Functional expression of CXC chemokine recepter-4 mediates the secretion of matrix metalloproteinases from mouse hepatocarcinoma cell lines with different lymphatic metastasis ability

CXC chemokine recepter-4 (CXCR4) and its ligand, stromal cell-derived factor-1alpha (SDF-1alpha) have been implicated in the organ-specific metastasis of several malignancies. Hca-F and its syngeneic cell line Hca-P are mouse hepatocarcinoma cell lines with high and low potential of lymphatic metastasis, respectively. Previous studies showed that the secretion of matrix metalloproteinases (MMPs) associated with the metastatic ability of Hca-F and Hca-P cell line depending on the lymph node environment. However, the mechanism of this process has remained unclear. This study investigated the roles of CXCR4 on Hca-F cell and SDF-1alpha of lymph node in lymphatic metastasis. The RT-PCR and Flow cytometry analysis results show that Hca-F cells express higher level CXCR4 mRNA and cell-surface CXCR4 protein, as compared with Hca-P cells. Treatment of recombinant SDF-1alpha proteins induced greater amount of calcium-flux in Hca-F cells than that in Hca-P cells, demonstrating higher functional CXCR4 expression on Hca-F cells than that on Hca-P cells. Furthermore, both the cell-free extratcs of lymph node and recombinant SDF-1alpha proteins induced secretions of active MMP-9 and MMP-2 from Hca-F cells in vitro. But those secretions were significantly reduced by blockade of cell surface CXCR4 with rabbit anti-mouse CXCR4 polyclonal antibody (pAb) and neutralization of SDF-1alpha in lymph node extracts with rabbit anti-mouse SDF-1alpha pAb as well. These results suggest that the CXCR4/SDF-1alpha system mediates active MMP-9 and MMP-2 secretion from Hca-F and Hca-P cells, which facilitates lymphogenous metastasis of those cells consequently.