Secreted Wnt Inhibitors in the Biology of Osteosarcoma

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DESCRIPTION (provided by applicant): Applicant: Dr. Hoang, the candidate, is currently a tenure-track Assistant Professor at the University of California, Irvine. As evident from his biography, the candidate has demonstrated a steadfast commitment to a career in academic medicine. To this end, he would like to continue his research training in a mentored environment with the goal of becoming an independent investigator in musculoskeletal oncology. Environment: The candidate is jointly mentored by several nationally and internationally recognized experts in Wnt signaling in human cancer and the genetics of osteosarcoma. The University of California, Irvine is a collegial environment with a tradition of nurturing career development of young clinician scientists. Research: Osteosarcoma (OS) remains a pediatric bone cancer with substantial mortality due to a high metastatic rate. Although Wnt signaling is activated in several human malignancies, its role in the pathobiology of OS progression is largely unknown. Our preliminary work suggested that secreted Wnt inhibitors modulate the following pro-invasive pathways in OS: (1) Transcriptional repressors Slug and Twist, (2) MMP-2 and 9, and (3) the hepatocyte growth factor receptor Met. Blocking receptor-mediated Wnt signaling by a dominant negative receptor or by the secreted inhibitor Dkk-3 dramatically decreases the invasive potential and motility of OS cells. These findings lead us to propose the following specific aims: 1) To examine whether secreted Wnt inhibitors can decrease invasive capacity of OS cells by suppressing E-cadherin transcriptional repressors; 2) To test the hypothesis that secreted Wnt inhibitors decrease OS invasiveness by suppressing MMP-2 and 9 or by regulating Met-dependent activity; 3) To determine whether overexpression of Wnt inhibitors will reduce lung metastasis in vivo in a tail-vein injection nude mouse model. These studies will bridge a gap in our knowledge on the role of secreted Wnt inhibitors in the biology of OS. Lessons learned from this investigation may be applicable to a wider range of human sarcomas and serves as a basis for future studies by the applicant as an independent investigator in musculoskeletal oncology.