JAK2 and B-cell chronic lymphocytic leukemia: We and other groups previously demonstrated that bone marrow mesenchymal stromal cells (BMSCs), the most represented stromal cells within the bone marrow, support the survival as well as the drug resistance of CLL cells through cell-cell contacts and soluble molecules such as CXCL10, CXCL12 [13], and interleukin 6 (IL-6), the main activator of JAK2/STAT3 signaling [14].