Inhibition of N-(4-hydroxyphenyl)retinamide-induced autophagy at a lower dose enhances cell death in malignant glioma cells.
The question whether chemotherapy-induced autophagy is causative to the demise of the cells or a part of the survival mechanism activated during cellular distress is unclear. Others and we have previously demonstrated apoptosis-inducing capacity of N-(4-hydroxyphenyl)retinamide (4-HPR) in malignant glioma cells. We provide evidences of 4-HPR-induced autophagy at a lower concentration (5 microM). Suboptimal dose of 4-HPR treatment of malignant glioma cell lines increased G(2)/M arrest, whereas cell accumulated in S phase at a higher concentration. 4-HPR-induced autophagy was associated with acidic vacuole [acidic vesicular organelle (AVO)] formation and recruitment of microtubule-associated protein light chain 3 (LC3). At a higher concentration of 10 microM of 4-HPR, glioma cells undergoing apoptosis manifested autophagic features indicated by autophagosome formation, AVO development and LC3 localization. Autophagy inhibition at an early stage by 3-methyl adenine inhibited the AVO formation and LC3 localization with an enhancement in cell death. Bafilomycin A1, a specific inhibitor of vacuolar type Hthorn-ATPase also prevented AVO formation without effecting LC-3 localization pattern and also enhanced the extent of 4-HPR-induced cell death. 4-HPR activated c-jun and P38(MAPK) at both 5 and 10 microM concentrations, whereas increased activation of extracellular signal-regulated kinase 1/2 and NF-kappaB was seen only at lower dose. Inhibiting phosphoinositide 3-kinase and mitogen-activated protein kinases pathways modulated 4-HPR-induced cell death. This is the first report that provides evidences that besides apoptosis induction 4-HPR can also induce autophagy. These results indicate that 4-HPR-induced autophagy in glioma cell may provide survival advantage and inhibition of autophagy may enhance the cytotoxicity to 4-HPR.
Tiwari
Meenakshi
M
Department of Endocrinology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Raebareli Road, Lucknow 226 014, India.
Bajpai
Virendra Kumar
VK
Sahasrabuddhe
Amogh Anant
AA
Kumar
Ashok
A
Sinha
Rohit Anthony
RA
Behari
Sanjay
S
Godbole
Madan Madhav
MM
D001343:Autophagy / Q000187:drug effects*; D001932:Brain Neoplasms / Q000473:pathology*; D016923:Cell Death / Q000187:drug effects*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D017313:Fenretinide / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D005434:Flow Cytometry; D005910:Glioma / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D011494:Protein Kinases / Q000378:metabolism
D017313:Fenretinide; D011494:Protein Kinases