The role of bone morphogenetic protein 2 in ovarian cancer migration

The transforming growth factor-β (TGF-β) superfamily member bone morphogenetic protein 2 (BMP2) is over-expressed in epithelial ovarian cancer cells, and correlates with decreased survival time in advanced stage ovarian cancer patients. BMP2 has been shown to stimulate cell motility in ovarian cancer cell lines, however little is known about the molecular mechanisms underlying these pro-migratory effects. The aim of my study was to test the hypothesis that BMP2-induced ovarian cancer cell migration is mediated by the differential expression of cadherin cell adhesion molecules via activation of SMAD-dependent signaling. Treatment of SKOV3 clear cell or endometrioid human ovarian cancer cells with BMP2 increased cell migration and N-cadherin mRNA and protein levels, while decreasing E-cadherin mRNA and protein levels. Importantly, small interfering RNA (siRNA)-mediated knockdown of N-cadherin inhibited BMP2-induced cell migration. BMP2 treatment induced both canonical SMAD1/5/8 phosphorylation and non-canonical SMAD2/3 phosphorylation, mediated by the BMP type I receptor ALK3, but not ALK2 or ALK6. Co-treatment with the BMP type I receptor inhibitors Dorsomorphin or DMH-1, but not the TGF-β type I receptor inhibitor SB-431542, reversed the effects of BMP2 on SMAD2/3 phosphorylation, N-cadherin (not blocked by SB-431542), and cell migration, but not E-cadherin. Moreover, BMP2-induced cell migration was reduced by siRNA-mediated knockdown of either SMAD2 or SMAD3. This study provides evidence of the possible dominant and critical role of N-cadherin over E-cadherin in promoting cancer cell migration. Conversely, treatment of OVCAR8 high-grade serous human ovarian cancer cells with BMP2 did not increase cell migration and instead suppressed N-cadherin protein levels. BMP2 treatment in OVCAR8 also induced canonical SMAD1/5/8 phosphorylation, but not non-canonical SMAD2/3 phosphorylation. Likewise, treatment of OVCAR5 high-grade serous human ovarian cancer cells with BMP2 yielded a marginal increase in cell migration while N-cadherin remains undetectable. BMP2 treatment in OVCAR5 also induced canonical SMAD1/5/8 phosphorylation and maybe non-canonical SMAD3 but not SMAD2 phosphorylation. This study provides important insights into the molecular mechanisms underlying BMP2-induced human ovarian cancer cell migration. I report here that BMP2 induces SKOV3 ovarian cancer cell migration by up-regulating N-cadherin expression in a SMAD2/3-dependent manner, and that variability in the BMP2 response may be subtype-dependent.Medicine, Faculty ofObstetrics and Gynaecology, Department ofGraduat