title: Hedgehog signaling inhibition by the small molecule smoothened inhibitor GDC-0449 in the bone forming prostate cancer xenograft MDA PCa 118b.
abstract: BACKGROUND
  Hedgehog signaling is a stromal-mesenchymal pathway central to the development and homeostasis of both the prostate and the bone. Aberrant Hedgehog signaling activation has been associated with prostate cancer aggressiveness. We hypothesize that Hedgehog pathway is a candidate therapeutic target in advanced prostate cancer. We confirm increased Hedgehog signaling in advanced and bone metastatic castrate resistant prostate cancer and examine the pharmacodynamic effect of Smoothened inhibition by the novel reagent GDC-0449 in an experimental prostate cancer model.
  
  
  METHODS
  Hedgehog signaling component expression was assessed in tissue microarrays of high grade locally advanced and bone metastatic disease. Male SCID mice subcutaneously injected with the bone forming xenograft MDA PCa 118b were treated with GDC-0449. Hedgehog signaling in the tumor microenvironment was assessed by proteomic and species specific RNA expression and compared between GDC-0449 treated and untreated animals.
  
  
  RESULTS
  We observe Hedgehog signaling in high grade locally advanced and bone marrow infiltrating disease. Evidence of paracrine activation of Hedgehog signaling in the tumor xenograft, was provided by increased Sonic Hedgehog expression in human tumor epithelial cells, coupled with increased Gli1 and Patched1 expression in the murine stromal compartment, while normal murine stroma did not exhibit Hh signaling expression. GDC-0449 treatment attenuated Hh signaling as evidenced by reduced expression of Gli1 and Ptch1. Reduction in proliferation (Ki67) was observed with no change in tumor volume.
  
  
  CONCLUSIONS
  GDC-0449 treatment is pharmacodynamically effective as evidenced by paracrine Hedgehog signaling inhibition and results in tumor cell proliferation reduction. Understanding these observations will inform the clinical development of therapy based on Hedgehog signaling inhibition.
authors.affiliation: Department of Genitourinary Medical Oncology, The David Koch Center for Applied Research of Genitourinary Cancers, The Stanford Alexander Tissue Derivatives Laboratory, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030-4009, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Karlou
authors.forename: Jing-Fang
authors.initials: JF
authors.lastname: Lu
authors.forename: Guanglin
authors.initials: G
authors.lastname: Wu
authors.forename: Sankar
authors.initials: S
authors.lastname: Maity
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Tzelepi
authors.forename: Nora M
authors.initials: NM
authors.lastname: Navone
authors.forename: Anh
authors.initials: A
authors.lastname: Hoang
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Logothetis
authors.forename: Eleni
authors.initials: E
authors.lastname: Efstathiou
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000813:Anilides / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D053823:Hedgehog Proteins / Q000037:antagonists & inhibitors*; D006801:Humans; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D009999:Ossification, Heterotopic / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D010012:Osteogenesis / Q000187:drug effects*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011725:Pyridines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D046888:Tissue Array Analysis; D014183:Transplantation, Heterologous; D023041:Xenograft Model Antitumor Assays
chemical_list: D000813:Anilides; D000970:Antineoplastic Agents; D053823:Hedgehog Proteins; C538724:HhAntag691; D011725:Pyridines