TYMP and cancer: el-Kouni et al (1993) described that specificity of TP for substrates varied between two different organs Q2and cancers from mouse and humans. In Colo320 cells, another pyrimidine nucleoside phosphorylase may be active, that uses 5′DFUR as a substrate but for which TdR is not a substrate (Woodman et al, 1980; Cao et al, 2002).