Cholangiocarcinoma (CCA) is a highly invasive and metastatic form of carcinoma with bleak prognosis due to limited therapies, frequent relapse, and chemotherapy resistance. There is an urgent need to identify the molecular regulators of CCA in order to develop novel therapeutics and advance diseases diagnosis. Many cellular proteins including histones may undergo a series of enzyme-mediated post-translational modifications including acetylation, methylation, phosphorylation, sumoylation, and crotonylation. Histone deacetylases (HDACs) play an important role in regulating epigenetic maintenance and modifications of their targets, which in turn exert critical impacts on chromatin structure, gene expression, and stability of proteins. As such, HDACs constitute a group of potential therapeutic targets for CCA. The aim of this review was to summarize the role that HDACs perform in regulating epigenetic changes, tumor development, and their potential as therapeutic targets for CCA.

It is well established that Cholangiocarcioma (CCA) drug resistance plays a crucial role in the spread and survival of cancer cells. The major enzyme in the nicotinamide-adenine dinucleotide (NAD+)-mediated pathways, nicotinamide phosphoribosyltransferase (NAMPT), is essential for cancer cell survival and metastasis. Previous research has shown that the targeted NAMPT inhibitor FK866 reduces cancer cell viability and triggers cancer cell death; however, whether FK866 affects CCA cell survival has not been addressed before. We show herein that NAMPT is expressed in CCA cells, and FK866 suppresses the capacity of CCA cells to grow in a dose-dependent manner. Furthermore, by preventing NAMPT activity, FK866 significantly reduced the amount of NAD+ and adenosine 5′-triphosphate (ATP) in HuCCT1, KMCH, and EGI cells. The present study’s findings further show that FK866 causes changes in mitochondrial metabolism in CCA cells. Additionally, FK866 enhances the anticancer effects of cisplatin in vitro. Taken together, the results of the current study suggest that the NAMPT/NAD+ pathway may be a possible therapeutic target for CCA, and FK866 may be a useful medication targeting CCA in combination with cisplatin.

Our study reveals a novel link between primary cilia and DNA repair in cholangiocytes. We show that DNA damage response (DDR) and repair proteins localize to cilia, and deciliation impairs survival and induces S-phase arrest under genotoxic stress. Deciliated cells exhibit increased DNA damage after cisplatin, irradiation, or methyl methanesulfonate (MMS) challenge. Following irradiation, Ataxia Telangiectasia Mutated protein (ATM), p53, and p21 are downregulated in deciliated cells. Similarly, IFT88 knockout mice show heightened DNA damage, highlighting the role of primary cilia in genome stability.

Primary cilia have been considered tumor-suppressing organelles in cholangiocarcinoma (CCA), though the mechanisms behind their protective role are not fully understood. This study investigates how the loss of primary cilia affects DNA damage response (DDR) and DNA repair processes in CCA. Human cholangiocyte cell lines were used to examine the colocalization of DNA repair proteins at the cilia and assess the impact of experimental deciliation on DNA repair pathways. Deciliation was induced using shRNA knockdown or CRISPR knockout of IFT20, IFT88, or KIF3A, followed by exposure to the genotoxic agents cisplatin, methyl methanesulfonate (MMS), or irradiation. Cell survival, cell cycle progression, and apoptosis rates were evaluated, and DNA damage was assessed using comet assays and γH2AX quantification. An in vivo liver-specific IFT88 knockout model was generated using Cre/Lox recombination. Results showed that RAD51 localized at the cilia base, while ATR, PARP1, CHK1 and CHK2 were found within the cilia. Deciliated cells displayed dysregulation in critical DNA repair. These cells also showed reduced survival and increased S-phase arrest after genotoxic challenges as compared to ciliated cells. Enhanced DNA damage was observed via increased γH2AX signals and comet assay results. An increase in γH2AX expression was also observed in our in vivo model, indicating elevated DNA damage. Additionally, key DDR proteins, such as ATM, p53, and p21, were downregulated in deciliated cells after irradiation. This study underscores the crucial role of primary cilia in regulating DNA repair and suggests that targeting cilia-related mechanisms could present a novel therapeutic approach for CCA. New and Noteworthy: Our findings reveal a novel connection between primary cilia and DNA repair in cholangiocytes. We showed that DDR and DNA repair proteins localize to cilia, and that deciliation leads to impaired cell survival and S-phase arrest under genotoxic stress. Deciliated cells exhibit heightened DNA damage, evidenced by increased γH2AX signals and comet assay results, a phenotype mirrored in in vivo IFT88 knockout mice. Furthermore, key DDR regulators, including ATM, p53, and p21, are downregulated in deciliated cells following irradiation, highlighting a crucial role for primary cilia in maintaining genome stability.