title: Secreted Frizzled-Related Protein 3 (SFRP3) Is Required for Tumorigenesis of PAX3-FOXO1-Positive Alveolar Rhabdomyosarcoma.
abstract: OBJECTIVE
  Rhabdomyosarcoma (RMS) is a soft tissue sarcoma associated with the skeletal muscle lineage. Of the two predominant subtypes, known as embryonal (eRMS) and alveolar (aRMS), aRMS has the poorer prognosis, with a five-year survival rate of <50%. The majority of aRMS tumors express the fusion protein PAX3-FOXO1. As PAX3-FOXO1 has proven chemically intractable, this study aims to identify targetable proteins that are downstream from or cooperate with PAX3-FOXO1 to support tumorigenesis.
  
  
  METHODS
  Microarray analysis of the transcriptomes of human skeletal muscle myoblasts expressing PAX3-FOXO1 revealed alteration of several Wnt pathway gene members, including secreted frizzled related protein 3 (SFRP3), a secreted Wnt pathway inhibitor. Loss-of-function using shRNAs against SFRP3 was used to interrogate the role of SFRP3 in human aRMS cell lines in vitro and conditional murine xenograft systems in vivo. The combination of SFRP3 genetic suppression and the chemotherapeutic agent vincristine was also examined.
  
  
  RESULTS
  In vitro, suppression of SFRP3 inhibited aRMS cell growth, reduced proliferation accompanied by a G1 arrest and induction of p21, and induced apoptosis. In vivo, doxycycline-inducible suppression of SFRP3 reduced aRMS tumor growth and weight by more than three-fold, in addition to increasing myogenic differentiation and β-catenin signaling. The combination of SFRP3 suppression and vincristine was more effective at reducing aRMS cell growth in vitro than either treatment alone, and ablated tumorigenesis in vivo.
  
  
  CONCLUSIONS
  SFRP3 is necessary for the growth of human aRMS cells both in vitro and in vivo and is a promising new target for investigation in aRMS.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Julie J G
authors.initials: JJ
authors.lastname: Kephart
authors.affiliation: School of Medicine, Duke University Medical Center, Durham, North Carolina.
authors.forename: Rosanne G J
authors.initials: RG
authors.lastname: Tiller
authors.affiliation: Department of Pediatrics, Duke University Medical Center, Durham, North Carolina.
authors.forename: Lisa E S
authors.initials: LE
authors.lastname: Crose
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Katherine K
authors.initials: KK
authors.lastname: Slemmons
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Po-Han
authors.initials: PH
authors.lastname: Chen
authors.affiliation: Department of Pediatrics, Duke University Medical Center, Durham, North Carolina.
authors.forename: Ashley R
authors.initials: AR
authors.lastname: Hinson
authors.affiliation: School of Medicine, Duke University Medical Center, Durham, North Carolina. Department of Pathology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Rex C
authors.initials: RC
authors.lastname: Bentley
authors.affiliation: School of Medicine, Duke University Medical Center, Durham, North Carolina. Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Jen-Tsan Ashley
authors.initials: JT
authors.lastname: Chi
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina. School of Medicine, Duke University Medical Center, Durham, North Carolina. Department of Pediatrics, Duke University Medical Center, Durham, North Carolina. corinne.linardic@dm.duke.edu.
authors.forename: Corinne M
authors.initials: CM
authors.lastname: Linardic
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D016000:Cluster Analysis; D004195:Disease Models, Animal; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000235:genetics*; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D032446:Myoblasts / Q000187:drug effects / Q000378:metabolism; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D018232:Rhabdomyosarcoma, Alveolar / Q000188:drug therapy / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D047368:Tumor Burden / Q000187:drug effects; D014750:Vincristine / Q000494:pharmacology; D051153:Wnt Proteins / Q000037:antagonists & inhibitors; D060449:Wnt Signaling Pathway / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D000099274:Frizzled-Related Proteins
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D034741:RNA, Small Interfering; D014750:Vincristine; D051153:Wnt Proteins; D000099274:Frizzled-Related Proteins; C085126:FOXO1 protein, human; C489409:PAX3 protein, human