[1565] Activation of Canonical Wnt Signalling Inhibits Proliferation or Promotes Differentiaiton in High-Grade Osteosarcoma

YP Cai, AB Mohseny, M Karperien, GY Zhou, PCW Hogendoorn, AM Cleton-Jansen. Leiden University Medical Center, Leiden, Netherlands; School of Medicine, Jinan, Shandong, China; University Twente, Enschede, Netherlands

Background: Osteosarcoma (OS) is the most frequent primary malignant bone tumor. High-grade central OS frequently affects children and young adolescence. The prognosis has changed dramatically after the introduction of neoadjuvant chemotherapy, but the overall survival has reached a plateau. Frequent locations of OS at metaphysis of long bones as well as the age of the patients during the most rapid bone growth suggest that the pathogenesis of OS is closely related to high bone turnover. Recent research has demonstrated that canonical wnt pathway is required for osteogenic linage differentiation. Active wnt signalling contributes to carcinogenesis, however, little is known about the possible involvement of bone differentiation pathway in OS.
Design: A canonical wnt signalling luciferase reporter construct was transfected in 4 OS cell lines. -catenin expression was determined in 4 OS cell lines and a tissue array consist of 144 OS samples from 88 patients .The effect of wnt signalling modulation on cell proliferation as well as osteogenic differentiation capability was assessed.
Results: Canonical wnt signalling is not active in 4 OS cell lines as determined by the luciferase reporter assay. Negative nuclear -catenin staining was found in all 4 OS cell lines and 87% of cases in our OS tissue array. Upregulation of wnt signalling was determined upon treatment with GIN(GSK3 inhibitor) by reporter assay as well as -catenin translocation to the nuclear in 4 OS cell lines by immunofluorescence staining. Around 50% inhibition of cell growth was observed in MG-63 and U-2-OS with high level of GIN-mediated activation of wnt signalling. However, little inhibition was found in SJSA and HOS cell lines, which had low level of wnt restoration. SJSA and HOS but not MG-63 and U-2-OS cell lines retain capablity toward osteogenic differentiation. Stimulation of wnt signalling enhances ALP (alkaline phosphatase) activity and mineralization in SJSA and HOS but not MG-63 and U-2-OS.
Conclusions: Wnt signalling is shown to be inactive in osteosarcoma. Activation of wnt sigalling has been known for involvement in carcinomagenesis, however, here we show that restoration of wnt sigalling inhibits cell proliferation or promotes osteogenic linage differentiation in osteosarcoma cell lines.
Category: Pediatrics

Monday, March 9, 2009 1:00 PM

Poster Session II # 211, Monday Afternoon