Interleukin 2 does not promote the in vitro and in vivo proliferation and growth of human acute leukaemia cells of myeloid and lymphoid origin

Prognostic Relevance of Cytokine Receptor Expression in Acute Myeloid Leukemia: Interleukin-2 Receptor α-Chain (CD25) Expression Predicts a Poor Prognosis

A variety of cytokine/cytokine receptor systems affect the biological behavior of acute leukemia cells. However, little is known about the clinical relevance of cytokine receptor expression in acute myeloid leukemia (AML). We quantitatively examined the expression of interleukin-2 receptor α-chain (IL-2Rα, also known as CD25), IL-2Rβ, IL-3Rα, IL-4Rα, IL-5Rα, IL-6Rα, IL-7Rα, the common β-chain (βc), γc, granulocyte-macrophage colony-stimulating factor (GM-CSF)Rα, G-CSFR, c-fms, c-mpl, c-kit, FLT3, and GP130 in leukemia cells from 767 adult patients with AML by flow cytometry and determined their prevalence and clinical significance. All cytokine receptors examined were expressed at varying levels, whereas the levels of IL-3Rα, GM-CSFRα, IL-2Rα, γc, c-kit, and G-CSFR exhibited a wide spectrum of ≥10,000 sites/cell. In terms of their French-American-British classification types, GM-CSFRα and c-fms were preferentially expressed in M4/M5 patients, G-CSF in M3 patients, and IL-2Rα in non-M3 patients. Elevated levels of IL-3Rα, GM-CSFRα, and IL-2Rα correlated with leukocytosis. In patients ≤60 years old, higher levels of these 3 receptors correlated with poor responses to conventional chemotherapy, but only IL-2Rα was associated with a shorter overall survival. By incorporating IL-2Rα status into cytogenetic risk stratification, we could sort out a significantly adverse-risk cohort from the cytogenetically intermediate-risk group. Analyses with various phenotypical risk markers revealed the expression of IL-2Rα as an independent prognostic indicator in patients with intermediate-risk cytogenetics. These findings were not observed in patients >60 years old. Our results indicate that several cytokine receptors were associated with certain cellular and clinical features, but IL-2Rα alone had prognostic value that provides an additional marker to improve current risk evaluation in AML patients ≤60 years old.

Interleukin-2 receptor alpha-chain (CD25) expression on leukaemic blasts is predictive for outcome and level of residual disease in AML

We investigated the role of CD25 as a prognostic marker in acute myeloid leukaemia (AML). Seventy-two newly diagnosed patients < or =60 years were retrospectively analysed by flow cytometry for CD25 positivity of AML blasts. Patients with CD25 expression of >10%, when compared to < or =10%, had a significantly shorter overall survival (OS, p=0.0005) and relapse-free survival (RFS, p=0.005). In multivariate analysis CD25 expression is an independent adverse factor for OS and RFS. High CD25 combined with FLT3-ITD positivity resulted in the poorest OS and RFS (p=0.001 and p=0.003, respectively). CD25 expression remained prognostic within the intermediate cytogenetic risk group. In addition, after the first cycle of chemotherapy, a significantly higher MRD frequency was found in patients expressing CD25 above cut-off (p=0.003). Our results show that CD25 expression is an independent adverse prognostic marker in AML patients < or =60 and correlates with MRD.

Clinical and prognostic significance of cytokine receptor expression in adult acute lymphoblastic leukemia: interleukin-2 receptor α-chain predicts a poor prognosis

