# Project 2 - Chemotherapy-induced Complex DNA Alkylation Products - Repair, Replication and Toxicity

> **NIH NIH P01** · VANDERBILT UNIVERSITY · 2020 · $346,465

## Abstract

Project Summary
With the advent of routine DNA sequencing of individual tumor and normal tissue samples, opportunities to
utilize these data for therapeutic intervention with personalized medicine are currently possible. Insights gained
through an understanding of tumor-specific altered DNA repair and tolerance pathways, cell cycle checkpoint
control, and intra- and intercellular signaling provide the foundation from which to design combination
treatments that leverage mutations and deficiencies in these pathways to achieve synergistic cytotoxicities in
tumor versus normal tissues. However, to translate this potential into a clinical reality, it is essential to design
treatments that maximize these differential cytotoxic responses. Herein, we propose new DNA adducts that
preferentially kill cells that are deficient in homologous recombination (HR), such as those found in BRCA1-
and BRCA2-deficient breast and ovarian cancers. The discovery of DNA adducts that arise from the formation
of covalent linkage of anthracycline drugs, such as doxorubicin, to exocyclic amino groups in DNA bases, led
to a related discovery of novel DNA adducts composed of doxorubicin covalently linked at abasic sites.
Strategies are designed that maximize potential therapeutic efficacy through treatments with DNA alkylating
agents that rapidly depurinate, leaving abasic sites readily available for secondary reaction with anthracyclines.
These first-in-class damages will be engineered into site-specific DNA oligodeoxynucleotides (Project 1) and
characterized for their capacity to block DNA replication and RNA transcription. Mechanisms that moderate
cytotoxicity such as DNA repair and translesion DNA synthesis will be investigated. Further, cytotoxicities will
be optimized in HR-deficient versus proficient cells through selective choice of alkylating agents and temporal
delivery of the anthracyclines. Differential cellular responses relative to HR status will be analyzed by tracking
alterations in DNA damage response genes. An additional consequence of treatment of cells with alkylating
agents is that a subset of these chemotherapeutic agents form interstrand DNA crosslinks. These crosslinks,
such as produced by reaction with cyclophosphamide, are also subject to spontaneous decomposition to
imidazole ring-opened Fapy-dG adducts and abasic sites in close proximity on complementary strands. These
adducts are anticipated to be highly cytotoxic via processing to double-stranded breaks. Analyses of replication
and transcription blockage will be performed in addition to analyses of adduct-induced mutagenesis. This
approach for combinatorial drug treatments that function via novel DNA adducts to enhance tumor cell killing
while using significantly lower doses of drugs, has potential to decrease overall patient dosing and minimize
the adverse side-effects of doxorubicin.

## Key facts

- **NIH application ID:** 9982807
- **Project number:** 5P01CA160032-28
- **Recipient organization:** VANDERBILT UNIVERSITY
- **Principal Investigator:** R. Stephen Lloyd
- **Activity code:** P01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $346,465
- **Award type:** 5
- **Project period:** — → —

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9982807

## Citation

> US National Institutes of Health, RePORTER application 9982807, Project 2 - Chemotherapy-induced Complex DNA Alkylation Products - Repair, Replication and Toxicity (5P01CA160032-28). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9982807. Licensed CC0.

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