Restricting 2 Amino Acids eliminated Cancer in Clinical Trial!

Summary

A 2024 study investigated whether restricting the amino acids serine and glycine could help the immune system attack cancer. In mouse models, the restriction reduced tumor weight. In an early human trial, most participants’ tumors shrank or stabilized, while some continued to grow. The video’s striking example of a tumor nearly disappearing after nine weeks is not representative of every participant.

The proposed mechanism involves CD8-positive cytotoxic T cells, which recognize and kill target cells. Removing these cells in experiments eliminated the apparent benefit of the amino-acid restriction, suggesting they were necessary for the effect. The restriction did not appear to kill cancer cells on its own; instead, it may make tumors more vulnerable to immune attack.

Tumors may respond by increasing an immune-evasion pathway involving PD-L1 and PD-1, as well as a process called lactylation. The study paired the diet with immunotherapy targeting this evasion pathway.

Trial approach and limitations

• Participants followed a supplied diet without appreciable amounts of serine or glycine for up to nine weeks, in three-week cycles.
• Researchers checked blood measures every three weeks. Participants received enough food to largely maintain their weight—about 30 kcal per kg and 1.5 g of protein per kg daily.
• The trial included people with several cancer types, mostly colorectal cancer, as well as esophageal, gastric, liver, and other cancers.
• Participants differed in how long they followed the protocol; some completed only one three-week cycle. Longer exposure appeared associated with stabilization or shrinkage, but this relationship was not conclusive.
• This was a small, early-phase, uncontrolled trial with no comparison group. It cannot establish how much of the outcome was caused by the diet, the immunotherapy, or other factors.
• The results do not show that all cancers respond or that serine and glycine restriction alone eliminates cancer. The video emphasizes that more research is needed and that the findings are not a reason for healthy people to restrict these amino acids. It also notes that glycine’s effects may differ across cancer types.

Researchers and source featured

Tong H, Jiang Z, Song L, et al. “Dual impacts of serine/glycine-free diet in enhancing antitumor immunity and promoting evasion via PD-L1 lactylation.” Cell Metabolism. 2024;36(12):2493–2510. doi:10.1016/j.cmet.2024.10.019.