Immunological evaluation of patients with hematological malignancies receiving ambulatory cytokine-mediated immunotherapy with recombinant human interferon-alpha 2a and interleukin-2

Novel insights into immune cells modulation of tumor resistance

Tumor resistance poses a significant challenge to effective cancer treatment, making it imperative to explore new therapeutic strategies. Recent studies have highlighted the profound involvement of immune cells in the development of tumor resistance. Within the tumor microenvironment, macrophages undergo polarization into the M2 phenotype, thus promoting the emergence of drug-resistant tumors. Neutrophils contribute to tumor resistance by forming extracellular traps. While T cells and natural killer (NK) cells exert their impact through direct cytotoxicity against tumor cells. Additionally, dendritic cells (DCs) have been implicated in preventing tumor drug resistance by stimulating T cell activation. In this review, we provide a comprehensive summary of the current knowledge regarding immune cell-mediated modulation of tumor resistance at the molecular level, with a particular focus on macrophages, neutrophils, DCs, T cells, and NK cells. The targeting of immune cell modulation exhibits considerable potential for addressing drug resistance, and an in-depth understanding of the molecular interactions between immune cells and tumor cells holds promise for the development of innovative therapies. Furthermore, we explore the clinical implications of these immune cells in the treatment of drug-resistant tumors. This review emphasizes the exploration of novel approaches that harness the functional capabilities of immune cells to effectively overcome drug-resistant tumors.

Interferon-α Is Effective for Treatment of Minimal Residual Disease in Patients with t(8;21) Acute Myeloid Leukemia After Allogeneic Hematopoietic Stem Cell Transplantation: Results of a Prospective Registry Study

BACKGROUND

RUNX1-RUNX1T1 transcript levels were established as a powerful marker for predicting relapse in patients with t(8;21) acute myeloid leukemia (AML). We aimed to identify the efficacy of minimal residual disease (MRD)-directed interferon-alpha (IFN-α) treatment in patients with t(8;21) AML who were positive for MRD after allogeneic hematopoietic stem cell transplantation (allo-HSCT; n=42).

SUBJECTS, MATERIALS, AND METHODS

MRD-positive status was defined as a <4.5-log reduction from diagnosis in RUNX1-RUNX1T1 transcripts and/or the loss of a ≥4.5-log reduction after 3 months after HSCT. Patients with positive MRD received six cycles of IFN-α treatment (twice or thrice weekly of every 4 weeks cycle).

RESULTS

The 1-year cumulative incidence of severe acute and chronic graft-versus-host disease after MRD-directed IFN-α treatment was 7.1% and 4.8%, respectively. After the treatment, 15 (35.7%), 5 (11.9%), 3 (7.1%), and 9 (21.5%) patients achieved MRD negativity at 1, 2, 3, and >3 months, respectively. Three patients relapsed after the IFN-α treatment, in which the 1-year cumulative incidence of relapse was 7.2%. One patient died of severe infection at 460 days after treatment. The 1-year probabilities of event-free survival, disease-free survival, and overall survival after treatment were 76.0%, 92.4%, and 92.5%, respectively. The clinical outcomes in patients who received MRD-directed IFN-α treatment were significantly better than those of the MRD-positive patients without any interventions in the historical cohort.

CONCLUSION

MRD-directed IFN-α treatment is effective for patients with t(8;21) AML who were MRD-positive after allo-HSCT. The study was registered at http://clinicaltrials.gov as NCT02027064.

IMPLICATIONS FOR PRACTICE

In patients with t(8;21) acute myeloid leukemia (AML), the presence of post-allogeneic hematopoietic stem cell transplantation (allo-HSCT) minimal residual disease (MRD), measured by RUNX1-RUNX1T1 transcript levels, has been established as a powerful marker for predicting relapse. Interferon-alpha (IFN-α) could exert a relatively strong graft-versus-leukemia effect, and MRD-directed IFN-α treatment is effective for patients with t(8;21) AML who were MRD-positive after allo-HSCT.

