Altered lys-ophosphatidic acid (LPA) signaling occurs in other cancers, yet the role of
LPA in HCC remains poorly understood. We sought to determine the expression and function of LPARs1-3 in human samples and SKHep1 cells, metastatic human liver cell lines. LPAR1-3 mRNA and protein expression was measured in human HCC, pair-matched non-tumor liver (NTL) and cultured SKHep1 cells, and compared to histologically normal liver (NL). Cultured SKHep1 cells were treated with LPA [0-10ng/ml) with or without Ki16425 (LPAR1-3 antagonist; 10^M), pertussis toxin (PTx; Gi-protein inhibitor, 100ng/ml) or CT04 (Rho inhibitor I, 1^g/ml). Cell Buparlisib purchase proliferation, motility, and intracellular signaling activity (PI3K-Akt, MAPK-ERK, and Rho) were measured. Finally, SKHep1 cells were stably transfected with shRNAs to down-regulate
LPAR1 or 3 expression and cell signaling/function analyzed following LPA-treatment. Human HCC demonstrated increased LPAR 1 and 3 mRNA expression in 4/9 samples vs NTL and LPAR3 mRNA was elevated in 8/9 NTL samples vs NL. Further analysis by IHC demonstrated a 3.4±0.1 fold increase in LPAR3 score in HCC vs NTL (p<0.01, n=17). These data were mirrored in SKHep1 cells with significantly increased LPAR1/3 expression vs NL. Treatment of SKHep1 cells with LPA led to dose-dependent increases in SKHep1 migration (84±14% increase, p<0.05, n=3) and motility (32±5% increase, p<0.05, FK228 in vivo n=3) in the absence of significant changes in proliferation. Following treatment LPA significantly stimulated Rho and PI3K-Akt activity, an effect abolished in the presence of Ki16425. Inhibition of Rho (CT04) did not significantly affect motility, migration, or proliferation, effects mirrored by inhibiting LPAR1 expression using an shRNA (83±2% decrease in LPAR1 expression). Blocking Gi-protein signaling (PTx) significantly inhibited
downstream PI3K-Akt activity and abrogated cell motility/migration. MCE Decreasing LPAR3 expression (81 ±1% decrease) mirrored the effects of PTx; no significant PI3K-Akt activation or cell migration being measured following LPA-stimulation in cells expressing LPAR3 shRNA. These data demonstrate human HCC and SKHep1 cells are characterized by elevated LPAR1/3 expression vs. histologically NL. In SKHep1 cells LPA stimulates cell migration via a LPAR3-Gi-protein-PI3-Akt-dependent pathway independent of LPAR1-Rho signaling. These data suggest LPAR1/3 are potential targets for future therapeutic intervention, particularly since LPAR1/3 are weakly expressed in NL and LPAR1/3 antagonists are currently undergoing clinical trial to treat other cancers. Disclosures: David A.