IL-8 and its CXCR1 and CXCR2 receptors participate in the control of megakaryocytic proliferation, differentiation, and ploidy in myeloid metaplasia with myelofibrosis

Myeloproliferation, myelofibrosis, and neoangiogenesis are the 3 major intrinsic pathophysiologic features of myeloid metaplasia with myelofibrosis (MMM). The myeloproliferation is characterized by an increased number of circulating CD34(+) progenitors with the prominent amplification of dystrophic megakaryocytic (MK) cells and myeloid metaplasia in the spleen and liver. The various biologic activities of interleukin 8 (IL-8) in hematopoietic progenitor proliferation and mobilization as well as in neoangiogenesis prompted us to analyze its potential role in MMM. We showed that the level of IL-8 chemokine is significantly increased in the serum of patients and that various hematopoietic cells, including platelets, participate in its production. In vitro inhibition of autocrine IL-8 expressed by CD34(+) cells with either a neutralizing or an antisense anti-IL-8 treatment increases the proliferation of MMM CD34(+)-derived cells and stimulates their MK differentiation. Moreover, addition of neutralizing anti-IL-8 receptor (CXC chemokine receptor 1 [CXCR1] or 2 [CXCR2]) antibodies to MMM CD34(+) cells cultured under MK liquid culture conditions increases the proliferation and differentiation of MMM CD41(+) MK cells and restores their polyploidization. Our results suggest that IL-8 and its receptors participate in the altered MK growth that features MMM and open new therapeutic prospects for this still incurable disease. (C) 2005 by The American Society of Hematology.