Endogenous gamma-interferon activates thymidine phosphorylase in colorectal cancer tissue.

We measured neopterin (NPT), an indirect marker of gamma (gamma)-interferon, and the activity of thymidine phosphorylase (dThdPase) in the advancing front of colorectal carcinoma and in normal mucosa. Cancer showed a higher concentration of NPT than normal mucosa and also showed significantly higher (p < 0.0001) dThdPase activity than normal mucosa. There was a strong correlation between NPT concentration and dThdPase activity in cancerous and normal mucosa. These results suggest that endogenous gamma-interferon could activate dThdPase activity, which is essential to nucleic acid metabolism because it regulates the availability of thymidine.