Ceramide triggers caspase activation during gamma-radiation-induced apoptosis of human glioma cells lacking functional p53.
We have previously shown that treatment of human glioma U87-MG cells expressing wild-type p53 with a DNA topoisomerase II inhibitor, etoposide resulted in ceramide-dependent apoptotic cell death. However, U87-W E6 cells lacking functional p53 due to the expression of human papilloma virus type 16 (HPV-16) E6 oncoprotein were resistant to etoposide. In order to gain insight into the roles of p53 and ceramide in gamma-radiation-induced glioma cell death, we used U87-W E6 and vector-infected U87-LXSN cells. U87-LXSN glioma cells expressing wild-type p53 were relatively resistant to gamma-radiation. U87-W E6 cells, which lost functional p53, became susceptible to radiation-induced apoptosis. Activation of caspase-3, and formation of ceramide by acid sphingomyelinase, but not by neutral sphingomyelinase, were associated with p53-independent apoptosis. Radiation-induced caspase activation and apoptotic death in U87-W E6 cells were modified by the agents which affected ceramide metabolism. SR33557, an inhibitor of acid sphingomyelinase, suppressed radiation-induced caspase activation and then apoptotic cell death. In contrast, N-oleoylethanolamine (OE) and D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), which inhibit ceramidase and UDP-glucose:ceramide glucosyltransferase-1, respectively, and then augment ceramide formation, enhanced radiation-induced caspase activation. These results indicate that glioma cells with functional p53 were relatively resistant to gamma-radiation, and that ceramide may play an important role in caspase activation during gamma-radiation-induced apoptosis of glioma cells lacking functional p53.
Hara
Shigeru
S
Department of Neurosurgery, Gifu University School of Medicine, Gifu 500-8705, Japan. nohgeka@cc.gifu-u.ac.jp
Nakashima
Shigeru
S
Kiyono
Tohru
T
Sawada
Motoshi
M
Yoshimura
Shin-Ichi
S
Iwama
Toru
T
Sakai
Noboru
N
D017209:Apoptosis / Q000528:radiation effects*; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D002518:Ceramides / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005720:Gamma Rays; D005910:Glioma / Q000473:pathology*; D006801:Humans; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency* / Q000235:genetics*
D002518:Ceramides; D016159:Tumor Suppressor Protein p53; D020169:Caspases