Mirror Molecule Shows Promise Starving Cancer Cells While Sparing Healthy Tissues

University of Geneva researchers have discovered that D-cysteine — a mirror-image version of the amino acid cysteine — can selectively slow cancer growth by targeting a specific transporter found only on certain cancer cells.

The approach, published in Nature Metabolism, works by entering cancer cells through the xCT transporter (also known as CD98), which is overexpressed on many solid tumors but rare on healthy cells. Once inside, D-cysteine blocks the NFS1 enzyme in mitochondria, disrupting iron-sulfur cluster production that cancer cells need for energy and DNA maintenance.

"This difference between cancer cells and healthy cells is easily explained: D-Cys is imported into cells via a specific transporter that's present only on the surface of certain cancer cells," said Joséphine Zangari, a PhD student and first author of the study.

In mouse models with aggressive breast tumors, the treatment significantly slowed tumor progression. Importantly, healthy cells were largely unaffected because they lack the xCT transporter.

The research was conducted in collaboration with the University of Marburg. The team cautions this is preclinical work — years from any human therapy.