Strong antitumor synergy between DNA crosslinking and HSP90 inhibition causes massive premitotic DNA fragmentation in ovarian cancer cells.
All current regimens for treating ovarian cancer center around carboplatin as standard first line. The HSP90 inhibitor ganetespib is currently being assessed in advanced clinical oncology trials. Thus, we tested the combined effects of ganetespib and carboplatin on a panel of 15 human ovarian cancer lines. Strikingly, the two drugs strongly synergized in cytotoxicity in tumor cells lacking wild-type p53. Mechanistically, ganetespib and carboplatin in combination, but not individually, induced persistent DNA damage causing massive global chromosome fragmentation. Live-cell microscopy revealed chromosome fragmentation occurring to a dramatic degree when cells condensed their chromatin in preparation for mitosis, followed by cell death in mitosis or upon aberrant exit from mitosis. HSP90 inhibition caused the rapid decay of key components of the Fanconi anemia pathway required for repair of carboplatin-induced interstrand crosslinks (ICLs), as well as of cell cycle checkpoint mediators. Overexpressing FancA rescued the DNA damage induced by the drug combination, indicating that FancA is indeed a key client of Hsp90 that enables cancer cell survival in the presence of ICLs. Conversely, depletion of nuclease DNA2 prevented chromosomal fragmentation, pointing to an imbalance of defective repair in the face of uncontrolled nuclease activity as mechanistic basis for the observed premitotic DNA fragmentation. Importantly, the drug combination induced robust antitumor activity in xenograft models, again accompanied with depletion of FancA. In sum, our findings indicate that ganetespib strongly potentiates the antitumor efficacy of carboplatin by causing combined inhibition of DNA repair and cell cycle control mechanisms, thus triggering global chromosome disruption, aberrant mitosis and cell death.
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.
Daniela
D
Kramer
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.
Nadine
N
Stark
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.
Ramona
R
Schulz-Heddergott
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.
Norman
N
Erytch
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.
Shelley
S
Edmunds
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.
Laura
L
Roßmann
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.
Holger
H
Bastians
Department of Obstetrics and Gynaecology, Medical University of Innsbruck, Innsbruck, Austria.
Nicole
N
Concin
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.|Department of Pathology, School of Medicine, Stony Brook University, Stony Brook, NY 11794, USA.
Ute M
UM
Moll
Institute of Molecular Oncology, Göttingen Center of Molecular Biosciences (GZMB), University Medical Center Göttingen, Göttingen D-37077, Germany.
Matthias
M
Dobbelstein
D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D016190:Carboplatin / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000187:drug effects*; D053938:DNA Fragmentation / Q000187:drug effects*; D004265:DNA Helicases / Q000378:metabolism; D004359:Drug Therapy, Combination; D052217:Fanconi Anemia Complementation Group A Protein / Q000235:genetics / Q000378:metabolism; D005260:Female; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D008938:Mitosis / Q000187:drug effects; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D014183:Transplantation, Heterologous; D014230:Triazoles / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D000076183:Tripartite Motif-Containing Protein 28 / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
D000970:Antineoplastic Agents; C498471:FANCA protein, human; D052217:Fanconi Anemia Complementation Group A Protein; D018841:HSP90 Heat-Shock Proteins; C533237:STA 9090; D014230:Triazoles; D016159:Tumor Suppressor Protein p53; D016190:Carboplatin; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28; D004265:DNA Helicases; C509908:DNA2 protein, human