The rocky road to personalized medicine in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a malignant disorder of the myeloid blood lineage characterized by impaired differentiation and increased proliferation of hematopoietic precursor cells. Recent technological advances have led to an improved understanding of AML biology but also uncovered the enormous cytogenetic and molecular heterogeneity of the disease. Despite this heterogeneity, AML is mostly managed by a ‘one‐size‐fits‐all’ approach consisting of intensive, highly toxic induction and consolidation chemotherapy. These treatment protocols have remained largely unchanged for the past several decades and only lead to a cure in approximately 30–35% of cases. The advent of targeted therapies in chronic myeloid leukaemia and other malignancies has sparked hope to improve patient outcome in AML. However, the implementation of targeted agents in AML therapy has been unexpectedly cumbersome and remains a difficult task due to a variety of disease‐ and patient‐specific factors. In this review, we describe current standard and investigational therapeutic strategies with a focus on targeted agents and highlight potential tools that might facilitate the development of targeted therapies for this fatal disease. The classes of agents described in this review include constitutively activated signalling pathway inhibitors, surface receptor targets, epigenetic modifiers, drugs targeting the interaction of the hematopoietic progenitor cell with the stroma and drugs that target the apoptotic machinery. The clinical context and outcome with these agents will be examined to gain insight about their optimal utilization.     

Immunoreactive calcitonin in leukaemia.

A radioimmunoassay was used to measure concentrations of immunoreactive human calcitonin (HCT) in plasma and leucocytes from patients with various leukaemic and myeloproliferative disorders. Plasma immunoreactive HCT concentrations were increased in 32 out of 33 patients with chronic granulocytic leukaemia (CGL) and in all eight patients with acute myeloid leukamia (AML) at presentation or in relapse. Out of 11 patients with other myeloproliferative disorders, eight had increased plasma immunoreactive HCT concentrations. Buffy-coat-cell extracts and culture media from peripheral leucocytes of patients with CGL also contained increased immunoreactive HCT concentrations. In contrast, plasma from patients with chronic lymphocytic leukaemia, acute lymphoblastic leukaemia, and AML in remission had low or undetectable immunoreactive HCT concentrations. Increased plasma and cellular concentrations of immunoreactive HCT may be a consequence of abnormal proliferation of myeloid cells and might prove to be valuable in predicting relapse in patients with myeloid leukaemias.     

Remission-induction of acute lymphoblastic transformation of chronic myeloid leukaemia, followed by long-term maintenance therapy

Acute lymphoblastic transformation of chronic myeloid leukaemia (LT-CML) of 7 consecutive patients was treated according to a remission-induction and maintenance therapy used for de novo acute lymphoblastic leukaemia (ALL). All 7 patients achieved a second chronic phase with a median remission duration of 15 months. Two patients showed an isolated central nervous system (CNS) relapse. This did not occur in the 4 patients, who received prophylactic therapy with intrathecal methotrexate. The second transformation was nonlymphoblastic in nature in 4 out of the 5 patients. A treatment protocol similar to that of a bad risk ALL, including long-term maintenance therapy and CNS-prophylaxis is indicated in lymphoblastic transformation of CML.     

Active Immunotherapy Used Alone for Maintenance of Patients with Acute Myeloid Leukaemia

A total of 32 patients suffering from acute myeloid leukaemia were initially treated with daunorubicin and cytosine arabinoside, and eight who achieved full remission were given a brief cytoreduction course of cyclophosphamide and thioguanine. Of these eight patients seven were then actively immunized with 10 irradiated allogeneic acute myeloid leukaemia cells and B.C.G. at weekly intervals. Six of these patients have survived in apparent good health for more than one year. Bone marrow changes suggestive of relapse were used as an indication for further short courses of chemotherapy, and except on single occasions in two different patients clinical relapse has been prevented. The average duration of first (bone marrow) remission appears to be comparable with the best achieved in trials using regular chemotherapy for maintenance, though criteria for determining relapse may be different. The rate of reinduction of remissions (bone marrow) in this series was high, with a subsequent increase in overall survival time. Possible explanations for the high rate of reinduction include, firstly, the effects of active immunization with specific leukaemia antigen; secondly, non-specific adjuvant effect; thirdly, avoidance of drug resistance; and, fourthly, early diagnosis of relapse by frequent bone marrow examinations.     

