R Hamm1, Y-R Chen2, Ean-Jeong Seo1, Maen Zeino1, Ching-Fen Wu1, R Müller3, N-S Yang2, T Efferth4. 1. Institute of Pharmacy and Biochemistry, Department of Pharmaceutical Biology, Johannes Gutenberg University, Staudinger Weg 5, 55128 Mainz, Germany. 2. Agricultural Biotechnology Research Center, Academia Sinica, Taipei, Taiwan. 3. Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Centre for Infection Research and Department of Pharmaceutical Biotechnology, Saarland University, Saarbrücken, Germany. 4. Institute of Pharmacy and Biochemistry, Department of Pharmaceutical Biology, Johannes Gutenberg University, Staudinger Weg 5, 55128 Mainz, Germany. Electronic address: efferth@uni-mainz.de.
Abstract
BACKGROUND: Resistance of cancer cells towards chemotherapeutics represents a major cause of therapy failure. The objective of our study was to evaluate cellular defense strategies in response to the novel vacuolar H(+)-ATPase inhibitor, archazolid B. EXPERIMENTAL APPROACH: The effects of archazolid B on T24 bladder carcinoma cells were investigated by combining "omics" technologies (transcriptomics (mRNA and miRNA) and proteomics). Free cholesterol distribution was determined by filipin staining using flow cytometry and fluorescence microscopy. Flow cytometry was performed for LDLR surface expression studies. Uptake of LDL cholesterol was visualized by confocal microscopy. SREBP activation was determined performing Western Blotting. The efficiency of archazolid B/fluvastatin combination was tested by cytotoxicity assays. RESULTS: Archazolid B led to accumulation of free cholesterol within intracellular compartments and drastic disturbances in cholesterol homeostasis resulting in activation of SREBP-2 (sterol regulatory element-binding protein 2) and up-regulation of target genes including HMGCR (HMG-CoA reductase), the key enzyme of cholesterol biosynthesis. LDLR surface expression was reduced and LDL uptake was completely inhibited after 24h, indicating newly synthesized cholesterol to be the main source of cholesterol in archazolid B treated cells. By combining archazolid B with the HMGCR inhibitor fluvastatin, cholesterol was reduced and cell viability decreased by about 20% compared to archazolid B treatment alone. CONCLUSIONS: Our study revealed cholesterol biosynthesis as an important resistance mechanism in T24 cells after archazolid B treatment. The combination of archazolid B with statins may be an attractive strategy to potentiate archazolid B induced cell killing by affecting cholesterol biosynthesis.
BACKGROUND: Resistance of cancer cells towards chemotherapeutics represents a major cause of therapy failure. The objective of our study was to evaluate cellular defense strategies in response to the novel vacuolar H(+)-ATPase inhibitor, archazolid B. EXPERIMENTAL APPROACH: The effects of archazolid B on T24 bladder carcinoma cells were investigated by combining "omics" technologies (transcriptomics (mRNA and miRNA) and proteomics). Free cholesterol distribution was determined by filipin staining using flow cytometry and fluorescence microscopy. Flow cytometry was performed for LDLR surface expression studies. Uptake of LDL cholesterol was visualized by confocal microscopy. SREBP activation was determined performing Western Blotting. The efficiency of archazolid B/fluvastatin combination was tested by cytotoxicity assays. RESULTS:Archazolid B led to accumulation of free cholesterol within intracellular compartments and drastic disturbances in cholesterol homeostasis resulting in activation of SREBP-2 (sterol regulatory element-binding protein 2) and up-regulation of target genes including HMGCR (HMG-CoA reductase), the key enzyme of cholesterol biosynthesis. LDLR surface expression was reduced and LDL uptake was completely inhibited after 24h, indicating newly synthesized cholesterol to be the main source of cholesterol in archazolid B treated cells. By combining archazolid B with the HMGCR inhibitor fluvastatin, cholesterol was reduced and cell viability decreased by about 20% compared to archazolid B treatment alone. CONCLUSIONS: Our study revealed cholesterol biosynthesis as an important resistance mechanism in T24 cells after archazolid B treatment. The combination of archazolid B with statins may be an attractive strategy to potentiate archazolid B induced cell killing by affecting cholesterol biosynthesis.
Authors: Karin Bartel; Maria Winzi; Melanie Ulrich; Andreas Koeberle; Dirk Menche; Oliver Werz; Rolf Müller; Jochen Guck; Angelika M Vollmar; Karin von Schwarzenberg Journal: Oncotarget Date: 2017-02-07