Hubert, C. G. | bioRxiv Science

bioRxiv2021

The WRAD complex represents a therapeutically exploitable target for cancer stem cells in glioblastoma

Glioblastomas (GBMs) are heterogeneous, treatment-resistant tumors that are driven by populations of cancer stem cells (CSCs). Despite their importance for tumor growth, few molecular mechanisms critical for CSC population maintenance have been exploited for therapeutic development. We developed a spatially resolved loss-of-function screen in GBM patient-derived organoids to identify essential epigenetic regulators in the SOX2-enriched, therapy resistant niche and identified WDR5 as indispensable for this population. WDR5 is a component of the WRAD complex, which promotes SET1-family-mediated Lys4 methylation of histone H3, associated with positive regulation of transcription. In GBM CSC models, WDR5 inhibitors blocked WRAD complex assembly and reduced H3K4 trimethylation and expression of genes involved in CSC-relevant oncogenic pathways. H3K4me3 peaks lost with WDR5 inhibitor treatment occurred disproportionally on POU transcription factor motifs, including the POU5F1(OCT4)::SOX2 motif. We incorporated a SOX2/OCT4 motif driven GFP reporter system into our CSC cell models and found that WDR5 inhibitor treatment diminished reporter activity. Further, WDR5 inhibitor treatment altered the stem cell state, disrupting CSC in vitro growth and self-renewal as well as in vivo tumor growth. These findings highlight the role of WDR5 and the WRAD complex in maintaining the CSC state and provide a rationale for therapeutic development of WDR5 inhibitors for GBM and other advanced cancers. SignificanceIn this study, we perform an epigenetic-focused functional genomics screen in glioblastoma organoids and identify WDR5 as an essential epigenetic regulator in the SOX2-enriched, therapy resistant cancer stem cell niche. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=135 HEIGHT=200 SRC="FIGDIR/small/461125v2_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@bc5c5eorg.highwire.dtl.DTLVardef@545a2borg.highwire.dtl.DTLVardef@1ebd3c9org.highwire.dtl.DTLVardef@19d5d30_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2020

Altered lipid metabolism marks glioblastoma stem and non-stem cells in separate tumor niches

BackgroundGlioblastoma (GBM) is marked by cellular heterogeneity, including metabolic heterogeneity, that varies among cellular microenvironments in the same tumor. Altered cellular metabolism in cancer is well-established, but how lipid metabolism is altered to suit different microenvironmental conditions and cellular states within a tumor remains unexplored. MethodsWe assessed GBM organoid models that mimic the transition zone between nutrient-rich and nutrient-poor pseudopalisading/perinecrotic tumor zones and performed spatial RNA-sequencing of cells to interrogate lipid metabolism. Using targeted lipidomic analysis, we assessed differences in acutely enriched cancer stem cells (CSCs) and non-CSCs from multiple patient-derived models to explore the link between the stem cell state and lipid metabolism. ResultsSpatial analysis revealed a striking difference in lipid content between microenvironments, with lipid enrichment in the hypoxic organoid cores and the perinecrotic and pseudopalisading regions of primary patient tumors. This was accompanied by regionally restricted upregulation of hypoxia-inducible lipid droplet-associated (HILPDA) gene expression in organoid cores and in clinical GBM specimens, but not lower-grade brain tumors, that was specifically localized to pseudopalisading regions of patient tumors. CSCs have low lipid droplet accumulation compared to non-CSCs in organoid models and xenograft tumors, and prospectively sorted lipid-low GBM cells are functionally enriched for stem cell activity. Targeted lipidomic analysis revealed that CSCs had decreased levels of major classes of neutral lipids compared to non-CSCs but had significantly increased polyunsaturated fatty acid production due to high fatty acid desaturase (FADS1/2) expression. ConclusionsOur data demonstrate that lipid metabolism is differentially altered across GBM microenvironments and cellular hierarchies, providing guidance for targeting of these altered lipid metabolic pathways. Key pointsO_LIGBM cells in nutrient-poor tumor regions have increased accumulation of lipid droplets. C_LIO_LICSCs have reduced lipid content compared to non-CSCs. C_LIO_LIGBM CSCs and non-CSCs have disparate lipid metabolisms that may be uniquely targetable. C_LI Importance of the StudyMetabolic targeting has long been advocated as a therapy against many tumors including GBM, and it remains an outstanding question whether cancer stem cells (CSCs) have altered lipid metabolism. We demonstrated striking differences in lipid metabolism between diverse cell populations from the same patient. These spatially and phenotypically distinct lipid phenotypes occur clinically in the majority of patients and can be recapitulated in laboratory models. Lipidomic analysis of multiple patient-derived models shows a significant shift in lipid metabolism between GBM CSCs and non-CSCs, suggesting that lipid levels may not be simply a product of the microenvironment but also may be a reflection of cellular state. Our results suggest that therapeutic targeting of GBM lipid metabolism must consider multiple separate tumor cell populations to be effective, and we provide a methodologic framework for studying these metabolically diverse cellular populations.

cancer biology↗