title: Telomerase-dependent virotherapy overcomes resistance of hepatocellular carcinomas against chemotherapy and tumor necrosis factor-related apoptosis-inducing ligand by elimination of Mcl-1.
abstract: Hepatocellular carcinomas (HCC) are drug-resistant tumors that frequently possess high telomerase activity. It was therefore the aim of our study to investigate the potential of telomerase-dependent virotherapy in multimodal treatment of HCC. In contrast to normal liver, HCC xenografts showed high telomerase activity, resulting in tumor-restricted expression of E1A by a telomerase-dependent replicating adenovirus (hTERT-Ad). Neither tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or chemotherapy alone nor the combined treatment with both agents resulted in significant destruction of HCC cells. Application of hTERT-Ad at low titers was also not capable to destroy HCC cells, but telomerase-dependent virotherapy overcame the resistance of HCC against TRAIL and chemotherapy. The synergistic effects are explained by a strong down-regulation of Mcl-1 expression through hTERT-Ad that sensitizes HCC for TRAIL- and chemotherapy-mediated apoptosis. To investigate whether down-regulation of Mcl-1 alone is sufficient to explain synergistic effects observed with virotherapy, Mcl-1 expression was inhibited by RNA interference. Treatment with Mcl-1-siRNA significantly enhanced caspase-3 activity after chemotherapy and TRAIL application, confirming that elimination of Mcl-1 is responsible for the drug sensitization by hTERT-Ad. Consistent with these results, heterologous overexpression of Mcl-1 significantly reduced the sensitization of hTERT-Ad transduced cells against apoptosis-inducing agents. Chemotherapy did not interfere with quantitative hTERT-Ad production in HCC cells. Whereas hTERT-Ad virotherapy alone was only capable to inhibit the growth of Hep3B xenografts, virochemotherapy resulted in vast destruction of the drug-resistant HCC. In conclusion our data indicate that telomerase-dependent virotherapy is an attractive strategy to overcome the natural resistance of HCC against anticancer drugs by elimination of Mcl-1.
authors.affiliation: Department of Gastroenterology, Hepatology and Endocrinology, Medical School Hannover, Hannover, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wirth
authors.forename: Florian
authors.initials: F
authors.lastname: Kühnel
authors.forename: Bettina
authors.initials: B
authors.lastname: Fleischmann-Mundt
authors.forename: Norman
authors.initials: N
authors.lastname: Woller
authors.forename: Meta
authors.initials: M
authors.lastname: Djojosubroto
authors.forename: Karl Lenhard
authors.initials: KL
authors.lastname: Rudolph
authors.forename: Michael
authors.initials: M
authors.lastname: Manns
authors.forename: Lars
authors.initials: L
authors.lastname: Zender
authors.forename: Stefan
authors.initials: S
authors.lastname: Kubicka
mesh_terms: D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D017500:Adenovirus E1A Proteins / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000235:genetics / Q000628:therapy* / Q000821:virology; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000628:therapy* / Q000821:virology; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics; D053221:TNF-Related Apoptosis-Inducing Ligand; D019098:Telomerase / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D017500:Adenovirus E1A Proteins; D051017:Apoptosis Regulatory Proteins; C579094:Mcl1 protein, mouse; D008562:Membrane Glycoproteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; C505654:Tnfsf10 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D019098:Telomerase