# Biology of R-Spondin-Induced Sensitization to Asparaginase in Colorectal Cancer

> **NIH NIH R01** · BOSTON CHILDREN'S HOSPITAL · 2022 · $618,702

## Abstract

ABSTRACT
Colorectal cancer (CRC) is the second-leading cause of cancer deaths in the US, and unlike many other tumor
types, there are no known effective therapies targeting dominant oncogenic drivers. Almost all CRCs have
mutations that activate canonical Wnt/β-catenin signaling, but direct inhibition of β-catenin is difficult, and
blocking Wnt ligand activity leads to significant on-target bone toxicity. Thus, while targeting Wnt directly is
challenging, aberrant Wnt pathway activation may induce tumor-specific vulnerabilities that can be exploited for
CRC therapy. Using a genome-wide genetic screen, we found that Wnt activation induces profound
sensitization to therapeutic asparagine depletion using asparaginase in drug-resistant leukemias. This effect is
dependent on Wnt-induced inhibition of GSK3, but is independent of APC or β-catenin. Instead, asparaginase
sensitization is mediated by Wnt-induced inhibition of GSK3-dependent protein degradation, a catabolic source
of amino acids required for asparaginase resistance. CRC provides a unique context in which to test
predictions from our model, because these tumors almost all have mutations that activate Wnt/β-catenin, but
these can function either upstream or downstream of GSK3. Using human CRC cell lines and genetically
engineered mouse intestinal organoids, we found that asparaginase had little effect on CRCs with mutations of
the downstream Wnt factor APC, but was profoundly toxic to cases with R-spondin translocations, which
activate Wnt signaling via ligand-induced inhibition of GSK3, and thus inhibit GSK3-dependent protein
degradation. Importantly, this approach has little detectable toxicity to normal intestinal or epithelial cells. This
suggests that this approach has a potent therapeutic index that could transform clinical outcomes for the
thousands of patients who die of CRC every year, and a clinical trial based on these data is under
development. However, we do not understand key aspects of the biology underlying this RSPO/Wnt-induced
therapeutic vulnerability. Defining the precise molecular events that dictate RSPO/Wnt induced asparaginase
sensitivity is critical for prospectively identifying clinical responders, designing rational approaches to improve
therapeutic response, and overcoming treatment resistance. These knowledge gaps will be addressed in the
following Aims: 1) Determine how RSPO ligands induce sensitization to asparaginase. 2) Investigate the role
of GSK3α body formation as a cellular response to asparagine starvation. 3) Determine the role of oncogenic
KRAS and TP53 mutations in therapeutic response of RSPO fusion CRC to asparaginase. This proposal is
expected to provide fundamental insights into the amino acid starvation response and its impairment by
aberrant Wnt signaling, cellular processes fundamental to metazoan life whose molecular basis and
therapeutic exploitation remain poorly understood. Given our highly complementary expertise in asparaginase
biology and...

## Key facts

- **NIH application ID:** 10434148
- **Project number:** 5R01CA249678-02
- **Recipient organization:** BOSTON CHILDREN'S HOSPITAL
- **Principal Investigator:** LUKAS Edward DOW
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $618,702
- **Award type:** 5
- **Project period:** 2021-08-01 → 2026-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10434148

## Citation

> US National Institutes of Health, RePORTER application 10434148, Biology of R-Spondin-Induced Sensitization to Asparaginase in Colorectal Cancer (5R01CA249678-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10434148. Licensed CC0.

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