BcR/CD40 stimulation led to a significant increase in CYP24A1+ cells in U-CLL (n = 4, FD: 5.9, p < 0.01) but not in M-CLL (n = 3) (Figure 4C), yet co-stimulation of CLL cells with calcitriol/anti-IgM/CD40 ligand did not confer any additional change compared to calcitriol alone both in U-CLL and M-CLL (Figure 4D). Here, CD40 is linked to B-cell chronic lymphocytic leukemia.