We quantitatively assessed the expression of cytokine receptors (interleukin-2 receptor (IL-2R), IL-3R, IL-4R, IL-5R, IL-6R, IL-7R, granulocyte-macrophage colony-stimulating factor R (GM-CSFR), G-CSFR, c-fms, c-mpl, c-kit and FLT3) in cells from 211 adults with acute lymphoblastic leukemia (ALL) by flow cytometry and determined their prevalence and clinical significance. Although all cytokine receptors were expressed to various degrees, the levels of IL-3R alpha-chain (IL-3Ralpha), IL-2Ralpha, IL-2Rbeta, IL-7Ralpha, common-Rgamma(gammac), c-mpl, c-kit and FLT3 exhibited a wide spectrum > or =2000 sites/cell. Among them, IL-3Ralpha, IL-2Ralpha and FLT3 were highly expressed in B-lineage ALL, whereas IL-7Ralpha, gammac and c-kit predominated in T-lineage ALL. Higher levels of IL-3Ralpha, IL-2Ralpha, c-kit and FLT3 correlated with the expression of CD13/33. Increased IL-2Ralpha levels related to the presence of Philadelphia chromosome (Ph), leukocytosis and shorter event-free survival (EFS). C-kit preferred in male. Elevated FLT3 levels correlated with age > or =60 years. Multivariate analysis in B-lineage ALL revealed only IL-2Ralpha (P=0.028) and Ph (P=0.020) as independent factors for EFS. These findings suggest that several cytokine receptors associated with certain cellular and clinical features, but IL-2Ralpha solely had a prognostic value and should be considered as a major prognostic factor for adult ALL that is comparable with Ph.

Immunotherapy of high-risk acute leukemia with a recipient (autologous) vaccine expressing transgenic human CD40L and IL-2 after chemotherapy and allogeneic stem cell transplantation

CD40L generates immune responses in leukemia-bearing mice, an effect that is potentiated by IL-2. We studied the feasibility, safety, and immunologic efficacy of an IL-2- and CD40L-expressing recipient-derived tumor vaccine consisting of leukemic blasts admixed with skin fibroblasts transduced with adenoviral vectors encoding human IL-2 (hIL-2) and hCD40L. Ten patients (including 7 children) with high-risk acute myeloid (n = 4) or lymphoblastic (n = 6) leukemia in cytologic remission (after allogeneic stem cell transplantation [n = 9] or chemotherapy alone [n = 1]) received up to 6 subcutaneous injections of the IL-2/CD40L vaccine. None of the patients were receiving immunosuppressive drugs. No severe adverse reactions were noted. Immunization produced a 10- to 890-fold increase in the frequencies of major histocompatibility complex (MHC)-restricted T cells reactive against recipient-derived blasts. These leukemia-reactive T cells included both T-cytotoxic/T-helper 1 (Th1) and Th2 subclasses, as determined from their production of granzyme B, interferon-gamma, and interleukin-5. Two patients produced systemic IgG antibodies that bound to their blasts. Eight patients remained disease free for 27 to 62 months after treatment (5-year overall survival, 90%). Thus, even in heavily treated patients, including recipients of allogeneic stem cell transplants, recipient-derived antileukemia vaccines can induce immune responses reactive against leukemic blasts. This approach may be worthy of further study, particularly in patients with a high risk of relapse.

Animal models of acute myelogenous leukaemia - development, application and future perspectives

From the early inception of the transplant models through to contemporary genetic and xenograft models, evolution of murine leukaemic model systems have been critical to our general comprehension and treatment of cancer, and, more specifically, disease states such as acute myelogenous leukaemia (AML). However, even with modern advances in therapeutics and molecular diagnostics, the majority of AML patients die from their disease. Thus, in the absence of definitive in vitro models which precisely recapitulate the in vivo setting of human AMLs and failure of significant numbers of new drugs late in clinical trials, it is essential that murine AML models are developed to exploit more specific, targeted therapeutics. While various model systems are described and discussed in the literature from initial transplant models such as BNML and spontaneous murine leukaemia virus models, to the more definitive genetic and clinically significant NOD/SCID xenograft models, there exists no single compendium which directly assesses, reviews or compares the relevance of these models. Thus, the function of this article is to provide clinicians and experimentalists a chronological, comprehensive appraisal of all AML model systems, critical discussion on the elucidation of their roles in our understanding of AML and consideration to their efficacy in the development of AML chemotherapeutics.

Interleukin-2 after autologous stem-cell transplantation for adult patients with acute myeloid leukemia in first complete remission

PURPOSE

To determine the disease-free survival (DFS) and toxicity of administering interleukin-2 (IL-2) immunotherapy early after autologous stem-cell transplantation (ASCT) to simulate a graft versus leukemia effect observed in allogeneic transplantation.

