BIOM-14. METHODS FOR SCREENING AND MONITORING BY GBM MASTER REGULATORY GENE MARKERS IN LIQUID BIOPSY

BACKGROUND

Current liquid-based cancer screening relies on massive deep NGS to detect rare cancer cell-derived genetic materials - a costly method fraught with high false-negative and false-positive rates. We aim to develop a non-NGS-centered, AI-directed liquid-based detection of GBM stem-like cells (GSC).

METHODS

Utilized a robust AI suite, NETZEN, we defined a common master regulatory gene network (MRGN) in GSC. Since master regulators (MR) in MRGN are developmentally restricted, their chromosomal loci are accessible in GSC but not in normal cells. Downstream factors in MRGN are massively overexpressed in GSC compared to normal cells. Thus, we measured 1) accessibility of MR genes using transposase/transposons carrying unique barcodes that can be detected after insertion into the MR’s predetermined accessible locations, and 2) expression of downstream factors using nested qRT-PCR, in PBMC from healthy controls spiked with known quantities of GSC or patients with GBM.

RESULTS

We characterized 10 MR genes in GSC with ≥1 GC-rich promoter region that is hypomethylated and accessible (ATACseq) in GBM/GSC per GSE70175/92460/52271 (19 samples) and GSE67633/96088 (14 samples), and hypermethylated and inaccessible in lymphocytes/PBMC per GSE98837 (6) and GSE74912 (13), respectively. Using barcoded transposons, we specifically disrupted 4 MR’s accessible regions only in GSC, not in PBMC. We also characterized 50 upregulated downstream factors with the top 20 having 3 to 5-orders-of-magnitude higher mean expression in GSC compared to PBMC (GSE79362/86884, 451 samples). Currently our method has a detection limit of 0.2–1 GSC in 106 PBMC. Using the first iteration, we detected GSC’s MRGN in blood samples of 14/14 GBM patients before resection, compared to in none of 15 healthy donors.

CONCLUSIONS

Chromosomal accessibility of MR and signal amplification in MRGN of GSC provide powerful substrates for a non-NGS, low-cost, liquid-based GBM detection system with potentially high sensitivity and specificity. Further testing and optimization are ongoing.

IMMU-42. DUAL ACTIVATION OF THE cGAS-STING PATHWAY AND AIM2-INDUCED PYROPTOSIS BY TUMOR-TREATING FIELDS PRODUCES ANTI-TUMOR IMMUNITY IN GLIOBLASTOMA

OBJECTIVES

Tumor Treating Fields (TTFields) was approved in combination with adjuvant temozolomide chemotherapy for newly diagnosed Glioblastoma (GBM) patients and resulted in a significant improvement in overall survival. TTFields are low-intensity alternating electric fields that are thought to disturb mitotic macromolecules’ assembly. In many patients, a transient stage of increased peritumoral edema is often observed early during TTFields treatment, suggesting that a major component of therapeutic efficacy by TTFields may be an immune mediated process. We hypothesize that TTFields activate the immune system by triggering pyroptosis and type I Interferon (IFN) response.

METHODS

A panel of GBM cell lines were treated with TTFields at the clinically approved frequency of 200 kHz using an in vitro TTFields system. Cells were analyzed for the production of micronuclei and activation of both pyroptosis and STING pathways using immunostaining, quantitative PCR, ELISA and cytometry. Pre-treated mouse GBM cells were injected into mouse brain to monitor survive and immunophenotyping. GBM patients’ blood was collected, and PBMC were isolated and analyzed by single cell RNAseq.

RESULTS

TTFields resulted in a significantly higher rate of micronuclei structures released into the cytoplasm, which were co-localized with two upstream dsDNA sensors AIM2 and cGAS. TTFields-activated micronuclei-dsDNA sensor complexes led to i) induction of pyroptotic cell death, as measured by LDH release assay, and through AIM2-recruited caspase1 activation and cleavage of pyroptosis-specific Gasdermin D; and ii) activation of STING pathway leading to the increase of type I IFNs and pro-inflammatory cytokines. In mouse model, double knocking down of STING/AIM2 eliminated the tumor suppression effects caused by TTFields. TTFields pretreated wild type cells successfully elevated dendritic cell level in mouse cervical lymph nodes which can be reversed by double knocking down.

CONCLUSIONS

These results provide compelling evidence that TTFields induces effective anti-tumor immunity in GBM cells and patients.

CTIM-04. UPDATES FOR A PHASE 2 OPEN-LABELED STUDY OF PEMBROLIZUMAB PLUS TTFIELDS PLUS MAINTENANCE TEMOZOLOMIDE IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA (2-THE-TOP)

INTRODUCTION

Tumor-treating fields (TTFields) are a new standard anti-mitotic treatment for newly diagnosed glioblastoma (ndGBM). Emerging data indicate that TTFields also stimulate innate immunity, leading to adaptive immunity. We hypothesize that immune checkpoint inhibitors synergize with TTFields to promote anti-tumor immunity in ndGBM.

