BCR signaling is not the only driver of CLL proliferation in vivo. Cytokines and chemokines in the tumor microenvironment activate Janus Kinases (JAKs) and mediate many of the pathological features of CLL cells. Cytokine signaling pathways have been shown to be rewired in aggressive tumor cells to support rapid growth and will eventually overcome the effects of inhibiting BCR-signaling. Preclinical findings suggest that JAK inhibitors will also have a place in the treatment of CLL.