Supporting this argument, the addition of calcitriol to the co-culture system induced pERK levels (n = 8, FD: 1.3, p < 0.01) (Figure 5E) and strongly reduced HS5-induced NF-κB p65 phosphorylation (n = 6, FD: 1.6, p < 0.05) (Figure 5B) as in mono-cultured CLL cells. This evidence concerns the gene NFKB1 and B-cell chronic lymphocytic leukemia.