PTPN22 and B-cell chronic lymphocytic leukemia: As tonic BCR signal acts principally to activate AKT, results from this study suggest that HSP90 may regulate the PI3K/AKT signaling axis in CLL cells at multiple points via stabilization of: (i) BCAP protein which recruits PI3Kδ to the BCR signalosome, (ii) AKT protein, and finally, (iii) PTPN22 which also activates AKT [16].