Bone marrow transplantation for leukaemia in Europe

The European Bone Marrow Transplant Leukaemia Registry has collected data from 52 European centers between 1979 and 1986. More than 2,000 transplants performed for a haematological malignancy were reported. The present analysis shows that the most important factor influencing leukaemia free survival, transplant related mortality and relapse incidence is the stage of the disease at the time of the transplant. Outcome is highly better when the transplant is performed for acute myeloid and acute lymphocytic leukaemia in first complete remission and for chronic myelocytic leukaemia in first chronic phase. Additional prognostic factors are age, the method for graft-versus-host disease prevention and the donor recipient sex combination. Results are better for younger patients, for patients given cyclosporine for prevention of graft-versus-host disease and are worse for male patients receiving a female donor bone marrow. The results are not influenced by the year of the transplant per se and by the center size.     

Response to the combined administration of interferons alpha and gamma after failure of single interferon therapy in chronic myelogenous leukaemia

A previously untreated patient with benign phase chronic myelogenous leukaemia (CML) was treated with recombinant Interferon alpha-2 b. Haematological remission was induced for a total of twelve months. Thereafter, the patient developed resistance to Interferon alpha manifested by an increase in leucocyte counts despite dose escalation (up to 7 x 10(6) IU/day s.c.). Subsequent treatment with recombinant Interferon gamma failed to control myeloid proliferation. However, combined administration of both Interferon alpha and Interferon gamma resulted in a renewed haematological remission which lasted six months.     

Epigenetic dysregulation of ID4 predicts disease progression and treatment outcome in myeloid malignancies

Promoter hypermethylation‐mediated inactivation of ID4 plays a crucial role in the development of solid tumours. This study aimed to investigate ID4 methylation and its clinical relevance in myeloid malignancies. ID4 hypermethylation was associated with higher IPSS scores, but was not an independent prognostic biomarker affecting overall survival (OS) in myelodysplastic syndrome (MDS). However, ID4 hypermethylation correlated with shorter OS and leukaemia‐free survival (LFS) time and acted as an independent risk factor affecting OS in acute myeloid leukaemia (AML). Moreover, ID4 methylation was significantly decreased in the follow‐up paired AML patients who achieved complete remission (CR) after induction therapy. Importantly, ID4 methylation was increased during MDS progression to AML and chronic phase (CP) progression to blast crisis (BC) in chronic myeloid leukaemia (CML). Epigenetic studies showed that ID4 methylation might be one of the mechanisms silencing ID4 expression in myeloid leukaemia. Functional studies in vitro showed that restoration of ID4 expression could inhibit cell proliferation and promote apoptosis in both K562 and HL60 cells. These findings indicate that ID4 acts as a tumour suppressor in myeloid malignancies, and ID4 methylation is a potential biomarker in predicting disease progression and treatment outcome.     

Proteomics‐based discovery of biomarkers for paediatric acute lymphoblastic leukaemia: challenges and opportunities

There are important breakthroughs in the treatment of paediatric acute lymphoblastic leukaemia (ALL) since 1950, by which the prognosis of the child majority suffered from ALL has been improved. However, there are urgent needs to have disease‐specific biomarkers to monitor the therapeutic efficacy and predict the patient prognosis. The present study overviewed proteomics‐based research on paediatric ALL to discuss important advances to combat cancer cells and search novel and real protein biomarkers of resistance or sensitivity to drugs which target the signalling networks. We highlighted the importance and significance of a proper phospho‐quantitative design and strategy for paediatric ALL between relapse and remission, when human body fluids from cerebrospinal, peripheral blood, or bone‐marrow were applied. The present article also assessed the schedule for the analysis of body fluids from patients at different states, importance of proteomics‐based tools to discover ALL‐specific and sensitive biomarkers, to stimulate paediatric ALL research via proteomics to ‘build’ the reference map of the signalling networks from leukemic cells at relapse, and to monitor significant clinical therapies for ALL‐relapse.     

The evolving landscape in the therapy of acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous clonal disorder of myeloid precursors arrested in their maturation, creating a diverse disease entity with a wide range of responses to historically standard treatment approaches. While signifi cant progress has been made in characterizing and individualizing the disease at diagnosis to optimally inform those affected, progress in treatment to reduce relapse and induce remission has been limited thus far. In addition to a brief summary of the factors that shape prognostication at diagnosis, this review attempts to expand on the current therapies under investigation that have shown promise in treating AML, including hypomethylating agents, gemtuzumab ozogamicin, FLT3 tyrosine kinase inhibitors, antisense oligonucleotides, and other novel therapies, including aurora kinases, mTOR and PI3 kinase inhibitors, PIM kinase inhibitors, HDAC inhibitors, and IDH targeted therapies. With these, and undoubtedly many others in the future, it is the hope that by combining more accurate prognostication with more effective therapies, patients will begin to have a different, and more complete, outlook on their disease that allows for safer and more successful treatment strategies.     

