Successful treatment of a chronic-phase T-315I-mutated chronic myelogenous leukemia patient with a combination of imatinib and interferon-alfa

C/EBPβ is a critical mediator of IFN-α-induced exhaustion of chronic myeloid leukemia stem cells

Even in the era of ABL tyrosine kinase inhibitors, eradication of chronic myeloid leukemia (CML) stem cells is necessary for complete cure of the disease. Interferon-α (IFN-α) has long been used for the treatment of chronic-phase CML, but its mechanisms of action against CML stem cells remain unclear. We found that IFN-α upregulated CCAAT/enhancer binding protein β (C/EBPβ) in BCR-ABL-expressing mouse cells by activating STAT1 and STAT5, which were recruited to a newly identified 3' distal enhancer of Cebpb that contains tandemly aligned IFN-γ-activated site elements. Suppression or deletion of the IFN-γ-activated site elements abrogated IFN-α-dependent upregulation of C/EBPβ. IFN-α induced differentiation and exhaustion of CML stem cells, both in vitro and in vivo, in a C/EBPβ-dependent manner. In addition, IFN-α upregulated C/EBPβ and induced exhaustion of lineage^- CD34⁺ cells from CML patients. Collectively, these results clearly indicate that C/EBPβ is a critical mediator of IFN-α-induced differentiation and exhaustion of CML stem cells.

Assessing Measurable Residual Disease in Chronic Myeloid Leukemia. BCR-ABL1 IS in the Avant-Garde of Molecular Hematology

Chronic myelogenous leukemia (CML) is a malignancy of the myeloid cell lineage characterized by a recurrent chromosomal abnormality: the Philadelphia chromosome, which results from the reciprocal translocation of the chromosomes 9 and 22. The Philadelphia chromosome contains a fusion gene called BCR-ABL1. The BCR-ABL1 codes for an aberrantly functioning tyrosine kinase that drives the malignant proliferation of the founding clone. The advent of tyrosine kinase inhibitors (TKI) represents a landmark in the treatment of CML, that has led to tremendous improvement in the remission and survival rates. Since the introduction of imatinib, the first TKI, several other TKI have been approved that further broadened the arsenal against CML. Patients treated with TKIs require sensitive monitoring of BCR-ABL1 transcripts with quantitative real-time polymerase chain reaction (qRT-PCT), which has become an essential part of managing patients with CML. In this review, we discuss the importance of the BCR-ABL1 assay, and we highlight the growing importance of BCR-ABL1 dynamics. We also introduce a mathematical correction for the BCR-ABL1 assay that could help homogenizing the use of the ABL1 as a control gene. Finally, we discuss the growing body of evidence concerning treatment-free remission. Along with the continuous improvement in the therapeutic arsenal against CML, the molecular monitoring of CML represents the avant-garde in the struggle to make CML a curable disease.

Ponatinib in chronic myeloid leukemia (CML): Consensus on patient treatment and management from a European expert panel

Five tyrosine kinase inhibitors (TKIs) are currently approved in the European Union for treatment of chronic myeloid leukemia (CML) and all have considerable overlap in their indications. While disease-specific factors such as CML phase, mutational status, and line of treatment are key to TKI selection, other important features must be considered, such as patient-specific comorbidities and TKI safety profiles. Ponatinib, the TKI most recently approved, has demonstrated efficacy in patients with refractory CML, but is associated with an increased risk of arterial hypertension, sometimes severe, and serious arterial occlusive and venous thromboembolic events. A panel of European experts convened to discuss their clinical experience in managing patients with CML. Based on the panel discussions, scenarios in which a CML patient may be an appropriate candidate for ponatinib therapy are described, including presence of the T315I mutation, resistance to other TKIs without the T315I mutation, and intolerance to other TKIs.

Deep molecular response by IFN-α and dasatinib combination in a patient with T315I-mutated chronic myeloid leukemia

The T315I mutation is especially challenging as it confers resistance to all first- and second-generation tyrosine kinase inhibitors. We present here a chronic myeloid leukemia patient harboring the T315I and E255V BCR-ABL1 mutation successfully achieved deep molecular response with a combined treatment of dasatinib and IFN-α. To our knowledge, this is the second case of a T315I-bearing chronic myeloid leukemia patient displaying satisfactory response to the combination therapy of dasatinib and IFN-α.

