Biology subjects

Baisiwala, S.

Publications and source records attributed to Baisiwala, S..

9 recordsLinked to original sources

bioRxiv2026

Glutamatergic neuron-tumor synapses shape human glioblastoma cell states through radial glia plasticity

Glioblastoma (GBM) is a devastating primary brain tumor with remarkable inter- and intra-tumoral heterogeneity. GBM cells assume a spectrum of neurodevelopmental-like phenotypes and co-opt normal neurophysiological processes, which include synaptic integration with their neuronal microenvironment. This is mediated by neuron-tumor synapses (NTS) that predominantly involve glutamatergic receptors, which drive calcium elevations that promote tumor proliferation and invasion. The exact relationship between synaptic signaling and tumor cell fate specification, however, remains largely unexplored. Here, we develop and leverage a synapse-optimized human organoid tumor transplantation (so-HOTT) model of GBM to decipher how glutamatergic signaling impacts GBM lineage trajectories. so-HOTT preserves patient tumor heterogeneity, features excitatory NTS, and enables clonal lineage tracing of tumor cells after NTS perturbations. Genetic and pharmacological inhibition of AMPA and kainate receptors in so-HOTT shifts tumor cell composition from neuronal fates toward progenitor-proximal astrocytic/mesenchymal states. This occurs through the attenuation of calcium signaling and reduced plasticity of malignant radial glia (RG)-like progenitors, a previously unrecognized target of NTS. Through the integration of inputs from the neuronal microenvironment into glutamatergic signaling, progenitor populations modulate their transcriptional programs and cell fate, ultimately shaping GBM tumor heterogeneity. Targeting synaptic input may thus constrain the heterogeneity that fuels GBM adaptation and therapeutic escape.

cancer biology↗

bioRxiv2026

Predictable clonal hierarchies from restricted progenitors provide a framework for cell type-specific therapies in glioblastoma

Extensive molecular profiling has revealed profound heterogeneity in glioblastoma (GBM), yet how cellular lineages organize over time to govern tumor propagation and therapeutic response remains poorly understood. Existing single-cell approaches define transcriptional states but provide limited insight into how clonal dynamics shape functional tumor behavior. Here, we integrate high-complexity combinatorial DNA barcoding with single-cell transcriptomics in direct-from-patient IDH1-wild-type GBM, enabling lineage-resolved mapping of progenitor organization in a human microenvironmental context. Across 235,155 malignant cells from nine tumors, clonal relationships form reproducible lineage tracks in which distinct progenitor populations give rise to specific differentiated cell types, revealing that tumor growth is sustained by multiple non-redundant progenitors rather than a single dominant population. These progenitors exhibit distinct propensities for self-renewal, fate restriction, and cross-compartment interactions, collectively accounting for the full spectrum of tumor states. Using this lineage-resolved framework, we identify complementary drug targets in distinct progenitor compartments and demonstrate that hierarchy-informed combination therapies disrupt progenitor-progenitor interactions and reshape lineage output. These findings move beyond descriptive heterogeneity to define functional logic underlying GBM propagation and establish a generalizable framework for rational, cell type-specific combinatorial therapies.

cancer biology↗

bioRxiv2025

A Human Tumor-Immune Organoid Model of Glioblastoma

A major obstacle to identifying effective therapies for the aggressive brain tumor glioblastoma is the lack of human-specific, immunocompetent models that reflect the human tumor microenvironment. To address this, we developed the immune-Human Organoid Tumor Transplantation (iHOTT) model. This is an autologous co-culture platform that integrates patient-derived tumor cells and matched peripheral blood mononuclear cells (PBMCs) within human cortical organoids, enabling the study of the patient-specific immune response to the tumor and tumor-immune interactions. This platform preserves tumor and immune populations, immune signaling, and cell-cell interactions observed in patient tumors. Treatment of iHOTT with pembrolizumab, a checkpoint inhibitor, mirrored cell type shifts and cell interactions observed in patients. TCR sequencing further revealed pembrolizumab-driven expansion of stem-like CD4-T-cell clonotypes exhibiting patient-specific repertoires. These findings establish iHOTT as a physiologically relevant platform for exploring autologous tumor-immune interactions and underscore the critical need for antigen-targeted strategies to enhance immunotherapy in glioblastoma.

cancer biology↗

bioRxiv2024

THOC1 complexes with SIN3A to regulate R-loops and promote glioblastoma progression

ABSTRACTGlioblastoma (GBM), the most common and aggressive malignant brain tumor in adults, has a median survival of 21 months. To identify drivers of GBM proliferation, we conducted a CRISPR-knockout screen, which revealed THO Complex 1 (THOC1) as a key driver. Knocking down THOC1 significantly reduced GBM cell viability across patient-derived xenograft (PDX) lines, enhancing survival (p<0.01) in primary PDX models. Conversely, overexpressing THOC1 in non-cancerous cells bolstered viability, decreasing survival and causing tumor engraftment in vivo (p<0.01). Further investigation revealed THOC1s robust interaction with SIN3A, a histone deacetylase complex. Histone deacetylation has been previously shown to prevent the buildup of R-loops, structures that form normally during transcription but can be lethal in excess. We found that THOC1-knockdown leads to elevated R-loop levels and reduced histone deacetylation levels. Next, to understand the networks specifically regulated by THOC1-mediated R-loop prevention, we conducted unbiased RNA-sequencing on control and THOC1-knockdown GBM cells. We found that THOC1s role in R-loop prevention primarily affects telomeres, critical regions for cell replication. We further show that THOC1-knockdown results in significantly increased telomeric R-loop levels and shortened telomeres. Ultimately, this study suggests that targeting THOC1 shows promise as a therapeutic strategy to disrupt the delicate R-loop landscape and undermine GBMs replicative potential.

cancer biology↗

bioRxiv2021

Ribonucleotide Reductase Regulatory Subunit M2 as a Driver of Glioblastoma TMZ-Resistance through Modulation of dNTP Production

Glioblastoma (GBM) remains one of the most resistant and fatal forms of cancer. Previous studies have examined primary and recurrent GBM tumors, but it is difficult to study tumor evolution during therapy where resistance develops. To investigate this, we performed an in vivo single-cell RNA sequencing screen in a patient-derived xenograft (PDX) model. Primary GBM was modeled by mice treated with DMSO control, recurrent GBM was modeled by mice treated with temozolomide (TMZ), and during therapy GBM was modeled by mice euthanized after two of five TMZ treatments. Our analysis revealed the cellular population present during therapy to be distinct from primary and recurrent GBM. We found the Ribonucleotide Reductase gene family to exhibit a unique signature in our data due to an observed subunit switch to favor RRM2 during therapy. GBM cells were shown to rely on RRM2 during therapy causing RRM2-knockdown (KD) cells to be TMZ-sensitive. Using targeted metabolomics, we found RRM2-KDs to produce less dGTP and dCTP than control cells in response to TMZ (p<0.0001). Supplementing RRM2-KDs with deoxycytidine and deoxyguanosine rescued TMZ-sensitivity, suggesting an RRM2-driven mechanism of chemoresistance, established by regulating the production of these nucleotides. In vivo, tumor-bearing mice treated with the RRM2-inhibitor, Triapine, in combination with TMZ, survived longer than mice treated with TMZ alone (p<0.01), indicating promising clinical opportunities in targeting RRM2. Our data present a novel understanding of RRM2 activity, and its alteration during therapeutic stress as response to TMZ-induced DNA damage.

cancer biology↗

bioRxiv2021

CRISPR-Cas9 Screen Reveals PSMB3 Contributes to Gliomagenesis Through Proteasome-Dependent and Independent Mechanisms

Glioblastoma (GBM) is the most common adult malignant brain tumor, with a median survival of 21 months and a 100% recurrence rate. Even though many of the critical oncogenic drivers for GBM have been identified, the basis of gliomagenesis is still under investigation. To identify novel genes that contribute to GBM progression, we performed a genome-wide CRISPR-Cas9 knockout screen. We identified four previously unstudied genes - PSMB3, CHCHD4, SPDYE5, HSPA1 - which had elevated expression in cancer and demonstrated a significant positive correlation with respect to GBM growth and patient survival in vivo and patient datasets. Furthermore, overexpression of PSMB3 and HSPA5 in neural stem cells resulted in transformation to a cancer phenotype. Further investigation of PSMB3, a subunit of the proteasome, allowed us to identify both ubiquitin-mediated and non-ubiquitin-mediated mechanisms of oncogenesis. Ultimately, the data from our CRISPR screens suggests that these genes drive tumor progression, making them promising therapeutic targets for GBM.

cancer biology↗

bioRxiv2021

ARF4-mediated Retrograde Trafficking Drives Chemoresistance in Glioblastoma

Glioblastoma (GBM) is the most common type of adult malignant brain tumor, with a median survival of only 21 months. This is partly due to the high rate of resistance to conventional therapy, including temozolomide (TMZ), leading to recurrence rates close to 100%. It still remains unknown what drives the development of this resistance. To identify the unknown genes driving the development of this resistance, we performed a genome-wide CRISPR knockout screen comparing a DMSO-treated population with a TMZ-treated population over 14 days. We identified 4 previously unstudied genes - ARF4, PLAA, SPTLC1, and PIGK - that showed significant elevations in expression in recurrent tumors in patient datasets, along with significant survival benefits corresponding to low gene expression. Further investigation of ARF4, known to be involved in retrograde trafficking, allowed us to identify a mechanism of resistance that is mediated by increased retrograde transport of EGFR into the nucleus. Ultimately, our CRISPR-Cas9 screen has identified a promising therapeutic target, ARF4, which may drive GBMs high resistance to chemotherapy.

cancer biology↗

bioRxiv2018

Activation of dopamine receptor 2 (DRD2) prompts transcriptomic and metabolic plasticity in glioblastoma

Glioblastoma (GBM) is one of the most aggressive and lethal tumor types. Evidence continues to accrue indicating that the complex relationship between GBM and the brain microenvironment contributes to this malignant phenotype. However, the interaction between GBM and neurotransmitters, signaling molecules involved in neuronal communication, remains incompletely understood. Here we examined, in both sexes of humans and mice, how the monoamine dopamine influences GBM cells. We demonstrate that GBM cells express DRD2, with elevated expression in the glioma-initiating cell (GIC) population. Stimulation of DRD2 caused neuron-like depolarization exclusively in GICs. In addition, long-term activation of DRD2 heightened the sphere-forming capacity of GBM cells as well as tumor engraftment efficiency. Mechanistic investigation revealed that DRD2 signaling activates the hypoxia response and functionally alters metabolism. Finally, we found that GBM cells synthesize and secrete dopamine themselves, suggesting a potential autocrine mechanism. These results identify dopamine signaling as a potential therapeutic target in GBM and further highlight neurotransmitters as a key feature of the pro-tumor microenvironment.\n\nSignificance StatementThis work offers critical insight into the role of the neurotransmitter dopamine in the progression of GBM. We show that dopamine induces specific changes in the state of tumor cells, augmenting their growth and shifting them to a more stem-cell like state. Further, we show that dopamine can alter the metabolic behavior of GBM cells, increasing glycolysis. Finally, we show that GBM cells, including tumor samples from patients, can synthesize and secrete dopamine, suggesting an autocrine signaling process underlying these results. These results describe a novel connection between neurotransmitters and brain cancer, further highlighting the critical influence of the brain milieu on GBM.

cancer biology↗

bioRxiv2018

Interleukin-8/CXCR2 signaling regulates therapy-induced plasticity and enhances tumorigenicity in glioblastoma

Glioblastoma (GBM) remains one of the least treatable types of cancer. Recent work highlights two key factors contributing to this resistant phenotype--cellular plasticity, the ability of GBM cells to adopt many phenotypes, and the microenvironment. Here, we provide evidence that Interleukin-8 (IL-8) plays a vital role in promoting cellular plasticity and cancer initiating cells (CICs) niche during anti-glioma chemotherapy. IL-8 expression is significantly elevated during chemotherapy, and immunohistochemical analysis of matched primary and recurrent patient GBM tissues revealed about 60% of recurrent tissues IL-8 expression is upregulated. In silico analysis of the TCGA data indicated that IL-8 signaling could promote epigenetic plasticity by altering the polycomb repressor complex activity. We are proposing that such regulation my promote epigenetic plasticity, which allows the GBM cells to adapt therapy and may promote therapeutic resistance. Our data show that IL-8 is a crucial microenvironmental factor involved in developing therapeutic adaptation and can be targeted in combination with conventional chemo-and radiotherapy to prevent disease recurrence.\n\nABSTRACTEmerging evidence reveals enrichment of glioma initiating cells (GICs) following therapeutic intervention. This enrichment occurs partly by dedifferentiation of non-GICs to GICs within the tumor, which may contribute to therapeutic resistance and the generation of lethal recurrent tumors. To elucidate the molecular mechanisms governing therapy-induced cellular plasticity, we performed genome-wide chromatin immunoprecipitation sequencing (ChIP-Seq) and gene expression analysis (gene microarray analysis) during treatment with standard of care temozolomide (TMZ) chemotherapy. Analysis revealed significant enhancement of open chromatin marks in known astrocytic enhancers for Interleukin-8 (IL-8) loci as well as elevated expression during anti-glioma chemotherapy. The Cancer Genome Atlas and Ivy Glioblastoma Atlas Project data demonstrated that IL-8 transcript expression is negatively correlated with GBM patient survival (p=0.001) and positively correlated with that of genes associated with the CIC phenotype such as KLF4, c-Myc and HIF2 (p<0.001). Immunohistochemical analysis of patient samples demonstrated elevated IL-8 expression in about 60% of recurrent GBM tumors relative to matched primary tumors and this expression also positively correlates with time to recurrence. Exposure to IL-8 significantly enhanced the self-renewing capacity of patient-derived xenograft (PDX) GBM (average 3-fold, p<0.0005). Furthermore, IL-8 knockdown significantly delayed PDX GBM tumor growth in vivo (p<0.0005). Finally, guided by in silico analysis of TCGA data, we examined the effect of therapy-induced IL-8 expression on the epigenomic landscape of GBM cells and observed increased trimethylation of H3K9 and H3K27. Our results show that IL-8 alters cellular plasticity and mediates alterations in histone status. These finding suggest that IL-8 signaling participates in regulating GBM adaptation to therapeutic stress and therefore represents a promising target for combination with conventional chemotherapy in order to limit GBM recurrence.

cancer biology↗