Measuring heart toxicity of cancer drugs in a dish

| Written by Jessica Moore
Heart muscle cells (actin filaments in green, nuclei in blue)

A class of cancer drugs known as tyrosine kinase inhibitors (TKIs) are often damaging to the heart, sometimes to the degree that they can’t be used in patients. These toxic effects are not always predictable using current preclinical methods, so they may not be discovered until they make it to clinical trials.

New research could make it possible to tell which TKIs cause heart toxicity without putting any humans at risk. The collaborative study, involving Wesley McKeithan, a Ph.D. student in the Sanford Burnham Prebys Medical Discovery Institute (SBP) graduate program and Mark Mercola, Ph.D., adjunct professor at SBP and a professor at Stanford University, used lab-grown heart muscle cells to assess the drugs’ potential to cause damaging effects.

“This new method of screening for cardiotoxicity should help pharma companies focus their efforts on TKIs that will be safe,” says Mercola, who collaborated with Joseph Wu, M.D., Ph.D., also a professor at Stanford, on the study published in Science Translational Medicine. “That could mean better new TKIs will make it to the market, since we will be able to predict whether or not they cause heart problems early in the development process.”

TKIs with tolerable cardiac side effects, which include imatinib (Gleevec) and erlotinib (Tarceva), are widely used to treat multiple types of cancer. Because tumors often become resistant to these drugs, new compounds in this class continue to be developed to provide replacement treatments. Other TKIs can harm the heart in a variety of ways, from altering electrical patterns to causing arrhythmias, reducing pumping capacity, or even increasing risk of heart attacks.  

Mercola and Wu’s team used heart muscle cells derived from induced pluripotent stem cells (iPSCs), which can be generated from adult skin or blood cells. After treating heart muscle cells with one of 21 TKIs, they assessed their survival, electrical activity, contractions (beating) and communication with adjacent cells. They used a new method for measuring heart cell contraction developed by the lab of Juan Carlos del Álamo, Ph.D., at UC San Diego to create a ‘cardiac safety index’, which correlates in vitro assay results with the drugs’ serum concentrations in humans. Importantly, the safety index values matched nicely with clinical reports on the cardiotoxicity of currently used TKIs.

The study also identified a possible way to protect heart muscle cells from impairment caused by TKIs—treating them with insulin or insulin-like growth factor. Although more research is needed, the findings suggest that it may be possible to alleviate some of the heart damage in patients receiving these chemotherapies.

Mercola adds, “By using cells derived from a broader group of individuals, this screening strategy could easily be adopted by the pharma industry to predict cardiotoxicity.”

This story is based in part on a press release from Stanford University School of Medicine.

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