Antiproliferative effect of immunoliposomes containing 5-fluorodeoxyuridine-dipalmitate on colon cancer cells

We have investigated the antiproliferative action towards CC531 colon adenocarcinoma cells of target cell-specific immunoliposomes containing the amphiphilic dipalmitoyl derivative of 5-fluorodeoxyuridine (FUdR-dP). FUdR-dP incorporated in immunoliposomes caused a 13-fold stronger inhibition of CC531 cell growth in vitro, during a 72-h treatment, than FUdR-dP in liposomes without antibody, demonstrating that the prodrug is efficiently hydrolysed to yield the active drug, FUdR, intracellularly. The intracellular release of active FUdR was confirmed by determining the fate of H-3-labelled immunoliposomal FUdR-dP. Treatments shorter than 72 h with FUdR-dP in immunoliposomes resulted in anti-tumour activities comparable to, or even higher than, that of free FUdR. The shorter treatments reflect more closely the in vivo situation and illustrate the potential advantage of the use of immunoliposomes over non-targeted liposomal FUdR-dP or free FUdR. Association of tumour cell-specific immunoliposomes with CC531 cells was up to tenfold higher than that of liposomes without antibody or with irrelevant IgG coupled, demonstrating a specific interaction between liposomes and target cells which causes an efficient intracellular delivery of the drug. Since biochemical evidence indicates a lack of internalization or degradation of the liposomes as such; we postulate that entry of the drug most likely involves the direct transfer of the prodrug from the immunoliposome to the cell membrane during its antigen-specific interaction with the cells. followed by hydrolysis of FUdR-dP leading to relatively high intracellular FUdR-levels. In conclusion, we describe a targeted liposomal formulation for the anticancer drug FUdR, which is able to deliver the active drug to colon carcinoma cells with high efficiency, without the need for the cells to internalize the liposomes as such

In vivo distribution and antitumour activity of liposomal 3′,5′-O-dipalmitoyl-5-fluoro-2′-deoxyuridine

3',5'-O-dipalmitoyl-5-fluoro-2'-deoxyuridine (FUdR-dipalmitate), a lipophilic prodrug of 5-fluoro-2'-deoxyuridine (FUdR), was incorporated in different types of liposomes. The in vivo distribution and intrahepatic deacylation of liposomal FUdR-dipalmitate was found to be strongly dependent on liposome composition and on drug to lipid ratio, The use of fluid-type liposomes (egg PC/PS/CHOL) rendered FUdR-dipalmitate more susceptible to enzymatic breakdown than solid-type liposomes (DSPC/DPPG/CHOL). A decrease of the retention of the drug in the body was also obtained when FUdR-dipalmitate was incorporated in solid-type liposomes with high drug to lipid ratio (1 : 10) than with low ratio (1:50). In spite of these substantial differences in the rates at which FUdR was liberated from liposomes with different fluidity, size, or drug to lipid ratio, only minor differences in therapeutic effect were observed in a number of murine tumour models (P388 leukaemia, Lewis Lung carcinoma, B16 melanoma and a C26 adenocarcinoma liver metastasis model). The lipophilic prodrug of FUdR exhibited antitumour activity at 100-600 times lower doses than the free drug. However, at these therapeutic doses FUdR-dipalmitate was also far more toxic. This prohibited the use of higher doses to increase antitumour activity

Toxicity of liposomal 3'-5'-O-dipalmitoyl-5-fluoro-2'-deoxyuridine in mice

Toxicities of 5-fluoro-2'-deoxyuridine (FUdR) and its liposome incorporated dipalmitoyl derivative (FUdR-dipalmitate) to mouse bone marrow, spleen, liver and ileum were compared after treatment for 6 consecutive days. The applied doses of the two formulations, which were shown earlier to have equal antitumor activity in mouse tumor models, were 600 and 2 mumol/kg respectively. When applied in these doses, toxicity to the hemopoietic system, measured as a decreases in progenitor and precursor cells of the erythroid and granuloid/macrophage lineage in bone marrow and spleen, was more severe for FUdR than for liposomal FUdR-dipalmitate. In the liver, mitotic figures, as indicators of cell division, were absent for both drugs while in control livers the number of cells in mitosis was approximately 2%. Toxicity to the ileum was more severe for liposomal FUdR-dipalmitate than for FUdR and was manifested by granulocyte infiltration, the presence of cell debris, loss of columnar epithelial cells and enlarged nuclei with prominent nucleoli in these cells. Thus, by prolonging the retention time of FUdR in vivo, using liposomes as a vehicle and FUdR-dipalmitate as a lipophilic prodrug, the dose-limiting toxicity appears to shift from bone marrow to the gastrointestinal tract

Phylogeny of the core Malvales: evidence from ndh

The monophyly of the group comprising the core malvalean families, Bombacaceae, Malvaceae, Sterculiaceae, and Tiliaceae, was recently confirmed by molecular studies, but the internal structure of this clade is poorly understood. In this study, we examined sequences of the chloroplast ndhF gene (aligned length 2226 bp) from 70 exemplars representing 35 of the 39 putative tribes of core Malvales. The monophyly of one traditional family, the Malvaceae, was supported in the trees resulting from these data, but the other three families, as traditionally circumscribed, are nonmonophyletic. In addition, the following relationships were well supported: (1) a clade, /Malvatheca, consisting of traditional Malvaceae and Bombacaceae (except some members of tribe Durioneae), plus Fremontodendron and Chiranthodendron, which are usually treated as Sterculiaceae; (2) a clade, /Malvadendrina, supported by a unique 21‐bp (base pair) deletion and consisting of /Malvatheca, plus five additional subclades, including representatives of Sterculiaceae and Tiliaceae, and Durionieae; (3) a clade, /Byttneriina, with genera traditionally assigned to several tribes of Tiliaceae, plus exemplars of tribes Byttnerieae, Hermannieae, and Lasiopetaleae of Sterculiaceae. The most striking departures from traditional classifications are the following: Durio and relatives appear to be more closely related to Helicteres and Reevesia (Sterculiaceae) than to Bombacaceae; several genera traditionally considered as Bombacaceae (Camptostemon, Matisia, Phragmotheca, and Quararibea) or Sterculiaceae (Chiranthodendron and Fremontodendron) appear as sister lineages to the traditional Malvaceae; the traditional tribe Helictereae (Sterculiaceae) is polyphyletic; and Sterculiaceae and Tiliaceae, as traditionally circumscribed, represent polyphyletic groups that cannot sensibly be maintained with their traditional limits for purposes of classification. We discuss morphological characters and conclude that there has been extensive homoplasy in characters previously used to delineate major taxonomic groups in core Malvales. The topologies here also suggest that /Malvatheca do not have as a synapormophy monothecate anthers, as has been previously supposed but, instead, may be united by dithecate, transversely septate (polysporangiate) anthers, as found in basal members of both /Bombacoideae and /Malvoideae. Thus, “monothecate” anthers may have been derived at least twice, independently, within the /Bombacoideae (core Bombacaceae) and /Malvoideae (traditional Malvaceae)