Radiation-Induced Autophagy Contributes to Cell Death and Induces Apoptosis Partly in Malignant Glioma Cells.
- Author:
Guk Heui JO
1
;
Oliver BOGLER
;
Yong Joon CHWAE
;
Heon YOO
;
Seung Hoon LEE
;
Jong Bae PARK
;
Youn Jae KIM
;
Jong Heon KIM
;
Ho Shin GWAK
Author Information
- Publication Type:Original Article
- Keywords: Apoptosis; Autophagy; Cell death; Glioma; Radiation
- MeSH: Apoptosis*; Autophagy*; Blotting, Western; Cell Death*; Cell Line; Cell Survival; Fluorescent Antibody Technique; Glioma*; Organelles; Poly(ADP-ribose) Polymerases; Transfection
- From:Cancer Research and Treatment 2015;47(2):221-241
- CountryRepublic of Korea
- Language:English
- Abstract: PURPOSE: Radiation-induced autophagy has been shown to play two different roles, in malignant glioma (MG) cells, cytocidal or cytoprotective. However, neither the role of radiation-induced autophagy for cell death nor the existence of autophagy-induced apoptosis, a well-known cell-death pathway after irradiation, has been verified yet. MATERIALS AND METHODS: We observed both temporal and dose-dependent response patterns of autophagy and apoptosis to radiation in MG cell lines. Additionally, we investigated the role of autophagy in apoptosis through knockdown of autophagy-related proteins. RESULTS: Autophagic activity measured by staining of acidic vesicle organelles and Western blotting of LC-3 protein increased in proportion to radiation dose from day 1 to 5 after irradiation. Apoptosis measured by annexin-V staining and Western blotting of cleaved poly(ADP-ribose) polymerase demonstrated relatively late appearance 3 days after irradiation that increased for up to 7 days. Blocking of pan-caspase (Z-VAD-FMK) did not affect apoptosis after irradiation, but silencing of Atg5 effectively reduced radiation-induced autophagy, which decreased apoptosis significantly. Inhibition of autophagy in Atg5 knockdown cells was shown to be beneficial for cell survival. Stable transfection of GFP-LC3 cells was observed after irradiation. Annexin-V was localized in cells bearing GFP-LC3 punctuated spots, indicating autophagy in immunofluorescence. Some of these punctuated GFP-LC3 bearing cells formed conglomerated spots and died in final phase. CONCLUSION: These findings suggest that autophagy appears earlier than apoptosis after irradiation and that a portion of the apoptotic population that appears later is autophagy-dependent. Thus, autophagy is a pathway to cell death after irradiation of MG cells.