PATIENTS AND METHODS

Fifty-six patients with acute myeloid leukemia in first remission received a single consolidation of high-dose cytarabine-idarubicin at a median of 1.1 month postremission with the intent to proceed to ASCT and IL-2 9 x 10(6) U/m(2)/24 h for 4 days, followed by 10 days of IL-2 1.6 x 10(6) U/m(2)/24 h on hematologic recovery.

RESULTS

Eighty-four percent of patients received the intended ASCT, and 68% of patients received IL-2 treatment. With a median follow-up of 39.4 months (range, 1.2 to 76.3 months), the 2-year cumulative probability of DFS for all 56 patients is 68% (95% confidence interval [CI], 55% to 80%) and 74% (95% CI, 57% to 85%) for the 39 patients undergoing IL-2 treatment after ASCT. The 2-year cumulative probability of DFS for favorable, intermediate, and unfavorable cytogenetics is 88% (95% CI, 59% to 97%), 48% (95% CI, 26% to 67%), and 70% (95% CI, 23% to 93%), respectively. Toxicities from IL-2 were mainly thrombocytopenia, leukopenia, fever, and fluid retention. Two septic deaths occurred during neutropenia, which includes one during consolidation and one during transplant, for an overall 4% mortality rate.

CONCLUSION

These results suggest that a moderate dose of IL-2 after high-dose cytarabine-idarubicin-mobilized ASCT is associated with a low regimen-related toxicity and may improve DFS. A phase III study of IL-2 is now warranted.

Developmental approaches in immunological control of acute myelogenous leukaemia

After many years of hope and disillusionment, the possibility of utilizing immune-mediated approaches to control neoplastic clones has become a reality in various haematological malignancies. This is largely a consequence of the continuous advances in knowledge and the progressive development of more refined technologies that have led to a better understanding of the biology of the malignant cells and of the host immune system, to a more precise definition of disease entities and to the design of innovative therapeutic programmes. In this chapter, we will review different immunological strategies that have reached clinical practice in patients with acute myelogenous leukaemia (AML), the focus of this volume, and discuss pre-clinical developments that may in the near future translate into the design of new immunotherapeutic protocols for the management of AML. Treatment of AML with antibody directed therapy will also be discussed.

Cellular immunotherapy and autologous transplantation for hematologic malignancy

The success of allogeneic transplantation is in part due to the immunotherapeutic effect mediated by the graft. Autologous transplantation is hampered by the absence of this effect, leading to a higher relapse rate. We have conducted a series of studies designed to augment the immunologic activity of the graft after autologous transplant with a view towards introducing an autologous graft-versus-tumor effect that could decrease the rate of relapse after autologous transplant. These studies have included IL-2 activation of marrow followed by post-transplant infusional IL-2, the development of a novel protocol for the generation of highly efficient cytotoxic effector cells, termed cytokine-induced killer (CIK) cells, with broad and potent antitumor activity. In order to determine the potential for generating peptide-specific cytolytic T cells, studies have been conducted upon transducing antigen-presenting cells (APC) with AAV vector-mediated gene transfer, a vector capable of transducing non-proliferating target cells. Transduction of human monocytes and macrophages resulted in high expression of the transduced gene. This latter study forms the basis for determining whether genetic modification of APC can potentiate specific immune responses to tumor-specific gene products. Taken together, these strategies will hopefully increase the therapeutic efficacy of autologous transplantation.

The biological therapy of acute and chronic leukemia

With the increasing knowledge of the mechanisms of immune-mediated cytotoxicity, immunotherapeutic strategies are rapidly being incorporated into chemotherapy treatment schemes for acute and chronic leukemias. This includes the use of mAbs, immunotoxins, tumor-specific T cells, and, most recently, vaccines. Much of the new information is derived from bone marrow transplant data, where immune enhancement from IL-2 and donor T-cell infusions are being studied. Trials using humanized mAbs that permit prolonged and repeated dosing will allow better evaluation of the effectiveness of mAb therapy. More sophisticated molecular tests have been developed, allowing the detection of minimal residual disease to a greater degree. It is likely that biological and immunological therapy of leukemia will have its greatest impact here.

