# Extracellular pH mapping as therapeutic readout of drug delivery in glioblastoma

> **NIH NIH R01** · YALE UNIVERSITY · 2020 · $614,738

## Abstract

Extracellular acidosis (i.e., low pHe) is a tumor microenvironment hallmark, caused by atypical metabolism
and perfusion. Acidic pHe enhances cancer growth, proliferation, and builds therapy resistance. The prognosis
remains dismal for most brain tumor patients. Malignant gliomas, including glioblastoma multiforme (GBM), fail
treatments because gliomas invade outside tumor boundaries conventionally demarked by MRI contrast and
the blood-brain barrier (BBB) blocks most drugs. Furthermore conventional MRI methods are insensitive to
physicochemical parameters like pHe and mainly track intratumoral volume.
 Among the primary MRI methods are paramagnetic agents for longitudinal (T1) contrast, where assessment
of treatment response involves 2D or 3D measurement with Gd3+ enhanced MRI contrast. However, such
methods are not reliable in distinguishing pseudoprogression and pseudoresponse from actual changes in
tumor status. Thus there is an urgent need for alternative MR techniques sensitive to metabolic changes,
which can aid in effective monitoring of therapeutic response in addition to measuring the tumor size.
 Because acidic pHe milieu is conducive to tumor growth and builds resistance to therapies, simultaneous
mapping of pHe inside and outside the tumor (i.e., intratumoral-peritumoral pHe gradient) is an important cancer
imaging need. A novel way to map intratumoral-peritumoral pHe gradient is using lanthanide III (Ln3+) agents
with BIRDS methods, where physicochemical factors like pHe contribute to shifts of non-exchangeable protons.
 To meet the need for MR readouts of the tumor physicochemical state, we developed BIRDS to map the
intratumoral-peritumoral pHe gradient, and found that it is a sensitive readout of cancer growth and treatment.
Based on preliminary data obtained from GBM models (e.g., U251), including patient-derived xenograft (PDX)
models, we will validate high-resolution pHe mapping with BIRDS as therapeutic readout of chemotherapy
drugs delivered into human GBM models.
 Although we detected 1-2 mm diameter tumors with BIRDS using non-methylated agents, higher resolution
mapping of intratumoral-peritumoral pHe gradients will be reached with a novel methylated multiplexed agent in
Aim 1. In Aim 2 we will validate intratumoral-peritumoral pHe gradient mapping by BIRDS with fluorescent pHe
probes. We will use BIRDS to examine how intratumoral-peritumoral pHe gradients change with tumor
aggression (Aim 3). We will also test compatibility of pHe mapping with BIRDS for tracking response to
chemotherapy drugs (e.g., Temozolomide and Sorafenib) being used to treat GBMs (Aim 4). Both of these
drugs are known to cross the BBB and are used in GMB therapy. Temozolomide activates apoptosis by
alkylating DNA to stall cell replication and Sorafenib is a multiple kinase inhibitor targeting several oncogenic
pathways and enhances glycolysis. If successful, pHe mapping by BIRDS will enable monitoring of therapeutic
response of various chemotherapy ...

## Key facts

- **NIH application ID:** 9850256
- **Project number:** 5R01EB023366-04
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Dewan Syed Fahmeed Hyder
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $614,738
- **Award type:** 5
- **Project period:** 2017-04-01 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9850256

## Citation

> US National Institutes of Health, RePORTER application 9850256, Extracellular pH mapping as therapeutic readout of drug delivery in glioblastoma (5R01EB023366-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9850256. Licensed CC0.

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