LILRA3 attenuates U937 cell migration by decreasing expression of certain chemokines
A transwell test was applied to investigate cell migration. We found that after 6 hours of incubation in 10% FBS containing RPMI-1640, few of the U937 cells overexpressing LILRA3 had migrated into the lower chamber compared with cells harboring the null vector (p < 0.001) (Figure 3F). Chemokines and their seven-transmembrane, G-protein coupled receptors are recognized as key mediators physiologically directing cell migration. We then performed Elisa assay to detect expression of two CC-type chemokines (CCL2, CCL3) and other two CXC-type chemokines (CXCL8/IL-8, CXCL10), which were predominantly expressed in monocytes. Interestingly, we found that CCL2, CCL3, IL-8, CXCL10 were significantly suppressed by LILRA3 (p < 0.001) (Figure 3G). To verify our findings, we then added a certain amount of recombinant CCL2 or CXCL8 (Peprotech, Rocky Hill, USA) to the upper chamber, and the migration assay results showed that the migration capacity, inhibited by LILRA3, was reversed by the exogenous IL-8 (p<0.01) (Figure 3H). The data suggest that LILRA3 attenuates the migration capacity of U937 cell lines mainly by suppressing IL-8 secretion.