Deregulated WNT signaling during osteoblastogenesis contributes to osteosarcoma pathogenesis Free

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BACKGROUND: Osteosarcoma (OS) is the most common primary malignant bone tumor with most lesions arising in the second decade of life. Although OS has a high mortality rate, the only useful predictor of outcome is histological response following chemotherapy. Little is known about OS etiology and pathogenesis. Canonical WNT signaling plays a critical role in normal skeletogenesis, and we hypothesize that de-regulated WNT signaling during osteoblastogenesis contributes to OS pathogenesis. METHODS: We applied Affymetrix oligonucleotide microarrays to identify differentially-expressed prognosis associated genes in 70 primary OS. We employed our own customized software, Genetrix^TM, to assemble meaningful and relevant gene-expression subsets in context with clinical covariate data. In addition, OS cell lines were also compared against mesenchymal stem cells (MSC) and osteoblasts. We profiled WNT signaling genes during osteoblastogenesis using Q-RT-PCR, and we are knocking down and inducing target genes using siRNA and conditioned media, respectively. RESULTS: In primary tumors, we identified WNT5A (U95A arrays) and PPP3CA (U133A arrays) to be associated with a more favorable OS prognosis. OS cell lines exhibit low WNT5A expression levels compared to both MSC and osteoblasts, and WNT5A expression is dramatically induced upon osteoblast differentiation. Moreover, OS cell lines exhibit both high LRP6 expression levels and TCF-luciferase reporter activity. We are currently studying the effects of LRP6 siRNA and Wnt5a conditioned media on OS cell growth, survival, motility, and substrate-independent growth. CONCLUSIONS: Our results support a role for deregulated WNT signaling in OS pathogenesis and biologic behavior.