Folic acid degradation is not a property specific to cancer cells in culture.

It has recently been claimed that degradation of folic acid to pterin-6-aldehyde (or 6-hydroxymethylpterin) is a property of tumour cells, but not of normal cells in culture, and that pterin-6-aldehyde is found in the urine of cancer patients only. The existence of such a cancer-specific metabolic pathway, if confirmed, would have tremendous significance for all branches of cancer biology and medicine. The results presented in this paper, however, demonstrate that normal human skin fibroblasts in culture readily degrade folic acid to pterin-6-aldehyde or a closely-related substance. Evidence is presented that this is a metabolic property of the normal cells themselves, and is not related to latent mycoplasma contamination.