ceramide-1-phosphate and Neoplasm-Metastasis

Ceramide kinase (CerK) phosphorylates ceramide to ceramide-1-phosphate (C1P), a bioactive sphingolipid. Since the mechanisms responsible for regulating the proliferation and migration/metastasis of cancer cells by the CerK/C1P pathway remain unclear, we conducted the present study. The knockdown of CerK in A549 lung and MCF-7 breast cancer cells (shCerK cells) increased the formation of lamellipodia, which are membrane protrusions coupled with cell migration. Mouse embryonic fibroblasts prepared from CerK-null mice also showed an enhanced formation of lamellipodia. The overexpression of CerK inhibited lamellipodium formation in A549 cells. The knockdown of CerK increased the number of cells having lamellipodia with Rac1 and the levels of active Rac1-GTP form, whereas the overexpression of CerK decreased them. CerK was located in lamellipodia after the epidermal growth factor treatment, indicating that CerK functioned there to inhibit Rac1. The migration of A549 cells was negatively regulated by CerK. An intravenous injection of A549-shCerK cells into nude mice resulted in markedly stronger metastatic responses in the lungs than an injection of control cells. The in vitro growth of A549 cells and in vivo expansion after the injection into mouse flanks were not affected by the CerK knockdown. These results suggest that the activation of CerK/C1P pathway has inhibitory roles on lamellipodium formation, migration, and metastasis of A549 lung cancer cells.

Topics: A549 Cells; Animals; Cell Movement; Ceramides; Gene Knockdown Techniques; Humans; Lung Neoplasms; Male; MCF-7 Cells; Mice; Neoplasm Invasiveness; Neoplasm Metastasis; Phosphotransferases (Alcohol Group Acceptor); Pseudopodia; rac1 GTP-Binding Protein; RNA, Small Interfering; Signal Transduction; Xenograft Model Antitumor Assays

Evidence suggests that bioactive lipids may regulate pathophysiologic functions such as cancer cell metastasis. Therefore, we determined that the bioactive lipid chemoattractants sphingosine-1-phosphate (S1P) and ceramide-1-phosphate (C1P) strongly enhanced the in vitro motility and adhesion of human rhabdomyosarcoma (RMS) cells. Importantly, this effect was observed at physiologic concentrations for both bioactive lipids, which are present in biologic fluids, and were much stronger than the effects observed in response to known RMS prometastatic factors such as stromal derived factors-1 (SDF-1/CXCL12) or hepatocyte growth factor/scatter factor (HGF/SF). We also present novel evidence that the levels of S1P and C1P were increased in several organs after γ-irradiation or chemotherapy, which indicates an unwanted prometastatic environment related to treatment. Critically, we found that the metastasis of RMS cells in response to S1P can be effectively inhibited in vivo with the S1P-specific binder NOX-S93 that is based on a high-affinity Spiegelmer. These data indicate that bioactive lipids play a vital role in dissemination of RMS and contribute to the unwanted side effects of radio/chemotherapy by creating a prometastatic microenvironment.

Topics: Actins; Animals; Antineoplastic Agents; Aptamers, Nucleotide; Bone Marrow; Cell Adhesion; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Survival; Cellular Microenvironment; Ceramides; Cytoskeleton; Down-Regulation; Enzyme Activation; Humans; Lysophospholipids; Mice; Mice, Inbred C57BL; Mitogen-Activated Protein Kinases; Neoplasm Metastasis; Proto-Oncogene Proteins c-akt; Receptors, Lysosphingolipid; Rhabdomyosarcoma; Sphingosine