Role of interleukin-2 in human hematological malignancies

Clinical studies with Interleukin-2 (IL-2) in human hematologic malignancies were initiated in the late 1980s. Based on clinical studies on various solid tumors, and laboratory research on hematopoietic cells, IL-2 was shown to be effective in 150 acute myeloid leukemia (AML) patients mainly for maintenance therapy in first complete remission, or with residual blast cells in the marrow. IL-2 has also been shown to be effective in remission induction in 10 patients with chronic myeloid leukemia (CML). The role of IL-2 in lymphoma patients remains to be established. IL-2 alone or in combination with Interferon-alpha, may intensify remission and prolong disease-free survival when given post autologous bone marrow transplantation (BMT) to patients with lymphoma and myeloid leukemia, and to a lesser degree, to patients with acute lymphatic leukemia (ALL). IL-2 in combination with HLA-matched or mismatched peripheral blood lymphocytes was also used post autologous BMT in preliminary studies. IL-2 was administered with or without peripheral blood lymphocytes, for prevention of relapse post T-cell-depleted allogeneic BMT in CML, ALL and AML, with encouraging results. The same strategy was shown to be effective in the reinduction of remission in patients with CML, who relapsed post BMT.

Early development of acute myelogenous leukemia following kidney transplantation: possible role of multiple serum cytokines

We report a patient who at the time of kidney transplantation for polycystic kidney disease was found to have an enlarged inguinal lymph node which later demonstrated evidence of extra medullary granulopoiesis. During the first two weeks following kidney transplantation, a striking leukemoid pattern developed and 2 months after transplant the patient was diagnosed with acute myelogenous leukemia (AML). Retrospective analysis of peripheral blood cytokines over this time revealed elevated levels of GMCSF and gamma IFN at the time of peak peripheral blood WBC with subsequent peaks in IL-4, IL-6 and IL-2 as the peripheral blood WBC fell. A rise in levels of TNF alpha also preceded the peripheral blood WBC rise (although these concentrations were at or below those following uncomplicated kidney transplants). The clinical course of AML in this patient was marked by relentless relapse despite chemotherapy. The possibility of cytokine facilitated tumor growth is discussed.

AML blasts variably express interleukin 2 receptor alpha, beta or gamma chains without measurable effects on proliferation, cytokine message expression or surface expression of adhesion molecules upon stimulation with interleukin 2

Preliminary clinical studies including interleukin 2 (IL-2) in chemotherapy strategies for treatment of acute myeloblastic leukemia (AML) suggest that IL-2 may improve the disease-free survival of the patients. Because of reports showing interleukin 2 receptor expression on AML blasts, it is important to know whether IL-2 may directly influence these leukemic cells. In initial studies using flow cytometry to analyze surface expression of interleukin 2 receptors (IL-2R), we found expression of the IL-2R alpha chain on blast cells in 26% and of the IL-2R beta-chain in 81% of the patients. To confirm these results at the transcriptional level, we studied the expression of RNA of the IL-2R alpha, beta, and gamma chains by RT-PCR in the bone marrow of 38 newly diagnosed patients with AML and in three AML-derived cell lines. RNA of the alpha chain was detectable in 11/38 patients, the beta chain in 10/38 patients and the gamma chain in 30/38 patients with AML. Blast cells obtained from colonies growing in semisolid media expressed mRNA for IL-2R. RNA for all three IL-2R chains was expressed in lines KG1, HEL 92.1.7 and K562. In comparison with unstimulated cell lines, incubation of the three lines with various amounts of IL-2 over 3 and 14 days did not increase their growth or change message expression of IL-2R, IL-10, and TGF-beta and surface expression of the adhesion molecules CD 11, CD 18, CD 29 and CD 54. In conclusion, despite expression of IL-2 receptors, AML blasts do not respond to IL-2 by proliferation, message expression for various cytokine genes and surface expression of cellular adhesion molecules.

Relapse of acute myelogenous leukemia during low dose interleukin-2 (IL-2) therapy. Phenotypic evolution associated with strong expression of the IL-2 receptor alpha chain

BACKGROUND

Interleukin-2 (IL-2) has produced remissions in patients with solid tumors, predominantly malignant melanoma and renal cell carcinoma. Recently, clinical trials have assessed the therapeutic benefit of this cytokine in acute myelogenous leukemia (AML). However, little is known about the potential of IL-2 to promote the growth of leukemic cells in vivo.

