Citations

Glioblastoma (GBM) is the most prevalent and aggressive malignant primary brain tumor. GBM proximal to the lateral ventricles (LVs) is more aggressive, potentially because of subventricular zone contact. Despite this, cross-talk between GBM and neural stem/progenitor cells (NSC/NPCs) is not well understood. Using cell-specific proteomics, we show that LV-proximal GBM prevents neuronal maturation of NSCs through induction of senescence. In addition, GBM brain tumor–initiating cells (BTICs) increase expression of cathepsin B (CTSB) upon interaction with NPCs. Lentiviral knockdown and recombinant protein experiments reveal that both cell-intrinsic and soluble CTSB promote malignancy-associated phenotypes in BTICs. Soluble CTSB stalls neuronal maturation in NPCs while promoting senescence, providing a link between LV-tumor proximity and neurogenesis disruption. Last, we show LV-proximal CTSB up-regulation in patients, showing the relevance of this cross-talk in human GBM biology. These results demonstrate the value of proteomic analysis in tumor microenvironment research and provide direction for new therapeutic strategies in GBM.

Abstract Glioblastoma (GBM) is the most common and lethal primary brain tumor in adults. Within the tumor, there is a subtype of cells deemed brain tumor initiating cells (BTICs), which contribute to tumor progression, therapy resistance, and tumoral heterogeneity. The tumor microenvironment, surrounding tumors, contains an ecosystem of cells in which BTICs can interact with and further promote tumor progression. In the lateral wall of the lateral ventricles, the neurogenic niche of the subventricular zone (SVZ), contains neural progenitor cells (NPCs) that self-renew and generate highly migratory neuroblasts. Interestingly, GBM tumors proximal to the SVZ are more proliferative, migratory, and negatively impact the survival of patients. We have previously observed that the presence of GBM induces reciprocal changes to the SVZ altering its neurogenic capacity and resulting in a more proliferative tumor. BTICs share similar self-renewal capacity to NPCs and may exert intercellular communication resulting in increased malignancy features. The mechanisms of intercellular communication, present in the SVZ include paracrine, autocrine, direct cell contact, gap junctions, nanotubes, and more recently extracellular vesicles (EVs). However, the exact mechanisms of how BTICs communicate with NPCs is not well understood. EVs are a heterogenous group of cell-derived membranous structures that serve as means of intercellular communication, allowing for cells to exchange proteins, lipids, RNA, and other genetic material. Cancer cells release higher amounts of EVs than non-malignant cells, and these EVs help communicate with other nearby cells, leading to promotion of tumorigenesis. We have observed that BTICs-derived EVs increase the proliferation of human NPCs, while altering their morphology and expression of stem cell markers. These effects are not observed when NPCs are treated with vesicle-free BTIC-derived secreted factors. To investigate the distinctions between BTIC secreted factors and protein cargo contained in BTIC-EVs, we employ the proximity protein labelling system, TurboID, and express this system in BTIC-EVs. The overarching goal of this project is to characterize BTIC-derived EV cargo to identify proteins that modify the GBM tumor microenvironment. We hypothesize that the phenotype of non-cancer NPCs is altered by distinct protein cargo contained in BTIC-derived EVs. The results of these experiments will help us to elucidate what BTIC-specific EV cargo impacts the tumor microenvironment, with the potential of revealing therapeutic targets for GBM. Citation Format: Marissa Russo, Maria Jose Ulloa Navas, Emily Norton-Ramos, Alfredo Quiñones Hinojosa, Hugo Guerrero Cazares. Exploring the differences between brain tumor initiating cell extracellular vesicles and secreted factors that influence the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2776.

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.

Abstract Background Mesenchymal stromal cells (MSCs) have a dynamic secretome that plays a critical role in tissue repair and regeneration. However, studying the MSC secretome in mixed-culture disease models remains challenging. This study aimed to develop a mutant methionyl-tRNA synthetase-based toolkit (MetRSL274G) to selectively profile secreted proteins from MSCs in mixed-culture systems and demonstrate its potential for investigating MSC responses to pathological stimulation.Methods We used CRISPR/Cas9 homology-directed repair to stably integrate MetRSL274G into cells, enabling the incorporation of the non-canonical amino acid, azidonorleucine (ANL), and facilitating selective protein isolation using click chemistry. MetRSL274G was integrated into both in H4 cells and induced pluripotent stem cells (iPSCs) for a series of proof-of-concept studies. Following iPSC differentiation into induced-MSCs, we validated their identity and co-cultured MetRSL274G-expressing iMSCs with naïve or lipopolysaccharide- (LPS) treated THP-1 cells. We then profiled the iMSC secretome using antibody arrays.Results Our results showed successful integration of MetRSL274G into targeted cells, allowing specific isolation of proteins from mixed-culture environments. We also demonstrated that the secretome of MetRSL274G-expressing iMSCs can be differentiated from that of THP-1 cells in co-culture, and is altered when co-cultured with LPS-treated THP-1 cells compared to naïve THP-1 cells.Conclusions The MetRSL274G-based toolkit we have generated enables selective profiling of the MSC secretome in mixed-culture disease models. This approach has broad applications for examining not only MSC responses to models of pathological conditions, but any other cell type that can be differentiated from iPSCs. This can potentially reveal novel MSC-mediated repair mechanisms and advancing our understanding of tissue regeneration processes.

