an increase in the percentage of cycling cells overall, the fraction of cycling proneural cells decreased while the fraction of cycling mesenchymal cells increased. These changes were concomitant with a significant increase in the percentage of tumor-infiltrating monocytic-lineage cells derived from the periphery. Taken together, these findings support a proneural-to-mesenchymal shift at recurrence due to an increase in the birth rate of mesenchymal cells, supported by an expansion of myeloid-derived cells from peripheral blood. Although the percentages of glioblastoma-infiltrating T-cells are generally low (~1% on average in our data), we found a statistically significant increase in T-cell abundance at recurrence. We identified a cohort of T-cell outliers that demonstrate 2-to-8-fold increases in T-cells over average levels. We validated that T-cells in these tumors have extravasated beyond the perivascular space and into the cellular tumor via immunohistochemistry and single-cell spatial profiling. We present our ongoing analysis of the paracrine signals, upstream transcription-factor expression, and cis-regulatory grammars utilized in immune-outlier GBMs. We describe how these programs change under therapy. These studies shed light on the effect of standard therapy in shaping GBM composition at recurrence.

CSIG-04. ROLE OF c-Met/β1 INTEGRIN COMPLEX IN THE METASTATIC CASCADE

Metastases cause 90% of human cancer deaths. The metastatic cascade involves 5 steps: local invasion, intravasation, extravasation, metastatic site colonization, and proliferation. While individual mediators of these processes have been investigated, interactions between these mediators remain less well defined. We previously identified a structural complex between receptor tyrosine kinase c-Met and β1 integrin in metastases that form under certain biological and therapeutic inducers, including bevacizumab. Using novel cell culture and in vivo assays, we found that c-Met/β1 complex induction promotes breast cancer intravasation and adhesion to the vessel wall but does not increase extravasation. These effects may be driven by the ability of the c-Met/β1 complex to increase mesenchymal and stem cell characteristics in breast cancer cells. Multiplex transcriptomic analysis revealed upregulated Wnt and hedgehog pathways after c-Met/β1 complex induction in breast cancer cells. We subsequently used CRISPR to introduce a β1 integrin point mutation that prevented binding to c-Met and led to reduced intravasation, confirming the importance of c-Met/β1 integrin binding for the metastatic cascade. OS2966, a therapeutic B1 integrin blocking antibody, disrupted c-Met/β1 binding as well, and decreased invasion, mesenchymal gene expression, and mesenchymal morphology of breast cancer cells. Bone-seeking breast cancer cells exhibited higher c-Met/β1 complex levels than parental controls and preferentially adhere to tissue-specific matrix. Patient bone metastases demonstrated higher c-Met/β1 complex levels than brain metastases. Thus, our research suggests the c-Met/β1 complex drives breast cancer cell intravasation and preferential affinity for bone tissue-specific matrix. Pharmacological targeting of the complex may prevent metastases, particularly osseous metastases.

PATH-37. IDENTIFYING HIGH-RISK PATIENTS FOR WHO GRADE I MENINGIOMA RECURRENCE USING HISTOPATHOLOGICAL FEATURES AND THE MIB-1 INDEX

BACKGROUND

In this study, we identify clinical, radiographic, and histopathologic prognosticators of overall, early, and post-median recurrence in World Health Organization (WHO) grade I meningiomas. We also determine a clinically relevant cutoff for MIB-1 to identify patients at high risk for recurrence.

METHODS

A retrospective review of WHO grade I meningioma patients with available MIB-1 index data who underwent treatment at our institution from 2007-2017 was performed. Univariate and multivariate analyses, and recursive partitioning analysis (RPA), were used to identify risk factors for overall, early (within 24 months), and post-median (greater than 24 months post-treatment) recurrence.

RESULTS

A total of 239 patients were included. The mean age was 60.0 years, and 69.5% of patients were female. The average follow-up was 41.1 months. All patients received surgery and 2 patients each received either adjuvant radiotherapy or gamma knife treatment. The incidence of recurrence was 10.9%, with an average time to recurrence of 33.2 months (6-105 months). Posterior fossa tumor location (p=0.004), MIB-1 staining (p=0.008), nuclear atypia (p=0.003), and STR (p&lt; 0.001) were independently associated with an increased risk of recurrence on cox-regression analysis. RPA for overall recurrence highlighted extent of resection, and after gross total resection (GTR), a MIB-1 index cutoff of 4.5% as key prognostic factors for recurrence. Patients with a GTR and MIB-1 &gt;4.5% had a similar incidence of recurrence as those with STR (18.8vs.18.6%). Variables independently associated with early recurrence on binary logistic regression modeling included STR (p=0.002) and nuclear atypia (p=0.019). RPA confirmed STR as associated with early recurrence. MIB-1 index (p=0.010) was identified as an independent predictor of post-median recurrence using similar methods.

