CD5 and B-cell chronic lymphocytic leukemia: Consistent with results in Jurkat cells (Fig 3B), PNA alone does not induce cell death whereas, interestingly, in combination with fludarabine, PNA treatment significantly increased the percentage of apoptotic cells (22.5% in P3 and 13% in P4), also supporting the physiological significance of PNA-dependent CD5 down-modulation in CLL.