OBJECTIVE The vertebral column is the most common site for skeletal metastasis, often leading to debilitating pain and weakness. Metastatic cancer has unique genetic drivers that potentiate tumorigenicity. There is an unmet need for novel targeted therapy in patients with spinal metastatic disease. METHODS The authors assessed the effect of verteporfin-induced yes-associated protein (YAP) inhibition on spine metastatic cell tumorigenicity and radiation sensitivity in vitro. Animal studies used a subcutaneous xenograft mouse model to assess the use of systemic intraperitoneal verteporfin (IP-VP) and intratumoral verteporfin microparticles (IT-VP) to inhibit the tumorigenicity of lung and breast spinal metastatic tumors from primary patient-derived tissue. RESULTS Verteporfin led to a dose-dependent decrease in migration, clonogenicity, and cell viability via inhibition of YAP and downstream effectors cyclin D1, CTGF, TOP2A, ANDRD1, MCL-1, FOSL2, KIF14, and KIF23. This was confirmed with knockdown of YAP. Verteporfin has an additive response when combined with radiation, and knockdown of YAP rendered cells more sensitive to radiation. The addition of verteporfin to YAP knockdown cells did not significantly alter migration, clonogenicity, or cell viability. IP-VP and IT-VP led to diminished tumor growth (p < 0.0001), especially when combined with radiation (p < 0.0001). Tissue analysis revealed diminished expression of YAP (p < 0.0001), MCL-1 (p < 0.0001), and Ki-67 (p < 0.0001) in tissue from verteporfin-treated tumors compared with vehicle-treated tumors. CONCLUSIONS This is the first study to demonstrate that verteporfin-mediated inhibition of YAP leads to diminished tumorigenicity in lung and breast spinal metastatic cancer cells. Targeting of YAP with verteporfin offers promising results that could be translated to human clinical trials.

Abstract Glioblastoma (GBM) is the most common and aggressive primary neoplasm of the central nervous system. The location of GBM contributes significantly to patient outcomes, where tumors contacting the lateral ventricles (LVs) have increased expression of stem cell genes, increased incidence of distal recurrence, and decreased overall survival. While the reasons for these findings are not fully understood, we hypothesize they arise due to interactions with the subventricular zone (SVZ), the largest neurogenic niche in mammals. We examined bidirectional signals between GBM cells and neural progenitor cells (NPCs) in vitro and in vivo using a combination of patient-derived intraoperative samples, preclinical animal models, and the methionine tRNA synthetase L274G (MetRS*) nascent proteomic labeling system, which allows for cell-specific proteomics analysis from complex in vivo systems. In co-culture with NPCs, GBM cells increase their viability, proliferation, migration, and expression of malignancy-promoting proteins, including migratory proteins such as TAGLN, PALLD, and STAT1. In vivo, tumor proximity to the SVZ results in increased proliferation, increased expression of stemness markers, decreased survival, and altered tumor-specific proteome. We then examined the reciprocal effect of GBM cells on NPC biology. In vitro and in vivo, GBM cells decreased NPC proliferation and induced decreased neuronal maturation of NPCs. To determine NPC proteomic changes in vivo, we created a transgenic mouse line Nestin-CreERT2; STOPflox R26-MetRS L274G, where upon tamoxifen administration Nestin+ NPCs express GFP and MetRS*. Our results indicate that LV-proximal GBM induces decreased expression of neuronal maturation proteins such as Eml1, VGLUT1, and EAAT2, and an increase in pro-migratory factors such as Lamc1 in NPCs. In conclusion, there are bidirectional proteomic interactions between GBM cells and NPCs that contributes to altered neurogenesis and increased tumor malignancy of LV-proximal GBM. The signaling factors identified in our studies will result in identification of novel therapeutic targets for GBM.

Abstract Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. GBM tumors proximal to the lateral ventricles have a worse prognosis with multifocality, recurrence, and lower overall survival. Studies suggest this increased aggressiveness is attributed to cerebrospinal fluid (CSF), as we have previously observed transcriptomic changes in GBM cells upon CSF exposure. GlioVis database reveals chitinase 3-like protein 1 (CHI3L1), a glycoprotein secreted by immune and cancer cells, is associated with poor prognosis and co-expressed with pro-inflammatory and tissue remodeling genes. We suggest exposure to CSF elevates CHI3L1 expression, consequently impacting malignancy-associated gene expression in patient-derived GBM lines. We first evaluated if patient CSF influences the expression of CHI3L1. GBM cells were treated with artificial CSF, non-cancer CSF, or cancer CSF for 72 hours. qPCR revealed significant increases in CHI3L1 (p&lt; 0.0001), SPP1, and CD44 expression in cancer CSF groups compared to artificial CSF. CHI3L1 expression at the protein level is also increased by cancer CSF when profiled using Western Blot. Additionally, ELISA results indicated significantly higher levels of CHI3L1 in CSF samples obtained from patients with high-grade tumors compared to non-cancer samples. Next, we assessed if exogenous CHI3L1 stimulates GBM malignancy at the cellular level. An effective concentration of recombinant human CHI3L1 was determined through Alamar Blue assay, showing 500 ng/ml CHI3L1 increases viability in primary patient cell lines compared to non-treated media. Recombinant CHI3L1 also increases cell migration in Transwell assay. qPCR revealed Vimentin (p&lt; 0.001) and Twist (p&lt; 0.0001) expression significantly increases while E-cadherin (p&lt; 0.001) significantly decreases in CHI3L1-treated groups, consistent with EMT and migratory activity. Ultimately, this study shows CHI3L1 is a CSF-induced factor in GBM and could be a therapeutic target as it enhances tumor malignancy by increasing proliferation, migration, and malignancy-promoting gene expression.