CONCLUSIONS

STR, posterior fossa location, nuclear atypia, and elevated MIB-1 index are prognostic factors for WHO grade I meningioma recurrence. Moreover, MIB-1 index &gt;4.5% is prognostic for recurrence in patients with GTR.

NCOG-54. SAFETY OF TRANSSPHENOIDAL SURGERY FOR NONFUNCTIONING PITUITARY ADENOMA IN ELDERLY PATIENTS

INTRODUCTION

Life expectancy has increased over the past century, shifting the demographic distribution towards older age groups. Elderly patients comprise up to 14% of patients with pituitary tumors, with most lesions being nonfunctioning adenomas (NFPAs). Here, we compare clinical and surgical outcomes and post-operative complications between non-elderly adult (age ≥ 18 years and ≤ 65 years) and elderly (age &gt; 65 years) NFPA patients.

METHODS

Retrospective review of 908 patients undergoing transsphenoidal surgery for NFPA at a single institution from 2007-2019.

RESULTS

Elderly patients represented 32.4% of patients. Both groups were similar in gender (57.3% vs 60.5% male;P=0.4), tumor size (2.56 vs 2.46 cm;P=0.2), and cavernous sinus invasion (35.8% vs 33.7%;P=0.6). Regarding post-operative outcomes, length of stay (1 vs 2 days; P=0.5), extent of resection (59.8% vs 64.8% GTR;P=0.2), CSF leak requiring surgical revision (4.3% vs 1.4%;P=0.06), 30-day readmission (8.1% vs 7.3%;P=0.7), infection (3.1% vs 2.0%;P=0.5), and new hypopituitarism (13.9% vs 12.0%;P=0.3) were similar between both groups. Elderly patients were less likely to have adjuvant radiation (8.7% vs 16.3%;P=0.009), future re-operation (3.8% vs 9.5%;P=0.003), and post-operative diabetes insipidus (DI) (3.7% vs 9.4%;P=0.002), and more likely to have post-operative hyponatremia (26.7% vs 16.4%;P&lt; 0.001) and new cranial nerve deficit (1.9% vs 0.0%;P=0.01). Elderly patients’ post-operative sodium peaked and troughed on POD3 (mean=138.7 mEq/L) and POD9 (mean=130.8 mEq/L), respectively, compared to non-elderly patients (peak POD2 mean=139.9 mEq/L, trough POD8 mean=131.3 mEq/L).

CONCLUSION

Our analysis revealed that elderly patients experienced more post-operative hyponatremia, while non-elderly patients experienced more post-operative DI. Elderly patients also experience later peak and trough in serum sodium, suggesting age-related differences in stalk-related morbidities of NFPA resection. Overall, our results show that transsphenoidal surgery for NFPA in elderly patients is safe with low complication rates. We hope our results will guide discussions with elderly patients regarding possible risks and outcomes.

STEM-27. miR-10b-5p MODULATES 5hmC EXPRESSION AND THE STEM-LIKE PHENOTYPE IN GBM

Epigenetic alterations such as DNA methylation and dysregulation of non-coding RNAs (e.g. miRNAs) are found in all types of cancer and are thought to play important roles in tumorigenesis. GBM is characterized by small subsets of cells, referred to as glioma stem cells (GSCs), that display stem-like properties implicated in tumor initiation, therapeutic resistance, and recurrence. DNA methylation patterns are altered in GBM and GSCs and are thought to play critical roles in tumor initiation and propagation. DNA methylation is a reversible process catalyzed, in part, by the ten-eleven translocation (TET) family of enzymes. These enzymes function as deoxygenases that catalyze the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Multiple studies found negative correlations between 5hmC levels and glioma grade and loss of 5hmC correlates with poor prognosis of GBM patients. However, the mechanisms leading to the loss of 5hmC in glioma and the role this phenomenon plays in gliomagenesis remains poorly understood. We found that Sox2 expression decreases TET2 expression and its product 5hmC in GSCs and identified miR-10b-5p as a molecular intermediary of this process. We show that miR-10b-5p expression is high in GBM compared to non-tumor in clinical specimens and high levels of this miRNA correlate with poor patient outcome. Expression of transgenic miR-10b-5p enhanced sphere formation capacity of GSCs and the expression of stem cell markers and drivers. Additionally, using a combination of molecular and biochemical endpoints, we show that miR-10b-5p modifies 5hmC levels by regulating TET2 in GSCs. Finally, we show that repression of miR-10b-5p increases 5hmC levels and inhibits tumor propagation in GBM xenograft models. Taken together, these results present a new molecular mechanism that controls 5hmC and the tumor propagating capacity of GSCs and suggests that miR-10b-5p inhibition and other strategies for enhancing TET2 function can be developed to treat GBM.

