Abstract
BACKGROUND: Bone metastasis affects nearly 70% of patients with advanced breast cancer, significantly influencing patient survival. Osteoclasts play a crucial role in osteolysis and the proliferation of bone tumor cell metastasis. Although previous studies have established Anxa2 as a critical factor in the invasion and metastasis of breast cancer, its involvement in bone metastasis remains poorly understood. METHODS: The correlation between ANXA2 expression and survival was analyzed in breast cancer cohorts. Enrichment analysis was performed to explore ANXA2-associated signaling pathways. RAW264.7 cells were induced to differentiate into osteoclasts using conditioned media from breast cancer cells, and osteoclastogenesis was quantified using the TRAP assay. Breast cancer cell lines with either Anxa2 overexpression or knockdown were established to assess the impact on osteoclastogenesis. The mRNA and protein expression levels were analyzed by RT-PCR and Western blot. The role of STAT3 in regulating RANKL expression was evaluated using a dual luciferase reporter assay. RESULTS: ANXA2 was significantly upregulated in breast cancer patients and associated with poor survival. GO and KEGG analyses revealed that ANXA2 substantially modulated signaling pathways involved in bone metastasis. Furthermore, ANXA2 notably enhanced the differentiation of RAW264.7 cells into osteoclasts and upregulated genes associated with osteoclast differentiation. Additional investigation showed that ANXA2 markedly activated the STAT3 signaling pathway and increased RANKL expression. The dual luciferase reporter assay demonstrated that STAT3 directly bound to the -1804 region of the RANKL promoter, thereby regulating RANKL expression. CONCLUSION: This study identifies ANXA2 as a key regulator of osteoclast differentiation through STAT3-mediated upregulation of RANKL, driving bone metastasis in breast cancer. These results highlight the potential of targeting the ANXA2/STAT3/RANKL axis as a therapeutic strategy to combat bone metastasis.