[Thymidine phosphorylase is correlated with DPD in colon cancer]

Analysis of thymidine phosphorylase (TP), thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) or their mRNA are now being applied before-the start of chemotherapy to predict the therapeutic efficacy. Although these key enzymes were reported to be basically independent, we found the differences in TS between cancer and adjacent mucosa was reversely correlated with the difference in DPD. We found a significant relationship between TP and DPD in 52 patients with colon cancer. TP and DPD were measured by EIA. Statistical analysis was made non-parametrically using Statview 5.0. TP was significantly higher in cancer (78 +/- 58 U/mg protein) than in the adjacent mucosa (43 +/- 24 U/mg protein). Conversely, DPD was significantly lower in cancer(43 +/- 32 U/mg protein) than in the adjacent mucosa (55 +/- 18 U/mg protein). The amount of TP and DPD in cancer were not correlated with the clinicopathological parameters. TP was significantly (r = 0.70) correlated with DPD in cancer but not in adjacent mucosa. The difference in TP between cancer and adjacent mucosa was significantly (r = 0.69) correlated with the difference in DPD as well. In the colon cancer with low TP, DPD in cancer is lower than in the adjacent mucosa, however, the more TP in cancer increased, the higher the DPD in cancer increased over that in the adjacent mucosa. Modulation of DPD as well as TP may be necessary when high levels of TP or DPD are measured in the cancer tissue. The understanding of the basic relationship among these key enzymes will improve the 5-FU-based chemotherapeutic prediction.