EPCO-32. AN EPIGENETIC SINGLE-CELL ATLAS OF IDH-MUTANT GLIOMA REVEALS THE ROLE OF ATRX IN SHAPING TUMOR COMPOSITION

Recent single-cell RNA-sequencing studies have identified a hierarchy of cell types that is common to all isocitrate dehydrogenase (IDH) -mutant gliomas. This finding is somewhat paradoxical since the genetic differences between IDH-mutant astrocytomas and IDH-mutant oligodendrogliomas are prognostic, predictive of therapeutic response, and correlated with differences in immune infiltrates. To integrate these disparate findings, we constructed a single-cell atlas of 28 human IDH-mutant primary untreated grade-II/III gliomas. All specimens were profiled by single-cell assay for transposase-accessible chromatin, with additional cohorts profiled via single-cell RNA-sequencing and single-cell spatial proteomics. We determined the cell-type specific differences between IDH-mutant gliomas in transcription-factor utilization, associated targeting and cis-regulatory grammars. To elucidate the role of the chromatin remodeler ATRX (inactivated in over 86% of IDH-mutant astrocytomas) in shaping observed differences in open chromatin, we knocked out ATRX in an immunocompetent model of IDH-mutant glioma and subjected murine tumors to single-cell profiling. We found: 1. ATRX-deficient, IDH-mutant human and murine gliomas both upregulate an astrocytic regulatory program driven by Nuclear Factor I genes and downregulate an oligodendrocytic program driven by basic helix-loop-helix transcription factors. 2. Both human and mouse ATRX-deficient, IDH-mutant gliomas up-regulate genes that promote myeloid-cell chemotaxis and both have significantly higher percentages of myeloid-derived immune-suppressive cells than controls; 3. A transcription-factor program is conserved between human and murine ATRX-deficient tumors that shapes glial identity and promotes local immunosuppression. These studies elucidate how IDH-mutant gliomas from different subtypes can have distinct cellular morphologies and tumor micronenvironments despite a common lineage hierarchy.

Clinical characteristics and outcomes in elderly patients undergoing transsphenoidal surgery for nonfunctioning pituitary adenoma

OBJECTIVE

Life expectancy has increased over the past century, causing a shift in the demographic distribution toward older age groups. Elderly patients comprise up to 14% of all patients with pituitary tumors, with most lesions being nonfunctioning pituitary adenomas (NFPAs). Here, the authors evaluated demographics, outcomes, and postoperative complications between nonelderly adult and elderly NFPA patients.

METHODS

A retrospective review of 908 patients undergoing transsphenoidal surgery (TSS) for NFPA at a single institution from 2007 to 2019 was conducted. Clinical and surgical outcomes and postoperative complications were compared between nonelderly adult (age ≥ 18 and ≤ 65 years) and elderly patients (age > 65 years).

RESULTS

There were 614 and 294 patients in the nonelderly and elderly groups, respectively. Both groups were similar in sex (57.3% vs 60.5% males; p = 0.4), tumor size (2.56 vs 2.46 cm; p = 0.2), and cavernous sinus invasion (35.8% vs 33.7%; p = 0.6). Regarding postoperative outcomes, length of stay (1 vs 2 days; p = 0.5), extent of resection (59.8% vs 64.8% gross-total resection; p = 0.2), CSF leak requiring surgical revision (4.3% vs 1.4%; p = 0.06), 30-day readmission (8.1% vs 7.3%; p = 0.7), infection (3.1% vs 2.0%; p = 0.5), and new hypopituitarism (13.9% vs 12.0%; p = 0.3) were similar between both groups. Elderly patients were less likely to receive adjuvant radiation (8.7% vs 16.3%; p = 0.009), undergo future reoperation (3.8% vs 9.5%; p = 0.003), and experience postoperative diabetes insipidus (DI) (3.7% vs 9.4%; p = 0.002), and more likely to have postoperative hyponatremia (26.7% vs 16.4%; p < 0.001) and new cranial nerve deficit (1.9% vs 0.0%; p = 0.01). Subanalysis of elderly patients showed that patients with higher Charlson Comorbidity Index scores had comparable outcomes other than higher DI rates (8.1% vs 0.0%; p = 0.006). Elderly patients’ postoperative sodium peaked and troughed on postoperative day 3 (POD3) (mean 138.7 mEq/L) and POD9 (mean 130.8 mEq/L), respectively, compared with nonelderly patients (peak POD2: mean 139.9 mEq/L; trough POD8: mean 131.3 mEq/L).

