# Mechanism(s) of TAL1- and NOTCH1-mediated Leukemogenesis

> **NIH NIH R01** · UNIV OF MASSACHUSETTS MED SCH WORCESTER · 2024 · $377,922

## Abstract

Project Summary/Abstract
Despite significant advances in T cell acute lymphoblastic leukemia (T-ALL) therapy, 25% of patients relapse.
Recent evidence suggests that failure to eliminate dormant leukemia-initiating cells (L-IC) underlies relapse.
Efforts to prospectively isolate L-IC from ALL patients to define the critical pathways of L-IC dormancy and
chemoresistance have thus far been unsuccessful.
Research from my lab has shown that mouse double negative DN stage 3 (DN3) thymic progenitors are enriched
in L-IC that contribute to resistance to Notch targeted therapy, however the L-IC remains an undefined subset of
the leukemic DN3 population. To identify the L-IC, we profiled leukemia progression in vivo at the single cell level
and uncovered dormant and proliferative DN3 clusters that are transcriptionally distinct. In Aim 1, we will use
nucleosome labeling to track the mitotic history of dormant and proliferative DN3 leukemic cells to functionally
assess their ability to initiate leukemia and tolerate chemotherapy in vivo. We will also use scRNA-seq to profile
chemotherapy response in vivo in order to determine whether chemotherapy enriches for dormant DN3 or selects
for additional DN3 heterogeneity. We find Btg2, known to mediate T cell quiescence by deadenylating Myc,
enriched in mouse dormant DN3 leukemic cells and in ALL patient label retaining cells and ALL patients with
minimal residual disease, leading us to hypothesize that Btg2 regulates dormancy in mouse and human L-IC.
We will test this hypothesis in Aim 2 by deleting Btg2 in mouse DN3 cells and examining effects on Myc
expression, dormancy and L-IC frequency. Dormancy may also reflect Polycomb repressor complex (PRC) 2
mediated silencing of the Myc enhancer as we find PRC targets enriched in dormant DN3. We will use CUT&Tag
to interrogate the Myc enhancer to uncover how Myc is suppressed in these Notch1-active dormant DN3 cells.
The work proposed in Aim 3 builds on our siRNA screen to identify glucocorticoid (GC) resistance genes
associated with relapse. We identified Estrogen Related Receptor b (ESRRb) as a novel GC resistance gene
that we find under-expressed in therapy resistant ALL patients. We demonstrate that ESRRb silencing interferes
with GC target gene expression by unclear mechanisms. We will determine if ESRRb increases glucocorticoid
receptor (GR) binding and mediates chromatin looping to potentiate GR transcription. Finally, the knowledge
gained in mouse T-ALL models will be translated to human T-ALL by determining the effect(s) of ESRRb
activation on the GC response and overall survival in GC resistant or relapsed pediatric T-ALL patient-derived
xenografts. Together, these studies will advance understanding of T-ALL pathogenesis and therapy failure by
identifying the dormant L-IC signature, revealing Btg2 and Myc as critical regulators of L-IC dormancy and by
developing novel GC re-sensitizing strategies to prevent relapse in pediatric T-ALL patients.

## Key facts

- **NIH application ID:** 10872126
- **Project number:** 5R01CA096899-18
- **Recipient organization:** UNIV OF MASSACHUSETTS MED SCH WORCESTER
- **Principal Investigator:** MICHELLE ALICE KELLIHER
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $377,922
- **Award type:** 5
- **Project period:** 2004-08-01 → 2027-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10872126

## Citation

> US National Institutes of Health, RePORTER application 10872126, Mechanism(s) of TAL1- and NOTCH1-mediated Leukemogenesis (5R01CA096899-18). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10872126. Licensed CC0.

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