Human lymphokine-activated killer (LAK) cells--II. Studies of various L-amino acid methyl esters on LAK generation at high cell density

Autologous lymphokine-activated killer cell therapy of lymphoproliferative disorders arising in organ transplant recipients

Lymphoreticular malignancies, collectively called posttransplant lymphoproliferative disorders (PTLD), eventually develop in 2–5% of organ transplant recipients. They frequently undergo regression when immunosuppression is reduced or stopped. This feature has been associated with a previous or de novo Epstein-Barr virus (EBV) infection. We herein describe immunotherapy with autologous lymphokine-activated killer (LAK) cells in seven patients with PTLD (four EBV-positive patients and three EBV-negative patients). Autologous peripheral blood mononuclear cells were obtained by leukapheresis, depleted of monocytes, and cultured in the presence of interleukin 2 for 10 to 11 days. A single dose of 5.2 × 109 to 5.6 × 1010 LAK cells was given intravenously. Systemic interleukin 2 was not administered.

The four patients with EBV+ PTLD had complete tumor regression; two of them developed controllable rejection. Three patients are well 13–16 months after treatment; the fourth patient died of pneumonia 41 days after infusion. Three patients with EBV− lymphomas had no response despite prior evidence that their tumors also were subject to immune surveillance. Two of these three patients died after being given other treatment, and the third patient has persistent tumor.

In conclusion, autologous LAK cell infusion was effective for treatment of four EBV+ organ transplant recipients. LAK cell efficacy for three patients with EBV− PTLD was not evaluable under the management circumstances in which this treatment was utilized.

Biologic effects of the adoptive transfer of cells depleted of monocytes with L-phenylalanine methyl ester

Monocytes macrophages have negative regulatory effects on many immunologic responses. Depletion of monocytes from peripheral blood using the lysosomotropic agent, L-phenylalanine methyl ester (PME), has been shown to improve lymphokine activated killer (LAK) cell expansion in vitro. A pilot study of the adoptive transfer of LAK cells expanded with PME was performed in patients with metastatic renal cell carcinoma. Patients received interleukin-2 (IL-2) by continuous infusion for 5 days. Leukopheresis was performed daily for 4 days during the second week. Cells obtained from 8 patients were depleted of monocytes using PME in an one-step procedure; < or = 3% of the remaining cells were monocytes. All cells were expanded for 10 days in air-porous plastic bags with IL-2. Cells expanded 2.7-fold when depleted with PME and 1.7-fold when not depleted (P = 0.02). Expanded cells were administered together with IL-2. Patients received up to 60 x 10(10) PME-depleted cells (mean = 26 x 10(10)) with LAK activity (% lysis) of 60 +/- 12%. Lymphocyte phenotype and cytolytic activity were not modulated by PME-depletion, and clinical toxicities and systemic immunologic effects observed in patients receiving PME-depleted cells were similar to that of 5 patients receiving cells not expanded with PME. Thus, the use of PME to deplete monocytes ex vivo can result in the yield of large number of effectors that retain immunologic activity for potential clinical use. The process is convenient, efficient, and does not add clinical toxicity.

Antileukemic activity of phenylalanine methyl ester (PME): a lysosomotropic peptide methyl ester

The antileukemic activities of the lysosomotropic compounds, such as phenylalanine methyl ester (PME), have received little attention. In this study, a 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay was used to investigate the antileukemic activity of PME. Leukemic specimens from untreated patients that contained greater than or equal to 75% blasts were used. Leukemic cells were treated with PME at 37 degrees C and 22 degrees C in concentrations ranging from 0.5 to 50 mM. Normal blood mononuclear cells served as controls. At both 37 degrees C and 22 degrees C, the recovery of normal peripheral blood cells was approximately 28% following incubation with 50 mM PME. At 37 degrees C, 50 mM PME caused greater than one log reduction of leukemic cells in 13/16 acute myelogenous leukemia (AML), 7/9 acute lymphocytic leukemia (ALL), and 8/8 in blast crisis of chronic myelogenous leukemia (CML-BC) specimens. PME had less activity at 22 degrees C than at 37 degrees C. PME was compared with 100 micrograms/ml 4-hydroperoxycyclophosphamide (4HC). In contrast to PME, 4HC was associated with a greater than one log reduction of leukemic cells in only 1/13 AML, 1/3 ALL and 0/6 CML-BC specimens. 4HC activity exceeded PME activity in only one case each of ALL and prolymphocytic leukemia (PLL). In a case of CD34+ B cell ALL, synergy of PME and 4HC was demonstrated. These studies indicate 1) PME has antileukemic activity and 2) 4HC has less antileukemic activity than PME.

Effects of L-leucyl-L-leucine methyl ester on human marrow and protection of progenitor cells by IL-1

In murine models, L-leucyl-L-leucine methyl ester (LLME) is effective as an ex vivo purging agent for the prevention of graft-versus-host disease. However, reduction of progenitor cells by LLME raises concerns about the engraftment potential of LLME-treated marrow. Therefore, the effects of LLME on human marrow were investigated. Concentrations of LLME from 0.005 mM to 5 mM were used to examine the effects of LLME on marrow cells. Concentrations of LLME less than or equal to 0.05 mM had no effect on recovery of nucleated marrow cells, mononuclear cells (MNC), myeloid cells or monocytes. At 0.5 mM, nucleated marrow cell recovery was 25%, and MNC recovery was 93%. As determined by cytochemical stains, 0.5 mM LLME eliminated myeloid cells and monocytes. At 0.005 mM, LLME had little effect on marrow progenitor cells; progenitor cell recovery with 0.05 mM LLME was 35% for granulocyte-macrophage colony forming units (CFU-GM) and 23% for erythroid burst forming units (BFU-E) (p less than 0.05 compared to 0.005 mM). At higher LLME concentrations, recoveries of both CFU-GM and BFU-E were less than 1%. To determine if earlier hematopoietic cells remained after treatment with LLME, progenitor cell experiments were repeated with 0.5 mM LLME using recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF) or recombinant human interleukin 3 (rhIL-3) plus or minus recombinant human mast cell growth factor (rhMGF) as sources of colony-stimulating activity. In this system, both IL-3 and GM-CSF induced rare progenitor cells (less than 6/5 x 10(4) cells plated).(ABSTRACT TRUNCATED AT 250 WORDS)