CONCLUSIONS

The authors’ analysis revealed that TSS for NFPA in elderly patients is safe with low complication rates. In this cohort, more elderly patients experienced postoperative hyponatremia, while more nonelderly patients experienced postoperative DI. These findings, combined with the observation of higher DI in patients with more comorbidities and elderly patients experiencing later peaks and troughs in serum sodium, suggest age-related differences in sodium regulation after NFPA resection. The authors hope that their results will help guide discussions with elderly patients regarding risks and outcomes of TSS.

WHO Grade I Meningioma Recurrence: Identifying High Risk Patients Using Histopathological Features and the MIB-1 Index

Objective: In this study, we identify clinical, radiographic, and histopathologic prognosticators of overall, early, and post-median recurrence in World Health Organization (WHO) grade I meningiomas. We also determine a clinically relevant cutoff for MIB-1 to identify patients at high risk for recurrence.

Method: A retrospective review of WHO grade I meningioma patients with available MIB-1 index data who underwent treatment at our institution from 2007 to 2017 was performed. Univariate and multivariate analyses, and recursive partitioning analysis (RPA), were used to identify risk factors for overall, early (within 24 months), and post-median (>24 months post-treatment) recurrence.

Result: A total of 239 patients were included. The mean age was 60.0 years, and 69.5% of patients were female. The average follow-up was 41.1 months. All patients received surgery and 2 patients each received either adjuvant radiotherapy (2/239) or gamma knife treatment (2/239). The incidence of recurrence was 10.9% (26/239 patients), with an average time to recurrence of 33.2 months (6–105 months). Posterior fossa tumor location (p = 0.004), MIB-1 staining (p = 0.008), nuclear atypia (p = 0.003), and STR (p < 0.001) were independently associated with an increased risk of recurrence on cox-regression analysis. RPA for overall recurrence highlighted extent of resection, and after gross total resection (GTR), a MIB-1 index cutoff of 4.5% as key prognostic factors for recurrence. Patients with a GTR and MIB-1 >4.5% had a similar incidence of recurrence as those with STR (18.8 vs. 18.6%). Variables independently associated with early recurrence on binary logistic regression modeling included STR (p = 0.002) and nuclear atypia (p = 0.019). RPA confirmed STR as associated with early recurrence.

Conclusion: STR, posterior fossa location, nuclear atypia, and elevated MIB-1 index are prognostic factors for WHO grade I meningioma recurrence. Moreover, MIB-1 index >4.5% is prognostic for recurrence in patients with GTR. Verification of our findings in larger, multi-institutional studies could enable risk stratification and recommendations for adjuvant radiotherapy following resection of WHO grade I meningiomas.

CSIG-10. ROLE OF c-Met/β1 INTEGRIN COMPLEX IN THE ESTABLISHMENT OF BRAIN METASTASES

INTRODUCTION

Metastases cause 90% of human cancer deaths. The metastatic cascade involves five steps: invasion, intravasation, extravasation, colonization, and proliferation. While individual mediators of these processes have been investigated, their interactions remain undefined. We previously demonstrated increased formation of a structural complex between receptor tyrosine kinase c-Met and β1 integrin in metastases compared to primary tumors. We used novel cell culture models and in vivo assays to define the role of this complex in individual steps of the metastatic cascade.

METHODS

The iDimerize heterodimer system was inserted into MDA-MB-231 breast adenocarcinoma cells, allowing c-Met/β1 heterodimerization induction via A/C heterodimerizer treatment. Scratch assays and novel transwell assay modifications were used to measure migration, invasion, intravasation, and extravasation. Proximity ligation assay was performed to measure c-Met/β1 complex. Nanostring panel was used to transcriptionally profile cells.