Dendritic cell-based immunotherapy for myeloid leukemias

Acute and chronic myeloid leukemia (AML, CML) are hematologic malignancies arising from oncogene-transformed hematopoietic stem/progenitor cells known as leukemia stem cells (LSCs). LSCs are selectively resistant to various forms of therapy including irradiation or cytotoxic drugs. The introduction of tyrosine kinase inhibitors has dramatically improved disease outcome in patients with CML. For AML, however, prognosis is still quite dismal. Standard treatments have been established more than 20 years ago with only limited advances ever since. Durable remission is achieved in less than 30% of patients. Minimal residual disease (MRD), reflected by the persistence of LSCs below the detection limit by conventional methods, causes a high rate of disease relapses. Therefore, the ultimate goal in the treatment of myeloid leukemia must be the eradication of LSCs. Active immunotherapy, aiming at the generation of leukemia-specific cytotoxic T cells (CTLs), may represent a powerful approach to target LSCs in the MRD situation. To fully activate CTLs, leukemia antigens have to be successfully captured, processed, and presented by mature dendritic cells (DCs). Myeloid progenitors are a prominent source of DCs under homeostatic conditions, and it is now well established that LSCs and leukemic blasts can give rise to "malignant" DCs. These leukemia-derived DCs can express leukemia antigens and may either induce anti-leukemic T cell responses or favor tolerance to the leukemia, depending on co-stimulatory or -inhibitory molecules and cytokines. This review will concentrate on the role of DCs in myeloid leukemia immunotherapy with a special focus on their generation, application, and function and how they could be improved in order to generate highly effective and specific anti-leukemic CTL responses. In addition, we discuss how DC-based immunotherapy may be successfully integrated into current treatment strategies to promote remission and potentially cure myeloid leukemias.

Interferon-α in acute myeloid leukemia: an old drug revisited

Interferon-α (IFN-α), a type I IFN, is a well-known antitumoral agent. The investigation of its clinical properties in acute myeloid leukemia (AML) has been prompted by its pleiotropic antiproliferative and immune effects. So far, integration of IFN-α in the therapeutic arsenal against AML has been modest in view of the divergent results of clinical trials. Recent insights into the key pharmacokinetic determinants of the clinical efficacy of IFN along with advances in its pharmaceutical formulation, have sparked renewed interest in its use. This paper reviews the possible applicability of IFN-α in the treatment of AML and provides a rational basis to re-explore its efficacy in clinical trials.

Therapeutic use of Aldara in chronic myeloid leukemia

The potent clinical responses seen in patients with chronic myeloid leukemia (CML) after administration of donor-specific lymphocytes, as well as the correlation between the presence of antigen specific T cells and prolonged remission in these patients, suggests a role for the immunological control of CML. Here we propose Aldara™, a clinically used formulation of imiquimod, as an agent for augmenting immune responses to CML antigens. Our proposition is based upon 3 tenets: 1) Endogenous dendritic cells (DC) of CML patients, which are known to be derived from the malignant clone, express and present various leukemic antigens; 2) CML-antigen reactive T cell clones exist in the patient but in many situations are ineffectively stimulated to cause significant hematological responses; and 3) Antigen presentation by mature, activated DC, which endogenously express CML-antigens may endow the pre-existing ineffective T cell responses with ability to control CML progression. The practical use of Aldara™ as a localized activator of DC in the context of present day leukemic therapeutics, as well as various properties of this unique immune modulator will be discussed.

Immune reconstitution following allogeneic stem cell transplantation in recipients conditioned by low intensity vs myeloablative regimen

We have investigated the immune status of patients with hematologic malignancies treated with a low intensity conditioning in preparation for allogeneic stem cell transplantation. Conditioning consisted of fludarabine, anti-T lymphocyte globulin and low-dose busulfan, followed by infusion of allogeneic blood stem cells. This protocol resulted in rapid engraftment and complete replacement of host with donor hematopoietic cells. Immunological parameters of these patients were compared to those patients who were conditioned by an aggressive myeloablative regimen. Distribution of cell surface markers of lymphocyte subsets from both groups of patients was similar, but different from that of normal control cells. Reduced intensity or non-myeloablative conditioning prior to allogeneic stem cell transplantation (NST), hardly lowered the normal T cell-dependent mitogenic response even during the early period following transplant, while the myeloablative treatments resulted in a suppressed mitogenic reaction and in slow immune recovery. Reactivity of non-MHC restricted cytotoxic T cells was also at a normal level in patients who were treated with NST. We conclude that stem cell engraftment following reduced conditioning may result in early reconstitution of immune responses assessed in vitro. We hypothesize that clinical application of NST may lead to faster development of effective immune responses against residual host-type malignant and abnormal non-malignant hematopoietic cells, although the role of fludarabine on post-transplant infections remains to be investigated in a larger cohort of patients.