L-Asparaginase in Treatment of Acute Leukaemia and Lymphosarcoma

L-Asparaginase was used to treat 40 patients with acute leukaemia or lymphosarcoma. Fifteen with acute lymphoblastic leukaemia either untreated or in relapse after previous therapy were given “Squibb,” “Bayer,” or “Porton” L-asparaginase. Five of these patients had complete remission of their disease, and four had good partial remission. Eleven patients with acute myeloid leukaemia were treated for a short period with L-asparaginase alone. None of them went into remission though a pronounced fall in the numbers of circulating white cells was seen. Six patients with lymphosarcoma received L-asparaginase, two of them having good partial remissions.The toxic side-effects of the L-asparaginase from the three sources seemed to vary, and L-asparaginase from Erwinia carotovora appeared to be antigenically different from the enzyme produced by Escherichia coli.The way in which leukaemic cells become resistant to the action of the enzyme requires further investigation. To overcome this resistance asparaginase should be used in combination with other drugs in the treatment of acute leukaemia.     

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

Summary 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.     

Stem cell and kinase activity-independent pathway in resistance of leukaemia to BCR-ABL kinase inhibitors

BCR-ABL tyrosine kinase inhibitors, such as imatinib (Gleevec) are highly effective in treating human Philadelphia chromosome-positive (Ph+) chronic myeloid leukaemia (CML) in chronic phase but not in terminal acute phase; acquired drug resistance caused mainly by the development of BCR-ABL kinase domain mutations prevents cure of the leukaemia. In addition, imatinib is ineffective in treating Ph+ B-cell acute lymphoblastic leukaemia (B-ALL) and CML blast crisis, even in the absence of the kinase domain mutations. This type of drug resistance that is unrelated to BCR-ABL kinase domain mutations is caused by the insensitivity of leukaemic stem cells to kinase inhibitors such as imatinib and dasatinib, and by activation of a newly-identified signalling pathway involving SRC kinases that are independent of BCR-ABL kinase activity for activation. This SRC pathway is essential for leukaemic cells to survive imatinib treatment and for CML transition to lymphoid blast crisis. Apart from BCR-ABL and SRC kinases, stem cell pathways must also be targeted for curative therapy of Ph+ leukaemia.     

Adoptive transfer of T cells transduced with a chimeric antigen receptor to treat relapsed or refractory acute leukemia: efficacy and feasibility of immunotherapy approaches

Treatment outcomes of acute leukemia(AL) have not improved over the past several decades and relapse rates remain high despite the availability of aggressive therapies. Conventional relapsed leukemia treatment includes second allogeneic hematopoietic stem cell transplantation(allo-HSCT) and donor lymphocyte infusion(DLI), which in most cases mediate, at best, a modest graft-versus-leukemia effect, although their clinical efficacy is still limited. Although allo-HSCT following myeloablative conditioning is a curative treatment option for younger patients with acute myeloid leukemia(AML) in a first complete remission(CR), allo-HSCT as a clinical treatment is usually limited because of treatment-related toxicity. The overall DLI remission rate is only 15%–42% and 2-year overall survival(OS) is approximately 15%–20%, with a high(40%–60%) incidence of DLI-related graft-versus-host disease(GVHD). Therefore, development of new, targeted treatment strategies for relapsed and refractory AL patients is ongoing. Adoptive transfer of T cells with genetically engineered chimeric antigen receptors(CARs) is an encouraging approach for treating hematological malignancies. These T cells are capable of selectively recognizing tumor-associated antigens and may overcome many limitations of conventional therapies, inducing remission in patients with chemotherapy-refractory or relapsed AL. In this review, we aimed to highlight the current understanding of this promising treatment modality, discussing its adverse effects and efficacy.     

Laminar air flow versus barrier nursing in marrow transplant recipients

Forty-eight patients with acute leukaemia in relapse (n = 14), acute leukaemia in complete remission (n = 19), chronic myeloid leukaemia (n = 8) or severe aplastic anaemia (n = 7) received a marrow transplant. The first 26 patients were nursed in laminar-air-flow plastic isolators while the next 22 patients were treated in barrier nursing rooms. Gnotobiotic parameters and morbidity in the 2 groups are compared. Good decontamination of the gastro-intestinal tract was obtained using either of the 2 isolation techniques. The incidence of bacterial and mycotic infections, as well as the supportive care required by the patients was almost equal in both groups. Our results also suggest that the incidence of graft versus host disease may decrease with efficient decontamination of the patients.     

