arenobufagin and Liver-Neoplasms

Chansu, dried secretions from Bufonidae, has long been used for cancer treatment as a traditional Chinese medicine. In searching for effective anti-hepatoma agents from Chansu, our preliminary drug screening found that a bufadienolide, namely 1β-hydroxyl-arenobufagin (1β-OH-ABF), displays anti-hepatoma activities. However, the anti-hepatoma effects and molecular mechanisms of 1β-OH-ABF have not been defined.. To evaluate the anti-hepatoma activity of 1β-OH-ABF against liver cancer Hep3B and HepG2 cells in vitro and in vivo, as well as explore the underlying mechanisms.. The anti-proliferative effects of 1β-OH-ABF on liver cancer Hep3B, HepG2, HuH7, SK-HEP-1 and normal hepatocyte LO2 cells were examined by MTT assay and colony formation assay. Hoechst 33258 staining and Annexin V-FITC/PI staining assay were used to analyze apoptosis induced by 1β-OH-ABF. The collapse of the mitochondrial membrane potential (ΔΨm) was detected by JC-1 staining assay. Western blotting was used to examine the expression levels of targeted proteins. The role of mTOR in 1β-OH-ABF-induced apoptosis was investigated using small interfering RNA (siRNA) transfection. Zebrafish xenograft model was established to evaluate the anti-hepatoma effects of 1β-OH-ABF in vivo.. We found that 1β-OH-ABF inhibits the proliferation of Hep3B, HepG2, HuH7, SK-HEP-1 cells but has little cytotoxicity towards LO2 cells. 1β-OH-ABF induces mitochondria dysfunction and triggers mitochondria apoptotic pathway, which is accompanied by the loss of ΔΨm, upregulation and translocation of Bax, as well as cleavages of caspase-9, caspase-3 and PARP. Mechanistically, 1β-OH-ABF markedly decreases the expression level of p-AKT/AKT and p-mTOR (Ser2248 and Ser2481)/mTOR in a time-dependent manner. Inhibition of mTOR by siRNA strengthens 1β-OH-ABF-mediated apoptosis. Critically, 1β-OH-ABF shows a marked in vivo anti-hepatoma effect on human Hep3B cell xenografts in zebrafish model.. 1β-OH-ABF induces mitochondrial apoptosis through the suppression of mTOR signaling in vitro and in vivo, indicating that 1β-OH-ABF may serve as a potential agent for the treatment of liver cancer.

Topics: Animals; Antineoplastic Agents; Apoptosis; Bufanolides; Carcinoma, Hepatocellular; Hep G2 Cells; Hepatocytes; Humans; Liver Neoplasms; Mitochondria; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays; Zebrafish

Arenobufagin (ArBu) is an important anti-tumor ingredient of Chan'su which has long been used as traditional Chinese medicine in clinic for tumor therapy in China.. The purpose of our study is to investigate the lipid homeostasis regulation effects of ArBu on zebrafish model of liver cancer and hepatoma cells, and to provide a reference for further clarifying its active mechanisms.. The zebrafish xenograft model was established by injecting HepG2 cells stained with CM-Dil red fluorescent dye. Both the xenograft model and HepG2 cells were used to evaluate the anti-hepatoma activity of ArBu. High performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was the main method to study lipidomics, proteomics and the semiquantification of endogenous metabolites. Bioinformatics was used as an assistant tool to further explore the antitumor mechanism of ArBu.. The lipidomics analysis revealed that ArBu caused differential lipids changes in a dose-dependent manner, including PCs, PEs, TGs, SMs, DGs, Cer and PA. PCs, PEs, SMs and TGs were markedly altered in both two models. The influence of glycerophospholipid metabolism was the major and commonly affected pathway. Notably, DGs and Cer were significantly changed only in HepG2 cells. Furthermore, the proteomics research in HepG2 cells fished the target proteins related to lipid homeostasis abnormalities and tumor suppression. ArBu reduced the expression of 65 differential proteins associated with the lipid metabolism, apoptosis and autophagy, such as LCLAT1, STAT3, TSPO and RPS27. Meanwhile, 7 amino acids of 29 determined metabolites were significantly changed, including tyrosine, glutamate, glutamine, leucine, threonine, arginine and isoleucine.. ArBu has a significant anti-hepatoma effect in vitro and a therapeutic effect on zebrafish xenograft model. It regulated the lipid homeostasis. Activated SM synthase and arginine deiminase, inhibited sphingomyelinase, amino acid supply and JAK-STAT3 signaling pathway, and the affected glycerophospholipid metabolism might explain these results.

