Most cancer medicines attack cells that divide quickly. Unfortunately, they also damage normal cells, which can cause painful side effects. Researchers are looking for ways to hit only the cancer cells and leave healthy tissue alone.
What Is a Mirror‑Image Amino Acid?
Amino acids are tiny building blocks that join together to make proteins. Life uses 20 different amino acids, and each one can exist in two shapes that are mirror images of each other – like left and right hands. The body normally uses the "L" (left‑handed) shape. The "D" (right‑handed) shape is rare in humans.
D‑Cysteine Can Slow Cancer Cells
A team from the Universities of Geneva and Marburg studied many amino acids to see how they affect cancer growth. They found that D‑cysteine, a sulfur‑containing "D" form of the amino acid cysteine, stopped several cancer cell lines from multiplying. Healthy cells were not harmed.
How It Works Inside Cancer Cells
Inside a cell, a tiny structure called the mitochondrion makes energy. An enzyme named NFS1, located in the mitochondrion, builds iron‑sulfur clusters that are essential for breathing, DNA making, and keeping the genetic code stable. D‑cysteine blocks NFS1.
When NFS1 stops working, cancer cells lose energy, their DNA gets damaged, and they can no longer divide. This triple attack slows tumor growth.
Successful Tests in Mice
The researchers gave D‑cysteine to mice that carried aggressive breast tumors. The tumors grew much slower, and the mice showed no major side effects. This suggests the drug can target cancer cells without hurting the rest of the body.
What Comes Next?
Scientists are now asking if D‑cysteine can be given safely to people at doses that still work against cancer. If future studies confirm its safety, D‑cysteine could become a simple, selective treatment for cancers that take up the molecule quickly, and it might even help stop cancer from spreading.