METHODS

24 adult patients with ndGBM will be enrolled following radiotherapy with concurrent temozolomide. To identify TTFields-induced immune effects that are augmented by pembrolizumab, TTFields (200 kHz) is started with cycle 1 of maintenance TMZ while pembrolizumab (200mg Q3W) is added at cycle 2 and continued up to 2 years or until disease progression or unacceptable toxicities. The primary endpoint is PFS vs. historical controls (JAMA, 318:2306–2316). Secondary endpoints include toxicity/tolerability and immune activation by TTFields before and after pembrolizumab as determined by single-cell analysis of peripheral blood mononuclear cells.

RESULTS

As of 06/19/2020, there are 17 evaluable patients. The median follow-up is 12.2 months from cycle 1 of maintenance TMZ. 10 (59%) patients are progression-free, and 13 (76%) are alive. Of 9 patients with follow-up > 12 months, the median PFS is at least 11.2 months vs. historical median PFS of TTFields plus maintenance TMZ of 6.7 months. The most common serious adverse events are pain, weakness, lymphatic swelling, and metabolic disturbances observed in 3 (18%), 2 (12%), 2 (12%), and 1 (6%) patients, respectively. In response to TTFields, we detect a 2.26 (p=0.01) and 5.2-fold (p=0.07) mean increase in the number of classical and plasmacytoid dendritic cells (DC), respectively. Network analysis shows wide-spread pathway upregulation in responders, especially type 1 interferon response genes in DC (FDR=0.02) and cytotoxicity genes in CD8 T cells (FDR=0.03).

CONCLUSIONS

Pembrolizumab in combination with TTFields plus maintenance TMZ is generally well tolerated in patients with ndGBM. Preliminary data demonstrates activation of adaptive immunity and improved efficacy and will be updated.

CSIG-15. INNOVATIVE COMPUTATIONAL PLATFORM ADDRESSES PROSTAGLANDIN E RECEPTOR 3 AS THE MASTER REGULATOR MEDIATING RESISTANCE TO TUMOR TREATING FIELDS IN GLIOBLASTOMA CELLS

OBJECTIVES

Tumor Treating Fields (TTFields) are approved in combination with temozolomide for newly diagnosed glioblastoma (GBM). TTFields are low-intensity alternating electric fields that are thought to disturb mitotic macromolecules’ assembly. The addition of TTFields resulted in a significant improvement in overall survival. However, most GBM patients eventually develop resistance to TTFields and the mechanism remains unexplored.

METHODS

Multiple GBM cell lines were treated continuously at clinically approved frequency of 200 kHz using an in vitro TTFields system until cells with relative resistance to the cytotoxic effects of TTFields. A systems approach aided by innovative network ranking computational algorithms were utilized to analyze global gene expression profiles and identify resistance pathways, which were subsequently validated experimentally.

RESULTS

TTFields-induced chromosomal instability is preserved in resistant cells, indicating that TTFields resistance is mediated through a non-biophysical mechanism. This acquired TTFields resistance phenotype is associated with a transition of GBM cells to a stem-like state as determined by a neurosphere assay, stemness markers such as CD44 and increased tumorigenesis when implanted into mouse brain. Using an innovative computational platform-NETZEN, we methodically dissected this stemness program in resistant cells. 3 networks were found disrupted and all play critical roles in GBM stemness. Mechanistically, Prostaglandin E Receptor 3 (PTGER3) is the top ranked regulator responsible for resistance. PTGER3 is rapidly upregulated both in vitro and in vivo upon exposure to TTFields and further increases with prolonged treatment as resistance sets in. Immunofluorescence staining shows PTGER3’s nuclear translocation along with Lamin A/C disruption in response to TTFields. Pharmacological inhibition of PTGER3 using aspirin or PTGER3-specific inhibitors resensitized or prevent cells becoming resistance to TTFields.

CONCLUSIONS

We have identified a novel regulator PTGER3 at the apex that plays a critical role in TTFields resistance. This is a potential therapeutic target to reduce resistance to TTFields therapy in GBM.

IMMU-37. DIRECT REPROGRAMMING OF GLIOBLASTOMA TO ANTIGEN PRESENTING-LIKE CELLS BY MASTER REGULATORS PREDICTED FROM AN ARTIFICIAL INTELLIGENCE PLATFORM

Glioblastoma (GBM) is the most common and lethal malignant brain cancer in adults. Immunotherapy has emerged as a potentially powerful approach to achieve long-term survival in patients with GBM. Antigen presenting cells (APCs) play a central role in priming cancer-specific immune responses due to their ability to sample and present tumor neoantigens to the immune system. We hypothesis that antigen presenting cells could be induced by transdifferentiated from GBM in-situ so that these locally created APC will find themselves pre-planted in the tumor microenvironment (TME) with full access to tumor neoantigens. Top ten ranked candidate fate determinants for the GBM-DC transdifferentiation were predicted by NETZEN, an integrated deep-learning and gene network-based ranking artificial intelligence (AI) platform for precision medicine. We successfully transdifferentiated the murine GBM cell line GL261 into CD45+ immune cells accompanying morphological changes to less adhering cells by a combination of four factors (PU.1, IRF8, BATF3, ID2). Of these induced CD45 positive cells, a significant fraction also expresses high levels of the myeloid marker CD11b and antigen presenting molecules MHCII and MHCI by flow cytometry, suggesting these induced CD45+ cells are myeloid lineage APCs (iAPC).These iAPC exhibit phagocytic property, tested by incubating pHrodo Red bioparticles conjugated with Zymosan, an antigen found on the surface of fungi. More importantly, these induced iAPC appear to have lost their proliferative capacity characteristic of the parental GBM cells. Total live cell numbers were significantly reduced in 4F-induced culture compared to the EV control. In conclusion, we successfully transdifferentiated mouse GBM cells into APC-like cells based on NETZEN prediction and our work can potentially provide a novel therapeutic approach for developing an in-situ APC vaccine immunotherapy for GBM, and for other cancers.

Abstract 5524: Co-activation of STING pathway and immunogenic cell death by tumor treating fields produces effective antitumor immunity in glioblastoma

Objectives: Glioblastoma (GBM) is the most common and deadliest malignant brain cancer in adults. Tumor Treating Fields (TTFields) was approved in combination with adjuvant temozolomide chemotherapy for newly diagnosed GBM patients. The addition of TTFields resulted in a significant improvement in overall survival. TTFields are low-intensity alternating electric fields that are thought to disturb mitotic macromolecules' assembly. In many patients, a transient stage of increased peritumoral edema is often observed early during TTFields treatment followed subsequently by objective radiographic responses, suggesting that a major component of therapeutic efficacy by TTFields may be an immune mediated process. We hypothesize that TTFields activate the immune system by triggering pyroptosis and type I Interferon (IFN) response.

Methods: A panel of GBM cell lines were treated with TTFields at the clinically approved frequency of 200 kHz using an in vitro TTFields system. Cells were analyzed for the production of micronuclei and activation of both pyroptosis and STING pathways using immunostaining, quantitative PCR, ELISA and cytometry. Pre-treated mouse GBM cells were injected into B6 mouse brain, IVIS and immunophenotyping were performed post implantation.

Results: TTFields resulted in a significantly higher rate of micronuclei structures released into the cytoplasm, which were co-localized with two upstream dsDNA sensors AIM2 and cGAS. TTFields-activated micronuclei-dsDNA sensor complexes led to i) induction of pyroptotic cell death, as measured by LDH release assay, and through AIM2-recruited caspase1 activation and cleavage of pyroptosis-specific Gasdermin D; and ii) activation of STING pathway leading to the release of type I IFNs and pro-inflammatory cytokines downstream of the NFκB pathway. In a co-culture experiment of bone marrow cells with cells/supernatants obtained from GBM cells treated with TTFields, GBM cells depleted of AIM2 and STING failed to induce bone marrow cells. In mouse model, double knocking down of STING/AIM2 eliminated the tumor suppression effects caused by TTFields. TTFields pretreated wild type cells successfully elevated dendritic cell level in mouse cervical lymph nodes which can be reversed by double knocking down.

Conclusions: These results provide compelling evidence that TTFields activates the innate immune system in GBM cells, and a strong rationale for combining TTFields with immune checkpoint inhibitors to create a therapeutic synergy.

Citation Format: Dongjiang Chen, Nagheme Thomas, Jie Ren, Son Le, Mathew Sebastian, Changwang Deng, Dan Jin, David Tran. Co-activation of STING pathway and immunogenic cell death by tumor treating fields produces effective antitumor immunity in glioblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5524.

Retronychia: A Literature Review

Retronychia is an uncommonly reported condition among the category of nail pathologies. It often presents mimicking similar nail disorders, such as onychocryptosis, onychomycosis, and paronychia. This pathologic condition has recently seen an increased presence in the literature, mainly in the form of case studies. Literature on retronychia was collected using PubMed, the US National Library of Medicine, the National Institutes of Health's online database, life science journals, and online books. References cited by these articles were also reviewed for additional relevant publications. Reviews, case studies, and retrospective articles were compiled and analyzed for commonalities in cause, patient demographics, clinical signs, and treatment. Retronychia may be more common than previously suggested. Proper knowledge and education of this pathologic nail condition is important to health-care professionals to achieve early and correct diagnosis.

The utilization of snap-on provisionals for dental veneers: From an analog to a digital approach

OBJECTIVE

There are multiple treatment options to enhance a patient's smile, from conservative bleaching procedures to composite resins, porcelain veneers, or full-coverage crowns. Treating patients with porcelain veneers is a commonly used approach in esthetic dentistry. Provisional restorations for veneers can be time-consuming to make and difficult to retain. This article illustrates a technique for fabricating indirect snap-on provisional restorations for veneer cases, describing both analog and digital approaches.

CLINICAL CONSIDERATIONS

The present article presents an alternative provisionalization technique using snap-on restorations for dental veneers. Application of these techniques will allow for ease of cleansability by the patient leading to healthier soft tissues before the final cementation. Delivery of veneers is more predictable with healthy soft tissue, as bleeding and inflammation may affect the bonding process.

CONCLUSIONS

This technique is an effective provisionalization option in most veneer cases. This approach seems to be well accepted by patients and a good alternative in helping to maintain optimal gingival health with interim restorations before delivery.

CLINICAL SIGNIFICANCE

The use of snap-on provisionals for veneer restorations will allow the clinician to have an efficient technique with better tissue response before cementation. This prevents inflammation and facilitates a controlled delivery process.