Topics: Animals; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Autophagy; Autophagy-Related Proteins; Bufanolides; Carcinoma, Hepatocellular; Gene Expression Regulation, Neoplastic; Hep G2 Cells; Humans; Lipid Metabolism; Lipidomics; Liver Neoplasms; Protein Interaction Maps; Proteomics; Signal Transduction; Xenograft Model Antitumor Assays; Zebrafish

Arenobufagin, a representative bufadienolide, is the major active component in the traditional Chinese medicine Chan'su. It possesses significant antineoplastic activity in vitro. Although bufadienolide has been found to disrupt the cell cycle, the underlying mechanisms of this disruption are not defined. Here, we reported that arenobufagin blocked the transition from G2 to M phase of cell cycle through inhibiting the activation of CDK1-Cyclin B1 complex; The tumor suppressor p53 contributed to sustaining arrest at the G2 phase of the cell cycle in hepatocellular carcinoma (HCC) cells. Moreover, arenobufagin caused double-strand DNA breaks (DSBs) and triggered the DNA damage response (DDR), partly via the ATM/ATR-Chk1/Chk2-Cdc25C signaling pathway. Importantly, we used a synthetic biotinylated arenobufagin-conjugated chemical probe in live cells to show that arenobufagin accumulated mainly in the nucleus. The microscopic thermodynamic parameters measured using isothermal titration calorimetry (ITC) also demonstrated that arenobufagin directly bound to DNA in vitro. The hypochromicity in the UV-visible absorption spectrum, the significant changes in the circular dichroism (CD) spectrum of DNA, and the distinct quenching in the fluorescence intensity of the ethidium bromide (EB)-DNA system before and after arenobufagin treatment indicated that arenobufagin bound to DNA in vitro by intercalation. Molecular modeling suggested arenobufagin intercalated with DNA via hydrogen bonds between arenobufagin and GT base pairs. Collectively, these data provide novel insights into arenobufagin-induced cell cycle disruption that are valuable for the further discussion and investigation of the use of arenobufagin in clinical anticancer chemotherapy.

Topics: Antineoplastic Agents; Apoptosis; Ataxia Telangiectasia Mutated Proteins; Blotting, Western; Bufanolides; Calorimetry; Carcinoma, Hepatocellular; Cell Line, Tumor; Circular Dichroism; Comet Assay; G2 Phase Cell Cycle Checkpoints; Humans; Immunoprecipitation; Intercalating Agents; Liver Neoplasms; Models, Molecular; RNA, Small Interfering; Signal Transduction; Transfection

Hepatocellular carcinoma (HCC) is a deadly form of cancer without effective chemotherapy so far. Currently, only sorafenib, a multitargeted tyrosine kinase inhibitor, slightly improves survival in HCC patients. In searching for natural anti-HCC components from toad venom, which is frequently used in the treatment of liver cancer in traditional Chinese medicine, we discovered that arenobufagin, a bufadienolide from toad venom, had potent antineoplastic activity against HCC HepG2 cells as well as corresponding multidrug-resistant HepG2/ADM cells. We found that arenobufagin induced mitochondria-mediated apoptosis in HCC cells, with decreasing mitochondrial potential, as well as increasing Bax/Bcl-2 expression ratio, Bax translocation from cytosol to mitochondria. Arenobufagin also induced autophagy in HepG2/ADM cells. Autophagy-specific inhibitors (3-methyladenine, chloroquine and bafilomycin A1) or Beclin1 and Atg 5 small interfering RNAs (siRNAs) enhanced arenobufagin-induced apoptosis, indicating that arenobufagin-mediated autophagy may protect HepG2/ADM cells from undergoing apoptotic cell death. In addition, we observed the inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway by arenobufagin. Interestingly, inhibition of mTOR by rapamycin or siRNA duplexes augmented arenobufagin-induced apoptosis and autophagy. Finally, arenobufagin inhibited the growth of HepG2/ADM xenograft tumors, which were associated with poly (ADP-ribose) polymerase cleavage, light chain 3-II activation and mTOR inhibition. In summary, we first demonstrated the antineoplastic effect of arenobufagin on HCC cells both in vitro and in vivo. We elucidated the underlying antineoplastic mechanisms of arenobufagin that involve cross talk between apoptosis and autophagy via inhibition of the PI3K/Akt/mTOR pathway. This study may provide a rationale for future clinical application using arenobufagin as a chemotherapeutic agent for HCC.

Topics: Amphibian Venoms; Animals; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Autophagy-Related Protein 5; bcl-2-Associated X Protein; Beclin-1; Bufanolides; Carcinoma, Hepatocellular; Cell Line, Tumor; Hep G2 Cells; Humans; Liver Neoplasms; Male; Medicine, Chinese Traditional; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Nude; Microtubule-Associated Proteins; Neoplasm Transplantation; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; RNA Interference; RNA, Small Interfering; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays