Combination of N-(4-hydroxyphenyl) retinamide and apigenin suppressed starvation-induced autophagy and promoted apoptosis in malignant neuroblastoma cells.

Abstract

Autophagy is a catabolic process for recycling of cellular contents in response to metabolic stress in malignant tumors. We explored efficacy of the synthetic retinoid N-(4-hydroxyphenyl) retinamide (4-HPR) and the isoflavonoid apigenin (APG) in the serum-starved human malignant neuroblastoma cells. Combination of 0.5 μM 4-HPR and 50 μM APG synergistically decreased cell viability in the serum-starved neuroblastoma SH-SY5Y, SK-N-BE2, and IMR-32 cells. Acridine orange (AO) staining and LC3 II upregulation showed that serum-starvation for 12 and 24h progressively increased the formation of acidic vesicular organelles (AVO) and autophagy in SH-SY5Y cells. Further, AO staining and flow cytometry showed blockage of formation of AVO and accumulation of auophagic population, respectively, following the treatment of the serum-starved SH-SY5Y cells with combination of 0.5 μM 4-HPR and 50 μM APG. Combination therapy downregulated autophagy inducing proteins such as Beclin 1, LC3 II, TLR-4, and Myd88 while upregulated autophagy inhibitory p-Akt/mTOR singaling pathway. Consistent with the hypothesis that inhibition of autophagy could induce apoptosis, we noticed inhibition of autophagy and induction of apoptosis in the serum-starved SH-SY5Y cells with the suppression of the survival factor NF-κB, upregulation of pro-apoptotic Bax, downregulation of anti-apoptotic Bcl-2, activation of caspase-3, and degradation of poly(ADP-ribose) polymerase (PARP) after combination therapy. Collectively, combination of 4-HPR and APG worked synergistically to suppress autophagy and promote apoptosis in human malignant neuroblastoma cells.

• Authors: Nishant Mohan, Naren L Banik, Swapan K Ray
• Journal: Neuroscience letters (Neurosci Lett) Vol. 502 Issue 1 Pg. 24-9 (Sep 08 2011) ISSN: 1872-7972 [Electronic] Ireland
• PMID: 21801811 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Apoptosis Regulatory Proteins
• Culture Media, Serum-Free
• Fenretinide
• Apigenin

Topics

• Apigenin (pharmacology)
• Apoptosis (drug effects)
• Apoptosis Regulatory Proteins (metabolism)
• Autophagy (drug effects)
• Cell Line, Tumor
• Cell Survival (drug effects)
• Culture Media, Serum-Free
• Down-Regulation (drug effects)
• Drug Synergism
• Fenretinide (pharmacology)
• Humans
• Molecular Imaging (methods)
• Organelles (drug effects)
• Signal Transduction (drug effects)
• Up-Regulation (drug effects)