nu-7441 and Carcinoma--Hepatocellular

Hepatocellular carcinoma (HCC) is a frequent and deadly disease worldwide. The absence of effective therapies when the tumor is surgically unresectable leads to an extremely poor outcome of HCC patients. Thus, it is mandatory to elucidate the molecular pathogenesis of HCC in order to develop novel therapeutic strategies against this pernicious tumor. Mounting evidence indicates that suppression of the DNA damage response machinery might be deleterious for the survival and growth of the tumor cells. In particular, DNA dependent protein kinase catalytic subunit (DNA-PKcs), a major player in the non-homologous end-joining (NHEJ) repair process, seems to represent a valuable target for innovative anti-neoplastic therapies in cancer. DNA-PKcs levels are strongly upregulated and associated with a poor clinical outcome in various tumor types, including HCC. Importantly, DNA-PKcs not only protects tumor cells from harmful DNA insults coming either from the microenvironment or chemotherapeutic drug treatments, but also possesses additional properties, independent from its DNA repair activity, that provide growth advantages to cancer cells. These properties (metabolic and gene reprogramming, invasiveness and metastasis, resistance to apoptosis, etc.) have started to be elucidated. In the present review, we summarize the physiologic and oncogenic roles of DNA-PKcs, with a special emphasis on liver cancer. In particular, this work focuses on the molecular mechanism whereby DNA-PKcs exerts its pro-tumorigenic activity in cancer cells. In addition, the upstream regulator of DNA-PKcs activation as well as its downstream effectors thus far identified are illustrated. Furthermore, the potential therapeutic strategies aimed at inhibiting DNA-PKcs activity in HCC are discussed.

Topics: Apoptosis; Carcinoma, Hepatocellular; Cell Cycle Proteins; Checkpoint Kinase 2; Chromones; DNA Breaks, Double-Stranded; DNA Damage; DNA End-Joining Repair; DNA-Activated Protein Kinase; DNA, Neoplasm; Gene Expression Regulation, Neoplastic; Humans; Liver Neoplasms; Molecular Targeted Therapy; Morpholines; Nuclear Proteins; Polo-Like Kinase 1; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Signal Transduction; Thiophenes; Ubiquitin-Protein Ligases

Understanding differences in DNA double-strand break (DSB) repair between tumor and normal tissues would provide a rationale for developing DNA repair-targeted cancer therapy. Here, using knock-in mouse models for measuring the efficiency of two DSB repair pathways, homologous recombination (HR) and nonhomologous end-joining (NHEJ), we demonstrated that both pathways are up-regulated in hepatocellular carcinoma (HCC) compared with adjacent normal tissues due to altered expression of DNA repair factors, including PARP1 and DNA-PKcs. Surprisingly, inhibiting PARP1 with olaparib abrogated HR repair in HCC. Mechanistically, inhibiting PARP1 suppressed the clearance of nucleosomes at DNA damage sites by blocking the recruitment of ALC1 to DSB sites, thereby inhibiting RPA2 and RAD51 recruitment. Importantly, combining olaparib with NU7441, a DNA-PKcs inhibitor that blocks NHEJ in HCC, synergistically suppressed HCC growth in both mice and HCC patient-derived-xenograft models. Our results suggest the combined inhibition of both HR and NHEJ as a potential therapy for HCC.

Topics: Animals; Carcinoma, Hepatocellular; Chromones; DNA Breaks, Double-Stranded; DNA Damage; DNA End-Joining Repair; DNA Repair; DNA-Binding Proteins; Drug Therapy, Combination; Gene Knock-In Techniques; Homologous Recombination; Humans; Liver Neoplasms; Mice; Mice, Nude; Morpholines; Phthalazines; Piperazines; Poly (ADP-Ribose) Polymerase-1; Recombinational DNA Repair; Xenograft Model Antitumor Assays

Radiation therapy, one of the major treatments for liver cancer, causes DNA damage and cell death. Since the liver cancer cells have a strong capacity to repair irradiative injury, new medicines to enhance this treatment are urgently required. In this study, we investigated the effect of NU7441, a synthetic small-molecule compound, as a specific inhibitor of DNA-dependent protein kinase (DNA-PK) in radiosensitization of hepatocellular carcinoma HepG2 cells.. Cell Counting Kit-8 (CCK-8) was first used to evaluate the proliferation of HepG2 cells under NU7441 treatment. SDS-PAGE and Western blot were then performed to study the protein expression leading to the DNA damage repair. Further, neutral single cell gel electrophoresis and immunofluorescence assay were carried out to assess DNA repair. Finally, flow cytometry was implemented to examine the changes in cell cycle.. NU7441 reduced the CCK-8 counts in the HepG2 culture, further enhanced 60Cox03B3; radiation injury to HepG2 cells, which was manifested by decreasing the DNA-PKcs (S2056) protein expression, increasing x03B3;H2AX foci number, prolonging the tail moment of the comet cells, and inducing cell cycle arrest at G2/M phase.. NU7441 inhibited the growth of liver cancer cells, enhanced the radiosensitization of these cancer cells by interfering with the DNA repair and cell cycle checkpoint. These data implicate NU7441 as a potential radiotherapy sensitizer for the treatment of liver cancer.

Topics: Blotting, Western; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Survival; Chromones; Cobalt Radioisotopes; DNA Damage; DNA Repair; DNA-Activated Protein Kinase; Flow Cytometry; G2 Phase Cell Cycle Checkpoints; Hep G2 Cells; Histones; Humans; Liver Neoplasms; M Phase Cell Cycle Checkpoints; Microscopy, Fluorescence; Morpholines; Radiation Tolerance; Radiation, Ionizing