Abstract NG09: Bioengineered tissue mimetic hydrogels to study brain tumor biology and screen therapeutics
Authors: Pedron Sara 
Published: July 2021

Abstract
We have insufficient understanding of the complexity of the brain. Most in vitro systems do not recreate the biology and function of the brain. Moreover, the obstacles to studying the interactions between human genetics and environmental factors results in a gap of knowledge about the causes of brain diseases. Artificial tissues seek to integrate different brain cells in a controlled three-dimensional environmental configuration to obtain platforms that better recreate brain physiology in a simpler and affordable approach, easier to manipulate than traditional organoids. The development of low-cost, easy-to-use systems to evaluate treatments for neurological diseases would enhance the efficacy and toxicological assessment for specific patients, mitigating the limitations of current technologies, enhancing treatment options and improving patient's quality of life. These preclinical tools demonstrate the potential to revolutionize healthcare technology by improving human brain cancer modeling, and enabling a more accurate prediction of effective drugs, particularly important in cancers with low numbers of patients available for participation in clinical research. Recently, there has been a considerable progress in the development of three-dimensional in vitro brain models due to the advance in experimental methods such as induce pluripotent stem cells, biomaterials and microfabrication techniques. Biomaterial-based ex vivo models of healthy and diseased brain tissue are among those tools that may help study the complexity of cerebral tissue to better diagnose, prevent, and treat brain diseases. We have established engineered brain tumor biomaterials based on methacrylamide-functionalized gelatin hydrogels and used microfluidic-forming techniques to generate platforms that combine transitions of biophysical and biomolecular properties found in the glioblastoma tumor microenvironment, from the core to the tumor margins (1). Moreover, this biomaterial approach is able to monitor the response of patient-derived xenograft (PDX) cell populations with different molecular signatures; in particular, we have analyzed the amplified and the constitutively activated vIII mutant EGF receptor. We have also characterized PDX response to targeted inhibitors, such as erlotinib, a tyrosine kinase inhibitor that specifically blocks EGFR (2). Patients with glioblastoma (GBM) exhibit poor survival rates, tied both to the significant intra and interpatient heterogeneity of the tumor as well as the complex signaling pathways underlying malignancy. Spatial and temporal gradients regulate cell proliferation, migration, and differentiation during cancer. Therefore, the use of a microfluidic approach to fabricate patterned biomaterials, have the ability to examine transitions between defined environments (e.g., glioma core, periphery and neural tissue). Cells within these structured materials can be fully analyzed by imaging, secretomic and gene expression analyses (3). Cell morphology evolved to a more spread shape from low to high crosslinking density of gelatin and hypoxic levels depended on cell concentration. Using patient derived GBM tumor samples we are able to generate a miniaturized tumor tissue analog to examine how the heterogeneities within the tumor microenvironment impact glioma malignant phenotype, growth, and therapeutic efficacy. Gliomas exhibit high infiltration into brain parenchyma, impairing surgical resection and leading to recurrence. Using a library of stiffness-matched hydrogels with variable levels of matrix-bound HA, we reported that invasion is enhanced in softer hydrogels but reduced in the presence of matrix-bound HA (4). Inhibiting HA-CD44 interactions reduces invasion, even in hydrogels lacking matrix-bound HA. Analysis of HA biosynthesis suggests that GBM cells compensate for a lack of matrix-bound HA by producing soluble HA to stimulate invasion. Together, a robust method is showed to quantify GBM invasion over long culture times to reveal the coordinated effect of matrix stiffness, immobilized HA, and compensatory HA production on GBM invasion. Brain extracellular matrix (ECM) plays a key role in glioma invasion and therapeutic resistance (5, 6). In particular, the main component of brain ECM, hyaluronic acid (HA), has been associated to pathological conditions in its low molecular weight form (LMW) (7). We have investigated the influence of tumor ECM HA in glioblastoma progression and resistance to a targeted tyrosine kinase inhibitor. We speculate that increased high molecular HA production with low degradation is related to therapeutic resistance and controls cell invasion. The ability to manipulate tumor ECM can improve therapeutic outcomes and restrict glioma infiltration. This in vitro tumor model is able to analyze the relationship between HA and the invasive phenotype of GBM tumor cells. We show that cell growth, motility and proteomic responses of GBM cells within our platform were significantly altered by HA molecular weight in response to a tyrosine kinase inhibitor (2, 3). These results provide additional insights regarding the importance of extracellular microenvironment in the invasive potential of glioblastoma tumors. Recently, we demonstrated that repeated dosing of erlotinib promotes expression of PDGFRb in EGFR vIII mutant cells and that extracellular HA plays a favorable role in the inhibition of EGFR, through STAT3 deactivation (8). References.(1) Pedron S, Becka E, Harley BA (2015), Adv. Mater., 27: 1567. (2) Pedron S, Hanselman JS, Schroeder MA, Sarkaria JN, Harley BAC (2017), Adv. Healthcare Mater., 6: 1700529. (3) Pedron S, Polishetty H, Pritchard AM, Mahadik BP, Sarkaria JN, Harley BAC (2017), MRS Commun. 2017, 7 (3), 442-449. (4) Chen JE, Pedron S, Harley BAC. (2017). Macromolecular Biosci., 17 (8), 1700018. (5) Pedron S, Becka E, Harley BAC. (2013). Biomaterials 34 (30), 7408-7417. (6) Chen JE, Pedron S, Shyu P, Hu Y, Sarkaria JN, Harley BAC. (2018) Frontiers in Materials, 5:39. doi: 10.3389/fmats.2018.00039. (7) Liu M, Tolg C, Turley E (2019), Front. Immunol., 10: 947. (8) Pedron S, Wolter GL, Sarkaria JN, Harley BAC et al. (2019), Biomaterials, 219: 119371.
Citation Format: Sara Pedron. Bioengineered tissue mimetic hydrogels to study brain tumor biology and screen therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr NG09.