Ethionine regulates cell motile activity through LPA receptor-3 in liver epithelial WB-F344 cells

Spectroscopic, kinetic, and theoretical analyses of oxidation of dl-ethionine by Pt(IV) anticancer model compounds

Ethionine is an S-ethyl analog of methionine (Met) having a small change in structure. But it is a chemical carcinogen and an antagonist of Met, thus displaying a disparate biological profile. The oxidations of ethionine by biologically important oxidants have not been exploited. Oxidations of dl-ethionine by Pt(IV) anticancer model complexes trans-[PtX₂(CN₄)]^2- (X = Cl or Br) were thus analyzed by time-resolved and stopped-flow spectral techniques. Overall second-order kinetics was established, being first-order in [Pt(IV)] and [Ethionine]_tot (the total concentration of ethionine); the observed second-order rate constant k' versus pH profiles were obtained. A stoichiometry of Δ[Pt(IV)]:Δ[Ethionine]_tot = 1:1 was unraveled, indicating that ethionine was oxidized to ethionine-sulfoxide which was confirmed by NMR spectroscopic and high-resolution mass spectral analyses. In the proposed reaction mechanism which is similar to that for the oxidation of Met by the same Pt(IV) compounds, the rate-determining steps are rationalized in terms of a bridge formation between one of the coordinated halides in [PtX₂(CN₄)]^2- and the sulfur atom in ethionine, followed by an X⁺ transfer. Moreover, a large rate enhancement for the reaction of ethionine with [PtBr₂(CN₄)]^2- compared with [PtCl₂(CN₄)]^2- strongly supports an X⁺ transfer mechanism. Furthermore, a combined quantum-mechanical/molecular-mechanical (QM/MM) method was utilized to simulate a Cl⁺ transfer mechanism from trans-[PtCl₂(CN)₄]^2- to ethionine. The simulations unraveled the energetically stable structures of reactants and products, which favor the Cl⁺ transfer process. Rate constants of the rate-determining steps have been derived. Ratios of k (ethionine)/k (Met) are between 2.2 and 2.6 obtained for the three protolytic species of ethionine and Met; the enhanced reactivity might be partially responsible for the disparate biological profiles.

Different roles of GPR120 and GPR40 in the acquisition of malignant properties in pancreatic cancer cells

Free fatty acids (FFAs) act as extracellular signaling molecules through binding to G-protein-coupled FFA receptors (FFARs). GPR120 and GPR40 are identified as FFARs for medium- and long-chain fatty acids. In the present study, we investigated roles of GPR120 and GPR40 in cellular functions of pancreatic cancer PANC-1 cells, using GPR120 and GPR40 knockdown cells (PANC-sh120 and PANC-sh40 cells respectively). In cell motility assay, PANC-sh120 cells showed the low cell motility, compared with control cells. In contrast, the cell motility of PANC-sh40 cells was significantly higher than that of control cells. Activity levels of matrix metalloproteinases (MMPs) were measured by gelatin zymography. While PANC-sh120 cells indicated the reduced MMP-2 activity, MMP-2 activity in PANC-sh40 cells was significantly higher than that in control cells. On the other hand, no activation of MMP-9 was detected in all cells. In colony assay, the large sized colonies were markedly formed in PANC-sh40 cells. No colony formation was observed in PANC-sh120 cells as well as control cells. These results suggest that distinct effects of GPR120 and GPR40 are involved in the acquisition of malignant property in pancreatic cancer cells.

LPA signaling through LPA receptors regulates cellular functions of endothelial cells treated with anticancer drugs

Lysophosphatidic acid (LPA) signaling via LPA receptors provides a variety of cellular functions, including angiogenesis. In this study, to assess an involvement of LPA receptors in cell motile activities of endothelial cells during chemotherapy, F-2 cells were treated with cisplatin (CDDP) and doxorubicin (DOX) at a concentration of 0.01 μM every 24 h for at least 1 month. The treatment of CDDP and DOX inhibited the expression levels of the LPA receptor-1 (Lpar1), Lpar2, and Lpar3 genes in F-2 cells. The cell motile activities of CDDP and DOX treated cells were relatively lower than those of untreated cells. Next, we investigated whether cancer cells could stimulate the cell motile activities of F-2 cells treated with CDDP and DOX. For cell motility assay, CDDP- and DOX-treated cells were co-cultured with pancreatic cancer PANC-1 cells. The cell motile activities of CDDP- and DOX-treated cells were significantly enhanced by the existence of PANC-1 cells, correlating with the LPA receptor expressions. In addition, the elevated cell motile activities were suppressed by the pretreatment of an autotaxin inhibitor S32826. These results suggest that LPA signaling via LPA receptors may regulate the cell motile activities of F-2 cells treated with anticancer drugs.