He and colleagues at the University of Michigan reported in the Feb. 12 issue of Nature what appears to be one of the first metabolites implicated in cancer invasion. They looked at 1,126 metabolites in 262 samples taken from men with high PSA levels. They consistently found elevated levels of the amino acid sarcosine in the prostate tissues of men with cancer; levels were highest in what appeared to be the most aggressive tumors.
Sarcosine, a modified form of the amino acid glycine, was a known entity but its function was unclear. Scientists thought it might be a dumping ground for excess methyl groups needed to enable chemical changes of genes, proteins and other body components that can affect what and how much they do.
This process called methylation can be a good thing like when it's helping an embryo develop but when it goes badly, it can cause disease such as cancer. While sarcosine's dumping role seemed to protect from cancer, the Michigan scientists found its action actually helps induce tumors. In fact, when they added it to prostate cancer cells, the cells became more aggressive. Exactly how that process works is still under study but the findings were pretty consistent.
"When we looked at patients with metastatic disease, sarcosine levels were sky high compared to patients with localized tumors," says Dr. Sreekumar. "It's enabling invasion."
Because cancer and people are both very heterogenous, measures need to be taken in larger population samples, he says. Also, they found a small group of patients with negative biopsies and high sarcosine levels. "We don't know how many of them have missed cancer," says Dr. Sreekumar who joined the MCG faculty in February.
These are among the reasons he believes in strength in numbers. "In the real world of biomarkers, you want 100 percent sensitivit
|Contact: Toni Baker|
Medical College of Georgia