Autophagy-related cell death by pan-histone deacetylase inhibition in liver cancer

• Published in: Oncotarget Vol. 7; no. 20; pp. 28998 - 29010
• Main Authors: Di Fazio, Pietro, Waldegger, Petra, Jabari, Samir, Lingelbach, Susanne, Montalbano, Roberta, Ocker, Matthias, Slater, Emily P, Bartsch, Detlef K, Illig, Romana, Neureiter, Daniel, Wissniowski, Thaddeus T
• Format: Journal Article
• Language: English
• Published: United States Impact Journals LLC 17-05-2016
• Subjects: Animals; Antineoplastic Combined Chemotherapy Protocols - pharmacology; Autophagy - drug effects; Carcinoma, Hepatocellular - pathology; Cell Death - drug effects; Hep G2 Cells; Histone Deacetylase Inhibitors - pharmacology; Humans; Hydroxamic Acids - pharmacology; Indoles - pharmacology; Liver Neoplasms - pathology; Mice; Mice, Nude; Research Paper; Tamoxifen - pharmacology; Xenograft Model Antitumor Assays; cancer therapy; autophagic cell death; pan-deacetylase inhibitor; liver cancer; autophagosomes
• ISSN: 1949-2553; 1949-2553
• DOI: 10.18632/oncotarget.8585

Autophagy is a homeostatic, catabolic degradation process and cell fate essential regulatory mechanism. Protracted autophagy triggers cell death; its aberrant function is responsible for several malignancies. Panobinostat, a potent pan-deacetylase inhibitor, causes endoplasmic reticulum stress-induced cell death. The aim of this study was to investigate the role of autophagy in deacetylase inhibitor-triggered liver cancer cell death.HepG2 (p53wt) and Hep3B (p53 null) liver cancer cell lines were exposed to panobinostat. RT-qPCR and western blot confirmed autophagic factor modulation. Immuno-fluorescence, -precipitation and -histochemistry as well as transmission electron microscopy verified autophagosome formation. The cytotoxicity of panobinostat and autophagy modulators was detected using a real time cell viability assay.Panobinostat induced autophagy-related factor expression and aggregation. Map1LC3B and Beclin1 were significantly over-expressed in HepG2 xenografts in nude mice treated with panobinostat for 4 weeks. Subcellular distribution of Beclin1 increased with the appearance of autophagosomes-like aggregates. Cytosolic loss of p53, in HepG2, and p73, in Hep3B cells, and a corresponding gain of their nuclear level, together with modulation of DRAM1, were observed. Autophagosome aggregation was visible after 6 h of treatment. Treatment of cells stably expressing GFP-RFPtag Map1LC3B resulted in aggregation and a fluorescence switch, thus confirming autophagosome formation and maturation. Tamoxifen, an inducer of autophagy, caused only a block in cell proliferation; but in combination with panobinostat it resulted in cell death.Autophagy triggers cell demise in liver cancer. Its modulation by the combination of tamoxifen and panobinostat could be a new option for palliative treatment of hepatocellular carcinoma.