METHODS

A patient with acute myelocytic leukemia whose leukemic blasts displayed lymphoid (TdT+ and CD4+) and myeloid features (myeloperoxidase [MPO]+ and CD13+) is reported. The IL-2 receptor alpha chain (CD25 antigen) was present on 28.9% of his blasts. After entering complete remission with chemotherapy, he was treated on a protocol using IL-2 maintenance.

RESULTS

Six weeks after beginning low-dose IL-2, his leukocyte count increased to 448,000/microliters with 86% blasts. The phenotype of these blasts was different from that at diagnosis with expression of the CD25 antigen and the CD33 antigen on 75.9% and 74.8 of the blasts, respectively. Furthermore, 30% of the cells were TdT+, whereas MPO was not detectable.

CONCLUSION

The rapid course of relapse, phenotypic evolution, and the high expression of CD25 antigen on the blasts after IL-2 therapy raise the possibility that the cytokine therapy may have promoted the growth of leukemic cells.

Is there a place for immunotherapy with interleukin-2 to prevent relapse after autologous stem cell transplantation for acute leukemia?

Chemotherapy-resistant cells cause disease recurrence in a significant proportion of patients with acute leukemia treated with autologous stem cell transplantation due to the lack of immune-mediated effects which contribute significantly to the prevention of post-treatment disease recurrence. This conclusion is based on the observation that relapse after high dose chemotherapy supported by a stem cell transplant from a twin donor is 3-4 times higher than after transplant from an allogeneic donor. This anti-leukemic mechanism of transplanted donor cells has been termed graft-versus-leukemia (GVL) effect, and efforts are being directed toward utilizing such an immune-mechanism after autologous transplantation. Since interleukin-2 (IL-2) can induce remissions in selected patients with advanced leukemia, it has become a candidate cytokine to be used in attempts to introduce GVL after autologous stem cell transplantation. Here we review the available clinical data with IL-2 and critically evaluate whether IL-2 has a place as adjunct treatment to prevent relapse after autologous transplantation for acute leukemia.

Interleukin-2 bolus infusion as late consolidation therapy in 2nd remission of acute myeloblastic leukemia

The activation of autologous cytotoxic cells by interleukin-2 (IL-2) may be a promising tool for elimination of minimal residual blast populations in patients with acute myelocytic leukemia (AML) to prolong disease-free survival. Here, we report the results of a phase II study using IL-2 for consolidation therapy in patients with second remission of de novo AML. All patients in 1st relapse of AML received a uniform induction therapy consisting of intermediate high-dose AraC (iHDAraC) 2 x 600 mg/m2 d1-4 and VP-16 100 mg/m2 d1-7. Patients achieving 2nd remission were treated with 4 cycles recombinant IL-2 (rIL-2) 9 x 10(6) IU/m2 administered on d1-5 and 8-12/cycle as 1h infusion every six weeks. In 37/66 (56%) evaluable patients, complete remission (CR) was achieved. So far, 21/37 patients (4 after additional autologous bone marrow transplantation (ABMT) received rIL-2 consolidation. Three patients are too early for evaluation, 4 received allogeneic BMT, 6 relapsed before IL-2 was scheduled and 4 refused treatment with rIL-2. The median disease-free survival (DFS) was 11 (4-49+) months. Up to now, in 5/21 (24%) patients the duration of 2nd remission exceeded that of 1st remission 7/21 (33%) are in ongoing 2nd remission (7+ to 49+ months). The side effects of rIL-2 were generally moderate and manageable. Only in two patients, previously treated with ABMT, severe side effects occurred; septicaemia and pneumonia in one patient and desquamative erythrodermia in the second one. In accordance with other studies rebound lymphocytosis with a marked increase of CD56(+)-cells and release of secondary cytokines such as TNF-alpha, IFN-gamma and IL-6 was observed. The schedule is feasible and the data suggest a possible benefit for DFS, which, however has to be confirmed by randomized trials.

Interleukin-2 and gene therapy in the management of acute lymphoblastic leukaemia

The overall unfavourable prognosis of adult acute leukaemia patients has prompted the search for alternative therapeutic strategies. Probably the most sought challenge, which over the years has been met by consistent disillusion, has been immunotherapy. With little doubt the goal of stimulating the immune system of the host in the hope of controlling or eradicating residual disease following more conventional ablative regimens, remains conceptually a highly desirable approach. During the last few years an innovative strategy, based on the in vitro demonstration that IL2 is capable of inducing a previously unrecognized cytotoxic function directed against primary tumours and named LAK, has been applied with some success in solid tumour patients. Here, we shall review the pre-clinical data which indicate that IL2-based immunotherapy may be employed also in the management of patients with acute leukaemia. Clinical data which support a possible in vivo antileukaemic effect of IL2 are presented. The clinicohaematological modifications, as well as the biological modulations induced in the patients following the administration of IL2 are also discussed. In view of the recent demonstration that the IL2 gene can be successfully transduced into human neoplastic cells, we finally discuss the rationale of gene transfer approaches in an attempt to overcome some of the limitations associated with the administration of high doses of exogenous IL2.

Interleukin 2 treatment in acute myelogenous leukemia

Significant clinical responses obtained with interleukin 2 (IL-2) in solid tumors such as renal cell cancer and malignant melanoma prompted the use of this immunomodulatory drug to verify its activity in hematological malignancies. Several preclinical experiments showed an activity of IL-2 against leukemic cell lines in cultures, particularly in acute myeloid leukemia (AML), while only episodically a proliferative stimulus of IL-2 on the growth of leukemic blasts has been observed. Based on these preclinical studies, in the past five years several phase I-II clinical trials have verified IL-2 activity in AML in advanced phase, both in patients with active disease and in patients in further complete remission (CR). Data obtained are difficult to evaluate due to the low number and the heterogeneity of patients treated, but encouraging results have been reported in patients with "limited" disease (bone marrow blastosis < 30%), showing an antileukemic activity of IL-2 alone. Different international phase III trials are ongoing in AML patients in I CR after autologous bone marrow transplantation (Roussel-Uclaf, Romainville, France) and in II CR after conventional chemotherapy (Roche SpA, Milan, Italy) to verify the efficacy of IL-2 in reducing the risk of relapse and prolonging disease-free survival.

Agar capillary clonogenic microassays for cellular immunocytotoxic activities in human leukaemia and lymphoma

Current concepts of immunotherapeutic approaches in leukemias and lymphomas using activated cytotoxic lymphocytes and macrophages are briefly reviewed. Defective cellular immunocytotoxic activities and effects of interleukins and chemotherapeutic drugs thereupon are discussed. In vitro assays to measure lymphokine-activated killer (LAK) and natural killer (NK) cell activities suffer from various problems, depending on the quality of the endpoints. Our clonogenic microassay for LAK cell activity, using agar-containing glass capillaries, avoids some of the potential artifacts and offers several advantages that are discussed. As an example the stimulatory effect of low mafosfamide concentrations on the LAK cell activity versus K562 human myeloid leukemia cells is demonstrated. Thus, our clonogenic LAK microassay provides a valid tool for preclinical screening of immunomodulatory agents.

Effects of interleukin 2 on myelodysplastic syndromes

To evaluate the clinical usefulness of interleukin 2 (IL-2) on myelodysplastic syndromes (MDS), the serum IL-2 level, the effect of IL-2 on the proliferation of blasts, and the cell-mediated cytotoxic effect of IL-2 on blasts were examined in MDS patients. Of 18 patients, 2 patients had an increased serum IL-2 level. Although the proliferation of blasts in most cases, including the two patients having a high serum IL-2 level, was not stimulated by IL-2, the blasts of one case apparently proliferated in response to IL-2. It was also clearly shown that IL-2-stimulated normal peripheral blood mononuclear cells (PBMNC) showed cytotoxicity against MDS blasts, whereas the PBMNC of the advanced stages of MDS were usually defective in regard to this IL-2-dependent cytotoxicity. The therapeutic usefulness of IL-2 or lymphokine-activated killer cells for MDS was not established by the present study.

