Expansion of cytotoxic effectors with lytic activity against autologous blasts from acute myeloid leukaemia patients in complete haematological remission.

New therapeutic approaches are needed to improve the cure rates in acute myeloid leukaemia (AML). The present study was designed to investigate whether: (1) cytotoxic lymphocytes could be expanded from AML patients in complete remission; (2) their signal transduction machinery was preserved; (3) these cells were capable of producing cytokines involved in the cytolytic process; and (4) these cells showed cytotoxic activity against allogeneic and autologous blasts. By co-culturing blood mononuclear cells with feeder cells, we obtained an average 5.3-fold increase in the total cell number and a 35-fold increase in natural killer (NK) cells. Expression of the zeta chain and of tyrosine kinases of the Src and Syk-ZAP families involved in the triggering of NK functions was analysed on expanded cells. The results demonstrated a signal transduction apparatus preserved and quantitatively similar to that of normal donors. After phorbol myristate acetate and ionomicin stimulation, the ability of expanded cells to produce interferon gamma and tumour necrosis factor alpha was documented. Patients' expanded cells showed a cytotoxic activity against target lines and allogeneic blasts which was similar to that of normal donors. Purification experiments indicated that the NK cell fraction was responsible for most of the lytic effect. More significantly, these cells also exerted a lytic effect against autologous blasts that could be further enhanced following incubation with low-dose interleukin 2. These findings document the possibility of expanding cytotoxic effectors with preserved signal transduction machinery and autologous killing capacity from AML patients in remission, and suggest a new potential immunotherapeutic strategy for the management of early disease recurrence or of residual disease.