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

Abstract

Summary. 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 5á3-fold increase in the total cell number and a 35-fold increase in natural killer (NK) cells. Expression of the f 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 c and tumour necrosis factor a was documented. Patients' expanded cells showed a cytotoxic activity against target lines and allogeneic blasts which was similar to that of normal donors. Puri®cation experiments indicated that the NK cell fraction was responsible for most of the lytic effect. More signi®cantly, these cells also exerted a lytic effect against autologous blasts that could be further enhanced following incubation with low-dose interleukin 2. These ®ndings 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.

Use of Allogeneic NK Cells for Cancer Immunotherapy

“…Murine models have confirmed the support for NK cell-mediated killing of tumors in vivo [74]. More recently reported is the evidence for NK cell-mediated killing of freshly isolated human tumor cells from acute lymphocytic leukemia, multiple myeloma, neuroblastoma, ovarian, colon, renal and gastric cancers [75–83]. The first trials in the 1980s using adoptive cellular therapy to treat cancer however did not use NK cells specifically but were based on delivery of lymphokine-activated killer (LAK) cells [84–86].…”

Expansion and Activation of Natural Killer Cells for Cancer Immunotherapy

“…If stimulatory cells are used, it is important to prevent their overgrowth and to ensure than no viable cells are infused with the cultured NK cells. Irradiation, at doses of 30 Gy [49], 50 Gy [28], 70 Gy [29] or 100 Gy [19] is a safe and effective method.…”

Reovirus-Mediated Cytotoxicity and Enhancement of Innate Immune Responses Against Acute Myeloid Leukemia

“…This is because, when tumor burden is high on initial presentation or at relapse, immune effector cells may be suppressed, 30 while NK cells from AML patients in remission function in a similar manner to those from healthy donors. 31 In this context, and also to test patient AML blasts for their susceptibility as innate targets, we further investigated whether reovirus could enhance the activity of healthy donor NK cells against primary AML samples. As shown in Figure 6, reovirus increased NK cell activity against three different primary AML samples, with an increase in the percentage of NK cells degranulating after reovirus treatment (Fig.…”

“…Rather, we anticipate that reovirus would be administered in combination with, or post-, chemotherapy, with the aim of targeting minimal residual disease and preventing disease relapse. Since previous studies have demonstrated that NK cells expanded from AML and acute lymphoblastic leukemia patients in complete remission are functionally equivalent to those from normal donors, 31,50 it is likely that, following immune recovery after chemotherapy, patients' NK cells would function normally. Hence, the experiments presented in this study, describing normal donor NK cell interactions with AML targets, remain highly relevant to the clinical scenario of patients in partial or complete remission after initial treatment for AML.…”