Survival signals from auxiliary cells in the microenvironment might contribute to the upregulation of miR-155. Indeed, T cells or accessory cells of the lymphoid tissue can enhance expression of miR-155 by stimulating the BCR response via CD154/CD40 or BAFF/APRIL interaction and in vitro CLL cells stimulated with CD154 or BAFF/APRIL show reduced expression of SHIP1 and enhanced responsiveness to BCR ligation. This evidence concerns the gene BCR and B-cell chronic lymphocytic leukemia.