Glioblastoma (GBM) is the most aggressive and common form of primary brain cancer. Several decades of research have provided great insight into GBM progression; however, the prognosis remains poor with a median patient survival time of ~ 15 months. The tumour microenvironment (TME) of GBM plays a crucial role in mediating tumour progression and thus is being explored as a therapeutic target. Progress in the development of treatments targeting the TME is currently limited by a lack of model systems that can accurately recreate the distinct extracellular matrix composition and anatomic features of the brain, such as the blood-brain barrier and axonal tracts. Biomaterials can be applied to develop synthetic models of the GBM TME to mimic physiological and pathophysiological features of the brain, including cellular and ECM composition, mechanical properties, and topography. In this Review, we summarize key features of the GBM microenvironment and discuss different strategies for the engineering of GBM TME models, including 2D and 3D models featuring chemical and mechanical gradients, interfaces and fluid flow. Finally, we highlight the potential of engineered TME models as platforms for mechanistic discovery and drug screening as well as preclinical testing and precision medicine.

In the last few decades, hyaluronic acid (HA) has become increasingly employed as a biomaterial in both clinical and research applications. The abundance of HA in many tissues, together with its amenability to chemical modification, has made HA an attractive material platform for a wide range of applications including regenerative medicine, drug delivery, and scaffolds for cell culture. HA has traditionally been appreciated to modulate tissue mechanics and remodeling through its distinctive biophysical properties and ability to organize other matrix proteins. However, HA can influence cell behavior in much more direct and specific ways by engaging cellular HA receptors, which can trigger signals that influence cell survival, proliferation, adhesion, and migration. In turn, cells modify HA by regulating synthesis and degradation through a dedicated arsenal of enzymes. Optimal design of HA-based biomaterials demands full consideration of these diverse modes of regulation. This review summarizes how HA-based signaling regulates cell behavior and discusses how these signals can be leveraged to create cell-instructive biomaterials.

The structure and mechanics of many connective tissues are dictated by a collagen-rich extracellular matrix (ECM), where collagen fibers provide topological cues that direct cell migration. However, comparatively little is known about how cells navigate the hyaluronic acid (HA)-rich, nanoporous ECM of the brain, a problem with fundamental implications for development, inflammation, and tumor invasion. Here, we demonstrate that glioblastoma cells adhere to and invade HA-rich matrix using microtentacles (McTNs), which extend tens of micrometers from the cell body and are distinct from filopodia. We observe these structures in continuous culture models and primary patient-derived tumor cells, as well as in synthetic HA matrix and organotypic brain slices. High-magnification and superresolution imaging reveals McTNs are dynamic, CD44-coated tubular protrusions containing microtubules and actin filaments, which respectively drive McTN extension and retraction. Molecular mechanistic studies reveal that McTNs are stabilized by an interplay between microtubule-driven protrusion, actomyosin-driven retraction, and CD44-mediated adhesion, where adhesive and cytoskeletal components are mechanistically coupled by an IQGAP1–CLIP170 complex. McTNs represent a previously unappreciated mechanism through which cells engage nanoporous HA matrix and may represent an important molecular target in physiology and disease.

Glioblastoma (GBM) responses to bevacizumab are invariably transient with acquired resistance. We profiled paired patient specimens and bevacizumab-resistant xenograft models pre-and postresistance toward the primary goal of identifying regulators whose targeting could prolong the therapeutic window, and the secondary goal of identifying biomarkers of therapeutic window closure. Bevacizumab-resistant patient specimens and xenografts exhibited decreased vessel density and increased hypoxia versus preresistance, suggesting that resistance occurs despite effective therapeutic devascularization. Microarray analysis revealed upregulated mesenchymal genes in resistant tumors correlating with bevacizumab treatment duration and causing three changes enabling resistant tumor growth in hypoxia. First, perivascular invasiveness along remaining blood vessels, which co-opts vessels in a VEGFindependent and neoangiogenesis-independent manner, was upregulated in novel biomimetic 3D bioengineered platforms modeling the bevacizumab-resistant microenvironment. Second, tumorinitiating stem cells housed in the perivascular niche close to remaining blood vessels were enriched. Third, metabolic reprogramming assessed through real-time bioenergetic measurement and metabolomics upregulated glycolysis and suppressed oxidative phosphorylation. Single-cell sequencing of bevacizumab-resistant patient GBMs confirmed upregulated mesenchymal genes, particularly glycoprotein YKL-40 and transcription factor ZEB1, in later clones, implicating these changes as treatment-induced. Serum YKL-40 was elevated in bevacizumab-resistant versus bevacizumab-na€ ve patients. CRISPR and pharmacologic targeting of ZEB1 with honokiol reversed the mesenchymal gene expression and associated stem cell, invasion, and metabolic changes defining resistance.Honokiol caused greater cell death in bevacizumab-resistant than bevacizumab-responsive tumor cells, with surviving cells losing mesenchymal morphology. Employing YKL-40 as a resistance biomarker and ZEB1 as a target to prevent resistance could fulfill the promise of antiangiogenic therapy.