Sphingosine Suppresses Mesothelioma Cell Proliferation by Inhibiting PKC-δ and Inducing Cell Cycle Arrest at the G(0)/G(1) Phase

Cell Physiol Biochem. 2012 Sep 20;30(4):995-1004. [Epub ahead of print] [Link]

Okuwa H, Kanno T, Fujita Y, Gotoh A, Tabata C, Fukuoka K, Nakano T, Nishizaki T.

Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Japan.

Abstract

Background/Aims: Sphingosine regulates cellular differentiation, cell growth, and apoptosis. The present study aimed at understanding sphingosine-regulated mesothelioma cell proliferation.

Methods: Human malignant mesothelioma cells such as NCI-H28, NCI-H2052, NCI-H2452, and MSTO-211H cells were cultured. The siRNA to silence the protein kinase C (PKC)-δ-targeted gene was constructed and transfected into cells. MTT assay, cell cycle analysis using a flow cytometry, and cell-free PKC-δ assay were carried out.

Results: For all the cell types sphingosine inhibited cell growth in a concentration (1-100 µM)-dependent manner. The sphingosine effect was not prevented by rottlerin, an inhibitor of protein kinase C-δ (PKC-δ); conversely, rottlerin further enhanced the sphingosine effect or rottlerin suppressed mesothelioma cell growth without sphingosine. In the cell-free PKC assay, sphingosine attenuated PKC-δ activity. Knocking-down PKC-δ induced cell cycle arrest at the G0/G1 phase and inhibited cell growth.

Conclusion: The results of the present study show that sphingosine suppressed mesothelioma cell proliferation by inhibiting PKC-δ, to induce cell cycle arrest at the G0/G1 phase.