IL18 and leukemia: The increased expression of IL-18 in MEKi-treated MS5 stromal cells together with the detection of IL-18Rα/β in T-ALL primary cells and the finding that IL-18 incubation stimulates proliferation in more than half of the tested T-ALL samples strongly suggest that IL-18 also should be included among the microenvironmental signals supporting leukaemia development/progression.