# Mechanisms of Formation and Progression of Preleukemic Stem Cells

> **NIH NIH R01** · ALBERT EINSTEIN COLLEGE OF MEDICINE · 2021 · $397,371

## Abstract

ABSTRACT
Despite frequent initial response to chemotherapy, overall cure rates have remained below 20% in patients with
AML for the past 45 years, and relapse continues to be the most common cause of death. Recent evidence has
shown that the accumulation of stepwise genetic and epigenetic changes in HSC lead to the formation of pre-
leukemic stem cells (pre-LSC) that play a pivotal role not only in disease origination but also in leukemia
relapse. While the existence and essentiality of such pre-cancerous cell states has been demonstrated in mice
and humans, very little is known about the molecular mechanisms driving pre-LSC formation and progression.
The transcription factor PU.1 is frequently heterozygously mutated or otherwise impaired in patients with AML.
We have recently reported a mouse model of preleukemic-to-AML progression molecularly driven by
heterozygous PU.1 enhancer deletion. This novel model is characterized by definable, functionally altered pre-
leukemic stem cells and closely resembles human disease in key molecular, cell biological, and phenotypic
features, including disease heterogeneity. This model now permits the identification and functional study of
mechanisms driving the formation and progression of pre-leukemic stem cells. Furthermore, we have obtained
proof-of-concept that PU.1-low AML cells show an increased vulnerability to further PU.1 inhibition (as
complete loss of PU.1 leads to stem cell and hematopoietic failure), and we have developed first-in-class small-
molecule pharmacologic inhibitors of PU.1, which directly interfere with PU.1-chromatin binding. Strikingly,
we found that PU.1 inhibition by shRNA or small molecules has significant inhibitory effects on AML cells,
including at the level of leukemia-initiating cells, while only minimally affecting normal HSC. PU.1 inhibition
thus represents a new potential strategy to target AML.
Based on our recent findings we propose to: 1. Identify and study pathways that are functionally critical for pre-
LSC formation and maintenance; 2. Identify pathways that trigger the preleukemic-to-leukemic “switch”, and
progression of pre-LSC to different AML subtypes (mature/immature/bi-lineage), thus causing disease
heterogeneity; 3. Study the mechanisms underlying the anti-leukemic effects of PU.1 inhibition in AML cells.
We will employ our novel murine AML preLSC-to-LSC transition model as well as primary human MDS/AML
samples. We will longitudinally study molecular changes at the stem cell level and functionally test
dysregulated candidate pathways in vitro and in vivo. Furthermore, we will use shRNA and our novel drugs to
identify PU.1 targets that mediate the anti-leukemic effects of PU.1 inhibition in AML cells.
In summary, our study will improve our molecular understanding of pre-cancerous/leukemic cell states and
their progression to fully transformed AML. Furthermore, our study will extend our proof-of-concept and
understanding of PU.1 inhibition as a novel therapeutic ...

## Key facts

- **NIH application ID:** 10125829
- **Project number:** 5R01CA217092-06
- **Recipient organization:** ALBERT EINSTEIN COLLEGE OF MEDICINE
- **Principal Investigator:** Ulrich Steidl
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $397,371
- **Award type:** 5
- **Project period:** 2017-04-01 → 2022-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10125829

## Citation

> US National Institutes of Health, RePORTER application 10125829, Mechanisms of Formation and Progression of Preleukemic Stem Cells (5R01CA217092-06). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10125829. Licensed CC0.

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