CCL2 and B-cell chronic lymphocytic leukemia: Immature monocytes induced release of key CLL-associated pro-tumorigenic chemokines and cytokines, such as CCL2, CCL4, and interleukin-6, as well as the T-cell immunosuppressor PD-L1, whereas in vivo blocking of the EV-hY4 pathway in CLL-bearing mice decreased leukemia development [97].