Several cytokines and growth factors are involved in the regulation of megakaryocytopoieses and platelet formation. Interleukin-11 (IL-11), IL-6, IL-3, IL-1b, and thrombopoietin (TPO) act synergistically to promote proliferation and maturation of megakaryocytes. Recombinant IL-11 and TPO are under clinical investigation as supplements to stimulate thrombopoiesis in patients with cancer. We investigated the plasma levels of TPO in 127 patients with chronic lymphocytic leukemia (CLL) and correlated these levels with platelet counts and various laboratory and clinical characteristics. TPO levels were significantly higher in patients with CLL (median, 232 pg/mL; range, 26.4–2714.5 pg/mL) than in healthy control subjects (P <0.01). More importantly, higher levels of TPO were associated with advanced Rai stage (P <0.0001), higher b-2-microglublin (b2-M) levels (P<0.001), and the presence of mutation in the IgVH gene (P <0.001). TPO levels were inversely correlated with platelet count (P = 0.002). Univariate Cox proportional hazard models demonstrated that high TPO levels in CLL patients were associated with shorter survival (P <0.0001); multivariate analysis demonstrated that this association was independent of the IgVH mutation status, b2-M levels, and Rai stage. Recursive partitioning showed that a cut-point of 639.4 pg/mL separated CLL patients into two major groups with a significant difference in survival (P <0.0001). When b2-M level was added to this model, its effect was masked by the effects of TPO in patients with TPO >639.4 pg/mL. However, among patients with TPO levels =639.4 pg/mL, those with b2-M levels >4.95 mg/L had significantly shorter survival than those with lower b2-M levels. These data not only emphasize the importance of TPO in reflecting the aggressiveness of CLL, but also suggest that TPO and b2-M can be used to predict clinical behavior in this disease and may replace the need for determining IgVH mutation status. Further studies are needed to determine if the prognostic role of TPO is due to its direct effects on the growth of the leukemic clone or simply reflects a general failure in the homeostatic regulation of various cytokines.

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Topics:
chronic b-cell leukemias, chronic lymphocytic leukemia, prognostic marker, thrombopoietin, interleukin-11, cytokine, cancer, growth factor, interleukin-1 beta, interleukin-3

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2005, The American Society of Hematology
2004
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