Comparison of 5-fluoro-2'-deoxyuridine and 5-fluorouracil in the treatment of murine colon cancer; effects on thymidylate synthase

ALPPL2 Aptamer-Mediated Targeted Delivery of 5-Fluoro-2'-Deoxyuridine to Pancreatic Cancer

Nucleoside analogues are the most promising drugs for the treatment of pancreatic cancer to date. However, their use is often limited due to toxic side effects. Aptamer-mediated targeted delivery of these drugs to cancer cells could maximize their effectiveness and concomitantly minimize the toxic side effects by reducing uptake into normal cells. Previously, we identified a pancreatic cancer-specific, nuclease-resistant RNA aptamer, SQ2, which binds to alkaline phosphatase placental-like 2 (ALPPL2), a putative biomarker for pancreatic cancer. In this study, we demonstrate that the aptamer can be internalized into pancreatic cancer cells and can thus be used for the targeted delivery of therapeutics. Using the aptamer as a ligand, we established that glycophosphatidylinositol-anchored ALPPL2 is internalized by the cells through clathrin-independent and caveolae-dependent or dynamin-mediated cell-type-dependent pathways. Finally, we show that SQ2 can deliver nucleoside drug 5-fluoro-2'-deoxyuridine specifically to ALPPL2-expressing pancreatic cancer cells, inhibiting cell proliferation.

Cellular pharmacology of multi- and duplex drugs consisting of ethynylcytidine and 5-fluoro-2'-deoxyuridine

Prodrugs can have the advantage over parent drugs in increased activation and cellular uptake. The multidrug ETC-L-FdUrd and the duplex drug ETC-FdUrd are composed of two different monophosphate-nucleosides, 5-fluoro-2′deoxyuridine (FdUrd) and ethynylcytidine (ETC), coupled via a glycerolipid or phosphodiester, respectively. The aim of the study was to determine cytotoxicity levels and mode of drug cleavage. Moreover, we determined whether a liposomal formulation of ETC-L-FdUrd would improve cytotoxic activity and/or cleavage. Drug effects/cleavage were studied with standard radioactivity assays, HPLC and LC-MS/MS in FM3A/0 mammary cancer cells and their FdUrd resistant variants FM3A/TK⁻. ETC-FdUrd was active (IC₅₀ of 2.2 and 79 nM) in FM3A/0 and TK⁻ cells, respectively. ETC-L-FdUrd was less active (IC₅₀: 7 nM in FM3A/0 vs 4500 nM in FM3A/TK⁻). Although the liposomal formulation was less active than ETC-L-FdUrd in FM3A/0 cells (IC₅₀:19.3 nM), resistance due to thymidine kinase (TK) deficiency was greatly reduced. The prodrugs inhibited thymidylate synthase (TS) in FM3A/0 cells (80–90%), but to a lower extent in FM3A/TK⁻ (10–50%). FdUMP was hardly detected in FM3A/TK⁻ cells. Inhibition of the transporters and nucleotidases/phosphatases resulted in a reduction of cytotoxicity of ETC-FdUrd, indicating that this drug was cleaved outside the cells to the monophosphates, which was verified by the presence of FdUrd and ETC in the medium. ETC-L-FdUrd and the liposomal formulation were neither affected by transporter nor nucleotidase/phosphatase inhibition, indicating circumvention of active transporters. In vivo, ETC-FdUrd and ETC-L-FdURd were orally active. ETC nucleotides accumulated in both tumor and liver tissues. These formulations seem to be effective when a lipophilic linker is used combined with a liposomal formulation.