Increased autocrine interleukin-6 production is significantly associated with worse clinical outcome in patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) remains incurable with current standard therapy. We have previously reported that an increased expression of interleukin-6 (IL-6) receptor CD126 leads to resistance of CLL cells to chemotherapy and worse prognosis for patients with CLL. In this study, we determine whether autocrine IL-6 production by CLL B cells is associated with poor clinical outcome and explore IL-6-mediated survival mechanism in primary CLL cells. Our results demonstrate that higher levels of autocrine IL-6 are significantly associated with shorter absolute lymphocyte doubling time, patients received treatment, without complete remission, advanced Binet stages, 17p/11q deletion, and shorter time to first time treatment and progression-free survival. IL-6 activated both STAT3 and nuclear factor kappa B (NF-κB) in primary CLL cells. Blocking IL-6 receptor and JAK2 inhibited IL-6-mediated activation of STAT3 and NF-κB. Our study demonstrates that an increased autocrine IL-6 production by CLL B-cells are associated with worse clinical outcome for patients with CLL. IL-6 promotes CLL cell survival by activating both STAT3 and NF-κB through diverse signaling cascades. Neutralizing IL-6 or blocking IL-6 receptor might contribute overcoming the resistance of CLL cells to chemotherapy. We propose that the measurement of autocrine IL-6 could be a useful approach to predict clinical outcome.