Guerrero‐Cazares, Hugo

Abstract The extracellular matrix (ECM) plays a critical role in cancer progression, with its biophysical properties influencing cancer behavior. ECM stiffness can induce long-lasting adaptations in cancer cells, promoting sustained invasion through a process known as “mechanical memory” (MM). Glioblastoma (GBM) exhibits spatial heterogeneity in stiffness, with stiffer ECM found at the tumor periphery where invasive cells reside and promote recurrence. We hypothesize that increased stiffness at the tumor periphery primes GBM cells for sustained invasion through MM. METHODS Cell lines were established from image-guided human GBM samples from tumor margin and core (n=10 patients, 20 cell lines). Cells from random locations were conditioned in physiologically relevant extracellular matrices for two weeks. Human organotypic assay (n=3), Migration Assays, Atomic Force Microscopy (AFM), Immunocytochemistry, Western Blot, and RNA-sequencing (n=6) were performed. RESULTS GBM cells at higher stiff surfaces displayed increased migration (p<0.01). Magnetic Resonance Elastography (n=9) confirmed GBM heterogeneity, with softer cores (0.2-0.5kPa) transitioning to stiffer margins (>2kPa). Organotypic scaffolds mimicking the tumor margin promoted enhanced migration of GFP-labeled GBM cells. Margin cells and cells conditioned on stiffer matrices demonstrated higher migratory potential compared to their core and soft-conditioned counterparts (p<0.05). These trends persist over time and across multiple passages. ECM stiffness exposure causes nanomechanical, cytoskeletal, and transcriptional adaptations. AFM shows that cells from the margin (n=6) are softer (p<0.01) and more deformable (p<0.01). RNAseq identified upregulation of MM-specific genes in GBM margin cells. The mechanosensitive transcription factor YAP1 emerged as a key driver of MM. Notably, YAP1 is targetable by the FDA-approved drug Verteporfin. YAP1 expression was elevated in margin and stiff-conditioned cells (p<0.05). Stiff-conditioned cells and margin cells displayed increased sensitivity to Verteporfin treatment (p<0.05), with treatment significantly reducing margin migration compared to the core (p<0.001). CONCLUSION Stiffer GBM margins promote the formation of aggressive phenotypes through MM. Targeting YAP1 with Verteporfin, a readily available drug, presents a promising strategy to halt GBM invasion and improve patient outcomes.

Abstract Glioblastoma (GBM) is the most common malignant primary brain tumor in adults with a median survival of 8-14 months and 5-year survival rate of 6.9%. Its aggressive nature arises mostly from molecular heterogeneity and resistance to standard of care (SOC), including radiation and temozolomide (TMZ). Recurrence is nearly inevitable, driven by highly invasive brain tumor initiating cells (BTICs). Our previous studies revealed that exposing BTICs to cerebrospinal fluid (CSF) from GBM patients increases cell migration and proliferation compared to non-cancer CSF. Transcriptomic analysis identified the upregulation of the SERPINA3 gene, which encodes alpha-1-antichymotrypsin (ACT). Silencing of SERPINA3 reduces BTIC migration and proliferation and abolishes the promigratory response to GBM-derived CSF, highlighting SERPINA3 as a potential therapeutic target. ACT has been reported to bind to DNA, although the implications of this interaction are unknown. We have previously observed higher levels of intranuclear ACT in human GBM compared to non-cancer brain tissues. We hypothesize that the nuclear localization of SERPINA3 in GBM contributes to increased malignancy, opening the possibility of therapeutically targeting its intranuclear transport. Here, we determined the intracellular localization of ACT in BTICs and GBM and compared it to non-cancer tissues. Additionally, we evaluated whether SOC affected intranuclear localization of ACT. Patient-derived BTICs were treated with TMZ, radiation, and a combination of both, to assess changes in ACT expression via Western Blot, PCR, and ICC. A decrease in cell confluency was correlated with a significant decrease (p<0.05) in SERPINA3 mRNA and overall protein expression when BTICs were treated with TMZ alone or in combination. Interestingly, confocal microscopy revealed a significant increase (p<0.05) in its nuclear localization, particularly with TMZ treatment, indicating a change in its intracellular distribution. Overall, nuclear translocation of SERPINA3 increases in response to SOC with potential implications as a treatment resistance mechanism.

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.

Glioblastoma (GBM) remains the most common and aggressive malignant primary brain tumor [...]

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.