Abstract:
Objective To investigate the protein expression characteristics of bone metastatic breast cancer cells and the underlying molecular mechanism driving bone metastasis.
Methods A firefly luciferase-overexpressing human breast cancer cell line, MCF-7-luc, and its bone metastasis subline, MCF-7- BOM-luc, were established. Additionally, a nude mouse model of breast cancer bone metastasis was established by injecting the aforementioned cells into the left ventricle. Bone metastasis and trabecular changes were assessed using micro-computed tomography (Micro-CT). Cell migration, and invasion were evaluated using the Transwell assays. Differential protein expression and epithelial-mesenchymal transition (EMT) were analyzed using proteomics, Western blot, and reverse transcription-quantitative PCR (qPCR). We measured the glucose uptake, L-lactic acid content, and cell energy metabolism parameters using 2-NBDG, ELISA, and a Seahorse energy metabolizer.
Results MCF-7-BOM-luc cells exhibited stronger migration, invasion, and EMT characteristics as well as more pronounced bone metastasis capabilities than the MCF-7-luc cells. Proteomic analysis revealed increased S100 calcium-binding protein A (S100A4) expression in MCF-7-BOM-luc cells, with other differentially expressed proteins being primarily involved in metabolic pathways. Additionally, MCF-7-BOM-luc cells displayed increased expression of E-box binding homeobox 1/2 (zinc finger E-box binding homeobox 1/2, ZEB1/2) and Vimentin and reduced E-cadherin expression. MCF-7-BOM-luc cells also exhibited enhanced glucose uptake, L-lactic acid production, and glycolysis rates as well as increased phosphorylation levels of extracellular signal-regulated kinases 1/2 (ERK1/2) and signal transducer and activator of transcription 3 (STAT3).
Conclusions MCF-7-BOM-luc cells promote S100A4 expression through ERK1/2 and STAT3 signaling pathway activation, which in turn enhances the EMT process and glycolysis rate, thereby contributing to malignant bone metastasis. Proteomic analysis of breast cancer bone metastasis-related protein characteristics could offer potential targets for the diagnosis, prevention, and treatment of breast cancer bone metastasis.