Interleukin-2 receptor alpha chain on acute myelocytic leukemia cells is involved in cell-to-cell interactions

Leukemic cells from 21 to 197 adult patients with de novo acute myelocytic leukemia (AML) were positive for IL-2R alpha chain (IL-2R alpha), whereas IL-2R beta chain (IL-2R beta), which is responsible for IL-2 signal transduction, was not found on leukemic cells from any of these cases tested. The expression of IL-2R alpha was closely associated with that of adhesion molecules CD4, CD11b and CD22, and endopeptidase CD10. None of the IL-2R alpha (+) AML cells responded to recombinant human IL-2. These data suggest that IL-2R alpha on AML cells may not be involved in cellular proliferation as one of growth factor receptors but may have a role in the control of cell-to-cell interactions.

IL2 treatment for cancer: from biology to gene therapy

In this review we shall discuss the biological rationale and the clinical findings obtained using Interleukin 2 (IL2)-based immunotherapy in the management of cancer patients. Objective and long-lived clinical responses have been documented in a proportion of cases, particularly renal cell carcinoma, melanoma and acute myeloid leukaemia. Though encouraging, the clinical use of IL2 has so far been limited by toxicity, as well as by the heterogeneous and unpredictable responses and by the lack of specific anti-tumour effect. These considerations have led to the belief that more sophisticated technologies aimed at introducing the IL2 gene into the neoplastic cells may potentially overcome some of the limitations coupled to the in vivo infusion of high doses of IL2. The data accumulated in animal models and, more recently, also with human tumour cells indicate that the IL2 gene may be successfully inserted into neoplastic cells. The constitutive secretion of IL2 by the tumour cells leads to a reduced or abrogated tumorigenicity in several different tumour models. The evidence that in some experimental tumours the transduction of the IL2 gene into the neoplastic cells may elicit a specific cytotoxic response and confer anti-tumour memory, suggests that vaccination protocols based on this innovative strategy may represent a potential new tool in the management of cancer patients.

Trying to overcome residual disease after bone marrow transplantation for hematologic malignancies

Relapse after marrow transplantation occurs despite total body irradiation and high doses of chemotherapy used to prepare the recipient. Recurrence rate is particularly high after autologous transplantation. In order to eliminate minimal residual disease persistent after marrow grafting, immunotherapy is currently being explored as a treatment modality that is non-cross-reactive with radiation and chemotherapy. This review describes first clinical results on the use of interferons and interleukin-2 in marrow transplant recipients as well as attempts to induce graft-versus-leukemia effects.

Interleukin-2-induced increase of a monoclonal B-cell lymphocytosis. A novel in vivo interleukin-2 effect?

A 56-year-old man with refractory B-cell lymphocytic non-Hodgkin's lymphoma was treated in a Phase II study with interleukin-2 (IL-2) (Roussel-Uclaf, Romainville, France). The patient had involvement of multiple lymph nodes and medullary and peripheral blood (3.6 x 10(9) monoclonal CD19-positive [CD19+] B-lymphocytes/l). After a 5-day cycle of IL-2 treatment, an eightfold increase of the monoclonal CD19+ population was observed (27 x 10(9) monoclonal CD19+ cells). The lymphocytosis decreased dramatically during the second cycle (days 15 to 19) of IL-2 treatment, resulting in 6 x 10(9)/l peripheral lymphocytes, with 5.5 x 10(9) B-lymphocytes. As soon as day 20, peripheral B-cells again increased considerably, with 32 x 10(9) CD19+ cells/l at day 27. The CD19+ population remained monoclonal as assessed by kappa/lambda cell-surface phenotyping and kappa gene rearrangement evaluation. Kinetics of the monoclonal B-lymphocyte response to IL-2 paralleled the natural killer/lymphokine-activated killer and T-cell response, with a 4-day latency period, suggesting an indirect enhancing effect of IL-2. Before and during IL-2 treatment, peripheral B-lymphocytes never expressed detectable levels of the p55 IL-2 receptor. However, the p75 IL-2 receptor was expressed significantly in the IL-2-responsive monoclonal B-cell population. Tumor necrosis factor alpha, a known (in vitro) B-cell tumor growth factor, reached high serum levels during IL-2 treatment. Response evaluation at day 45 showed stability of the lymph node involvement and the marrow lymphocyte infiltrate. At day 45, peripheral B-cell lymphocytosis was 7.5 x 10(9)/l. To the knowledge of the authors, this is the first report of an in vivo IL-2-induced reversible increase of peripheral monoclonal B-cell lymphocytosis.

