Apoptosis

, Volume 14, Issue 3, pp 287–297 | Cite as

Induction of apoptosis of detached oral squamous cell carcinoma cells by safingol. Possible role of Bim, focal adhesion kinase and endonuclease G

  • Takayuki Noda
  • Soichi Iwai
  • Masakazu Hamada
  • Yusei Fujita
  • Yoshiaki Yura
Original Paper

Abstract

The protein kinase C (PKC) inhibitor safingol increased rounding and detachment of human oral squamous cell carcinoma (SCC) cells in monolayer cultures. When dissociated cells were incubated in the presence of safingol, cell adhesion was prevented and cell viability was lost gradually, while most cells survived in the absence of safingol even if their attachment was blocked by coating the culture plates with polyhydroxyethyl methacrylate. Flow cytometric analysis and agarose gel electrophoresis of cellular DNA revealed an increase in the proportion of sub-G1 cells and DNA fragmentation, indicating that safingol induced apoptosis of dissociated cells. During the induction of apoptosis in cell suspensions by safingol, there was an increase of the pro-apoptotic BH-3 only protein Bim and decrease of pro-survival Bcl-2 family proteins Bcl-xL and mitochondrial pro-apoptogenic factor endonuclease G translocated to the nucleus. The level of phosphorylated focal adhesion kinase (FAK) required for cell survival also rapidly decreased, followed by a decrease in the protein level. The introduction of siRNA against PKCα into SAS cells resulted in an increase of Bim, a decrease of Bcl-xL, the translocation of endonuclease G, and a decrease in the phosphorylation of FAK. These results suggest that Bim, Bcl-xL, FAK and endonuclease G are involved in safingol-induced apoptosis of detached oral SCC cells. Safingol can be used to induce apoptosis with cell detachment, anoikis, of oral SCC cells.

Keywords

Protein kinase C inhibitor Oral squamous cell carcinoma Bcl-2 family protein Focal adhesion kinase Endonuclease G Anoikis 

Abbreviations

BH

Bcl-2 homology

MTT

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide

ECM

Extracellular matrix

FAK

Focal adhesion kinase

ILK

Integrin-linked kinase

poly-HEMA

Polyhydroxyethyl methacrylate

PPARγ

Peroxisome proliferator-activated receptor γ

PKC

Protein kinase C

SCC

Squamous cell carcinoma

Notes

Acknowledgments

This work was supported in part by a Grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.

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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Takayuki Noda
    • 1
  • Soichi Iwai
    • 1
  • Masakazu Hamada
    • 1
  • Yusei Fujita
    • 1
  • Yoshiaki Yura
    • 1
  1. 1.Department of Oral and Maxillofacial SurgeryOsaka University Graduate School of DentistryOsakaJapan

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