OBJECTIVE.: Despite advances in chemotherapy and radical surgery, most advanced stage ovarian cancer patients die from their disease, highlighting the need for the development of novel treatment strategies. The Notch signaling pathway plays an important role in cellular differentiation, proliferation and apoptosis. We hypothesized that the active form of Notch 1, the Notch 1 intracellular domain (NICD), would be overexpressed in ovarian cancer cells and that depletion of NICD would lead to growth reduction. METHODS.: Following institutional review board approval, NICD expression was analyzed in human ovarian cancer specimens as well as the ovarian cancer cell lines OVCAR3, SKOV3, and CaOV3. In addition, the effects of Notch 1 depletion on ovarian cancer cell growth were detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) growth assay for 6 days following transfection with siRNA against Notch 1. RESULTS.: Western blot analysis revealed abundant NICD expression in all 3 ovarian cancer cell lines, as well as in 16 of 21 (76%) human ovarian cancer samples. Following treatment with Notch 1 siRNA, expression of NICD was greatly reduced in all three cell lines. Furthermore, this depletion of NICD was associated with significant growth inhibition of all three ovarian cancer cell lines. CONCLUSIONS.: NICD was frequently expressed in ovarian cancer cell lines and human ovarian cancer specimens. Importantly, depletion of Notch 1 led to growth inhibition of ovarian cancer cells. These findings support the hypothesis that Notch 1 plays a role in ovarian cancer proliferation, encouraging the investigation of this pathway as a therapeutic target.
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