Lipophilic prodrugs of a triazole-containing colchicine analogue in liposomes: biological effects on human tumor cells.

Colchicine site binders--blockers of tubulin polymerization--are potential antimitotic agents for anticancer therapy. To reduce their systemic toxicity and improve biodistribution, encapsulation in nanosized liposomes may be employed. Liposomes present a convenient means for preparation of injectable formulations of hydrophobic compounds, however colchicine as such is known to leak through the lipid bilayer. In this study, newly synthesized triazole-containing analogues of colchicine and allocolchicine, and their palmitic and oleic esters (lipophilic prodrugs) were tested for anti-proliferative activity and apoptosis-inducing potential. In contrast to colchicine conjugates, whose activities ranged with those of colchicine, allocolchicine derivatives exhibited drastically lower effects and were discarded. Liposomes of about 100 nm in diameter composed of egg phosphatidylcholine--yeast phosphatidylinositol--palmitic or oleic prodrug, 8 : 1: 1, by mol, were prepared by standard extrusion technique and tested in a panel of four human tumor cell lines. Liposome formulations preserved the biological activities of the parent colchicinoid the most towards human epithelial tumor cells. Moreover, liposomal form of the oleoyl bearing colchicinoid inhibited cell proliferation more efficiently than free lipophilic prodrug. Due to substantial loading capacity of the liposomes, the dispersions contain sufficient concentration of the active agent to test wide dose range in experiments on systemic administration to animals.

Gram-scale synthesis of pinusolide and evaluation of its antileukemic potential.

Pinusolide (1), a known platelet-activating factor (PAF) receptor binding antagonist, was synthesized from lambertianic acid (2), a labdane-type diterpene readily accessible in multigram quantities from the Siberian pine tree. It was shown that 1 not only decreases the proliferation activity of tumor cells at relatively low concentrations but specifically induces apoptosis at 100 microM via the mitochondrial pathway in the Burkitt lymphoma cell line BJAB. Also, using primary lymphoblasts and leukemic cells from children with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), a significant DNA fragmentation in pinusolide-treated cells could be detected in an ex vivo apoptosis assay.