SCIDOT-43. FINAL DATA ANALYSIS OF A PILOT STUDY TESTING THE EFFICACY OF USING LASER INTERSTITIAL THERMAL THERAPY (LITT) TO INDUCE TEMPORARY DISRUPTION OF THE PERITUMORAL BLOOD BRAIN BARRIER (BBB) TO IMPROVE EFFECTIVENESS OF BBB-IMPERMEANT CHEMOTHERAPY IN RECURRENT GLIOBLASTOMA

BACKGROUND

Poor CNS drug delivery is a major limiting factor in GBM therapy. Since most recurrences occur peritumorally where infiltrating glioma cells reside, peritumoral BBB disruption may help improve drug delivery and efficacy. LITT, a minimally invasive cytoreductive treatment for brain tumors, may disrupt BBB as evidenced by post-ablation contrast enhancement.

METHODS

Patients with recurrent GBM were treated with LITT. The degree of post-LITT peritumoral BBB disruption was measured by the vascular transfer constant (Ktrans) in brain DCE-MRI. Serum levels of brain-specific enolase (BSE) were quantified as an independent measure of BBB disruption. Forty enrollments were planned with equal randomization to weekly low-dose doxorubicin, a BBB-impermeant chemotherapy, either during the BBB-permeable window (Early Dox) or after the resolution of disruption (Late Dox). The primary endpoint is 6-month PFS rate (6-PFS).

RESULTS

Peritumoral Ktrans peaked immediately post LITT, followed by a gradual decline for the next 4 weeks. Similarly, serum BSE concentrations peaked in 1–3 weeks after LITT before decreasing to baseline by 6 weeks. 41 patients were randomized to Early and Late Dox. 31 patients (14 Early and 17 Late Dox) were evaluable for the primary endpoint. MGMT promoter methylation rate was 28% and 47% in the Early and Late Dox arms, respectively. 6-PFS was 57.1% (8/14) in Early Dox compared to 35.3% (6/17) in Late Dox. PFS was 5.8 (95%CI: 4.1–6.3) months vs. 4.9 (95%CI: 2.4–6.3) months, while OS was 12.8 (95%CI: 7.8–14.5) months vs. 13.6 (95%CI: 10.2–17.1) months, for Early vs. Late Dox, respectively. The most common grade 3–4 toxicities were cytopenia observed in 6 (16%) patients.

CONCLUSIONS

LITT induces temporary peritumoral BBB disruption lasting 4–6 weeks, providing a rare opportunity to enhance local delivery of potentially efficacious but BBB-impermeant therapeutic agents. 6-PFS strongly favors dox given early during the window of BBB disruption, thus supporting the hypothesis.

ATIM-39. PHASE 2 OPEN-LABELED STUDY OF ADJUVANT TEMOZOLOMIDE PLUS TUMOR TREATING FIELDS PLUS PEMBROLIZUMAB IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA (2-THE-TOP)

BACKGROUND/OBJECTIVE

Tumor treating Fields (TTFields) plus maintenance temozolomide is an approved standard treatment for newly diagnosed Glioblastoma (GBM). TTFields are alternating electric fields of low intensity and intermediate frequency delivered non-invasively via transducer arrays to tumor region. Immune checkpoints have not been studied widely in newly diagnosed GBM patients. TTFields combined with temozolomide elicit anti-mitotic effects on proliferative cancer cells and augment recruitment of immune effector cells specific for glioma cells to the tumor microenvironment where pembrolizumab further potentiates the immune reaction to achieve a synergistic therapeutic effect. This study [NCT03405792] will determine if adding pembrolizumab to TTFields and maintenance temozolomide (triple combination) increases progression-free survival (PFS) in patients with newly diagnosed GBM versus historical control (EF-14).

METHODS

This study will enroll patients (N=24) with pathologic diagnosis of newly diagnosed GBM WHO grade 4, > 18 years after maximal surgery or biopsy followed by radiation therapy with adjuvant temozolomide (Stupp protocol). The primary endpoint is increases in PFS compared to historical control data (EF-14). Secondary endpoints include: toxicity and tolerability of the triple combination; overall survival and response rates versus historical data; augmentation of TTFields-initiated glioma-specific immune reaction by pembrolizumab. Exploratory endpoints include: metabolomics signature of immune activation by TTFields and TTFields plus pembrolizumab in serum and urine, and correlation of mutation burden in primary tumor samples with response to pembrolizumab plus TTFields. We assumed an accrual period of 12 months, an accrual rate of 2 patients per month, an additional 18 months of follow-up, and proportional hazards. Per shape parameter estimate of k=0.88 with empirical 95% confidence interval (0.82, 0.95) obtained via simulation of historical control data, a sample size of 24 patients should detect an improvement in PFS of 6 to 8 months with 80% power and a 1-sided significance level of 0.05 (Wu and Xiong, 2014).

