Asmann, Yan W.

Abstract Glioblastoma (GBM) is the most devastating and common form of primary brain cancer in adults. Tumor location plays a significant role in patient prognosis; in particular, GBM tumors contacting the lateral ventricles (LVs) are more aggressive than LV-distal counterparts. This may be due to interaction of tumors with unique features of the LV microenvironment, including the cerebrospinal fluid (CSF) and neural progenitor cells (NPCs) of the subventricular zone. Despite LV contact having a role on tumor malignancy, studies using bulk tumor samples to identify molecular contributors to LV-contacting prognosis have been only moderately successful, in large part due to intratumoral heterogeneity. Here, we leverage intraoperative surgical navigation to collect matched biopsies of adult LV-contacting primary GBM at locations proximal (< 2 cm) and distal ( > 2 cm) from the LV. Matched samples were collected from ten patients with equal sex distribution and an age range of 46 to 81 years. RNA sequencing of biopsies revealed a localized transcriptional signature of gene expression in LV-proximal locations. These genes include those identified to be associated with GBM malignancy and upregulated in primary GBM cells by CSF exposure or co-culture with NPCs, such as SERPINA3, CD44, and CTSB, as well as many newly identified genes. Implicated biological pathways involved in this transcriptional signature involve inflammation, chemotaxis, Notch signaling, angiogenesis, integrin signaling, and more. The top 50 upregulated genes by LV-proximity of GBM were used to cluster patient transcriptomes from the TCGA GBM database and evaluate the contribution to patient outcome. This analysis revealed a cluster with significantly extended overall survival that displayed a general downregulation of LV-proximity genes. Ultimately, these studies provide evidence that regional tumoral analysis is essential in identifying molecular signatures associated with microenvironmental influence, and that LV-contacting GBM has regional gene expression changes in many genes associated with malignancy.

Cerebrovasculature is critical in maintaining brain homeostasis; its dysregulation often leads to vascular cognitive impairment and dementia (VCID) during aging. VCID is the second most prevalent cause of dementia in the elderly, after Alzheimer’s disease (AD), with frequent cooccurrence of VCID and AD. While multiple factors are involved in the pathogenesis of AD and VCID, APOE4 increases the risk for both diseases. A major apolipoprotein E (apoE) receptor, the low-density lipoprotein receptor-related protein 1 (LRP1), is abundantly expressed in vascular mural cells (pericytes and smooth muscle cells). Here, we investigated how deficiency of vascular mural cell LRP1 affects the cerebrovascular system and cognitive performance using vascular mural cell–specific Lrp1 -KO mice ( smLrp1 –/– ) in a human APOE3 or APOE4 background. We found that spatial memory was impaired in the 13- to 16-month-old APOE4 smLrp1 –/– mice but not in the APOE3 smLrp1 –/– mice, compared with their respective littermate control mice. These disruptions in the APOE4 smLrp1 –/– mice were accompanied with excess paravascular glial activation and reduced cerebrovascular collagen IV. In addition, blood-brain barrier (BBB) integrity was disrupted in the APOE4 smLrp1 –/– mice. Together, our results suggest that vascular mural cell LRP1 modulates cerebrovasculature integrity and function in an APOE genotype–dependent manner.

