# BIOCHEMICAL PHARMACOLOGY OF DNA INTERCALATING AGENTS

> **NIH NIH R01** · UNIVERSITY OF TX MD ANDERSON CAN CTR · 1991 · $132,010

## Abstract

The aim of this proposal is to define the pharmacologic, biochemical, and
molecular determinants of the resistance of a line of human leukemia cells
called HL-60/AMSA to topoisomerase (topo) II-reactive DNA intercalating
agents.  Purified HL-60/AMSA topo II is resistant to the inhibiting actions
of the intercalator m-AMSA.  HL-60/AMSA cells and topo II are also
resistant to a number of other topo II-reactive DNA intercalators.  However
HL-60/AMSA cells and topo II are not resistant to the nonintercalating topo
II-DNA-drug interaction that eventually produce cytolysis are intact in HL-
60/AMSA, but the initial interaction is clearly different for intercalators
and nonintercalators, and altered in the case of the HL-60/AMSA topo II-
intercalator-DNA interaction.

We will use assays devised by Osheroff and purified HL-60 and HL-60/AMSA
topo II to identify the precise steps in the topo II topoisomerization
cycle affected by intercalators and etoposide with particular focus on the
steps affected differently for the two drug classes.  This will identify
differences between the drug effects on these enzymes that could be
critical biochemical determinants of HL-60/AMSA's drug resistance.

We will amplify and clone the HL-60 and HL-60/AMSA topo II genes.  We will
sequence these genes looking for mutations in the HL-60/AMSA sequence.
Such mutations are likely as rearrangements in the HL-60/AMSA topo II gene
have been found and HL-60 contains only one topo II allele so that a change
in this single allele could have produced the resistance.  To prove that
the mutation or mutations produce the drug resistance we will transfect the
topo II gene into mammalian and yeast systems in which cellular and
biochemical pharmacologic studies can test whether the topo II genes confer
m-AMSA-sensitivity or resistance on the transfectants.  This will identify
the molecular determinants of HL-60/AMSA's drug resistance.

The manner in which HL-60/AMSA arose, repeated intermittent treatment with
a DNA-reactive drug, is analagous to the way human tumor resistance may
arise in the clinic.  Defining the precise biochemical and molecular
determinants of topo II-reactive drug resistance will give insight into the
process of induced drug resistance, identify the key sites of drug
cytolytic action, and suggest ways to design new agents to overcome drug
resistance.

## Key facts

- **NIH application ID:** 3179590
- **Project number:** 2R01CA040090-05A2
- **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:** 1991
- **Award amount:** $132,010
- **Award type:** 2
- **Project period:** 1985-07-01 → 1995-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3179590

## Citation

> US National Institutes of Health, RePORTER application 3179590, BIOCHEMICAL PHARMACOLOGY OF DNA INTERCALATING AGENTS (2R01CA040090-05A2). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3179590. Licensed CC0.

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