Endogenous gamma-interferon activates thymidine phosphorylase in colorectal cancer tissue

We measured activity of thymidine phosphorylase (dThdPase), interleukin-6 (IL-6) and neopterin (NPT) which is an indirect marker of gamma-interferon (g-IFN) in the advancing front of colorecal carcinoma and in the normal mucosa. Cancer showed higher concentration of NPT than normal mucosa and also showed significantly higher (p < 0.01) dThdPase activity than normal mucosa. In contrast, there was no difference between cancer and normal mucosa in the levels of IL-6. There was strong correlation between NPT concentration and dThdPase activity in cancer and normal mucosa. These results suggested that endogenous g-IFN could activate dThdPase activity which is essential to nucleic acid metabolism because it regulates the availability of thymidine.