RESULTS

c-Met/β1 complex induction promotes breast cancer invasion (p< 0.001), migration (p< 0.05), intravasation (p< 0.01), and adhesion to the vessel wall (p< 0.01). However, it does not increase extravasation in culture or in vivo. These effects may be driven by the ability of c-Met/β1 to increase mesenchymal character (p< 0.05) and stem cell population (p< 0.001). Nanostring analysis revealed upregulated Wnt and hedgehog pathways after c-Met/β1 complex induction, particularly WNT7B (p< 0.05). OS2966, an antibody preventing c-Met/β1 binding, decreased invasion (p< 0.05), intravasation (p< 0.05), and mesenchymal morphology (p< 0.001) and gene expression (p< 0.001). Brain- and bone-seeking breast cancer cells have higher c-Met/β1 complex than controls (p< 0.05) and preferentially adhere to tissue-specific matrix (p< 0.01).

CONCLUSIONS

The c-Met/β1 complex drives breast cancer cell intravasation. While extravasation is not affected by the complex, preferential affinity for tissue-specific matrix enables the c-Met/β1 complex to drive breast cancer metastases to brain and bone. Pharmacological targeting of the complex may prevent metastases, particularly to the brain and bone.

Abstract 829: SOX2-mediated 5hmC dysregulation in GBM stem cells

Primary brain tumors are among the most devastating forms of cancer and glioblastoma (GBM) represents the most aggressive and lethal form of the disease. We now know that GBM contains small subsets of cells that display tumor-propagating stem-like phenotypes (i.e. glioma stem cells or GSCs) that act as critical determinants of resistance to current treatments and tumor recurrence for which there is no proven therapy. Altered patterns of DNA methylation are widely reported in human GBM. However, substantial knowledge gaps remain in our understanding of the molecular mechanisms responsible for this epigenetic dysregulation, its downstream consequences and its role in the GBM tumor-propagating phenotype. Understanding and ultimately targeting the epigenetic mechanisms that induce and maintain these tumor-propagating cell subsets is critical to improving GBM therapy and patient outcomes.

DNA methylation generally occurs in cytosine-guanine (CpG) sequences and is established by DNMTs, which catalyze the conversion of cytosine to 5-methylcytosine (5mC). DNA methylation is dynamically regulated and reversible by the ten-eleven translocation (TET) family of deoxygenases that catalyze the conversion of 5mC to 5-hydroxymethylcytosine (5hmC). Levels of 5hmC closely align with the differentiation state of cells; terminally differentiated cells contain high levels of 5hmC and less differentiated cells have very low levels. Multiple studies found negative correlations between 5hmC levels and glioma grade and loss of 5hmC correlates with poor prognosis of GBM patients. This strongly suggests that tumor suppressing epigenetic mechanisms are driven by TET-dependent 5hmC generation.

We now show that SOX2, a reprogramming transcription factor that induces GSCs, represses the TET2 and decreases 5hmC in multiple GSC isolates. TET2 repression using two independent shRNA hairpins efficiently decreased 5hmc levels and significantly enhanced self-renewal capacity and tumor growth capacity of low-passage GSCs. We also show that low concentrations of vitamin C, a TET enzyme cofactor, significantly increases 5hmC in low-passage GSCs. This epigenetic change induced by vitamin C associated with increased GSC death induced by temozolomide (TMZ), the main chemotherapeutic used to treat GBM. These findings support a mechanism by which SOX2 induces loss of 5hmC in GSCs by repressing TET2 and show that vitamin C can reverse this epigenetic tumor promoting pathway and potentially enhance GBM chemotherapeutics.

Citation Format: Sweta Sudhir, Hernando Lopez-Bertoni, Maria Lugo-Fagundo, Bachchu Lal, John Laterra. SOX2-mediated 5hmC dysregulation in GBM stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 829.

Fascin regulates nuclear actin during Drosophila oogenesis

Study of Drosophila oogenesis reveals that the nuclear localization of actin is controlled by both development and Fascin. Fascin regulates both endogenous nuclear actin and ectopic nuclear actin rod formation by controlling Cofilin.

