A new model of multi-visceral and bone metastatic prostate cancer with perivascular niche targeting by a novel endothelial specific adenoviral vector

// Zhi Hong Lu 1, 2 , Sergey Kaliberov 2, 3, 4 , Rebecca E. Sohn 1, 2 , Lyudmila Kaliberova 2, 3, 4 , Yingqiu Du 1, 2 , Julie L. Prior 5 , Daniel J. Leib 6 , Anne Chauchereau 7 , Jennifer K. Sehn 2, 8 , David T. Curiel 2, 3, 4 , Jeffrey M. Arbeit 1, 2 1 Urology Division and Department of Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA 2 Siteman Cancer Center, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA 3 Biologic Therapeutics Center, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA 4 Department of Radiation Oncology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA 5 Radiology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA 6 Department of Orthopedic Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA 7 Prostate Cancer Group, INSERM U981, Gustave Roussy, Villejuif, F-94805, France 8 Department of Anatomic and Molecular Pathology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA Correspondence to: Jeffrey M. Arbeit, email: arbeitj@wudosis.wustl.edu David T. Curiel, email: dcuriel@radonc.wustl.edu Keywords: prostate, metastasis, endothelial, niche, adenovirus Received: August 12, 2016 Accepted: December 26, 2016 Published: January 17, 2017 ABSTRACT While modern therapies for metastatic prostate cancer (PCa) have improved survival they are associated with an increasingly prevalent entity, aggressive variant PCa (AVPCa), lacking androgen receptor (AR) expression, enriched for cancer stem cells (CSCs), and evidencing epithelial-mesenchymal plasticity with a varying extent of neuroendocrine transdifferentiation. Parallel work revealed that endothelial cells (ECs) create a perivascular CSC niche mediated by juxtacrine and membrane tethered signaling. There is increasing interest in pharmacological metastatic niche targeting, however, targeted access has been impossible. Here, we discovered that the Gleason 7 derived, androgen receptor negative, IGR-CaP1 cell line possessed some but not all of the molecular features of AVPCa. Intracardiac injection into NOD/SCID/IL2Rg -/- (NSG) mice produced a completely penetrant bone, liver, adrenal, and brain metastatic phenotype; noninvasively and histologically detectable at 2 weeks, and necessitating sacrifice 4-5 weeks post injection. Bone metastases were osteoblastic, and osteolytic. IGR-CaP1 cells expressed the neuroendocrine marker synaptophysin, near equivalent levels of vimentin and e-cadherin, all of the EMT transcription factors, and activation of NOTCH and WNT pathways. In parallel, we created a new triple-targeted adenoviral vector containing a fiber knob RGD peptide, a hexon mutation, and an EC specific ROBO4 promoter (Ad.RGD.H5/3.ROBO4). This vector was expressed in metastatic microvessels tightly juxtaposed to IGR-CaP1 cells in bone and visceral niches. Thus, the combination of IGR-CaP1 cells and NSG mice produces a completely penetrant metastatic PCa model emulating end-stage human disease. In addition, the metastatic niche access provided by our novel Ad vector could be therapeutically leveraged for future disease control or cure.