Overexpression of the STAT3 molecule has been shown in CLL cells and it has also been shown that it is constitutively phosphorylated at (Tyr) 705 and (Ser) 727 positions, while in normal peripheral B lymphocytes or CD5+ B cells isolated from tonsils, STAT3 is unphosphorylated [31,32]. This evidence concerns the gene STAT3 and B-cell chronic lymphocytic leukemia.