Accordingly, miR-15a and miR-16-1 directly targeted and downregulated the TP53 protein in primary CLL cells; however, at the same time, TP53 transactivated miR-15a/16-1 in leukemic cells, indicating the existence of a regulatory feedback loop between miR-15a/16-1 and TP53 [40]. This evidence concerns the gene TP53 and B-cell chronic lymphocytic leukemia.