Role of ether-linked lysophosphatidic acids in ovarian cancer cells

Naturally occurring alkyl- and alkenyl-lysophosphatidic acids (al-LPAs) are detected and elevated in ovarian cancer ascites compared with ascites from non-malignant diseases. Here we describe the biological functions and signaling properties of these ether-linked LPAs in ovarian cancer cells. They are elevated and stable in ovarian cancer ascites, which represents an in vivo environment for ovarian cancer cells. They stimulated DNA synthesis and proliferation of ovarian cancer cells. In addition, they induced cell migration and the secretion of a pro-angiogenic factor, interleukin-8 (IL-8), in ovarian cancer cells. The latter two processes are potentially related to tumor metastasis and angiogenesis, respectively. Al-LPAs induced diverse signaling pathways in ovarian cancer cells. Their mitogenic activity depended on the activation of the G_i/o protein, phosphatidylinositol-3 kinase (PI3K), and mitogen-activated protein (MAP) kinase kinase (MEK), but not p38 mitogen activated protein kinase (MAP kinase). S473 phosphorylation of protein kinase B (Akt) by these lipids required activation of the G_i/o protein, PI3K, MEK, p38 MAP kinase, and Rho. However, T308 phosphorylation of Akt stimulated by al-LPAs did not require activation of p38 MAP kinase. On the other hand, cell migration induced by al-LPAs depended on activities of the G_i/o protein, PI3K, and Rho, but not MEK. These data suggest that ether-linked LPAs may play an important role in ovarian cancer development.