Abstract Surgical resection of early stage soft-tissue sarcomas (STS) is a potentially curative treatment; however, many STS tumors will recur. Predicting recurrence and survival outcomes for patients with early stage STS remains a challenge. In this study, we identify prognostic biomarkers from clinical and transcriptomic data form a large set of early stage STS. Primary tumor samples from 69 subjects with STS were sequenced using the Tempus xT targeted DNA and whole transcriptome next-generation sequencing platforms. The most common histologies included were liposarcoma (n=22), gastrointestinal stromal tumor (n=19), and leiomyosarcoma (n=12). As expected, high-grade tumors were associated with decreased DFS and OS times while tumor histology was only correlated with OS. Single sample gene set enrichment analysis (ssGSEA) values for seven Hallmark genesets were correlated with both DFS and OS; including pro-tumor survival pathways (p53, Apoptosis, TNF-α via NF-κB), tumor proliferation pathways (MTORC1, MYC Targets, Mitotic Spindle), and UV Response signaling. These pathways are associated with tumor proliferation as well as an immunosuppressive tumor microenvironment (TME). To assess the TME of these tumors we estimated immune cell infiltration using CIBERSORTx. Of the 22 cell types accounted for by CIBERSORTx, only elevated infiltration of M2 Macrophages were associated with poor DFS and OS. To further determine TME activation we assessed the expression of 74 known immune response associated genes. Only PDCD1 (PD-1) was associated with reduced DFS and OS times. Clustering on the nine variables identified here to correlate with both DFS and OS revealed two distinct clusters demonstrating similar histologies. While histologies were similar across clusters, cluster 2 exclusively included high-grade tumors while cluster 1 was made up of 57.4% high-grade tumors. Sub-classifying cluster 1 into low and high-grade subgroups demonstrated a stepped biomarker expression pattern associated with both tumor grade and cluster membership. Using established TME genesets, high-grade tumors demonstrated higher tumor proliferative scores than low-grade tumors, while cluster 2 tumors demonstrated increased tumor associated macrophage signaling. In a multivariable model, cluster membership outperformed tumor grade and histology as the only significant predictor of DFS or OS. Taken together, while tumor grade is a strong predictor of clinical outcomes following surgical resection in STS, immunosuppressive signaling patters may help to identify patients at the highest risk. Citation Format: Nathan David Seligson, Yan W. Asmann, Tariq Almerey, Steven Attia, Sanjay P. Bagaria. Immune-suppressive tumor microenvironment leads to poor survival following curative intent surgical resection in soft-tissue sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 990.

Bcl-2 and Mcl-1 proteins play a role in multiple myeloma (MM) cell survival, for which targeted inhibitors are being developed. AT-101 is an oral drug, which disrupts Bcl-2 and Mcl-1 function, impedes mitochondrial bioenergetic processes and induces apoptosis in MM cells. When combined with lenalidomide and dexamethasone (Rd), AT-101 significantly reduced tumor burden in an in vivo xenograft model of MM. These data provided rationale for a phase I/II study to establish the effective dose of AT-101 in combination with Rd (ARd regimen) in relapsed/refractory MM. A total of 10 patients were enrolled, most with high-risk cytogenetics (80%) and prior stem cell transplant (70%). Three patients were lenalidomide-refractory, 2 were bortezomib-refractory and 3 were daratumumab-refractory. The ARd combination was well tolerated with most common grade 3/4 adverse events being cytopenia’s. The overall response rate was 40% and clinical benefit rate was 90%. The median progression free survival was 14.9 months (95% CI 7.1-NE). Patients responsive to ARd showed a decrease in Bcl-2:Bim or Mcl-1:Noxa protein complexes, increased CD8+ T and NK cells and depletion of T and B-regulatory cells. The ARd regimen demonstrated an acceptable safety profile and promising efficacy in patients with relapsed/refractory MM prompting further investigation in additional patients.

TREM2 is exclusively expressed by microglia in the brain and is strongly linked to the risk for Alzheimer’s disease (AD). As microglial responses modulated by TREM2 are central to AD pathogenesis, enhancing TREM2 signaling has been explored as an AD therapeutic strategy. However, the effective therapeutic window targeting TREM2 is unclear. Here, by using microglia-specific inducible mouse models overexpressing human wild-type TREM2 (TREM2-WT) or R47H risk variant (TREM2-R47H), we show that TREM2-WT expression reduces amyloid deposition and neuritic dystrophy only during the early amyloid seeding stage, whereas TREM2-R47H exacerbates amyloid burden during the middle amyloid rapid growth stage. Single-cell RNA sequencing reveals suppressed disease-associated microglia (DAM) signature and reduced DAM population upon TREM2-WT expression in the early stage, whereas upregulated antigen presentation pathway is detected with TREM2-R47H expression in the middle stage. Together, our findings highlight the dynamic effects of TREM2 in modulating AD pathogenesis and emphasize the beneficial effect of enhancing TREM2 function in the early stage of AD development.