IMMU-06. TTFIELDS INDUCES IMMUNOGENIC CELL DEATH AND STING PATHWAY ACTIVATION THROUGH CYTOPLASMIC DOUBLE-STRANDED DNA IN GLIOBLASTOMA CELLS

OBJECTIVES

Glioblastoma (GBM) is the most common and deadliest malignant brain cancer in adults. Tumor Treating Fields (TTFields) was approved in combination with adjuvant temozolomide chemotherapy for newly diagnosed GBM patients. The addition of TTFields resulted in a significant improvement in overall survival. TTFields are low-intensity alternating electric fields that are thought to disturb mitotic macromolecules’ assembly. In many patients, a transient stage of increased peritumoral edema is often observed early during TTFields treatment followed subsequently by objective radiographic responses, suggesting that a major component of therapeutic efficacy by TTFields may be an immune mediated process. We hypothesize that TTFields activate the immune system by triggering pyroptosis and type I Interferon (IFN) response.

METHODS

A panel of GBM cell lines were treated with TTFields at the clinically approved frequency of 200 kHz using an in vitro TTFields system. Cells were analyzed for the production of micronuclei and activation of both pyroptosis and STING pathways using immunostaining, quantitative PCR, ELISA and cytometry.

RESULTS

TTFields resulted in a significantly higher rate of micronuclei structures released into the cytoplasm, which were co-localized with two upstream dsDNA sensors AIM2 and cGAS. TTFields-activated micronuclei-dsDNA sensor complexes led to i) induction of pyroptotic cell death, as measured by LDH release assay, and through AIM2-recruited caspase1 and cleavage of pyroptosis-specific Gasdermin D; and ii) activation of STING pathway leading to the release of type I IFNs and pro-inflammatory cytokines downstream of the NFκB pathway. In a co-culture experiment of bone marrow cells with cells/supernatants obtained from GBM cells treated with TTFields, GBM cells depleted of AIM2 and STING failed to induce bone marrow cells.

CONCLUSIONS

These results provide compelling evidence that TTFields activates the innate immune system in GBM cells, and a strong rationale for combining TTFields with immune checkpoint inhibitors to create a therapeutic synergy.

DRES-06. PROSTAGLANDIN E RECEPTOR 3 MEDIATES RESISTANCE TO TUMOR TREATING FIELDS IN GLIOBLASTOMA CELLS

OBJECTIVES

Tumor Treating Fields (TTFields) are approved in combination with temozolomide for newly diagnosed glioblastoma (GBM). The addition of TTFields resulted in a significant improvement in overall survival. TTFields are low-intensity alternating electric fields that are thought to disturb mitotic macromolecules’ assembly. However, most GBM patients eventually develop resistance to TTFields. The mechanism of TTFields resistance remains largely unexplored. Understanding how GBM cells circumvent the biophysical forces of TTFields and their downstream effects will improve therapeutic efficacy of this novel anti-cancer treatment modality.

METHODS

A panel of GBM cell lines were treated continuously with TTFields at the clinically approved frequency of 200 kHz using an in vitro TTFields system until cells with relative resistance to the cytotoxic effects of TTFields. A systems approach aided by innovative network ranking computational algorithms were utilized to analyze global gene expression profiles and identify resistance pathways, which were subsequently validated experimentally.

RESULTS

TTFields-induced chromosomal instability such as the formation of cytoplasmic micronuclei is preserved in resistant cells, indicating that TTFields resistance is mediated through a non-biophysical mechanism. This acquired TTFields resistance phenotype is associated with a transition of GBM cells to a stem-like state as determined by a neurosphere assay. Using an innovative computational platform, we methodically dissected this stemness program in resistant cells. Mechanistically, Prostaglandin E Receptor 3 (PTGER3) is the top ranked master regulator responsible for resistance. PTGER3 is rapidly upregulated in GBM cells upon exposure to TTFields and further increases with prolonged treatment as resistance sets in. Pharmacological inhibition of PTGER3 either using aspirin to reduce prostaglandin E production or PTGER3-specific inhibitors resensitized cells to TTFields.

CONCLUSIONS

We have identified a novel pathway with PTGER3 at the apex that plays a critical role in TTFields resistance. This pathway is a potential therapeutic target to reduce resistance to TTFields therapy in GBM.

ACTR-60. A PHASE 2, HISTORICALLY CONTROLLED STUDY TESTING THE EFFICACY OF TTFIELDS WITH ADJUVANT TEMOZOLOMIDE IN HIGH-RISK WHO GRADE II AND III ASTROCYTOMAS (FORWARD)

BACKGROUND

A long-standing observation in neuro-oncology concerns a group of patients with WHO Grade II and III gliomas expressing isolated hTERT promoter mutations, which exhibit indolent histological features but are highly aggressive and resistant to standard chemoradiation therapy. These patients show an overall survival rate similar to glioblastoma WHO Grade IV, necessitating new treatment options. This represents the first study of its kind testing novel treatment for this rare subgroup of lower grade gliomas with high-risk cytogenetics.

METHODS

This Phase 2, single arm, multicenter open label study [NCT03906448] will enroll 100 adult patients with newly diagnosed WHO grade II and III astrocytoma without IDH mutations and 1p/19q codeletions and with isolated hTERT promoter mutations who have completed standard radiotherapy with concurrent temozolomide, followed by adjuvant temozolomide for 12 cycles in combination with 24 months of TTFields therapy. The primary endpoint is overall survival compared to historical controls. Secondary endpoints are safety, quality of life, and progression free survival. Correlative studies will examine the effect of TTFields on intratumoral immune microenvironment and the role of electric field distribution on disease control and outcomes. Sample size was based on improvement in median OS versus historical controls (N=59; median survival 22 months). Improvements in median overall survival was based on a one-sided Wald test of the Weibull regression coefficient (H0: beta=0, alpha=0.05). A consortium of 15 institutions across the US will participate, with the first enrollment May 2019. Total accrual of 100 is planned over 36 months. The survival results and the correlative studies are designed to provide new insights for future therapeutic development for these patients.

