# BIOCHEMICAL PHARMACOLOGY OF DNA INTERCALATING AGENTS

> **NIH NIH R01** · UNIVERSITY OF TX MD ANDERSON CAN CTR · 1988 · $79,908

## Abstract

Active antineoplastic DNA intercalating agents such as m-AMSA produce
breaks in the DNA of mammalian cells and their isolated nuclei.  These
cellular DNA breaks have been reproduced in an isolated chemical system
consisting solely of DNA, intercalator and the purified nuclear enzyme,
topoisomerase II (Topo II).  Intercalators stabilize a protein-DNA complex
which is an intermediate in the normal DNA breaking-rejoining cycle of Topo
II.  Thus the drugs inhibit the normal function of the enzyme.  The purpose
of this proposal is to investigate whether this enzyme inhibition is the
mechanism by which intercalators kill malignant cells.

Our previous work has suggested that intercalator-induced, DNA scission is
highest in rapidly proliferating cells, cell populations enriched in the
G1-S phase of the cell cycle or cells under hormonal stimulation to
proliferate.  We will extend these observations by examining m-AMSA-induced
DNA scission in a number of cell systems:  (1) quiescent vs. proliferating
human fibroblasts (HF), (2) HeLa cells synchronized in various phases of
the cell cycle, (3) epidermal growth factor (EGF)-stimulated HF, (4)
EGF-treated human epidermoid carcinoma (A431) cells, (5) cells putatively
deficient in Topo II and (6) an intercalator-sensitive/resistant cell
pair.  DNA filter elution will be used to quantify breakage.  C14-m-AMSA
transport and m-AMSA-induced cytotoxicity will also be quantified.

Nuclear Topo will be isolated from these cells.  Topo II will be purified
by proven techniques and characterized using DNA agarose gel
electrophoresis and a recently developed rapid filter-binding assay.  We
will focus particularly on the effects of m-AMSA on DNA cleaving,
unwinding, catenating, and binding properties of the Topo from these cells
to understand the biochemical basis for the differential cytotoxicity and
DNA cleavage produced by m-AMSA.  Topo II activity may also be found in the
A431 membrane-localized EGF-receptor and will be similarly studied.  This
receptor has a high degree of homology with the v-erb-b oncogene product.
Topo may be among the functions of a membrane receptor which is the product
of an oncogene, and thus preferentially expressed in malignant cells.  A
novel mechanism of tumor-specific drug action may be the inhibition of
"membrane-receptor Topo" by intercalating agents.  The Topo II activity of
isolated EGF receptor from A431 membranes will be compared with that from
A431 nuclei.

## Key facts

- **NIH application ID:** 3179593
- **Project number:** 5R01CA040090-04
- **Recipient organization:** UNIVERSITY OF TX MD ANDERSON CAN CTR
- **SAM.gov UEI:** S3GMKS8ELA16
- **Principal Investigator:** LEONARD A ZWELLING
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1988
- **Award amount:** $79,908
- **Award type:** 5
- **Project period:** 1985-07-01 → 1990-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3179593

## Citation

> US National Institutes of Health, RePORTER application 3179593, BIOCHEMICAL PHARMACOLOGY OF DNA INTERCALATING AGENTS (5R01CA040090-04). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3179593. Licensed CC0.

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