MCL1 and B-cell chronic lymphocytic leukemia: Early studies showed that several cytokines and growth factors related to CLL pathogenesis, i.e., interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), proMMP-9 and neutrophil gelatinase-associated lipocalin (NGAL), are implicated in CLL cell survival by activating the STAT3 (for VEGF and IL-6) and STAT3/Mcl-1 (for proMMP-9 and NGAL) signaling [45,73,74,75].