Glutamate (Glu) has emerged as an important molecule in the biology of malignant brain tumors, specifically gliomas1. Glu can reach toxic concentrations in peritumoral tissue, contributing to enhanced tumor growth and invasion, as well as peritumoral edema, excitotoxicity, and seizures2. Mediated by the cystine-glutamate exchanger, System xc- (SXC), Glu uptake supplies cystine for production of the intracellular antioxidant glutathione (GSH). GSH protects cells from endogenous and exogenous stressors3, including radiation and chemotherapy. GSH over-production confers resistance to radiation4-6 and ferroptosis7, an iron-dependent form of programmed cell death. In previous studies, we show that xCT, the catalytic subunit of SXC, is variably expressed among glioma patients8. Approximately half of tumors show elevated xCT expression and present with seizures and Glu excitotoxicity, whereas gliomas with low xCT expression do not. Similarly, in a clinical pilot study, we show that pharmacological inhibition of SXC reduces Glu release only in gliomas with elevated xCT expression8. Based on recent, data we now hypothesize that differences in the expression and function of SXC are due to its transcriptional and co-receptor regulation. We hypothesize that xCT is transcriptionally regulated by p53, with wild type p53 acting as transcriptional suppressor. As p53 is mutated or deleted in many gliomas, this alteration would result in aberrant overexpression of xCT, explaining the observed Glu release and downstream pathophysiology. We also hypothesize, based on preliminary findings, that the activity of SXC is regulated by extracellular matrix components activating the hyaluronic acid receptor CD44, which serves as a functional co-receptor for SXC. Both p53 and CD44 activity can alter glioma biology and determine peritumoral excitotoxicity, seizures, invasion, and growth. The proposed studies are significant and clinically relevant as they explore new strategies to interfere with the abnormal glutamate biology of gliomas at a transcription and expression level. This proposal provides superior strategies to currently available pharmacological inhibitors for SXC, which have poor specificity and bioavailability. Moreover, the expression of p53 and CD44 may have predictive value regarding potential personalized treatments for this subgroup of glioma in the future.

Public Health Relevance

Glutamate (Glu) release from malignant brain tumors occurs via the system Xc transporter, causing excitotoxicity, edema, peritumoral seizures, enhanced tumor growth and tumor invasion. Its regulation by an important growth control gene frequently mutated in cancer is being studied so as to define a novel way for treatment and diagnosis.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
1R01CA227149-01A1
Application #
9661611
Study Section
Clinical Neuroimmunology and Brain Tumors Study Section (CNBT)
Program Officer
Espey, Michael G
Project Start
2018-12-01
Project End
2023-11-30
Budget Start
2018-12-01
Budget End
2019-11-30
Support Year
1
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Virginia Polytechnic Institute and State University
Department
Miscellaneous
Type
Organized Research Units
DUNS #
003137015
City
Blacksburg
State
VA
Country
United States
Zip Code
24061