# Therapeutic potential of targeting DNA repair deficiency in TSC

> **NIH NIH R21** · MICHIGAN STATE UNIVERSITY · 2021 · $219,491

## Abstract

PROJECT SUMMARY/ ABSTRACT
Using next-generation sequencing, researchers have identified somatic mutations as essential for tumor etiology
and evolution. We now know that many cancers also have a substantial germline component. Germline
mutations increase the lifetime risk of cancer and often result in earlier onset and more advanced disease. A
significant portion of germline cancer mutations occur in DNA damage response (DDR) genes, which lead to the
failed repair of DNA lesions, the accumulation of somatic mutations and structural variants that promote
oncogenesis. In our recent genomic analysis of tuberous sclerosis (TSC) patients, we unexpectedly found that
double-strand break (DSB) repair deficiencies are frequent in the germline. TSC is a tumor syndrome
characterized by mutations in the tumor suppressors, TSC1 and TSC2, causing dysregulated activation of the
mTOR pathway. Breast, ovarian, and metastatic prostate cancers also harbor pathogenic germline mutations in
DDR repair genes and somatic mutations leading to hyperactive mTOR signaling. As such, we aim to evaluate
the therapeutic activity of DDR-targeted agents alone and in combination with mTOR inhibitors for reduced tumor
burden in TSC, which may also provide valuable insights for cancers characterized by hyperactive mTOR
signaling.
Our central hypothesis is that a defective DNA damage response cooperates with mTOR pathway activation to
drive tumor growth. We will use genome editing tools to introduce specific DSB repair variants into isogenic cell
lines and then measure DNA damage and mTOR signaling. We will assay cell viability and anchorage-
independent growth to determine if DSB mutations promote clonogenic potential and survival in isogenic cells.
Further, in Specific Aim 2, we plan to explore therapeutic potential using targeted agents to DDR alone and in
combination with mTOR inhibitors in vivo. Specifically, we will use syngeneic mouse models to evaluate the
efficacy of CHK inhibitors or PARP inhibitors as single agents and in combined dosing strategies with everolimus.
Through the proposed research, we will determine whether germline DSB repair defects create a unique
therapeutic opportunity in mTOR-driven tumors. Our results could have broad-reaching implications given the
essential roles of germline DDR mutations and somatic mTOR pathway mutations in tumor formation and
malignant lesions.

## Key facts

- **NIH application ID:** 10287856
- **Project number:** 1R21CA263133-01
- **Recipient organization:** MICHIGAN STATE UNIVERSITY
- **Principal Investigator:** Jeffrey Paul MacKeigan
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $219,491
- **Award type:** 1
- **Project period:** 2021-07-01 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10287856

## Citation

> US National Institutes of Health, RePORTER application 10287856, Therapeutic potential of targeting DNA repair deficiency in TSC (1R21CA263133-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10287856. Licensed CC0.

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