Continuous intravenous infusion of high-dose recombinant interleukin-2 for acute myeloid leukaemia--a phase II study

A group of 13 patients with acute myeloid leukaemia of differing disease status were treated with continuous intravenous infusion of high-dose recombinant interleukin-2 (rIL-2). There was up-regulation of the cellular cytotoxic functions in all these patients following the rIL-2 therapy, with increase in the natural killer (NK) activity, lectin-dependent cellular cytotoxicity, induction of cytotoxicity-linked cytoplasmic serine esterase and lymphocyte activation. However, the clinical response to rIL-2 in these patients was disappointing, especially in patients treated in frank relapse. Although 1 patient treated in early second relapse achieved a third complete remission, the duration of the remission was brief and lasted only 6 months. Adverse reactions among these patients were common. Whether or not lymphokine-activated killer cells are needed to improve the response rate over rIL-2 alone in these patients deserves further investigation.

Graft versus leukaemia effects after marrow transplantation in man

A graft versus leukaemia (GvL) effect makes a significant contribution to the lower risk of relapse seen in patients after BMT compared with patients receiving chemotherapy alone. Both T cell-dependent and T cell-independent effectors of GvL exist, and both may play an important role in the elimination of minimal residual disease after BMT. There is evidence that GvL activity may be separable from GvHD either by identifying T cell clones recognizing specific leukaemia antigens or by using immunomodulatory drugs or cytokines to enhance T cell-independent GvL mechanisms which operate without alloreactivity and therefore without concomitant exacerbation of GvHD. These approaches should improve survival after both autologous and allogeneic BMT.

Treatment of acute myeloid leukaemia patients with recombinant interleukin 2: a pilot study

Twelve patients with acute myeloid leukaemia (AML) with evidence of resistant disease were treated with recombinant interleukin 2 (rIL2) given intravenously by continuous infusion. No objective response to rIL2 alone was documented in the seven patients with advanced disease (20-90% resistant blasts in the marrow), except for a partial response to rIL2 plus chemotherapy in one. Of the five patients with limited disease (8-15% marrow blasts), three obtained a complete disappearance of the blasts following two to four 5d courses of rIL2 alone. One patient persists in fourth complete remission (CR) 30 months later, another obtained a third CR for 4 months, and the last remained in third CR for 9 months before relapsing. This latter patient achieved a fourth CR with low-dose cytarabine. The remissions have been maintained with low-dose monthly courses of rIL2 given on an out-patient basis. Two AML did not respond to rIL2 alone; one, however, obtained a fourth CR with chemotherapy and rIL2. Administration of rIL2 was accompanied by organomegaly and leucocytosis, with a frequent lymphocytosis and increase in eosinophils and large granular lymphocytes, both in the blood and in the marrow. Side effects, though often severe, were controllable using a daily dose escalating protocol and never required intensive care treatment. The results of this pilot study indicate that treatment of AML patients with rIL2 is feasible and may result in the disappearance of chemotherapy-resistant blasts in patients with limited but detectable disease. Further controlled trials in AML in CR appear warranted.

Growth of certain myeloid leukemic cells can be stimulated by interleukin-2

The effect of recombinant interleukin-2 (IL-2) on the proliferation of T-cell depleted leukemic blasts was evaluated in 23 patients with acute myelogenous leukemia (AML). For this purpose, the effect of IL-2 on cell growth, [3H]-thymidine incorporation into the blasts and the expression of IL-2 receptors on cell surface using T-cell depleted blasts were studied. The results showed that IL-2 stimulated [3H]-thymidine incorporation significantly in blasts of 8 out of 23 cases of AML. An IL-2 induced increase in cell number was directly demonstrated in seven out of eight IL-2 responsive patients studied. IL-2 stimulated the proliferation of blasts in monocytic lineage (M4 and M5), but not all M4/M5 leukemics responded to rIL-2. Stimulation of the growth of leukemic cells was not correlated with the expression of Tac antigen on the cell surface, but it was significantly correlated with the expression of IL-2 receptor (IL-2R) beta chain on the cell surface. These results indicate that IL-2 is an active growth factor in certain myeloid leukemia cells, especially of monocytic type.