B-Vitamin Sharing Promotes Stability of Gut Microbial Communities

Cross-feeding on intermediary and end-point metabolites plays an important role in the dynamic interactions of host-associated microbial communities. While gut microbiota possess inherent resilience to perturbation, variations in the intake of certain nutrients may lead to changes in the community composition with potential consequences on host physiology. Syntrophic relationships and mutualism at the level of major carbon and energy sources have been documented, however, relatively little is known about metabolic interactions involving micronutrients, such as B-vitamins, biosynthetic precursors of essential cofactors in the mammalian host and numerous members of the gut microbiota alike. In silico genomic reconstruction and prediction of community-wide metabolic phenotypes for eight major B-vitamins (B1, B2, B3, B5, B6, B7, B9, and B12), suggests that a significant fraction of microbial gut communities (>20% by abundance) are represented by auxotrophic species whose viability is strictly dependent on acquiring one or more B-vitamins from diet and/or prototrophic microbes via committed salvage pathways. Here, we report the stability of gut microbiota using humanized gnotobiotic mice and in vitro anaerobic fecal culture in the context of extreme variations of dietary B-vitamin supply as revealed by phylotype-to-phenotype prediction from 16S rRNA profiling and metabolomic measurements. The observed nearly unaltered relative abundance of auxotrophic species in gut communities in the face of diet or media lacking B-vitamins or containing them in great excess (∼30-fold above normal) points to a strong contribution of metabolic cooperation (B-vitamin exchange and sharing) to the stability of gut bacterial populations.

Abstract 2094: Prostaglandin E receptor 3 mediates resistance to tumor treating fields in glioblastoma cells

Glioblastoma (GBM) is the most common and deadliest malignant brain cancer in adults despite surgery and aggressive chemoradiotherapy. Tumor Treating Fields (TTFields) have been approved in combination with adjuvant temozolomide chemotherapy for newly diagnosed GBM. The addition of TTFields resulted in a significant improvement in overall survival. TTFields are low-intensity alternating electric fields that are thought to disturb mitotic macromolecules’ assembly, leading to disrupted chromosomal segregation and cell death. However, treatment resistance develops in many TTFields responders. The mechanism of TTFields resistance remains largely unexplored. Understanding how GBM cells circumvent the biophysical forces of TTFields and their downstream effects will provide new opportunities to improve therapeutic efficacy of this novel anti-cancer treatment. To accomplish these objectives, we have developed several human GBM cell lines that demonstrated relative resistance to the cytotoxic effects of TTFields compared to the parental cells. Importantly TTFields-induced chromosomal instability such as the formation of cytoplasmic micronuclei was preserved in resistant cells compared to their sensitive counterparts, indicating resistance to TTFields is mediated through a non-bioiphysical mechanism. Indeed, TTFields-induced inflammatory response was severely suppressed in resistant cells, supporting the hypothesis that that resistance to TTFields is conferred by a selective loss of the deleterious effects induced by the biophysical insults. Importantly, this acquired TTFields resistance phenotype was associated with a transition to a stem-like state as determined by a standard neurosphere assay. Using a systems approach aided by a suite of innovative computational platforms, we methodically dissected this stemness program in resistant cells to identify master regulators of the resistance mechanism. Interestingly, 3 networks were found disrupted, including nervous system developmental regulation, inflammatory response and cell-cell adhesion, all of which play critical roles in GBM stem-like cells, thus confirming our initial hypothesis. Utilizing a unique master regulator ranking system, we successfully identified Prostaglandin E Receptor 3 (PTGER3) as a key master regulator at the apex of these pathways and responsible for the resistant phenotype. PTGER3 is rapidly upregulated in GBM cells when exposed to TTFields and appears to channel treated cells away from the beneficial inflammatory pathways that TTFields also activates in parallel. Ongoing experiments are aimed at understanding the molecular mechanism of PTGER3-dependent TTFields resistance. Our goal is to develop targeted therapies to overcome resistance to TTFields.

Note: This abstract was not presented at the meeting.

Citation Format: Dongjiang Chen, Son Le, Nagheme Thomas, Changwang Deng, Dan Jin, Mathew Sebstian, Jie Ren, David Tran. Prostaglandin E receptor 3 mediates resistance to tumor treating fields in glioblastoma 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 2094.

Deep learning as a predictive tool for fetal heart pregnancy following time-lapse incubation and blastocyst transfer

STUDY QUESTION

Can a deep learning model predict the probability of pregnancy with fetal heart (FH) from time-lapse videos?

SUMMARY ANSWER

We created a deep learning model named IVY, which was an objective and fully automated system that predicts the probability of FH pregnancy directly from raw time-lapse videos without the need for any manual morphokinetic annotation or blastocyst morphology assessment.

