# Research Project 3: Cell fate decision of liver tumor-initiating stem-like cells induced by alcohol

> **NIH NIH P50** · UNIVERSITY OF SOUTHERN CALIFORNIA · 2020 · $112,052

## Abstract

Research Project #3: Cell fate decision of liver tumor-initiating stem-like cells induced by alcohol.
PROJECT SUMMARY/ABSTRACT
 Alcohol-associated hepatocellular carcinoma (HCC) is one of the leading causes of cancer deaths globally,
yet efficacious therapeutic options are still limited. Central to therapy-resistance of HCC is the liver tumor-initiating
stem-like cell (TIC) which we successfully isolated from HCC animal models and patients to understand their
self-renewal mechanisms. We have identified a novel oncoprotein in TICs, TBC1D15 which facilitates
phosphor-inactivation of the polarity protein NUMB by the TLR4-NANOG-AurkA-aPKCζ pathway, leading to
dissociation of p53 of NUMB, p53 ubiquitination and degradation, and TIC self-renewal. Functional significance
of this mechanism is confirmed by marked reductions in liver tumor incidence and tumor-associated NANOG+
TICs by hepatocyte-specific expression of non-phosphorylatable NUMB or hepatocyte-specific deficiency of
TBC1D15 in alcohol-fed HCV NS5A Tg mice. However, TBC1D15 expression endows non-transformed
p53-deficient mouse hepatoblasts self-renewal activity. This suggests TBC1D15 has an unknown oncogenic
mechanism besides promoting p53 loss. We have discovered TBC1D15 interacts with all NOTCH isoforms,
activates the NOTCH pathway, and induces Nanog and TIC self-renewal in a NOTCH-dependent manner. Our
data suggest TBC1D15 promotes NOTCH activation and antagonizes NUMB-mediated NICD destabilization.
Two putative functional CSL/NICD sites in the Nanog gene were identified in a -5kb distal enhancer and a
proximal promoter (-212/-151), both required for full Nanog transcription. We also mapped the TBC1D15-NICD
interaction domain and identified a novel small molecule inhibitor which blocks the interaction and
TBC1D15-dependent NICD-Hey1 and Nanog promoter activities. We hypothesize that TBC1D15 promotes
oncogenesis by obligatory cooperation with the NOTCH pathway thus an inhibitor of TBC1D15-NICD interaction is
therapeutic. We will pursue the following aims:
 Aim-1. Identify how TBC1D15 promotes the NOTCH pathway: Aim-1.1: Determine the role of
TBC1D15-NOTCH interaction in NICD stabilization; Aim-1.2: Determine if TBC1D15 activates NOTCH.
 Aim-2. Identify how TBC1D15-activated NOTCH pathway contributes to TIC self-renewal and tumorigenesis:
Aim-2.1: Determine how NICD supports Nanog transcription; Aim-2.2: Determine in vivo importance of the
putative Nanog CSL/NICD sites in TIC-mediated tumorigenesis; Aim-2.3. Test the therapeutic efficacy of the novel
inhibitor for the TBC1D15-NICD interaction in patient-derived xenograft (PDX) HCC model.
 Results from the proposed work will provide mechanistic insights into the novel oncogenic property of
TBC1D15 and a pre-clinical basis for a future clinical trial using the novel inhibitor that antagonizes the interaction
between TBC1D15 and NOTCH.

## Key facts

- **NIH application ID:** 9886171
- **Project number:** 5P50AA011999-22
- **Recipient organization:** UNIVERSITY OF SOUTHERN CALIFORNIA
- **Principal Investigator:** Keigo Machida
- **Activity code:** P50 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $112,052
- **Award type:** 5
- **Project period:** — → —

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9886171

## Citation

> US National Institutes of Health, RePORTER application 9886171, Research Project 3: Cell fate decision of liver tumor-initiating stem-like cells induced by alcohol (5P50AA011999-22). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9886171. Licensed CC0.

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