MAPK3 and B-cell chronic lymphocytic leukemia: Since it has been established that CLL cells have up-regulated expression of CXCR4 compared to normal B cells, and that CXCL12 stimulation of CLL cells activates Akt and ERK1/2 pathways, transwell migration assays were performed on purified CLL B cells and normal B cells to compare their ability to migrate towards CXCL12 [5], [8], [9].