WHAT IS KNOWN ALREADY

The contribution of time-lapse imaging in effective embryo selection is promising. Existing algorithms for the analysis of time-lapse imaging are based on morphology and morphokinetic parameters that require subjective human annotation and thus have intrinsic inter-reader and intra-reader variability. Deep learning offers promise for the automation and standardization of embryo selection.

STUDY DESIGN, SIZE, DURATION

A retrospective analysis of time-lapse videos and clinical outcomes of 10 638 embryos from eight different IVF clinics, across four different countries, between January 2014 and December 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The deep learning model was trained using time-lapse videos with known FH pregnancy outcome to perform a binary classification task of predicting the probability of pregnancy with FH given time-lapse video sequence. The predictive power of the model was measured using the average area under the curve (AUC) of the receiver operating characteristic curve over 5-fold stratified cross-validation.

MAIN RESULTS AND THE ROLE OF CHANCE

The deep learning model was able to predict FH pregnancy from time-lapse videos with an AUC of 0.93 [95% CI 0.92-0.94] in 5-fold stratified cross-validation. A hold-out validation test across eight laboratories showed that the AUC was reproducible, ranging from 0.95 to 0.90 across different laboratories with different culture and laboratory processes.

LIMITATIONS, REASONS FOR CAUTION

This study is a retrospective analysis demonstrating that the deep learning model has a high level of predictability of the likelihood that an embryo will implant. The clinical impacts of these findings are still uncertain. Further studies, including prospective randomized controlled trials, are required to evaluate the clinical significance of this deep learning model. The time-lapse videos collected for training and validation are Day 5 embryos; hence, additional adjustment would need to be made for the model to be used in the context of Day 3 transfer.

WIDER IMPLICATIONS OF THE FINDINGS

The high predictive value for embryo implantation obtained by the deep learning model may improve the effectiveness of previous approaches used for time-lapse imaging in embryo selection. This may improve the prioritization of the most viable embryo for a single embryo transfer. The deep learning model may also prove to be useful in providing the optimal order for subsequent transfers of cryopreserved embryos.

STUDY FUNDING/COMPETING INTEREST(S)

D.T. is the co-owner of Harrison AI that has patented this methodology in association with Virtus Health. P.I. is a shareholder in Virtus Health. S.C., P.I. and D.G. are all either employees or contracted with Virtus Health. D.G. has received grant support from Vitrolife, the manufacturer of the Embryoscope time-lapse imaging used in this study. The equipment and time for this study have been jointly provided by Harrison AI and Virtus Health.

The association between platelet dysfunction and adverse outcomes in cardiac surgical patients

Haemostatic activation during cardiopulmonary bypass is associated with prothrombotic complications. Although it is not possible to detect and quantify haemostatic activation directly, platelet dysfunction, as measured with point-of-care-assays, may be a useful surrogate. In this study, we assessed the association between cardiopulmonary bypass-associated platelet dysfunction and adverse outcomes in 3010 cardiac surgical patients. Platelet dysfunction, as measured near the end of the rewarming phase of cardiopulmonary bypass, was calculated as the proportion of non-functional platelets after activation with collagen. Logistic regression and multivariable analyses were applied to assess the relationship between platelet dysfunction and a composite of in-hospital death; myocardial infarction; stroke; deep vein thrombosis or pulmonary embolism; and acute kidney injury (greater than a two-fold increase in creatinine). The outcome occurred in 251 (8%) of 3010 patients. The median (IQR [range]) percentage platelet dysfunction was less for those without the outcome as compared with those with the outcome; 14% (8-28% [1-99%]) vs. 19% (11-45% [2-98%]), p < 0.001. After risk adjustment, platelet dysfunction was independently associated with the composite outcome (p < 0.001), such that for each 1% increase in platelet dysfunction there was an approximately 1% increase in the composite outcome (OR 1.012; 95%CI 1.006-1.018). This exploratory study suggests that cardiopulmonary bypass-associated platelet dysfunction has prognostic value and may be a useful clinical measure of haemostatic activation in cardiac surgery.

'I think we've had a health screen': New offshore screening, new refugee health guidelines, new Syrian and Iraqi cohorts: Recommendations, reality, results and review

AIM

To examine refugee health assessments in Syrian and Iraqi children in the context of changes to offshore immigration screening, updated Australian refugee health guidelines and the primary care refugee health model in Victoria.

METHODS

This is a retrospective audit of Syrian and Iraqi children aged 0-17 years attending a specialist immigrant health service from January 2015 to September 2017.

RESULTS

We saw 128 children (7 months-16 years, 64.8% male). Prior to arrival, 58.9% of children had experienced trauma, and 67.9% had missed at least 1 year of school. Almost all children (93.3%) were linked with a regular general practitioner in Australia, and 23.6% children were linked with a refugee health nurse; offshore health records were infrequently available. Of school-aged children, 25% were not enrolled in school 3 months after arrival. Only 2 of 113 (1.8%) children had completed a recommended refugee health assessment, and 55.1% had commenced appropriate catch-up vaccination in primary care. After screening completion, the most prevalent conditions were low vitamin D (63.6%); growth/nutrition (24.2%), neurological/metabolic (16.4%), learning/behaviour (15.6%) and mental health (12.5%) concerns; latent tuberculosis infection (11.8%); and developmental delay (10.2%). Sixteen children required surgery after arrival, and six children had life-threatening medical conditions on arrival - only one had an offshore critical alert; care for the other five children resulted in 133 unanticipated hospital admission days.

