The Role Of Annexin A1in Bone Metastasis Of Small Cell Lung Cancer

Globally, Lung cancer is the major cause of malignancy-related mortality, and itsincidence is on the rise in many countries. Bone Metastasis is one of the most seriouscomplications of lung cancer. Bone metastases are often associated with skeletal-relatedevents, which may decrease the quality of life for patients. Due to less known about themolecular mechanism of bone metastasis, little progress has been made in treating skeletalmetastasis, currently. In previous proteomic study, we found that Annexin A1wasoverexpressed in bone-metastatic small cell lung cancer (SCLC) cells. It indicated thatAnnexin A1might play roles in osteotropism metastasis of SCLC. In our present study, weperform a list of experiments to confirm this hypothesis.PurposeTo observe the biofunction of Annexin A1in SCLC cells in vitro and in vivo, prove that the Annexin A1is closely related to the bone metastasis of SCLC, and explore themolecular mechanism of Annexin A1related bone metastases.Methods1. Using Real-time PCR and Western blot assays to demonstrate the expression ofAnnexin A1in SCLC cell lines with different capability of bone metastasis.2. Constructing the Lentiviral vector mediated overexpression or siRNA targeteddownregulation of Annexin A1in SCLC cells, and observing the cell behavior includingproliferation, cell cycle, invasion and migration and the ability of bone adhesion in vitro.3. Using NOD/SCID mouse as bone metastasis model to detect the bone metastaticability of SCLC cells with different Annexin A1expression level.4. In order to explore the molecular mechanism of Annexin A1related bonemetastases, Real-time PCR, Western blot and Elisa assays were performed to detect theexpression of PTHrP induced by Annexin A1in different SCLC cells, and observe theeffection of Annexin A1on TGF-β/Smad signal passway in SCLC cells with or withoutTGF-β incubation.Results1. Annexin A1is overexpressed in bone-metastatic SCLC cell line SBC-5. Itindicates that the Annexin A1maybe associated with bone metastases in SCLC.2. Annexin A1is able to enhance SCLC cells proliferation，invasion, migration andbone adhesion in vitro.3. Annexin A1has the potential to promote the bone-metastatic ability of SCLCcells in NOD/SCID mouse.4. Annexin A1has ability to upregulate the synthesis and secretion of PTHrP inSCLC cells. With TGF-β incubation, Annexin A1is able to increase the secretion ofPTHrP through enhancing the phosphorylation of Smad2in SCLC cells.ConclusionAnnexin A1has the potential to promote the SCLC cells proliferaton, invasion,migration and bone adhesion in vitro and bone metastases in vivo. Annexin A1induced overexpression of PTHrP is involved in Annexin A1related bone metastases in SCLCcells. Annexin A1is able to enhance the PTHrP-TGF-β vicious cycle in tumor bonemetastasis though TGF-β/Smad passway.