# Gene expression signature based screening in Ewing sarcoma

> **NIH NIH R37** · UNIVERSITY OF IOWA · 2022 · $373,823

## Abstract

PROJECT SUMMARY
Ewing sarcoma is a highly aggressive bone and soft tissue cancer that is caused by the EWS-FLI1 fusion
protein. The EWS-FLI1 oncoprotein functions, in part, as an aberrant transcription factor and is required for
tumor growth and survival. However, directly targeting EWS-FLI1 with drugs has been challenging and, as a
result, there is a critical need to identify downstream targets of EWS-FLI1 and unique vulnerabilities incurred
by the oncoprotein. In order to identify downstream targets of EWS-FLI1, we used human embryonic stem cells
that express inducible EWS-FLI1 to model the initiation and development of Ewing sarcoma in a genetically
defined system. We then used this model system and a gene expression based approach to identify that Ewing
sarcoma cells are uniquely vulnerable to inhibitors of ribonucleotide reductase (RNR), including gemcitabine,
which impair DNA replication by blocking the synthesis of deoxyribonucleotides. Moreover, we have also
identified that the inhibition of RNR in Ewing sarcoma cells results replication stress, activation of the unfolded
protein response, and a block in the synthesis of proteins required for the response to impaired DNA
replication. Notably, the combination of gemcitabine with an inhibitor of checkpoint kinase 1 (CHK1), the major
regulator of the response to impaired DNA replication, results in synergy in vitro and a significant prolongation
of mouse survival in xenograft experiments. Guided by strong preliminary data, we will now pursue the
following specific aims: 1) dissect the molecular basis of the activation and regulation of the unfolded protein
response in Ewing sarcoma cells treated with inhibitors of ribonucleotide reductase; 2) test the in vivo efficacy
of gemcitabine and a second-generation CHK1 inhibitor, prexasertib, using Ewing sarcoma xenograft models;
and 3) use high-throughput screening to test candidate therapeutics identified using our gene expression
based approach for activity against Ewing sarcoma cells. These aims will be tested using a combination of
approaches in cancer cell lines, cell line xenografts, patient-derived xenografts, and our isogenic, genetically
defined cell lines. This work will be significant because it is expected to have translational relevance for the
treatment of children and adults with Ewing sarcoma tumors, as well as lead to a broader understanding of the
basic mechanisms of tumorigenesis in Ewing sarcoma tumors. The proposed research is innovative because it
integrates a novel, stem cell model of Ewing sarcoma with a gene expression signature based screening
approach to identify new therapeutic targets.

## Key facts

- **NIH application ID:** 10329929
- **Project number:** 5R37CA217910-05
- **Recipient organization:** UNIVERSITY OF IOWA
- **Principal Investigator:** David J Gordon
- **Activity code:** R37 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $373,823
- **Award type:** 5
- **Project period:** 2018-02-02 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10329929

## Citation

> US National Institutes of Health, RePORTER application 10329929, Gene expression signature based screening in Ewing sarcoma (5R37CA217910-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10329929. Licensed CC0.

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