TKT and neoplasm: After 5 days of 5-FC treatment, HeLa cells transfected with CEA-CD were not sensitized by the cytotoxicity, whereas transfected LoVo cells showed a cell growth inhibition of 72.7% [31]. In vivo studies demonstrated a similar effect in LoVo xenografts mice treated with the CEA-CD system [31] and in xenograft SGC7901 treatment with the double system CEA-CD-TK (46% tumor growth inhibition rate (TGIR) versus nontreated tumor control) [30].