Immunotherapy in conjunction with autologous and allogeneic blood or marrow transplantation in lymphoma

Relapse is the major obstacle for successful transplantations in lymphoma. One of the ways to reduce relapse rates is to intensify immune-mediated effector mechanisms. Graft-versus-lymphoma may be achieved either by administration of cytokines or by allogeneic cell-mediated adoptive immunotherapy. The use of allogeneic non-myeloablative stem cell transplantation (SCT) is another option which may be applicable to all age groups. It remains to be seen whether non-myeloablative SCT will result in a lesser degree of relapse and higher disease-free survival in lymphoma patients.

Immunotherapy With Recombinant Human Interleukin-2 and Recombinant Interferon-α in Lymphoma Patients Postautologous Marrow or Stem Cell Transplantation

Immune-mediated effects appear to play a major role in controlling minimal residual disease (MRD). We, therefore, investigated the role of recombinant human interleukin-2 (rIL-2) given concomitantly with interferon-α (IFN-α) in malignant lymphoma (ML) patients with responding disease following autologous bone marrow or blood stem cell transplantation (ABSCT). Fifty-six patients were included in this investigation. Thirty-two patients had non-Hodgkin's lymphoma (NHL) and 24 patients had Hodgkin's disease (HD). Sixty-one patients (NHL 36, HD 25) served as historical controls. Patients from both groups had similar demographic characteristics, the same stage of disease at presentation, status of disease at transplantation, conditioning regimens, and type of transplant. rIL-2 and IFN-α were selfadministered in two cycles beginning 2.5 to 10.5 months (median, 4 months) posttransplant and separated by a 4-week interval. Each cycle consisted of IFN-α subcutaneously (SC) 3 × 106 U/d × 5 d/wk combined with rIL-2 SC 3 to 6 IU/m2/d × 5 d/wk for 4 weeks. The incidence of survival and disease-free survival (DFS) was significantly higher in the group under investigation than in the historical controls (P < .01). Of 56 patients with ML treated with IFN-α + rIL-2, 45 patients are DFS (80.4%) after a follow-up of 7 to 78 months (median, 34 months), whereas in the historical controls, 32 of 61 (52.5%) patients are disease free, in a follow-up of 4 to 84 months (median, 23 months) posttransplant (P < .01). Our preliminary results are encouraging and suggest that home administered immunotherapy with IFN-α and rIL-2 is relatively well tolerated and may intensify remission in ML patients with MRD following ABSCT.

Activated long-term peripheral blood cultures as preparation for adoptive alloreactive cell therapy in cancer patients

Different modes of in vitro activation of peripheral blood mononuclear cells (PBMC) were compared for their effect on long-term propagation. PBMC cultures were activated by short exposures to the mitogen phytohemagglutinin (PHA) and the CD3 complex, with or without secondary signals provided by ligands of CD28 costimulatory molecules. Activation and long-term cultures were carried out in the presence of recombinant interleukin-2 (rIL-2). Addition of supernatant derived from IL-2-activated PBMC improved culture cell yield. Cumulative fold expansions ranged between 10(3) and 10(5) within 21 days. The highest cell yield was found after PHA activation. Fewer cells were obtained after activation with a combination of CD3 and CD28, and even fewer were obtained after CD3 activation alone. An increase in CD8+ and CD56+ cells, without change in CD4+ cells, was found in activated cultures when compared with fresh PBMC. Non-MHC-restricted cytotoxic activity was documented in all activated cultures. Cytotoxic activity per culture was highest in PHA-activated PBMC because of the high cell yield on the day of harvest. Successful in vitro expansion of PBMC might be helpful for gene transfer into T lymphocytes, as well as for the induction of an antitumor response, particularly for prevention and treatment of relapse of hematologic malignancies following allogeneic or autologous bone marrow transplantation.

Autologous bone marrow and peripheral blood stem cell transplantation in haematological malignancies: current status

Autologous bone marrow and peripheral blood stem cell transplants permit the use of higher doses of chemoradiotherapy than would have been possible without "rescuing' bone marrow function. This may well allow cure of malignant disorders in cases where this was previously not feasible. This short review attempts to summarize the current status of such a treatment approach for the various haematological malignancies.

