# Mismatch Repair Proteins as Drivers of Temozolomide Resistance in Glioblastoma

> **NIH NIH F32** · DANA-FARBER CANCER INST · 2020 · $67,446

## Abstract

Project Summary/Abstract
 Glioblastoma (GBM) is the most common malignant brain tumor across all ages. The standard of
care to treat these very aggressive tumors is surgical resection followed by radiotherapy and treatment
with the alkylating agent temozolomide (TMZ). However, most GBMs recur following treatment and are
usually fatal. The development of new targeted therapeutics to treat these highly malignant brain tumors
would have profound clinical implications. It has been shown that approximately 25% of recurrent GBMs
exhibit a hypermutated phenotype and harbor mutations in mismatch repair (MMR) genes. Therefore,
therapeutic strategies designed to target MMR-deficient gliomas are relevant to a large number of
patients. This study aims to elucidate the contribution of the major MMR protein complexes (MutS and
MutL) to the development of TMZ resistance in GBMs and to identify genetic dependencies that are
induced by loss of MMR proteins. This project will leverage isogenic patient-derived GBM cell lines in
which MMR protein members have been ablated using CRISPR-Cas9 technology. The research
proposed will assess the sensitivity of these isogenic MMR-knockout GBM cell lines to TMZ over time,
fueled by the hypothesis that loss of different MMR pathway members confers differential levels of TMZ
resistance. To acquire a better mechanistic understanding of MMR-associated TMZ resistance, this
work will investigate whether loss of specific MMR proteins induces changes in expression of other
MMR pathway members, or proteins in closely-related DNA repair pathways, at both RNA and protein
levels. Whole-genome sequencing of these isogenic MMR-knockout GBM cell lines in the absence and
presence TMZ treatment will also be performed to systematically catalogue the landscape of mutations,
copy-number variants, and rearrangements induced by loss of each MMR protein member, which will
become an invaluable reference for the interpretation of signatures identified in human tumors. This
project will then test the hypothesis that loss of MMR function in GBMs results in genetic dependencies
that could be leveraged as synthetically lethal therapeutic targets. Genome-scale RNAi dependency
data reveals that MMR-deficient colorectal cancers exhibit enriched dependencies on genes associated
with homologous recombination (HR), including Rad52, RPA2, RPA3, and POLD1. This work will
investigate whether these dependencies extend to the MMR-deficient glioma context. Lastly, genome-
scale CRISPR-Cas9 technology will be employed to identify additional dependencies in other DNA
repair pathways that could guide the development of therapeutic strategies to target these fatal brain
tumors.

## Key facts

- **NIH application ID:** 9974995
- **Project number:** 5F32CA243434-02
- **Recipient organization:** DANA-FARBER CANCER INST
- **Principal Investigator:** Adam Nathaniel Boynton
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $67,446
- **Award type:** 5
- **Project period:** 2019-07-01 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9974995

## Citation

> US National Institutes of Health, RePORTER application 9974995, Mismatch Repair Proteins as Drivers of Temozolomide Resistance in Glioblastoma (5F32CA243434-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9974995. Licensed CC0.

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