Recent studies suggest that overactivation of the Wnt pathway contributes to the pathogenesis of basal-like breast cancer, a subtype of estrogen receptor (ER)-negative breast cancer. This hormone-independent pathway leads to the nuclear localization of β-catenin where it forms a complex with T-cell factors or lymphoid enhancing factors (Tcf/Lef) and activates transcription of genes that drive proliferation. In colon cancer, loss of the tumor suppressor gene adenomatous polyposis coli (APC) also results in nuclear localization of β-catenin. Our collaborators have identified a chemopreventive regimen that selectively induces apoptosis in APC-deficient premalignant colon cells. Initial treatment with retinyl acetate (RAc) in this regimen upregulates tumor necrosis-related apoptosis-inducing ligand (TRAIL) receptors. When this is subsequently followed by treatment with TRAIL ligand, apoptosis is induced specifically in those premalignant cells with deregulated anti-apoptotic machinery. Since loss of APC and constitutive activation of Wnt signaling both result in nuclear localization of β-catenin, we hypothesize that sequential treatment with RAc/TRAIL will induce apoptosis in Wnt-dependent premalignant breast epithelial cells. To test this hypothesis, we are treating MMTV-Wnt1 transgenic mice which spontaneously develop both ER-positive and ER-negative mammary tumors with the RAc/TRAIL chemopreventive regimen. This study will enable us to determine the effectiveness of this novel treatment in the prevention of ER-negative tumors.
Lab members working on this project: