Oncotarget 2949 www.impactjournals.com/oncotarget www.impactjournals.com/oncotarget/ Oncotarget, 2017, Vol. 8, (No. 2), pp: 2949-2959 Refractory testicular germ cell tumors are highly sensitive to the second generation DNA methylation inhibitor guadecitabine Costantine Albany 1 , Mary P. Hever-Jardine 2 , Katherine M. von Herrmann 2 , Christina Y. Yim 2 , Janice Tam 2 , Joshua M. Warzecha 2 , Leah Shin 2 , Sarah E. Bock 2 , Brian S. Curran 2 , Aneeq S. Chaudhry 2 , Fred Kim 2 , George E. Sandusky 5 , Pietro Taverna 3 , Sarah J. Freemantle 4 , Brock C. Christensen 6 , Lawrence H. Einhorn 1 , Michael J. Spinella 4 1 Division of Hematology/Oncology, Melvin and Bren Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA 2 Departments of Pharmacology and Toxicology and Epidemiology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA 3 Astex Pharmaceutical, Pleasanton, CA, USA 4 Department of Comparative Biosciences, The University of Illinois at Urbana-Champaign, Urbana, IL, USA 5 Department of Pathology, Melvin and Bren Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA 6 Department of Epidemiology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA Correspondence to: Michael J. Spinella, email: spinella@illinois.edu Keywords: testicular cancer, embryonal carcinoma, DNA methylation, SGI-110, in vivo Received: October 20, 2016 Accepted: November 23, 2016 Published: December 07, 2016 ABSTRACT Testicular germ cell tumors (TGCTs) are the most common cancers of young males. A substantial portion of TGCT patients are refractory to cisplatin. There are no effective therapies for these patients, many of whom die from progressive disease. Embryonal carcinoma (EC) are the stem cells of TGCTs. In prior in vitro studies we found that EC cells were highly sensitive to the DNA methyltransferase inhibitor, 5-aza deoxycytidine (5-aza). Here, as an initial step in bringing demethylation therapy to the clinic for TGCT patients, we evaluated the effects of the clinically optimized, second generation demethylating agent guadecitabine (SGI-110) on EC cells in an animal model of cisplatin refractory testicular cancer. EC cells were exquisitely sensitive to guadecitabine and the hypersensitivity was dependent on high levels of DNA methyltransferase 3B. Guadecitabine mediated transcriptional reprogramming of EC cells included induction of p53 targets and repression of pluripotency genes. As a single agent, guadecitabine completely abolished progression and induced complete regression of cisplatin resistant EC xenografts even at doses well below those required to impact somatic solid tumors. Low dose guadecitabine also sensitized refractory EC cells to cisplatin in vivo. Genome-wide analysis indicated that in vivo antitumor activity was associated with activation of p53 and immune-related pathways and the antitumor effects of guadecitabine were dependent on p53, a gene rarely mutated in TGCTs. These preclinical fndings suggest that guadecitabine alone or in combination with cisplatin is a promising strategy to treat refractory TGCT patients. INTRODUCTION Testicular germ cell tumors (TGCTs) are the most common cancer in men 15 to 35 with increasing incidence in the last 30 years [1]. Testicular cancer patients are successfully treated with a combination of cisplatin, bleomycin and etoposide [2, 3]. However, 15–20% of all patients and 50% of patients with poor-risk disease are refractory to treatment and many eventually die from progressive disease [4–6]. Further, there are patients who initially respond to therapy but undergo late relapse. These patients are rarely cured if their disease is not amenable to surgical resection [7, 8]. Therapies to treat the cisplatin resistant population is a major un-met clinical need. Unlike most other cancers, morbidity and mortality due to testicular cancer occurs during the most productive years of a patient’s life. An average of more than 35 years of life is lost when a testicular cancer death occurs, well over Research Paper