Common gamma chain-signaling cytokines promote proliferation of T-cell acute lymphoblastic leukemia.

BACKGROUND AND OBJECTIVES: The identification of signals critical for the pathophysiology of T-cell acute lymphoblastic leukemia (T-ALL) should contribute to the development of novel, more effective therapeutic strategies. Common gamma-chain signaling cytokines (gammac-cytokines) - interleukins 2, 4, 7, 9 and 15 - differentially regulate T-cell development, survival, proliferation and differentiation. Although studies exist on some individual cytokines, no comprehensive analysis of the effects of the Zc-cytokine family on malignant T cells has been reported. Here, we examined the effect of Zc-cytokines on T-ALL proliferation.

DESIGN AND METHODS: Primary leukemic cells were collected at diagnosis from the blood or bone marrow of children with T-ALL. The cells were immunophenotyped and classified according to maturation stage. Proliferative responses to gammac-cytokines were assessed by 3H-thymidine incorporation.

RESULTS: All gammac-cytokines promoted proliferation of primary T-ALL cells. Interleukin (IL)-7 was the cytokine that most frequently induced leukemic cell proliferation and promoted the most robust responses. IL-4 preferentially stimulated proliferation of samples with a more mature immunophenotype, whereas CD1a-positive cortical T-ALL cells were less responsive to IL-9. Finally, combinations of two Zc-cytokines showed synergistic or additive proliferative effects.

INTERPRETATION AND CONCLUSIONS: This study indicates that all the gammac-cytokines tested can stimulate proliferation of leukemic T cells and suggests that synergistic effects may occur in vivo. We present the first demonstration that IL-9 and IL-15 can provide a proliferative signal to T-ALL cells. Importantly, our results support the hypothesis that IL-7 may function as a critical regulator of T-ALL and that its activity may be potentiated by other Zc-cytokines.