Phosphorylation of ERK1/2 allows for its translocation from the cytosol to the nucleus to activate transcription factors, such as Jun, Fos, Ets-1, Elk, HIF-1, and cyclic AMP receptor binding protein (CREB), which collectively enhance CLL-cell proliferation and survival [3, 37, 38]. Here, JUN is linked to B-cell chronic lymphocytic leukemia.