Lysophosphatidic acid (LPA) is a bioactive phospholipid that affects various biological functions, such as cell proliferation, migration, and survival, through LPA receptors. Among them, the motility of cancer cells is an especially important activity for invasion and metastasis. Recently, AMP-activated protein kinase (AMPK), an energy-sensing kinase, was shown to regulate cell migration. However, the specific role of AMPK in cancer cell migration is unknown. The present study investigated whether LPA could induce AMPK activation and whether this process was associated with cell migration in ovarian cancer cells. We found that LPA led to a striking increase in AMPK phosphorylation in pathways involving the phospholipase C-3 (PLC-3) and calcium/calmodulin-dependent protein kinase kinase  (CaMKK) in SKOV3 ovarian cancer cells. siRNA-mediated knockdown of AMPK␣1, PLC-3, or (CaMKK) impaired the stimulatory effects of LPA on cell migration. Furthermore, we found that knockdown of AMPK␣1 abrogated LPA-induced activation of the small GTPase RhoA and ezrin/radixin/moesin proteins regulating membrane dynamics as membrane-cytoskeleton linkers. In ovarian cancer xenograft models, knockdown of AMPK significantly decreased peritoneal dissemination and lung metastasis. Taken together, our results suggest that activation of AMPK by LPA induces cell migration through the signaling pathway to cytoskeletal dynamics and increases tumor metastasis in ovarian cancer.
Lysophosphatidic acid (LPA)2 has been shown to participate in diverse biological actions, including changes in cell shape, motility, and proliferation, in a variety of cell types (1). Previous studies have shown that LPA has a role in early signaling events, such as Ca 2ϩ mobilization, changes in cAMP accumulation, and the activation of several protein kinases (1-4). Among these pathological processes, the role of LPA in ovarian cancer has been most extensively studied. LPA contributes to the development, progression, and metastasis of ovarian cancer, and its concentration is increased up to 80 M (in comparison to the basal 1-5 M concentration) in both plasma and ascites of ovarian cancer patients (5). In vitro studies have shown that production of LPA levels was constitutively increased in ovarian cancer cells but not in normal ovarian epithelial cells (6, 7). Moreover, in a study of the expression of LPA receptor mRNA and protein levels in ovarian cancer tissues, LPA 2 and LPA 3 were aberrantly up-regulated, but LPA 1 was not changed (8, 9). Overexpression of LPA 2 and LPA 3 are closely associated with tumor progression in ovarian cancer cells (10 -13). As evidence of intracellular signaling in cancer cell migration, LPA induces activation of Ras-MEKK1 (14), Rac1 (15), Ca 2ϩ -dependent Pyk2 (16), and the Rho/ROCK pathway (17), which indicates that dynamic cytoskeletal rearrangement in LPA-mediated cell migration is regulated through the coordination of complex contexts (such as small GTPases, focal adhesion, and Ca 2ϩ -dependent signaling). However, the exact re...