The ether lipid inositol-C2-PAF is a potent inhibitor of cell proliferation in HaCaT cells.

The search for specific anticancer drugs that do not interfere with DNA synthesis or influence the cytoskeleton has led to the development of modified phospholipids with antiproliferative properties. These compounds cause remodeling of the structure and function of plasma membranes. Recently, we described novel compounds, the glycosidated phospholipids, that surprisingly inhibit cell proliferation. These compounds contain alpha-D-glucose in the sn-2 position of the glycerol backbone of phosphatidylcholine (PC) and platelet-activating factor (PAF), which gives rise to 2-glucophosphatidylcholine (Glc-PC) and 1-O-octadecyl-2-O-alpha-d-glucopyranosyl-sn-2-glycero-3-phosphatidylcholine (Glc-PAF), respectively. Glc-PC and Glc-PAF inhibit the growth of HaCaT cells at nontoxic concentrations. Here we report the introduction of myo-inositol, in place of alpha-D-glucose, in the sn-2 position of the glycerol backbone; this leads to two diastereomeric 1-O-octadecyl-2-O-(2-(myo-inositolyl)-ethyl)-sn-glycero-3-(R/S)-phosphatidylcholines (Ino-C2-PAF). The inositol-containing PAF enhances the antiproliferative capacity (IC(50)=1.8 microM) and reduces the cytotoxicity relative to Glc-PAF (LC(50)=15 microM). Through biological assays, we showed that, in HaCaT cells, Ino-C2-PAF causes upregulation of the keratinocyte-specific differentiation marker involucrin, increases the activity of the differentiation marker transglutaminase, and induces apoptosis at nontoxic concentrations. Ino-C2-PAF therefore seems to be a promising candidate for development as an antiproliferative drug for the treatment of hyperproliferative diseases of the skin.

Biochemical engineering of the N-acyl side chain of sialic acid leads to increased calcium influx from intracellular compartments and promotes differentiation of HL60 cells.

Sialylation of glycoconjugates is essential for mammalian cells. Sialic acid is synthesized in the cytosol from N-acetylmannosamine by several consecutive steps. Using N-propanoylmannosamine, a novel precursor of sialic acid, we are able to incorporate unnatural sialic acids with a prolonged N-acyl side chain (e.g., N-propanoylneuraminic acid) into glycoconjugates taking advance of the cellular sialylation machinery. Here, we report that unnatural sialylation of HL60-cells leads to an increased release of intracellular calcium after application of thapsigargin, an inhibitor of SERCA Ca2+-ATPases. Furthermore, this increased intracellular calcium concentration leads to an increased adhesion to fibronectin. Finally, we observed an increase of the lectin galectin-3, a marker of monocytic differentiation of HL60-cells.

Biochemical engineering of the acyl side chain of sialic acids stimulates integrin-dependent adhesion of HL60 cells to fibronectin.

Sialylation of glycoproteins and glycolipids plays an important role during development, regeneration and pathogenesis of several diseases. The physiological precursor of all sialic acids is N-acetyl- D-mannosamine. The N-acyl side chain of sialic acid can be modified by exposure of cells to synthetic N-acyl-modified D-mannosamines. In a new experimental approach cells were cultivated in the presence of N-propanoyl- D-mannosamine. This unnatural precursor of sialic acid is taken up by cells and efficiently metabolized to the respective N-acyl-modified neuraminic acid in vitro and in vivo. Here we report on the biological consequences of the incorporation of the unnatural N-propanoylneuraminic acid into glycoconjugates of HL60 cells. Biochemical engineering of the acyl side chain of neuraminic acids activates beta(1)-integrins (VLA4 or VLA5), resulting in an increased adhesion of HL60 cells to fibronectin.