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

Abstract

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.

Panobinostat mediated cell death: a novel therapeutic approach for osteosarcoma

“…The number of autophagosome vesicles was quantified based on a previously published method [ 13 , 32 , 33 ]. Statistical analysis was performed, as shown in Table 1 .…”

“…Autophagy describes the ability of eukaryote cells to degrade cellular molecules, organelles and proteins using autophagosomes as carriers [ 24 ]. Normally the induction of autophagy related cell stress is linked to the promotion of cell survival but [ 25 ], under certain conditions, elevated autophagy levels lead to cell demise representing an alternative way of cell death [ 13 , 24 , 26 , 27 ].…”

Metabolism of Histone Deacetylase Proteins Opsonizes Tumor Cells to Checkpoint Inhibitory Immunotherapies

“…Similar data in sarcoma cells using the multi-kinase inhibitor pazopanib combined with the novel HDAC inhibitor AR42 also resulted in a clinical trial (NCT02795819). Others have also demonstrated that autophagy is frequently a mechanism by which GI tumor cells can be killed by anti-cancer drugs, using the chemically dissimilar HDAC inhibitor panobinostat [6][7][8].…”

Comment on "A series of microRNA in the chromosome 14q32.2 maternally imprinted region related to progression of non-alcoholic fatty liver disease in a mouse model”

“…It has been shown that its modulation can be a promising target for cancer therapy in liver cancer. [13] The expression of miRNAs repressing autophagy regulators like AMPK could highlight the variations occurring at epigenetic level conferring to cells an altered metabolism that irreversibly modifies the liver cells and tissue. These alterations could be responsible to trigger further pathological cellular features leading to cirrhosis and furthermore liver carcinogenesis.…”