Inhibition of Invasiveness and Motility of Human Breast Cancer Cells by Sphingosine-1-Phosphate.
Annual rept. 1 Aug 97-31 Jul 98
GEORGETOWN UNIV WASHINGTON DC MEDICAL CENTER
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Sphingosine-l-phosphate SPP, a bioactive sphingolipid metabolite, inhibits chemoinvasiveness of the aggressive, estrogen-independent MDA-MB-231 human breast cancer cell line. In contrast to its strong mitogenic effects on many other cell types, SPP only slightly stimulated proliferation of MDA-MB-231 cells. Treatment of MDA-MB-231 cells with SPP had no significant effect on the adhesiveness of cells to Matrigel, and high concentrations of SPP partially inhibited matrix metalloproteinase 2 activation induced by Con A. However, SPP at a concentration that strongly inhibited invasiveness also markedly reduced chemotactic motility. To investigate the molecular mechanisms by which SPP interferes with cell motility, we examined tyrosine phosphorylation of focal adhesion kinase FAK and paxillin, which are important for organization of focal adhesions and cell motility. SPP rapidly increased tyrosine phosphorylation of FAK and paxillin and of the paxillin-associated protein Crk. Overexpression of FAK and kinase-defective FAK in MDA-MB-231 cells resulted in a slight increase in motility without affecting the inhibitory effect of SPP, whereas overexpression of FAK with a mutation of the major autophosphorylation site Y397F abolished the inhibitory effect of SPP on cell motility. Our results suggest that autophosphorylation of FAK on Y397 may play an important role in SPP signaling leading to decreased cell motility.
- Medicine and Medical Research