Bone marrow transplantation in childhood leukaemia--experience and strategies in the Federal Republic of Germany

BMT has gained its place in the treatment of childhood leukaemia. Nevertheless, there are still many questions open. In acute lymphoblastic leukaemia children should normally be grafted in 2nd remission (CR). Some high risk cases, however, should probably be grafted in 1st CR. It is not clear whether children with late relapses benefit more from BMT than from renewed chemotherapy. Children with a relapse during maintenance therapy, however, have a better survival rate with BMT. In acute nonlymphoblastic leukaemia certain high risk patients should be grafted in 1st CR but it has still to be shown that BMT is superior to chemotherapy in such cases. It is not clear whether children with a relapse following intensive chemotherapy (such as the BFM-protocols) will benefit from BMT at all. In chronic myelocytic leukaemia, BMT in chronic phase should be performed. Thus, for the first time cure has become possible for this disease. Waiting for acceleration or even the occurrence of a blast crisis decreases the chance of survival after BMT dramatically. Since complications of BMT such as graft-versus-host reaction or severe infections are less frequent in children, relapses remain the main problem after BMT in childhood leukaemia.     

Carboxyamidotriazole-orotate inhibits the growth of imatinib-resistant chronic myeloid leukaemia cells and modulates exosomes-stimulated angiogenesis

The Bcr/Abl kinase has been targeted for the treatment of chronic myelogenous leukaemia (CML) by imatinib mesylate. While imatinib has been extremely effective for chronic phase CML, blast crisis CML are often resistant. New therapeutic options are therefore needed for this fatal disease. Although more common in solid tumors, increased microvessel density was also reported in chronic myelogenous leukaemia and was associated with a significant increase of angiogenic factors, suggesting that vascularity in hematologic malignancies is a controlled process and may play a role in the leukaemogenic process thus representing an alternative therapeutic target. Carboxyamidotriazole-orotate (CTO) is the orotate salt form of carboxyamidotriazole (CAI), an orally bioavailable signal transduction inhibitor that in vitro has been shown to possess antileukaemic activities. CTO, which has a reduced toxicity, increased oral bioavailability and stronger efficacy when compared to the parental compound, was tested in this study for its ability to affect imatinib-resistant CML tumor growth in a xenograft model. The active cross talk between endothelial cells and leukemic cells in the bone marrow involving exosomes plays an important role in modulating the process of neovascularization in CML. We have thus investigated the effects of CTO on exosome-stimulated angiogenesis. Our results indicate that CTO may be effective in targeting both cancer cell growth and the tumor microenvironment, thus suggesting a potential therapeutic utility for CTO in leukaemia patients.     

Hydroxyurea,Leucopheresis, and Splenectomy in Chronic Myeloid Leukaemia at the Problastic Phase

Forty-three patients with chronic myeloid leukaemia have been treated with hydroxyurea in order to be subjected to leucopheresis for white cell transfusions. Hydroxyurea decreases leucocytosis when it is administered and the blood granulocyte number increases soon after the drug is stopped. The survival of the patients is not different from the survival of the patients treated with conventional chemotherapy (busulphan, mitobronitol) and it is superior to the survival of patients treated with external radiotherapy or with ³²P. Half of the patients were subjected to splenectomy during first remission for a phase II trial. They were not randomized, but the distribution according to age was similar in the two groups. A slight difference appears in favour of splenectomy so far as survival is concerned, but there were three post-operative deaths out of 18 patients. We conclude that a phase II trial on the value of splenectomy is indicated ethically, but that the patients should be operated on and nursed in a microbiologically controlled environment.     

BAG1 down-regulation increases chemo-sensitivity of acute lymphoblastic leukaemia cells

BCL2-associated athanogene-1 (BAG1) is a multi-functional protein that is found deregulated in several solid cancers and in paediatric acute myeloid leukaemia. The investigation of BAG1 isoforms expression and intracellular localization in B-cell acute lymphoblastic leukaemia (B-ALL) patient-derived specimens revealed that BAG1 levels decrease during disease remission, compared to diagnosis, but drastically increase at relapse. In particular, at diagnosis both BAG1-L and BAG1-M isoforms are mainly nuclear, while during remission the localization pattern changes, having BAG1-M almost exclusively in the cytosol indicating its potential cytoprotective role in B-ALL. In addition, knockdown of BAG1/BAG3 induces cell apoptosis and G1-phase cell cycle arrest and, more intriguingly, shapes cell response to chemotherapy. BAG1-depleted cells show an increased sensitivity to the common chemotherapeutic agents, dexamethasone or daunorubicin, and to the BCL2 inhibitor ABT-737. Moreover, the BAG1 inhibitor Thio-2 induces a cytotoxic effect on RS4;11 cells both in vitro and in a zebrafish xenograft model and strongly synergizes with pan-BCL inhibitors. Collectively, these data sustain BAG1 deregulation as a critical event in assuring survival advantage to B-ALL cells.