Glioblastoma remains one of the most lethal human cancers, and much of its lethality stems from a hidden population of tumor cells that behave like stem cells, capable of self-renewal, plasticity, and resistance to therapy. A new study published in the Journal of Cellular and Molecular Medicine offers a strikingly precise account of how that stem-like state is acquired, and it points to an unexpected timekeeper: the transcription factor SOX9. Rather than acting as a permanent engine of stemness, the research suggests that SOX9 functions during a narrow early window, priming the Hippo–YAP/TAZ signaling axis as glioma cells convert from astrocyte-like states into fully malignant ones.
The research team, led by investigators at the First Affiliated Hospital of Xinjiang Medical University, combined single-cell RNA sequencing, spatial transcriptomics, CRISPR-based gene editing, pharmacological pathway modulation, and xenograft modeling to trace SOX9’s role across both time and tissue space. Using a publicly available single-cell dataset, they reconstructed a pseudotime trajectory with Monocle3, mapping the continuous transition from astrocytes to malignant glioma cells. The analysis revealed substantial cellular heterogeneity within glioma samples, encompassing malignant cells alongside astrocytes, macrophages, T cells, B cells, monocytes, neurons, fibroblasts, and endothelial cells.
The most consequential finding to emerge from the trajectory analysis was SOX9’s temporal behavior. Its expression was concentrated almost exclusively in astrocyte and malignant cell populations, and along the inferred developmental arc it peaked early and then declined steadily as cells matured into malignant states. Correlation analysis confirmed this downward trend, with Pearson and Spearman coefficients both strongly negative and highly significant. At the level of trajectory nodes, SOX9 dominated the early, astrocyte-rich segments and faded in the terminal malignant zones, a pattern inconsistent with the conventional view of SOX9 as a constitutively active stemness factor.
To probe what SOX9 might be doing during that early window, the researchers scored the activity of the Hippo pathway, a master regulator of organ size and stem cell fate whose downstream effectors YAP and TAZ are established drivers of glioblastoma plasticity. Using Gene Set Variation Analysis, they quantified an upstream kinase module, including MST1/2, LATS1/2, SAV1, MOB1A/B, NF2, and WWC1, and a canonical YAP/TAZ target module containing genes such as CTGF, CYR61, ANKRD1, AXL, and BIRC5. Both modules showed inverse relationships with SOX9 expression, and generalized additive modeling revealed that pseudotime and SOX9 each contributed independent, nonlinear effects on pathway activity. In other words, the SOX9–Hippo relationship was phase-dependent, strongest during early-to-intermediate stages of the transition and not a simple monotonic association.
Spatial transcriptomics added a second, geographic dimension to the story. Analyzing four anatomically distinct regions of glioblastoma tissue—the tumor–normal interface, the pure tumor core, the perivascular compartment, and the tumor–necrosis interface—the team mapped SOX9 expression against the probability that each spatial spot contained malignant cells. The coupling between SOX9 and malignancy was weak or unstable at the tumor edges and the necrotic margin, modest in the tumor core, and most robust in the perivascular niche. There, SOX9 expression was markedly elevated, correlations with malignant cell probability were strongest, and neighborhood enrichment and spatial autocorrelation statistics all confirmed significant co-localization.
This regional specificity is biologically meaningful. The perivascular niche has long been recognized as a reservoir for stem-like glioblastoma cells, bathed in vascular, hypoxic, and paracrine signals that nurture cellular plasticity. The findings suggest that SOX9-dependent reprogramming is not only time-restricted but niche-conditioned, with perivascular regions providing the most permissive anatomical context for effective SOX9–Hippo–YAP/TAZ coupling. Elsewhere in the tumor, downstream malignant programs may be sustained through alternative inputs, weakening the spatial coherence of the axis.
Functional experiments brought the correlation studies into the laboratory. Using lentiviral vectors, the team generated U87 glioma cells stably overexpressing SOX9 and used CRISPR/Cas9 to knock out the gene in U251 cells, validating the edits by Sanger sequencing and confirming a frameshift-inducing deletion in the knockout clone. SOX9 overexpression modestly increased proliferation, migration, and invasion while reducing apoptosis, whereas SOX9 knockout produced the opposite phenotype across wound-healing, Transwell invasion, and flow-cytometric apoptosis assays. Critically, treatment with XMU-MP-1, an inhibitor of the upstream Hippo kinases MST1/2, partially rescued the defects caused by SOX9 loss, linking SOX9 function experimentally to Hippo pathway state.
