“Mirror” Molecule Starves Cancer Cells Without Harming Healthy Tissue
Most cancer treatments damage both cancerous and healthy cells, leading to debilitating side effects. Now, a groundbreaking discovery offers a potential solution: a “mirror” molecule, D-cysteine, that selectively targets and slows the growth of certain cancers while leaving healthy cells largely untouched. This innovative approach, spearheaded by researchers at the Universities of Geneva (UNIGE) and Marburg, could pave the way for more effective and less toxic cancer therapies.
Understanding Mirror-Image Amino Acids
Amino acids are the fundamental building blocks of proteins, essential for all life. There are 20 amino acids used to construct proteins, each existing in two structural forms: L (levorotatory) and D (dextrorotatory). These forms are mirror images of each other, akin to a person’s left and right hands. While human biology almost exclusively utilizes L-forms for protein synthesis, D-forms are rarely used. This unique specificity is now being exploited to target cancer cells.
How D-Cysteine Disrupts Cancer Cell Metabolism
Researchers, led by Jean-Claude Martinou, Honorary Professor in the Department of Molecular and Cellular Biology at the UNIGE Faculty of Science, found that the D-version of cysteine (D-Cys) strongly suppresses the growth of certain cancer cells in laboratory experiments without affecting healthy cells. 1
“This difference between cancer cells and healthy cells is easily explained: D-Cys is imported into cells via a specific transporter that is present only on the surface of certain cancer cells,” explains Joséphine Zangari, a PhD student in Professor Martinou’s laboratory and first author of the study. 2 “In fact, we observed that if we express this transporter on the surface of healthy cells, those cells stop proliferating in the presence of D-Cys.”
Further investigation, in collaboration with Professor Roland Lill and his team at the University of Marburg, revealed that D-Cys blocks an essential enzyme called NFS1, located within the mitochondria – the cell’s “powerhouses.” 3 NFS1 is crucial for producing iron-sulfur clusters, vital for cellular respiration, DNA and RNA production and maintaining genetic integrity. Blocking NFS1 leads to reduced respiration, DNA damage, and cell cycle arrest, effectively halting cancer cell growth.
Promising Results in Animal Studies
To assess the potential of this approach in a living organism, scientists treated mice with aggressive mammary tumors. The results were encouraging: tumor growth slowed significantly, and the animals exhibited minimal side effects. 4
“This is a very positive signal – we now know it’s possible to exploit this specificity to target certain cancer cells,” says Jean-Claude Martinou. 1 “However, we still demand to determine whether D-Cys could be administered at effective doses in humans without causing harm.”
Future Directions
If further studies confirm its safety and efficacy in humans, D-cysteine could become a relatively simple and selective therapy for cancers that express high levels of the transporter responsible for its uptake. This strategy may also prove effective in preventing metastasis, a critical stage in cancer progression. The research team is now focused on translating these promising findings into clinical trials to explore the potential of D-cysteine as a novel cancer treatment.