THE ROLE OF SMALL EXTRACELLULAR VESICLES IN MODULATING RADIATION RESISTANCE IN H3K27M-PEDIATRIC DIFFUSE MIDLINE GLIOMA

Author

• Viral Oza, University of KentuckyFollow

Author ORCID Identifier

https://orcid.org/0000-0003-4877-9618

Date Available

6-30-2026

Year of Publication

2026

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Medicine

Department/School/Program

Molecular and Cellular Biochemistry

Faculty

Jessica S. Blackburn

Faculty

Trevor Creamer

Abstract

Pediatric diffuse midline gliomas with H3K27M alteration (H3K27M-pDMG) are the leading cause of pediatric brain tumor-associated deaths. All H3K27M-pDMG are initially treated with fractionated radiotherapy, the standard of care, and most children succumb to their disease within two years of diagnosis. There are no universally effective chemotherapies and full resection is impossible due to the diffuse nature of the tumor and sensitive location. There has not been a significant clinical advancement in more than 40 years.

Tumors become completely resistant to radiation within the first six months of treatment. The mechanism of radiation resistance is unknown but is thought to be driven by 2 major observed features. 1) Tumors have multiple populations of cells called subclones that have traits similar to stem cells, primarily the ability to self-renew and differentiate.  Subclones are genetically and transcriptionally distinct giving the tumor a defining feature known as intratumoral heterogeneity that is unique to each patient. 2) Glioma subclones propagate oncogenic signaling in the tumor microenvironment through extracellular factors. The role and function of these extracellular factors in the context of radioresistance is unknown.

Intrinsic radioresistance in H3K27M-pDMG has largely been studied using bulk population models which are conflated by multiple subclonal phenotypes. Overall, this has resulted in over 200 clinical trials with no significant improvement in patient survival. There is a critical need to understand radiation resistance mechanisms in the context of intratumoral heterogeneity.

Extracellular vesicles (EVs), cell derived subcellular lipid enclosed particles, are a major contributor to extracellular signaling. Multiple studies across several cancers show that EVs have a role in oncogenic signaling, however, there have been no functional studies investigating the role of EVs in the context of radiation resistance in H3K27M-pDMG.

In my dissertation, I study intrinsic radioresistant mechanisms of treatment naïve patient derived H3K27M-pDMG cell lines by 1) developing a biosensor protocol to assess therapy resistant subpopulations at the single cell level, 2) isolating and characterizing radiation resistant subclonal populations, and 3) determining the role of extracellular factors such as EVs on radiation resistance at the single cell level. I discovered that highly radioresistant subclones with unique features exist in treatment naive H3K27M-pDMG. Furthermore, I demonstrate that radiation resistance may spread between tumor subclones via extracellular vesicle communication. Additionally, I characterized small EV uptake dynamics between H3K27M-pDMG tumor cells and identified key small EV surface proteins that could lead to new therapeutic targets.

Overall, my dissertation findings provide insights into the role of small EV-mediated intratumoral communication as a contributor to radiation resistance in H3K27M-pDMG. Finally, I suggest potential therapeutic strategies to disrupt this process and enhance radiation efficacy.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2026.332

Archival?

Archival

Funding Information

Funding for this research was provided by the National Cancer Institute, R37CA227656 (to J.S.B.) and F99CA294265 (to V.D.O.), the Chad Tough Defeat DIPG New Investigator Award (to J.S.B.), and the Kentucky Pediatric Cancer Research Trust Fund (to J.S.B.). This research was also supported by the Redox Metabolism and Flow Cytometry Shared Resources of the Markey Cancer Center (P30CA177558)

Recommended Citation

Oza, Viral, "THE ROLE OF SMALL EXTRACELLULAR VESICLES IN MODULATING RADIATION RESISTANCE IN H3K27M-PEDIATRIC DIFFUSE MIDLINE GLIOMA" (2026). Theses and Dissertations--Molecular and Cellular Biochemistry. 79.
https://uknowledge.uky.edu/biochem_etds/79