Epigenetically regulated stemness program and stem cell niche as targets in pediatric DIPG - Understanding the role of cancer stem cells (CSCs) in diffuse intrinsic pontine glioma (DIPG) is
crucial for preventing treatment resistance and tumor progression and for devising therapies that
may prolong the lives of the 200-400 pediatric DIPG patients diagnosed each year. Radiotherapy
remains the standard of care, but tumors recur in 100% of patients, resulting in dismal patient
survival of 8-11 months. Over 250 clinical trials have failed to move these numbers. Mechanistic
research is urgently needed to understand the underlying biology of CSCs and how they drive
treatment resistance to develop innovative combinatorial therapies that can change the natural
history of DIPG. Extensive preliminary data and existing literature, support the overarching
hypothesis that aldehyde hydrogenase positive (ALDH+) CSC cause therapeutic resistance and
drive tumor progression. We propose, in mechanistic studies, to characterize an epigenetically
regulated stemness program and stem cell niche (Aim 1 and 2) as potential targets (Aim 3) in
pediatric DIPG. Specifically, in Aim 1, we will determine the role and regulation of ALDH-positive
CSCs in DIPG. We will evaluate the regulation of specific ALDH isoforms, particularly ALDH1A3
and ALDH2 by H3 K27M mutation, and by IL1β secreted by microglia, respectively, in carefully
designed in vitro and in vivo assays using isogenic DIPG models. We will define the role of specific
ALDH isoforms, including ALDH1A3 and ALDH2, in cell differentiation, tumor initiation and
progression, and immunity. In Aim 2 we will evaluate whether ALDH+ CSCs are the cause of
therapeutic resistance and responsible for tumor progression. We will modulate expression of
disease relevant ALDH isoforms and evaluate whether therapeutic sensitivity can be restored.
We will characterize the therapy induced stem cell niche and mechanisms of immune evasion
with cutting-edge technologies, including single cell RNA sequencing (scRNA-seq) and CyTOF.
In Aim 3, we will target ALDH+ CSCs as the cause of resistance to prevent tumor progression.
In preclinical proof-of concept studies we will target ALDH (Disulfiram) and PI3K/mTOR (GDC-
0084), a cell intrinsic signaling of ALDH+ CSC, to enhance outcomes from standard of care
(radiotherapy) and to prevent progression. Therefore, our studies will (1) confirm that CSCs
present a mechanism of resistance and (2) provide a rationale to target these cells specifically
and (3) address an unmet clinical need for efficacious therapies.
In summary, our proposal will mechanistically address the role of ALDH+ CSCs in
therapeutic resistance and tumor relapse of DIPG and provide druggable targets, which
can accelerate clinical translation against this devastating pediatric disease.
