ABSTRACT
CD133 is widely used as a surface marker to isolate cancer stem cells (CSCs). Here we show that in CSCs CD133 contributes to ß-catenin-mediated transcriptional activation and to the self-renewal capacity of sphere-forming and side-population (SP) cells in cell lines from brain, colon and lung cancers, but not gastric or breast cancers. In chromatin immunoprecipitation assays, ß-catenin binding to the proximal promoter regions of ITGA2-4 and ITGA10-11 in brain, colon and lung cancer cell lines could be triggered by CD133, and ß-catenin also bound to the proximal promoter regions of ITGB6 and ITGB8 in cell lines from gastric and breast cancers. CD133 thus induces ß-catenin binding and transcriptional activation of diverse targets that are cancer type-specific. Cell migration triggered by wounding CD133+ cells cultured on ECM-coated dishes can induce polarity and lipid raft coalescence, enhancing CD133/integrin signaling and asymmetric cell division. In response to directional cues, integrins, Src and the Par complex were enriched in lipid rafts, and the assembly and activation of an integrated CD133-integrin-Par signaling complex was followed by Src/Akt/GSK3ß signaling. The subsequent increase and nuclear translocation of ß-catenin may be a regulatory switch to increase drug resistance and stemness properties. Collectively, these findings 1) indicate that a polarized cell migration-induced CD133/integrin/Src/Akt/GSK3ß/ß-catenin axis is required for maintenance of CSC properties, 2) establish a function for CD133 and 3) support the rationale for targeting CD133 in cancer treatment.
Subject(s)
Antigens, CD/metabolism , Cell Movement , Glycogen Synthase Kinase 3/metabolism , Glycoproteins/metabolism , Integrins/metabolism , Lung Neoplasms/pathology , Neoplastic Stem Cells/pathology , Peptides/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Proto-Oncogene Proteins pp60(c-src)/metabolism , beta Catenin/metabolism , AC133 Antigen , Animals , Apoptosis , Biomarkers, Tumor/metabolism , Blotting, Western , Cell Adhesion , Cell Proliferation , Chromatin Immunoprecipitation , Female , Glycogen Synthase Kinase 3 beta , Humans , Immunoenzyme Techniques , Lung Neoplasms/metabolism , Mice , Mice, SCID , Neoplastic Stem Cells/metabolism , Side-Population Cells/metabolism , Side-Population Cells/pathology , Tumor Cells, Cultured , Xenograft Model Antitumor AssaysABSTRACT
Wnt signaling contributes to the reprogramming and maintenance of cancer stem cell (CSC) states that are activated by epithelial-mesenchymal transition (EMT). However, the mechanistic relationship between EMT and the Wnt pathway in CSC is not entirely clear. Chromatin immunoprecipitation with high-throughput sequencing (ChIP-seq) indicated that EMT induces a switch from the ß-catenin/E-cadherin/Sox15 complex to the ß-catenin/Twist1/TCF4 complex, the latter of which then binds to CSC-related gene promoters. Tandem coimmunoprecipitation and re-ChIP experiments with epithelial-type cells further revealed that Sox15 associates with the ß-catenin/E-cadherin complex, which then binds to the proximal promoter region of CASP3. Through this mechanism, Twist1 cleavage is triggered to regulate a ß-catenin-elicited promotion of the CSC phenotype. During EMT, we documented that Twist1 binding to ß-catenin enhanced the transcriptional activity of the ß-catenin/TCF4 complex, including by binding to the proximal promoter region of ABCG2, a CSC marker. In terms of clinical application, our definition of a five-gene CSC signature (nuclear ß-catenin(High)/nuclear Twist1(High)/E-cadherin(Low)/Sox15(Low)/CD133(High)) may provide a useful prognostic marker for human lung cancer.
