INTERLEUKIN-2 THERAPY FOR MYELODYSPLASTIC SYNDROME - DOES IT WORK

Recent clinical studies suggested that interleukin-2 (IL-2) has therap eutic 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 immu nologic abnormalities. Examination of the effects of IL-2 on MDS in vi tro yielded the following results: (1) IL-2 did not induce the prolife ration of blasts in most MDS cases. (2) The cytotoxicity of IL-2-induc ed lymphokine-activated killer (LAK) cells for cell lines and MDS blas ts was reduced in the high-risk MDS group (refractory anemia with exce ss blasts (RAEB), RAEB in transformation and MDS transformed to acute leukemia), but it was still preserved in the low-risk MDS group (refra ctory anemia (RA) and RA with ringed sideroblasts). However, considera ble variation in LAK cell cytotoxicity was noted in each group. (3) Th e reduced LAK cell cytotoxicity observed in MDS was explained, at leas t in part, by the presence of a reduced of number of natural killer (N K) 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 subt ype and/or a low blood sIL-2R level, may be prone to respond to IL-2 t herapy. Clinical trials are mandatory in order to elucidate the effica cy of IL-2 therapy in the treatment of MDS.