CONCLUSIONS

There are substantial challenges with the current primary care screening model in Victoria. Disability, developmental and mental health concerns were prominent in this cohort, and many children had delays in education access, compounding prior disadvantage.

Quantification of cardiac subvolume dosimetry using a 17 segment model of the left ventricle in breast cancer patients receiving tangential beam radiotherapy

PURPOSE

Subacute changes following breast radiotherapy have been demonstrated in discrete areas of the left ventricle (LV), with recent guidelines being developed to help determine dose to subvolumes of the LV. This study aims to determine doses to the 17 segments of the LV as per the American Heart Association (AHA) and other cardiac subvolumes, and to correlate mean heart (MHD) dose with various subvolume dosimetric indices. These results may direct focus to specific left ventricular segments in studies of radiation-related heart disease incorporating surveillance imaging, help to determine more precise dose response relationships, and potentially aid prediction of late radiation effects.

METHODS AND MATERIALS

The heart and cardiac subvolumes of 29 patients treated with tangential radiotherapy for left breast cancer were contoured. Delineation of cardiac subvolumes (cardiac chambers, cardiac valves and the 17 segments of the LV) was undertaken using a novel contouring method on planning CT data reformatted into the cardiac axis. Individual segments were then combined to determine doses to the basal, mid and apical left ventricular regions, and the anterior, septal, inferior and lateral ventricular walls. Radiotherapy doses (including maximum, mean, D1cc, V25) were determined. Correlation analyses were performed between MHD and various substructure dosimetric indices.

RESULTS

Twenty five patients received tangential breast free breathing radiotherapy alone, and four patients received regional nodal irradiation including the internal mammary chain with deep inspiration breath hold (DIBH). For patients receiving breast only radiation, the median mean heart radiation dose was 2.62 Gy (range 1.52-3.90 Gy), and a heterogeneous dose distribution to the LV was noted, with the apical region receiving the highest median mean dose (14.99 Gy) compared with the mid and basal regions (3.10 Gy and 1.51 Gy respectively). The anterior LV wall received the highest median mean dose (9.21 Gy) with the remaining walls receiving similar mean doses (range 1.79-3.05 Gy). The anterior LV apical segment (segment 13) and apex (segment 17) received the highest individual median mean segment doses (26.73 Gy and 30.02 Gy respectively). Apical segments received the highest median mean doses (segments 13, 14, 15, 16), followed by the mid anterior (segment 7) and anteroseptal (segment 8) segments. Segments receiving the highest doses remained unchanged between the DIBH cohort and free breathing cohort. MHD showed a high correlation with the anterior wall r = 0.71, p < 0.05 and entire left ventricle r = 0.82, p < 0.05, but correlations varied from weak to high when MHD was correlated with segments receiving highest doses (range r = 0.43-0.76), p < 0.05.

CONCLUSIONS

In the setting of breast cancer radiotherapy, there are substantial RT dose variations within specific LV segments, with mid and apical anterior ventricular segments (segments 7, 13) and the apical region of the LV (segments 13, 14, 15, 16, 17) being consistently exposed to the highest radiation doses. Determining segmental and regional RT doses to the left ventricle may help guide focus in diagnostic cardiology in the post radiotherapy setting.

Bioactive extracellular compounds produced by the dinoflagellate Alexandrium minutum are highly detrimental for oysters

Blooms of the dinoflagellate Alexandrium spp., known as producers of paralytic shellfish toxins (PSTs), are regularly detected on the French coastline. PSTs accumulate into harvested shellfish species, such as the Pacific oyster Crassostrea gigas, and can cause strong disorders to consumers at high doses. The impacts of Alexandrium minutum on C. gigas have often been attributed to its production of PSTs without testing separately the effects of the bioactive extracellular compounds (BECs) with allelopathic, hemolytic, cytotoxic or ichthyotoxic properties, which can also be produced by these algae. The BECs, still uncharacterized, are excreted within the environment thereby impacting not only phytoplankton, zooplankton but also marine invertebrates and fishes, without implicating any PST. The aim of this work was to compare the effects of three strains of A. minutum producing either only PSTs, only BECs, or both PSTs and BECs, on the oyster C. gigas. Behavioral and physiological responses of oysters exposed during 4 days were monitored and showed contrasted behavioral and physiological responses in oysters supposedly depending on produced bioactive substances. The non-PST extracellular-compound-producing strain primarily strongly modified valve-activity behavior of C. gigas and induced hemocyte mobilization within the gills, whereas the PST-producing strain caused inflammatory responses within the digestive gland and disrupted the daily biological rhythm of valve activity behavior. BECs may therefore have a significant harmful effect on the gills, which is one of the first organ in contact with the extracellular substances released in the water by A. minutum. Conversely, the PSTs impact the digestive gland, where they are released and mainly accumulated, after degradation of algal cells during digestion process of bivalves. This study provides a better understanding of the toxicity of A. minutum on oyster and highlights the significant role of BECs in this toxicity calling for further chemical characterization of these substances.