Treatment of C57BL X DBA/2 F (hereafter called BD2F) mice bearing ascitic mammary adenocarcinoma-755 (ADC-755) with [3H]-5-fluoro-2'-deoxycytidine ([3H]FdCyd) plus tetrahydrouridine (H4Urd) resulted in antimetabolite pool sizes indicative of a tumor-selective, dual pathway metabolism of FdCyd via both cytidine deaminase and deoxycytidine kinase. In contrast to the high levels of all RNA- and DN...