VCAM-1 upregulation was demonstrated to be due to an overproduction by CD38/CD49d-expressing CLL cells of specific chemokines (CCL3 and CCL4) upon CD38 triggering, eventually capable to recruit TNFα-producing macrophages, which in turn are responsible for VCAM-1 upregulation by stromal/endothelial cells [148]. This evidence concerns the gene ITGA4 and B-cell chronic lymphocytic leukemia.