Diffuse intrinsic pontine gliomas (DIPG) are a highly aggressive pediatric brain tumor of the ventral pons (brain stem), with a five-year survival rate of less than 1% and a median survival of only 9 months [1,2]. While significant improvement in survival has been achieved in treating other forms of pediatric cancer, survival rate for DIPG has not changed in over three decades [1]. While the brain tumor niche itself is a 3D, multi-factorial environment, previous attempts have relied on standard 2D monolayer culture or animal models to mimic the disease phenotype. However, increasing evidence has shown that cancer cell behavior in 2D differs substantially from the in vivo phenotype [3]; whereas animal models are costly, lengthy to produce, and often cumbersome for mechanistic studies. Furthermore, previous studies were done almost exclusively with adult brain tumor cells, whereas adult and pediatric brain tumors have been shown to demonstrate distinct phenotypes in their sites of origin, clinical presentations and molecular mechanisms [4]. Through working at the interface of bioengineering, materials science, cancer biology, neurosurgery, and animal models, the goals of this proposal are to develop hydrogels with optimized niche cues to support DIPG proliferation and invasion in 3D, and to harness such in vitro model for elucidating the role of integrin receptors and cell-cell interactions in driving DIPG progression. The efficacy of blocking specific integrin receptors for inhibiting DIPG progression will be further validated in vivo using our established mouse models. I hypothesize that blocking DIPG adhesion through specific integrin receptors would inhibit DIPG proliferation and invasion in 3D. Furthermore, there is a need to find and advance combinational therapeutic strategies since DIPG has been shown to ultimately develop resistance even to promising single targeting regimes like HDAC inhibition [7,8]. I hypothesize that blocking integrin receptor would synergize with HDAC inhibition to further improve treatment outcome of DIPG by disrupting two distinct oncogenic pathways. I further hypothesize that 3D co-culture of DIPG with neural progenitor cells (NPCs) in 3D would enhance DIPG invasion, a phenotype that mimics the in vivo response. To test these hypotheses, I propose to: (1) Develop 3D hydrogels with brain-mimicking stiffness and optimized adhesive ligands that support DIPG proliferation, invasion and drug responses in 3D; (2) Evaluate the effects of blocking specific integrin receptors required for DIPG adhesion in inhibiting DIPG invasion using our 3D hydrogels models, and validate the efficacy using a mouse DIPG model; and (3) Develop a 3D co-culture model to recapitulate NPC-induced DIPG invasion, and identify key signals impacted by NPC/DIPG interactions using RNA microarray. The outcomes of the proposed work would lead to the development of a bioengineered 3D in vitro model for DIPG with controlled cell-matrix and cell-cell interactions that mimics in vivo phenotype. Under the mentorship of a team of basic and physician scientists, with complimentary expertise, I will gain valuable interdisciplinary trainings and be uniquely positioned to carry out the proposed work.
The outcomes of the proposed work would lead to the development of the first bioengineered 3D in vitro model for DIPG with optimized biochemical and physical cues that support DIPG proliferation and invasion that mimics in vivo phenotype. Such 3D in vitro models would enable mechanistic studies to elucidate mechanisms underlying how cell-ECM and cell-cell interactions drive DIPG progression with substantially reduced cost and time, and discover and validate potential novel therapeutics strategies for treating this devastating disease that has not improved in over three decades.
