"Let's assume you're going to go to the grocery store and you could walk, ride your bike or take the car," he said. "Those are different mechanisms of action. You will still get to the same place."

He added that researchers try to determine which pathway, or transportation choice, cells take after different amounts of exposure to topotecan. Their results suggest that when topotecan is given frequently in low doses, the drug could be changing the type of genes turned on in the tumor. These changes may be related to the structure or architecture of a gene -- not a change in gene sequence. Such changes could be considered epigenetic, but more research is needed, Arnold said.

The study suggests that metronomic dosing of topotecan can reduce prostate cancer growth at drug concentrations far below those that can be toxic to healthy cells in the body.

Given the limited treatment options for late-stage prostate cancer and clinical use of topotecan, new clinical trials could occur in the near future, Arnold said. The same research team is now studying the dosing effects of topotecan in breast cancer models.

Source: University of Georgia