Phosphorylation-level Western blotting sharpened the mechanistic picture. SOX9 overexpression raised the ratio of phosphorylated to total YAP and lowered the phosphorylated-to-total MOB1 ratio, while SOX9 knockout produced the reciprocal pattern. XMU-MP-1 shifted both readouts toward the SOX9-overexpression signature, and total MOB1 remained unchanged across groups, indicating that the pathway rewiring was phosphorylation-dependent rather than a simple change in protein abundance. YAP and TAZ mRNA and protein levels rose with SOX9 gain and fell with SOX9 loss, and drug treatment partially restored them in SOX9-deficient cells, extending the transcriptomic associations to protein-level pathway readouts.
In vivo, the story held. Subcutaneous xenografts in nude mice showed that SOX9 overexpression significantly accelerated U87-derived tumor growth from day 14 onward, while SOX9 knockout markedly suppressed U251-derived tumors. XMU-MP-1 treatment further enlarged SOX9-overexpressing tumors and partially reversed the growth inhibition caused by SOX9 loss. Histopathology mirrored these dynamics: SOX9-overexpressing tumors displayed increased necrosis and nuclear atypia, whereas knockout tumors showed milder pathology, and the drug partially reversed both patterns. Ki67 immunohistochemistry confirmed the corresponding changes in proliferative activity, and CD68 staining revealed that myeloid and macrophage-like cell accumulation also shifted with SOX9 status, adding an immune dimension to the tumor microenvironmental effects.
Taken together, the study proposes what the authors call an early priming–late decoupling model. SOX9 acts early, at the moment of astrocyte-to-malignant conversion, to initiate Hippo–YAP/TAZ-linked malignant reprogramming. Once downstream transcriptional networks consolidate, the tumor becomes progressively less dependent on sustained SOX9 expression, which explains why stemness programs can persist in advanced disease even as SOX9 levels fall. The translational implication is pointed: therapies aimed at SOX9 may work best before malignant programs fully consolidate, whereas in later-stage tumors, blocking SOX9 alone may prove insufficient. The results argue for stage-specific and niche-aware strategies targeting the SOX9/Hippo/YAP–TAZ axis, particularly in the perivascular compartment where the axis is most strongly engaged. Limitations remain, including the reliance on public cohorts of limited size, established cell lines, and subcutaneous rather than orthotopic models, and the absence of YAP/TAZ nuclear localization data or a second pathway inhibitor. Even so, the study repositions SOX9 from a static stemness marker to a dynamic state-switch regulator, and it provides a conceptual framework for timing future interventions against one of medicine’s most stubborn cancers.
Subject of Research: The temporal role of SOX9 in priming Hippo–YAP/TAZ signaling during glioblastoma stemness acquisition
Article Title: Early SOX9 Activation Primes Hippo–YAP/TAZ Rewiring During Glioblastoma Stemness Acquisition
Article References: Early SOX9 Activation Primes Hippo–YAP/TAZ Rewiring During Glioblastoma Stemness Acquisition. (n.d.). https://doi.org/10.1111/jcmm.71341
Image Credits: AI Generated
DOI: 10.1111/jcmm.71341
Keywords: glioblastoma, SOX9, Hippo pathway, YAP/TAZ, glioma stem cells, pseudotime analysis, spatial transcriptomics, perivascular niche, XMU-MP-1, CRISPR, tumor plasticity, xenograft
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Juliet Wilcox. (September 12, 2026). SOX9 Acts Early to Rewire Hippo–YAP/TAZ Signaling as Glioblastoma Cells Turn Stem-Like. Scienmag. https://scienmag.com/sox9-acts-early-to-rewire-hippo-yap-taz-signaling-as-glioblastoma-cells-turn-stem-like/
Juliet Wilcox. “SOX9 Acts Early to Rewire Hippo–YAP/TAZ Signaling as Glioblastoma Cells Turn Stem-Like.” Scienmag, 12 September 2026, https://scienmag.com/sox9-acts-early-to-rewire-hippo-yap-taz-signaling-as-glioblastoma-cells-turn-stem-like/. Accessed 12 September 2026.
Juliet Wilcox. “SOX9 Acts Early to Rewire Hippo–YAP/TAZ Signaling as Glioblastoma Cells Turn Stem-Like.” Scienmag. September 12, 2026. https://scienmag.com/sox9-acts-early-to-rewire-hippo-yap-taz-signaling-as-glioblastoma-cells-turn-stem-like/
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Tags: cancer stem cell plasticityCRISPRCRISPR gene editing in cancerearly tumor cell reprogrammingGlioblastomaglioma cell lineage transitionglioma stem cellsHippo pathwayHippo–YAP/TAZ signaling pathwayperivascular nichepseudotime analysisSingle-Cell RNA SequencingSOX9SOX9 transcription factorSpatial transcriptomicsspatial transcriptomics in gliomatherapeutic resistance in glioblastomatumor cell heterogeneitytumor microenvironment interactionstumor plasticityxenograftXMU-MP-1YAP/TAZ
