Irradiation with carbon ion beams induces apoptosis, autophagy, and cellular senescence in a human glioma-derived cell line.
OBJECTIVE
We examined biological responses of human glioma cells to irradiation with carbon ion beams (C-ions).


METHODS
A human glioma-derived cell line, NP-2, was irradiated with C-ions. Apoptotic cell nuclei were stained with Hoechst 33342. Induction of autophagy was examined either by staining cells with monodansylcadaverine (MDC) or by Western blotting to detect conversion of microtuble-associated protein light chain 3 (MAP-LC3) (LC3-I) to the membrane-bound form (LC3-II). Cellular senescence markers including induction of senescence-associated beta-galactosidase (SA-beta-gal) were examined. The mean telomere length of irradiated cells was determined by Southern blot hybridization. Expression of tumor suppressor p53 and cyclin/cyclin-dependent kinase inhibitor p21(WAF1/CIP1) in the irradiated cells was analyzed by Western blotting.


RESULTS
When NP-2 cells were irradiated with C-ions at 6 Gy, the major population of the cells died of apoptosis and autophagy. The residual fraction of attached cells (<1% of initially irradiated cells) could not form a colony: however, they showed a morphological phenotype consistent with cellular senescence, that is, enlarged and flattened appearance. The senescent nature of these attached cells was further indicated by staining for SA-beta-gal. The mean telomere length was not changed after irradiation with C-ions. Phosphorylation of p53 at serine 15 as well as the expression of p21(WAF1/CIP1) was induced in NP-2 cells after irradiation. Furthermore, we found that irradiation with C-ions induced cellular senescence in a human glioma cell line lacking functional p53.


CONCLUSIONS
Irradiation with C-ions induced apoptosis, autophagy, and cellular senescence in human glioma cells.
Jinno-Oue
Atsushi
A
Department of Virology and Preventive Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
Shimizu
Nobuaki
N
Hamada
Nobuyuki
N
Wada
Seiichi
S
Tanaka
Atsushi
A
Shinagawa
Masahiko
M
Ohtsuki
Takahiro
T
Mori
Takahisa
T
Saha
Manujendra N
MN
Hoque
Ariful S
AS
Islam
Salequl
S
Kogure
Kimitaka
K
Funayama
Tomoo
T
Kobayashi
Yasuhiko
Y
Hoshino
Hiroo
H
D017209:Apoptosis; D001343:Autophagy; D002244:Carbon / Q000494:pharmacology*; D045744:Cell Line, Tumor / Q000528:radiation effects; D016922:Cellular Senescence; D003114:Colony-Forming Units Assay; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D005910:Glioma / Q000378:metabolism / Q000473:pathology; D020450:Heavy Ions; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D016615:Telomere / Q000473:pathology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
D050759:Cyclin-Dependent Kinase Inhibitor p21; D008869:Microtubule-Associated Proteins; D016159:Tumor Suppressor Protein p53; D002244:Carbon; D001616:beta-Galactosidase