Central role of tumour necrosis factor, GM‐CSF, and interleukin 1 in the pathogenesis of juvenile chronic myelogenous leukaemia

Summary. In previous studies on patients with juvenile chronic myelogenous leukaemia (JCML), we found excessive proliferation of malignant monocyte‐macrophage elements in the absence of exogenous growth factor, and impaired growth of normal haematopoietic progenitors. In the current study, six newly‐diagnosed JCML patients were investigated to characterize the disease further. In co‐cultures, JCML cell culture supernatant as well as patient plasma obtained at diagnosis produced a striking reduction in numbers of control marrow BFU‐E, CFU‐GM, CFU‐Meg and CFU‐GEMM colonies. Monoclonal anti‐tumour necrosis factor alpha neutralizing antibodies (anti‐TNF‐α Ab) abolished these inhibitory properties. In sharp contrast, JCML supernatants exerted a marked growth‐promoting effect on autologous JCML cells cultured in clonogenic assays. Anti‐TNF‐α Ab and anti‐granulocyte‐macrophage colony‐stimulating factor neutralizing antibodies (anti‐GM‐CSF Ab) both reversed the stimulating effect. Recombinant GM‐CSF and recombinant TNF‐α produced a profound increase in JCML colonies when tested individually and anti‐GM‐CSF Ab reversed the TNF‐α effect. Expression studies of TNF‐α and TNF‐α receptor genes of cultured JCML cells demonstrated mRNAs for both. Further, TNF‐α activity was assayed in a wide variety of cell culture supernatants and in normal and patients’plasma, and only the JCML specimens showed increased TNF‐α values. Recombinant interleukin‐1 alpha (IL‐1α) also stimulated JCML colony growth, but polyclonal anti‐IL‐1 neutralizing antibodies did not suppress JCML colony numbers nor did it reverse the effects of TNF‐α or GM‐CSF. The evidence indicated that the JCML monokine which inhibits normal haematopoiesis is TNF‐α and that the endogenously‐produced TNF‐α and GM‐CSF from JCML cells play an important role in the pathogenesis of the disease by acting as autocrine growth factors. IL‐1α also stimulates JCML cell proliferation as an accessory factor and augments the effect of GM‐CSF, TNF‐α or both.