Interferon-α Revisited: Individualized Treatment Management Eased the Selective Pressure of Tyrosine Kinase Inhibitors on BCR-ABL1 Mutations Resulting in a Molecular Response in High-Risk CML Patients

Bone marrow transplantation or ponatinib treatment are currently recommended strategies for management of patients with chronic myeloid leukemia (CML) harboring the T315I mutation and compound or polyclonal mutations. However, in some individual cases, these treatment scenarios cannot be applied. We used an alternative treatment strategy with interferon-α (IFN-α) given solo, sequentially or together with TKI in a group of 6 cases of high risk CML patients, assuming that the TKI-independent mechanism of action may lead to mutant clone repression. IFN-α based individualized therapy decreases of T315I or compound mutations to undetectable levels as assessed by next-generation deep sequencing, which was associated with a molecular response in 4/6 patients. Based on the observed results from immune profiling, we assumed that the principal mechanism leading to the success of the treatment was the immune activation induced with dasatinib pre-treatment followed by restoration of immunological surveillance after application of IFN-α therapy. Moreover, we showed that sensitive measurement of mutated BCR-ABL1 transcript levels augments the safety of this individualized treatment strategy.

Sustaining integrating imatinib and interferon-α into maintenance therapy improves survival of patients with Philadelphia positive acute lymphoblastic leukemia ineligible for allogeneic stem cell transplantation

We report the clinical results of sustainedly integrating imatinib and interferon-α into maintenance therapy in the patients ineligible for allogeneic hematopoietic stem cell transplantation (allo-HSCT). Maintenance therapy lasted for 5 years with imatinib 400 mg daily, interferon-α 3 million units, 2∼3 doses per week, and chemotherapy including vindesine and dexamethasone scheduled monthly in first year, once every 2 months in second year, and once every 3 months in third year. The chemotherapy was discontinued after 3 years and the imatinib and interferon-α continued for another 2 years. For 41 patients without allo-HSCT with a median follow-up of 32 months, the 3-year DFS and OS were 42.7  ± 8.6% and 57.9  ± 8.4%, respectively. Our study suggests that sustaining maintenance with low-dose chemotherapy, imatinib and interferon-α improved survival of adult Philadelphia-positive acute lymphoblastic leukemia (Ph + ALL) patients ineligible for allo-HSCT, and even provided an opportunity for cure. BCR/ABL persistent negativity at 6 and 9 months may have benefit to choose suitable patients for the imatinib/interferon-α maintenance strategy.

Mechanisms of resistance to BCR-ABL TKIs and the therapeutic strategies: A review

BCR-ABL caused by the translocation of t(9,22) with elevated tyrosine-kinase activity could induce leukemia in mice, which established BCR-ABL as the molecular pathogenic event in CML (Chronic myeloid leukemia). In recent years, a variety of tyrosine kinase inhibitors (TKIs) targeting at BCR-ABL specifically and effectively have been developed, which has fundamentally promoted the treatment of CML. However, the efficacy of TKIs was limited by its resistance induced by the development of kinase domain mutations and other mechanisms illustrated. In this review, we summarized BCR-ABL inhibitors approved by Food and Drug Administration (FAD), with the same concerns focus on the resistant mechanisms of BCR-ABL inhibitors and therapeutic resistant strategies.

Immunology and immunotherapy of chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a clonal bone marrow stem cell neoplasia known to be responsive to immunotherapy. Despite the success of tyrosine kinase inhibitors (TKIs) targeting the BCR-ABL1 oncokinase, patients are not considered to be cured with the current therapy modalities. However, there have been recent advancements in understanding the immunobiology of the disease (such as tumor specific antigens and immunostimulatory agents), and this may lead to the development of novel, curative treatment strategies. Already there are promising results showing that a small proportion of CML patients are able to discontinue the therapy although they have a minimal amount of residual leukemia cells left. This implies that the immune system is able to restrain the tumor cell expansion. In this review, we aim to give a brief update of the novel aspects of the immune system in CML patients and of the developing strategies for controlling CML by the means of immunotherapy.

