Interleukin-2 therapy for myelodysplastic syndrome: does it work?

Recent clinical studies suggested that interleukin-2 (IL-2) has therapeutic potential for some hematologic malignancies, but the therapeutic role of IL-2 for myelodysplastic syndrome (MDS) is still unclear. MDS is a clonal malignant disorder which often involves a variety of immunologic abnormalities. Examination of the effects of IL-2 on MDS in vitro yielded the following results: (1) IL-2 did not induce the proliferation of blasts in most MDS cases. (2) The cytotoxicity of IL-2-induced lymphokine-activated killer (LAK) cells for cell lines and MDS blasts was reduced in the high-risk MDS group (refractory anemia with excess blasts (RAEB), RAEB in transformation and MDS transformed to acute leukemia), but it was still preserved in the low-risk MDS group (refractory anemia (RA) and RA with ringed sideroblasts). However, considerable variation in LAK cell cytotoxicity was noted in each group. (3) The reduced LAK cell cytotoxicity observed in MDS was explained, at least in part, by the presence of a reduced of number of natural killer (NK) cells amongst the LAK cells. (4) MDS patients who have a high blood soluble IL-2 receptor (sIL-2R) level often had defects in NK and CD8+ T cells. These in vitro findings suggest that the response to IL-2 is heterogeneous in MDS patients, and those who have a low-risk MDS subtype and/or a low blood sIL-2R level, may be prone to respond to IL-2 therapy. Clinical trials are mandatory in order to elucidate the efficacy of IL-2 therapy in the treatment of MDS.