HOXB9 and lung cancer: In addition, the expression of chemotactic factors including CXCL12 and its receptor CXCR4 was significantly higher in BM than in primary lung cancer; CXCR4 may improve the adhesion and chemoresistance of lung cancer cells, leading to BM (Chen et al. 2011; Paratore et al. 2011).One study of mice has shown that WNT/TCF signaling plays an important role in the formation of brain and bone metastasis through LEF1 and HOXB9 (Nguyen et al. 2009).