acy-1215 and Cholangiocarcinoma

HDAC6, a cytoplasmic localized deacetylase, is a positive regulator of cancer progression via modification of various substrates. We evaluated how the interaction between HDAC6 and glucose regulatory protein 78 (GRP78) affects the growth of cholangiocarcinoma (CCA).. The anti-tumor effects of ACY-1215, an HDAC6 specific inhibitor, in CCA cell lines were analyzed by cell viability assay, western blotting, flow cytometry, co-immunoprecipitation, and biotinylation assays. In vivo effects of ACY-1215 were evaluated in a xenograft model using CCA cell line TFK-1.. ACY-1215 increased the acetyl-form of GRP78 by approximately 50% compared to control, which impaired the translocation of GRP78 to the plasma membrane by 50% through alteration of cellular proliferative signaling via PI3K/AKT. Furthermore, ACY-1215 suppressed tumor growth by 50% compared to vehicle control in a CCA xenograft model.. Increase in GRP78 acetylation by HDAC6 inhibition suppressed GRP78 translocation to the cell surface, which inhibited proliferation and promoted apoptosis in CCA.

Topics: Animals; Cell Line, Tumor; Cell Membrane; Cell Proliferation; Cell Survival; Cholangiocarcinoma; Endoplasmic Reticulum Chaperone BiP; Flow Cytometry; Histone Deacetylase 6; Humans; Hydroxamic Acids; Mice; Phosphatidylinositol 3-Kinases; Protein Transport; Proto-Oncogene Proteins c-akt; Pyrimidines; Xenograft Model Antitumor Assays

Reduced ciliary expression is reported in several tumors, including cholangiocarcinoma (CCA). We previously showed primary cilia have tumor suppressor characteristics, and HDAC6 is involved in ciliary loss. However, mechanisms of ciliary disassembly are unknown. Herein, we tested the hypothesis that HDAC6-dependent autophagy of primary cilia, i.e., ciliophagy, is the main mechanism driving ciliary disassembly in CCA. Using the cancer genome atlas database, human CCA cells, and a rat orthotopic CCA model, we assessed basal and HDAC6-regulated autophagy levels. The effects of RNA-silencing or pharmacological manipulations of ciliophagy on ciliary expression were assessed. Interactions of ciliary proteins with autophagy machinery was assessed by immunoprecipitations. Cell proliferation was assessed by MTS and IncuCyte. A CCA rat model was used to assess the effects of pharmacological inhibition of ciliophagy in vivo. Autophagy is increased in human CCA, as well as in a rat orthotopic CCA model and human CCA cell lines. Autophagic flux was decreased via inhibition of HDAC6, while it was increased by its overexpression. Inhibition of autophagy and HDAC6 restores cilia and decreases cell proliferation. LC3 interacts with HDAC6 and ciliary proteins, and the autophagy cargo receptor involved in targeting ciliary components to the autophagy machinery is primarily NBR1. Treatment with chloroquine, Ricolinostat (ACY-1215), or their combination decreased tumor growth in vivo. Mice that overexpress the autophagy transcription factor TFEB show a decrease of ciliary number. These results suggest that ciliary disassembly is mediated by HDAC6-regulated autophagy, i.e., ciliophagy. Inhibition of ciliophagy may decrease cholangiocarcinoma growth and warrant further investigations as a potential therapeutic approach.

Topics: Animals; Autophagy; Cell Line, Tumor; Cell Proliferation; Cholangiocarcinoma; Cilia; Gene Expression Regulation, Neoplastic; Histone Deacetylase 6; Humans; Hydroxamic Acids; Hydroxychloroquine; Intracellular Signaling Peptides and Proteins; Male; Mice; Nuclear Proteins; Pyrimidines; Rats