Annexin A1 is a potential biomarker of bone metastasis in small cell lung cancer.

Small cell lung cancer (SCLC) is a subtype of lung cancer with a poor prognosis, with bone metastasis being one of the main causes of treatment failure. Therefore, investigating new biomarkers associated with bone metastasis may result in positive treatment outcomes. The present study detected the expression levels of annexin A1 (ANXA1) in the serum of 82 patients with SCLC using ELISA. ANXA1 expression in patients with SCLC with bone metastasis was significantly higher compared with that in patients without bone metastasis. Receiver operating characteristic analysis revealed that ANXA1 expression was significant in the diagnosis of bone metastasis in SCLC. ANXA1 was inhibited in SBC-5 cells and overexpressed in SBC-3 cells. Results revealed that ANXA1 was able to enhance SCLC cell proliferation, invasion, migration and bone adhesion in vitro. In vivo xenograft bone metastasis assays indicated that ANXA1 had the potential to promote the bone-metastasis ability of SCLC cells in NOD/SCID mice. Furthermore, ANXA1 increased parathyroid hormone-related protein secretion and enhanced Smad2 phosphorylation following TGF-β treatment in SCLC cells. Overall, ANXA1 may be involved in the pathogenesis of bone metastasis in SCLC and may be a potential biomarker for the diagnosis of SCLC.