CXCL13–CXCR5 co-expression regulates epithelial to mesenchymal transition of breast cancer cells during lymph node metastasis

We investigated the expression of –CXC chemokine ligand 13 (CXCL13) and its receptor –CXC chemokine receptor 5 (CXCR5) in 98 breast cancer (BC) patients with infiltrating duct carcinoma, out of which 56 were found lymph node metastasis (LNM) positive. Interestingly, co-expression of CXCL13 and CXCR5 showed a significant correlation with LNM. Since, epithelial to mesenchymal transition (EMT) is highly associated with metastasis we investigated EMT-inducing potential of CXCL13 in BC cell lines. In CXCL13-stimulated BC cells, expression of various mesenchymal markers (Vimentin, N-cadherin), EMT regulators (Snail, Slug), and matrix metalloproteinase-9 (MMP9) was increased, whereas the expression of epithelial marker E-cadherin was found to be decreased. In addition, expression of receptor activator of nuclear factor kappa-B ligand (RANKL), which is known to regulate MMP9 expression via Src activation, was also significantly increased after CXCL13 stimulation. Using specific protein kinase inhibitors, we confirmed that CXCL13 stimulated EMT and MMP9 expression via RANKL–Src axis in BC cell lines. To further validate this observation, we examined gene expression patterns in primary breast tumors and detected significantly higher expression of various mesenchymal markers and regulators in CXCL13–CXCR5 co-expressing patients. Therefore, this study showed the EMT-inducing potential of CXCL13 as well as demonstrated the prognostic value of CXCL13–CXCR5 co-expression in primary BC. Moreover, CXCL13–CXCR5–RANKL–Src axis may present a therapeutic target in LNM positive BC patients.