THYMIDYLATE SYNTHASE LEVELS IN TUMOR-BIOPSIES FROM PATIENTS WITH COLORECTAL-CANCER

Catalytic activity and FdUMP binding characteristics of thymidylate sy nthase (TS) were determined in 22 rumor biopsies of patients to be tre ated (15) or just treated (7) for colorectal cancer with 5-fluorouraci l and leucovorin. In 19 samples both parameters could be determined an d were found to represent a wide range (15-20 fold). High values of ac tivity correlated with no response, bur low values of binding or activ ity were found in responders as well as in non-responders. It is concl uded that the determination of parameters related to TS function is fe asible in tumor biopsies and its relevance for clinical management des erves further study.