Etoposide has been used as a reliable chemotherapy for treating various tumors for 40 years. Etoposide is effective because it targets Type IIA eukaryotic topoisomerases, or “topo IIs,” which are enzymes that allow cancer cells to replicate.
Recent research from Cornell University provides new insight into how the chemotherapy drug etoposide inhibits and kills vital enzymes that promote the growth of cancer cells.
The research, carried out in Michelle Wang’s lab at the College of Arts and Sciences, will aid in the understanding of various cancer inhibitors. Michelle Wang is a researcher with the Howard Hughes Medical Institute and the James Gilbert White Distinguished Professor of Physical Sciences. The researchers’ strategies will also make it possible to create sensitive screening tools for identifying pharmaceutical routes that might enhance patient care.
Etoposide Promotes DNA Loop Trapping and Barrier Formation by Topoisomerase II is the title of the group’s work, which appeared in Nature Chemical Biology on January 30. Tung Le, a research expert, and Meiling Wu, a postdoctoral researcher, are the co-lead authors.
Etoposide has been used as a reliable chemotherapy for treating various tumors for 40 years. Etoposide is effective because it targets Type IIA eukaryotic topoisomerases, or “topo IIs,” which are enzymes that allow cancer cells to replicate.
The lengthy, twisted, helical-coiled strands of DNA are at the center of that replication process. These strands must be untangled, rotated, and replicated by motor proteins in order for cancer to spread. Topo IIs are perfect for the task. By cutting the supercoiled DNA, swiftly inserting another DNA strand in the centre of it, and then sewing the cut DNA back together, they pull the DNA loose. The body performs all of that without harming the fragile genetic structure of the DNA, which is a remarkable feat of biology that occurs about 300 billion times every day.
The main benefit of etoposide is its ability to fix DNA double-strand breaks before they are repaired, which stops cancer cells from proliferating. The specifics of how etoposide interacts with the structure of DNA are yet unclear.
“We often ask: What is the best technique to research DNA-related molecular machinery?” Wang continued, “We aim to imitate potential cellular processes in order to comprehend how those enzymes function. The DNA is pulled or exerted a force against by motor proteins. We thus said, “Okay, let’s use a force and see what occurs.””
Three topo IIs—yeast topoisomerase II, human topoisomerase II alpha, and human topoisomerase II beta—provided by partners led by professor James Berger of Johns Hopkins University were employed by Wang’s group to investigate the effects of etoposide on each.
“People have a pretty hard time understanding DNA topology conceptually and in terms of torsional mechanical characteristics, according to Wang, who also noted that there aren’t many techniques to examine it. But we just so happen to have the necessary equipment. We’ve been working on creating the correct tools for the last 20 years, which is why we have them now. These resources and this issue just so happened to coincide at this precise moment.”
The first step was to demonstrate how etoposide compacts, releases, and breaks DNA as well as how it generates DNA loops using optical tweezers. Everyone was taken aback by this loop-trapping behavior since it disclosed an etoposide effect that had not previously been understood. It suggests that etoposide could encourage topo II to drastically change DNA topology and structure in vivo.
The scientists next simulated the motor removal of a bound protein by using optical tweezers to unzip double-stranded DNA into two single strands for high-resolution characterization of protein interactions with the DNA. The results imply that etoposide might change topo II into a potent inhibitor of the machinery involved in DNA processing.
In their third method, which is a kind of magnetic tweezers, they twisted DNA with a bound topo II and observed the topo II slowly unwind the DNA. Etoposide, which was added, staggered this pattern and introduced pauses that corresponded to the entrapment of supercoiled loops, they discovered.
The researchers now have a quantitative approach for defining how other topoisomerase medications behave by recording the many ways etoposide boosts these effects and interferes with topo II activity.
“According to Wang, “Everything we do matches what happens in vivo. I believe this offers us a set of tools that would allow us to research many other types of topoisomerases and other types of medicines in a very thorough way. We only carry it out in a calculated manner. It is extremely potent because of this.”