Abstract Introduction: Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. The interaction of GBM with the lateral ventricles (LVs) has a significant effect on patient outcome, where LV-proximal GBM results in increased distal recurrence, increased stem cell marker expression, and decreased overall survival compared to LV-distal counterparts. Though the reason for this is unknown, it may be due in part to interaction of GBM with the subventricular zone (SVZ), the largest neurogenic niche. The SVZ contains populations of neural stem cells (NSCs) throughout life that produce many proteins supporting stem cell growth and maintenance. The goal of this project is to identify a bidirectional signaling axis between GBM cells and NSCs and determine its contribution to GBM malignancy. Methods: In vitro, patient-derived GBM brain tumor initiating cells (BTICs) were co-cultured with human fetal NSCs for 48 hours. Both BTICs and NSCs were analyzed for levels of viability, proliferation, migration, and the expression of malignancy-associated factors at a gene and protein level. A method for unbiased cell-specific proteomic labeling was established in vitro by cloning L274G-mutated methionyl tRNA synthetase (MetRS*) into a lentivirus with puromycin resistance. In vivo, Nestin-Cre-ERT2 mice were crossed with the STOPflox R26-MetRS line to establish a tamoxifen-inducible model to label NSC proteins. Results: BTICs co-cultured with NSCs showed increased viability, proliferation, and migration compared to controls. NSCs showed decreased proliferation and increased migration when co-cultured with BTICs. Both show increased levels of malignancy-associated genes and proteins including osteopontin, vimentin, tenascin C, and PDGFA upon co-culture. MetRS*-labeled cells successfully incorporate azide-labeled methionine analog in a cell-specific manner, and labeled proteins are able to be isolated for future proteomic analysis. In vivo, tamoxifen successfully induces the expression of MetRS* and GFP. Conclusion: We have determined that there is a bidirectional signaling axis between NSCs and BTICs that contributes to proliferation, migration, and malignancy-associated factors in GBM. Future studies looking at proteomic changes in both GBM and NSCs using the MetRS* labeling are needed to fully characterize the interaction between these cells in vitro and in vivo to identify new therapeutic targets for LV-associated GBM. Citation Format: Emily S. Norton, Lauren A. Whaley, Anna Carrano, Natanael Zarco, Montserrat A. Lara-Velazquez, Alfredo Quinones-Hinojosa, Hugo Guerrero-Cazares. Exploring the malignancy-promoting interaction between neural stem cells and lateral ventricle-associated glioblastoma [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 3073.

Abstract Background Glioblastomas (GBMs) are the main primary brain tumors in adults with almost 100% recurrence rate. Patients with lateral ventricle proximal GBMs (LV-GBMs) exhibit worse survival compared to distal locations for unknown reasons. One hypothesis is the proximity of these tumors to the cerebrospinal fluid (CSF) and its chemical cues that can regulate cellular phenotype. We therefore investigated the role of CSF on GBM gene expression and the role of a CSF-induced gene, SERPINA3, in GBM malignancy in vitro and in vivo. Methods We utilized human CSF and GBM brain tumor-initiating cells (BTICs). We determined the impact of SERPINA3 expression in glioma patients using The Cancer Genome Atlas (TCGA) database. SERPINA3 expression changes were evaluated at mRNA and protein levels. The effects of knockdown (KD) and overexpression (OE) of SERPINA3 on cell migration, viability and cell proliferation were evaluated. Stem cell characteristics on KD cells were evaluated by differentiation and colony formation experiments. Tumor growth was studied by intracranial and flank injections. Results GBM-CSF increased BTIC migration accompanied by upregulation of the SERPINA3 gene. In patient samples and TCGA data, we observed SERPINA3 to correlate directly with brain tumor grade and indirectly with GBM patient survival. SERPINA3 KD induced a decrease in cell proliferation, migration, invasion, and stem cell characteristics, while SERPINA3 OE increased cell migration. In vivo, SERPINA3 KD BTICs showed increased survival in a murine model. Conclusions SERPINA3 plays a key role in GBM malignancy and its inhibition results in a better outcome using GBM preclinical models.