Effects of BCR-ABL antisense oligonucleotides (AS-ODN) on human chronic myeloid leukemic cells: AS-ODN as effective purging agents

We examined phosphorothioate oligodeoxyribonucleotides (ODNs) directed against bcr in exon 3 or exon 2, which are rearranged with exon 2 of abl (B3A2 and B2A2) at t(9;22) of chronic myelogenous leukemia (CML). Since these ODNs are designed to be CML cell specific, we studied their effects on the human CML cell line K562, which is known to have B3A2 rearrangement, and leukemic cells from patients, as well as normal hematopoietic stem cells in vitro. In vitro experiments were performed to determine a potential role of these two ODNs as ex vivo purging agents. Incubation of B3A2 antisense at 40, 80, and 120 micrograms/ml with K562 CML cells for 72 hours at 37 degrees C resulted in 44%, 56%, and 63% reduction of CFU-L as compared to controls. In contrast, B3A2 sense and B2A2 antisense had no significant growth inhibitory effect on K562 cells. Incubation of B3A2 and B2A2 antisense ODNs at concentration of 80 micrograms/ml at 37 degrees C for 36 hours with normal peripheral blood stem/progenitor cells (PBSC) resulted in 124% and 98% CFU-GM formation as compared to untreated controls, respectively. However, incubation of PBSC with B3A2 and B2A2 sense-ODNs resulted in a 22% and 44% reduction in CFU-GM, respectively. In order to determine the ex vivo purging effects of bcr-abl ODNs, the K562 cells were mixed with PBSC from normal donors at a ratio of 1:20 (CML:PBSC). The mixture of cells was then incubated with B3A2 antisense at 80 micrograms/ml for 36 hrs at 37 degrees C. After incubation, no CML cells were detected by fluorescence in situ hybridization (FISH) as compared to untreated controls. These results were confirmed by RT-PCR using bcr-abl primers and mRNA isolated from the mixture of cells. Further, these results support the hypothesis that bcr-abl antisense ODNs are potentially effective agents for ex vivo purging of autologous stem cells before transplantation to eliminate/reduce the burden of leukemic cells. No significant toxicity to normal hematopoietic stem/progenitor cell population by the bcr-abl antisense ODNs was observed. Although unanticipated reductions in normal hematopoietic progenitor cells (CFU-GM) were observed with sense ODNs, no reduction in CFU-GM was observed with unrelated phosphorothioate ODN controls.

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.

Relative roles of natural killer- and T cell-mediated anti-leukemia effects in chronic myelogenous leukemia patients treated with interferon-alpha

Potential anti-leukemia effects mediated by T cells or by natural killer (NK) cells were investigated in chronic myelogenous leukemia (CML) patients treated with interferon-alpha. Therapy-associated modulation of T cell and NK reactivity was monitored for one year from initiation in autologous mixed lymphocyte-tumor cell reactions and cytotoxicity directed against autologous CML cells, respectively. During the course of IFN-therapy, NK activity against autologous CML cells increased steadily, whereas T cell reactivity fluctuated randomly. Despite the high level of T cell reactivity to autologous tumor cells in short-term (6 days) culture, 1) they failed to respond to synthetic peptides corresponding to the bcr/abl fusion sequence of the patient, and 2) only one proliferative T cell clone (TCC) was isolated which specifically recognized HLA-DR-matched CML cells. This TCC appeared not to recognize synthetic peptides corresponding to the bcr/abl fusion sequence of the patient; the antigen to which it responds remains unknown. To assess potential immunogenicity of bcr/abl peptides, it was attempted to sensitize T cells from normal donors in vitro. Of 109 cell lines obtained from seven different donors, eleven showed peptide-dependent proliferation. Therefore, although these results show that it is possible to isolate apparently CML-specific T cells from patients, as well as to prime T cells against tumor-specific peptide in vitro, the frequency of such T cell-mediated reactivity appears low and its relevance to anti-leukemic effects questionable. On the other hand, the strong time-dependent enhancement of natural killing of autologous CML blasts during IFN-alpha treatment, a phenomenon not observed for T cell reactivity, suggests that natural immunity may be more important in controlling disease.