MAPK3 and B-cell chronic lymphocytic leukemia: Since we observed the involvement of the ZAP-70-ERK1/2-STAT3 axis in the induction of miR-21 expression in Ramos cells, we co-cultured primary CLL cells from 40 patients and observed a relative mean increase of 2.57 fold of miR-21 expression after 48 hours compared to the expression observed in cells kept in suspension (from 7.921 AU ± 1.091 to 20.35 AU ± 1.938; p < 0.0001) (Fig. 4a).