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Lysophophatidylcholine (Lyso PC) is an abundant constituent in human plasma. Patients with malignant cancer diseases have attenuated Lyso PC plasma levels, and thus Lyso PC has been examined as a metabolic biomarker for cancer prediction. Preclinical studies have shown that solid tumor cells drastically degrade Lyso PCs by incorporating their free fatty acids into cell membrane phospholipids. In this way, Lyso PC C18:0 reduced the metastatic spread of murine melanoma B16.F10 cells in mice. Although membrane rigidification may have a key role in the attenuation of metastasis, evidence for this has yet to be shown. Therefore, the present study aimed to determine how Lyso PC reduces the metastatic capacity of B16.F10 cells. Following cellular preincubation with Lyso PC C18:0 at increasing concentrations and lengths of time, cell migration was most significantly attenuated with 450 μ m Lyso PC C18:0 at 72 h. Biosensor measurements suggest that, despite their abundance in B16.F10 cells, Lyso PC-sensitive G protein-coupled receptors do not appear to contribute to this effect. Instead, the attenuated migration appears to result from changes in cell membrane properties and their effect on underlying signaling pathways, most likely the formation of focal adhesion complexes. Treatment with 450 μ m Lyso PC C18:0 activates protein kinase C ( PKC)δ to phosphorylate syndecan-4, accompanied by deactivation of PKCα. Subsequently, focal adhesion complex formation was attenuated, as confirmed by the reduced activity of focal adhesion kinase ( FAK). Interestingly, 450 μ m Lyso PC C18:1 did not affect FAK activity, explaining its lower propensity to affect migration and metastasis. Therefore, membrane rigidification by Lyso PC C18:0 appears to prevent the formation of focal adhesion complexes, thus affecting integrin activity as a key for metastatic melanoma spread. [ABSTRACT FROM AUTHOR]

Background: Metastasis is the leading cause of mortality in malignant diseases. Patients with metastasis often show reduced Lysophosphatidylcholine (LysoPC) plasma levels and treatment of metastatic tumour cells with saturated LysoPC species reduced their metastatic potential in vivo in mouse experiments. To provide a first insight into the interplay of tumour cells and LysoPC, the interactions of ten solid epithelial tumour cell lines and six leukaemic cell lines with saturated and mono-unsaturated LysoPC species were explored. Methods: LysoPC metabolism by the different tumour cells was investigated by a combination of cell culture assays, GC and MS techniques. Functional consequences of changed membrane properties were followed microscopically by detecting lateral lipid diffusion or cellular migration. Experimental metastasis studies in mice were performed after pretreatment of B16.F10 melanoma cells with LysoPC and FFA, respectively. Results: In contrast to the leukaemic cells, all solid tumour cells show a very fast extracellular degradation of the LysoPC species tofree fatty acids (FFA) and glycerophosphocholine. We provide evidence that the formerly LysoPC bound FFA were rapidly incorporated into the cellular phospholipids, thereby changing the FA-compositions accordingly. A massive increase of the neutral lipid amount was observed, inducing the formation of lipid droplets. Saturated LysoPC and to a lesser extent also mono-unsaturated LysoPC increased the cell membrane rigidity, which is assumed to alter cellular functions involved in metastasis. According to that, saturated and mono-unsaturated LysoPC as well as the respective FFA reduced the metastatic potential of B16.F10 cells in mice. Application of high doses of liposomes mainly consisting of saturated PC was shown to be a suitable way to strongly increase the plasma level of saturated LysoPC in mice. Conclusion: These data show that solid tumours display a high activity to hydrolyse LysoPC followed by a very rapid uptake of the resulting FFA; a mechanistic model is provided. In contrast to the physiological mix of LysoPC species, saturated and mono-unsaturated LysoPC alone apparently attenuate the metastatic activity of tumours and the artificial increase of saturated and mono-unsaturated LysoPC in plasma appears as novel therapeutic approach to interfere with metastasis. [ABSTRACT FROM AUTHOR]