Enlarged memory T-cell pool and enhanced Th1-type responses in chronic myeloid leukemia patients who have successfully discontinued IFN-α monotherapy

A small proportion of chronic myeloid leukemia patients treated with interferon-α (IFN-α) monotherapy are able to discontinue the treatment without disease relapse although residual leukemia cells are present. Recently, we showed that these patients have increased amount of NK-cells and a distinct blood cytokine profile. We now aimed to study the function of NK- and T-cells in order to understand the role of the immune system in maintaining the treatment response after IFN-α discontinuation. The study included 13 patients: 5 patients were still treated with IFN-α monotherapy (IFN-ON, median treatment time 163 months) and 8 had stopped the treatment successfully (IFN-OFF, median time without therapy 42 months). Detailed immunophenotype and cytokine production of NK- and T-cells was analyzed with flow cytometry. In addition, the cytotoxicity of NK-cells was studied using K562 as target cells and both the degranulation and direct killing was measured. Compared to healthy controls, IFN-OFF patients had increased proportion of CD4⁺ effector memory (CCR7⁻CD45RA⁻; median 23% vs. healthy 16%, p = 0.009) and CD8⁺ central memory T-cells (CCR7⁺CD45RA⁻; median 26% vs. healthy 14%, p = 0.004). Further, upon stimulation the IFN-γ/TNF-α cytokine secretion by CD4⁺ T-cells was significantly enhanced in IFN-OFF patients (median 13.7% vs. healthy 7.8%, p = 0.01), and CD4+ effector and central memory cells were the main cytokine producers. No similar increase was observed in IFN-ON group (6.5%). In addition, the proportion of NK-cells was significantly increased in IFN-OFF patients (median IFN-OFF 24%, healthy 13%, p = 0.04), but their direct killing of K562 cells was impaired. The cytotoxicity of NK-cells was also diminished in IFN-ON patients. To conclude, in addition to elevated NK-cell count, IFN-OFF patients have increased amount of memory T-cells, which are able to induce strong cytokine response upon stimulation. This activity may contribute to the maintenance of prolonged remission after successful IFN-α discontinuation.

Resistance to tyrosine kinase inhibition therapy for chronic myelogenous leukemia: a clinical perspective and emerging treatment options

The development of tyrosine kinase inhibitors (TKIs) has led to extended lifespans for many patients with chronic myelogenous leukemia (CML). However, 20% to 30% of patients fail to respond, respond suboptimally, or experience disease relapse after treatment with imatinib. A key factor is drug resistance. The molecular mechanisms implicated in this resistance include those that involve upregulation or mutation of BCR-ABL kinase and those that are BCR-ABL independent. The clinical consequences of these molecular mechanisms of resistance for disease pathogenesis remain open for debate. This review summarizes the molecular mechanisms and clinical consequences of TKI resistance and addresses the current and future treatment approaches for patients with TKI-resistant CML.

Interferons as inducers of apoptosis in malignant cells

Discovered as antiviral cytokines, interferons (IFNs) are now also recognized for their capacity to inhibit the growth of malignant cells via activation of programmed cell death, better known as apoptosis. In this review, we will cover recent advances made in this field, as it pertains to the various proposed mechanisms of IFN-induced apoptosis and the characterization of IFN-responsive genes not previously known to have apoptotic function. Also mentioned here is a description of the activation and crosstalk of survival signaling pathways as a mode of IFN resistance that remains a persistent clinical adversary to overcome and the future of IFNs as antitumor agents.

Re-emergence of interferon-α in the treatment of chronic myeloid leukemia

Treatment for chronic myeloid leukemia (CML) has evolved from chemotherapy (busulfan, hydroxyurea) to interferon-α (IFNα), and finally to tyrosine kinase inhibitors such as imatinib. Although imatinib has profoundly improved outcomes for patients with CML, it has limitations. Most significantly, imatinib cannot eradicate CML primitive progenitors, which likely accounts for the high relapse rate when imatinib is discontinued. IFNα, unlike imatinib, preferentially targets CML stem cells. Early studies with IFNα in CML demonstrated its ability to induce cytogenetic remission. Moreover, a small percentage of patients treated with IFNα were able to sustain durable remissions after discontinuing therapy and were probably cured. The mechanisms by which IFNα exerts its antitumor activity in CML are not well understood; however, activation of leukemia-specific immunity may have a role. Some clinical studies have demonstrated that the combination of imatinib and IFNα is superior to either therapy alone, perhaps because of their different mechanisms of action. Nonetheless, the side effects of IFNα often impede its administration, especially in combination therapy. Here, we review the role of IFNα in CML treatment and the recent developments that have renewed interest in this once standard therapy for patients with CML.