ABCC4 and cancer: Other studies suggest a vital role for MRP4 in T-cell migration, where inhibition of MRP4, either by viral shRNA or sildenafil, impaired the abilities of interstitial dendritic cells to migrate toward lymph node chemokines (van de Ven et al., 2008), raising the possibility that MRP4 could also influence migratory properties of either cancer cells or their neighbors.