Tryptophan metabolism in patients with breast cancer.

Plasma levels of total tryptophan were significantly lower in 51 patients with breast cancer than in 14 women with benign breast cancer following surgery and after 12 weeks. The urinary excretion of xanthurenic and 5-hydroxyindoleacetic acids were similar in patients with cancer and benign disease but the excretion of N'-methylnicotinamide (NMN) was significantly higher (P less than 0.001) in the cancer patients. It is suggested that the elevated urinary excretions of NMN is due to higher NAD activity reflecting elevated glycolysis through the Cori cycle.