# Molecular mechanisms underlying clonal expansion of hematopoietic stem cells

> **NIH NIH R01** · INDIANA UNIVERSITY INDIANAPOLIS · 2020 · $393,750

## Abstract

PROJECT SUMMARY
Clonal hematopoiesis of indeterminate potential (CHIP) is associated with increased risks of de novo and
therapy-related hematological neoplasms, suggesting that mutations identified in CHIP likely drive disease
development. Acquired somatic mutations in tumor suppressor gene TP53 rank in the top five among
mutations identified in CHIP. Clinical studies suggest that expansion of hematopoietic stem cells (HSCs) with
TP53 mutations predisposes the elderly to hematological neoplasms and other aging-related diseases.
However, there is a significant gap in knowledge regarding the mechanisms by which TP53 mutations promote
HSC expansion. We recently found that TP53 mutations identified in CHIP enhance HSC self-renewal in mice
in vivo. We showed that several mutant p53 proteins found in CHIP, but not wild–type p53, interact with
epigenetic regulator EZH2 and enhance its activity. Moreover, we discovered that mutant p53 increases the
chromatin accessibility to the NLRP1 inflammasome gene and that NLRP1 expression was upregulated in
mutant HSCs, leading to increased secretion of pro-inflammatory cytokine IL-1β. We hypothesize that mutant
p53 promotes mutant HSC expansion through two distinct mechanisms. First, mutant p53 interacts with and
enhances the activity of epigenetic regulator EZH2 to promote mutant HSC self-renewal. Second, mutant p53
suppresses wild type HSC function through NLRP1 inflammasome-mediated pro-inflammatory pathway. In this
proposed research, we will utilize biochemical, genetic, molecular, immunologic, and pharmacological
approaches as well as vertebrate models to investigate the cell autonomous and non-autonomous
mechanisms by which mutant p53 promotes clonal expansion of HSCs. To test if mutant p53 HSC expansion
is mediated through enhanced EZH2 activity and increased H3K27me3, we will determine the impact of
genetic and pharmacological inhibition of EZH2 activity on mutant p53 HSC self-renewal in mice. We will then
introduce hot-spot TP53 mutations identified in CHIP into human primary HSPCs using retroviruses and
examine if mutant p53 increases H3K27me3 levels and promotes HSPC expansion. To elucidate the cell non-
autonomous mechanisms of mutant p53-mediated NLRP1 inflammasome activation on HSC expansion, we
will determine if mutant p53 HSCs are more resistant to IL-1β exposure than wild-type HSCs. We will also
interrogate cytokine secretion in both mouse and human hematopoietic cells using cytokine arrays. Finally, we
will perform competitive bone marrow transplantation assays to determine the impact of genetic and
pharmacological inhibition of the NLRP1 inflammasome on the clonal expansion of both mouse and human
HSCs with TP53 mutations. Our results will provide novel insights into developing new potential target-based
therapeutics for prevention and treatment of CHIP and other aging-associated diseases.

## Key facts

- **NIH application ID:** 9975216
- **Project number:** 5R01HL150624-02
- **Recipient organization:** INDIANA UNIVERSITY INDIANAPOLIS
- **Principal Investigator:** Yan Liu
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $393,750
- **Award type:** 5
- **Project period:** 2019-07-15 → 2021-04-01

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9975216

## Citation

> US National Institutes of Health, RePORTER application 9975216, Molecular mechanisms underlying clonal expansion of hematopoietic stem cells (5R01HL150624-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9975216. Licensed CC0.

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