Drosophila oogenesis provides a developmental system with which to study nuclear actin. During Stages 5–9, nuclear actin levels are high in the oocyte and exhibit variation within the nurse cells. Cofilin and Profilin, which regulate the nuclear import and export of actin, also localize to the nuclei. Expression of GFP-tagged Actin results in nuclear actin rod formation. These findings indicate that nuclear actin must be tightly regulated during oogenesis. One factor mediating this regulation is Fascin. Overexpression of Fascin enhances nuclear GFP-Actin rod formation, and Fascin colocalizes with the rods. Loss of Fascin reduces, whereas overexpression of Fascin increases, the frequency of nurse cells with high levels of nuclear actin, but neither alters the overall nuclear level of actin within the ovary. These data suggest that Fascin regulates the ability of specific cells to accumulate nuclear actin. Evidence indicates that Fascin positively regulates nuclear actin through Cofilin. Loss of Fascin results in decreased nuclear Cofilin. In addition, Fascin and Cofilin genetically interact, as double heterozygotes exhibit a reduction in the number of nurse cells with high nuclear actin levels. These findings are likely applicable beyond Drosophila follicle development, as the localization and functions of Fascin and the mechanisms regulating nuclear actin are widely conserved.

Review of video-assisted thoracoscopy in children

Open thoracotomy is the standard procedure for various thoracic diseases against which other procedures are compared. Currently Video Assisted Thoracoscopic Surgery (VATS) has gained widespread acceptance in the management of a variety of thoracic disorders. It decreases the morbidity and duration of hospital stay. A total of 133 children with various thoracic diseases who presented at a University Teaching Hospital in the Department of Pediatric Surgery, from June 2000 to December 2007, were included. Of the 133 patients,116 patients had empyema, all of whom were subjected to VATS, and an attempt at debridement/decortication and drainage was made. Other thoracic disorders treated included lung abscesses, lung biopsies, hydatid cysts, and so on. Patients with empyema were treated according to their stage of disease. Of the 116 patients who underwent thoracoscopy, 16 had to be converted to open surgery due to various reasons. The mean duration for removal of drain was three days and the average total duration of hospital stay was six days. Similarly the application of VATS was advantageous in other thoracic diseases.

Comparison of the protective effect of Withaferin-'A' and hydrocortisone against CCL4 induced hepatotoxicity in rats

Protective effect of Withaferin-'A' against CCl4 induced hepatotoxicity has been assessed and the compound at 10 mg/kg dose was found to possess significant protective effect. A comparison of this protective effect with that of hydrocortisone showed it to be as effective as hydrocortisone dose per dose.

Acute effect of ethanol administration on platelet function

The acute effect of single dose of ethanol (1.5 g kg) and aspirin (10 mg/kg) alone and in combination, on platelet aggregation time and platelet adhesiveness were studied in rabbits. There was a significant and comparable increase in aggregation time both by aspirin and ethanol. Similarly platelet adhesiveness was decreased by both the agents.

Status of platelet functions in volunteers of various blood groups: effect of aspirin

Platelet functions (platelet aggregation and adhesiveness) were studied in volunteers of different blood groups. The platelet aggregation time was found to be significantly (P less than 0.01) more in blood group O as compared A, B and AB blood groups. Similarly, platelet adhesive index was higher in A, B and AB blood groups when compared to that of blood group O. The administration of a single dose of aspirin (4 mg/kg, po) increased the platelet aggregation time and reduced the platelet adhesive index in all the blood groups.

Cardiovascular effects of a withanolide from Withania coagulans, dunal fruits

A new withanolide, with a unique chemical structure similar to the aglycones of the cardiac glycosides, with mol. wt. 488 6, m. p. 260-261 degrees, isolated from the fruits of Withania coagulans, was screened for cardiovascular effects. At doses of 5 mg/kg body weight, the withanolide produced a moderate fall of blood pressure in dogs (34 +/- 2.1, mm Hg) which was blocked by atropine and not by mepyramine or propranolol. In rabbit Langendorff preparation and ECG studies, it produced myocardial depressant effects but in perfused frog heart it produced mild positive inotropic and chronotropic effects.

Enhanced platelet aggregation by oral contraceptives: effect of PG synthetase inhibitors

Platelet aggregation time was significantly (P less than 0.01) decreased in female rabbits treated with oral contraceptive (a preparation containing low dose of estrogen) as also by injection of diethylstilbestrol (10 mg/kg), while in animals that received indomethacin (10 mg/kg) or aspirin (30 mg/kg) (PG synthetase inhibitors) along with oral contraceptives or diethylstilbestrol there was no significant alteration in platelet aggregation time. The increased synthesis of prostaglandins or some of the intermediary product like TXA2 might be responsible for this effect.