Hypoxia suppresses the production of matrix metalloproteinases and the migration of human monocyte-derived dendritic cells.

As most solid tumors are hypoxic, dendritic cells (DC) in solid tumors are also exposed to hypoxia. While many adaptation responses of tumor cells to hypoxia are known, it is yet to be determined how hypoxia affects the functions of DC. To explore the effects of hypoxia on the functions of DC, we compared the expression of surface markers, cytokines, chemokine receptors and matrix metalloproteinases (MMP) of human monocyte-derived DC (hmDC) differentiated under hypoxia to those differentiated under normoxia. Both groups of hmDC expressed similar levels of surface markers and cytokines. However, expression of MMP-9 and membrane type-1-MMP, as well as migrating activity, was significantly suppressed in hmDC differentiated under hypoxia compared with their normoxia counterparts. We also demonstrated that trichostatin A restored the production of MMP-9 in hmDC, under hypoxia. Collectively, our findings show that a hypoxic microenvironment suppresses the production of MMP in hmDC, most probably through the deacetylation of promoter regions of MMP, thus suppressing the migrating activity of hmDC. Our results suggest that the hypoxic microenvironment in solid tumor tissues may suppress the function of DC.