Juan A. Bernal, Nao Suzuki, Marta Roche-Molina, Ana J. Narvaez, Hiroyoshi Hattori, Naoki Okamoto, Anand D. Jeyasekharan, Tomohiko Ohta, Ko Sato, Yuko Nakagawa, Anna S. Sedukhina, Satoi Nagasawa, and St. Marianna University
// Yuko Nakagawa 1, 2, * , Anna S. Sedukhina 1, * , Naoki Okamoto 2 , Satoi Nagasawa 1, 3 , Nao Suzuki 2 , Tomohiko Ohta 1 , Hiroyoshi Hattori 4 , Marta Roche-Molina 5 , Ana J. Narvaez 6 , Anand D. Jeyasekharan 7 , Juan A. Bernal 5 , Ko Sato 1 1 Department of Translational Oncology, St. Marianna University Graduate School of Medicine, Kawasaki 216–8511, Japan 2 Department of Obstetrics and Gynecology, St. Marianna University Graduate School of Medicine, Kawasaki 216–8511, Japan 3 Division of Breast and Endocrine Surgery, Department of Surgery, St. Marianna University Graduate School of Medicine, Kawasaki 216–8511, Japan 4 Laboratory of Advanced Therapy, Department of Hematology and Oncology Research, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya 460–0001, Japan 5 Department of Cardiovascular Development and Repair, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid 28029, Spain 6 MRC Cancer Unit at the University of Cambridge, Hutchison Research Centre, CB2 0XZ, UK 7 Cancer Science Institute of Singapore, National University of Singapore, Centre for Translational Medicine, 117599, Singapore * These authors have contributed equally to this work Correspondence to: Ko Sato, e-mail: kosato@marianna-u.ac.jp Received: August 12, 2014 Accepted: December 07, 2014 Published: January 12, 2015 ABSTRACT PARP inhibitors are a class of promising anti-cancer drugs, with proven activity in BRCA mutant cancers. However, as with other targeted agents, treatment with PARP inhibitors generates acquired resistance within these tumors. The mechanism of this acquired resistance is poorly understood. We established cell lines that are resistant to PARP inhibitor by continuous treatment with the drug, and then used RNA sequencing to compare gene expression. Pathway analysis on the RNA sequencing data indicates that NF-κB signaling is preferentially up-regulated in PARP inhibitor-resistant cells, and that knockdown of core components in NF-κB signaling reverses the sensitivity to PARP inhibitor in resistant cells. Of therapeutic relevance, we show that PARP inhibitor-resistant cells are sensitive to an NF-κB inhibitor in comparison to their parental controls. Malignancies with up-regulation of NF-κB are sensitive to bortezomib, a proteasome inhibitor that is currently used in the clinic. We also show that treatment with bortezomib results in cell death in the PARP inhibitor-resistant cells, but not in parental cells. Therefore we propose that up-regulation of NF-κB signaling is a key mechanism underlying acquired resistance to PARP inhibition, and that NF-κB inhibition, or bortezomib are potentially effective anti-cancer agents after the acquisition of resistance to PARP inhibitors.