New approaches in acute myeloid leukemia

Today, treatment of patients with acute myeloid leukemia (AML) remains predominantly a "one-fits-all" approach with intensive cytarabine-based chemotherapy as the mainstay, but we are finally beginning to reap the rewards of decades of basic, translational, and clinical research. Developing individualized, "targeted" therapy for each AML patient based on unique molecular features of disease remains a daunting goal, yet one that we can now begin to envision. Hypothesis-based study designs--from preclinical/laboratory experiments to phase 1 and subsequent efficacy trials--provide the foundation for advances in the diagnosis, risk stratification, and treatment of patients with AML. The following is an outline of several key areas of ongoing AML research.     

Chronic myeloid leukemia cells express tumor-associated antigens eliciting specific CD8+ T-cell responses and are lacking costimulatory molecules

Specific immunotherapies for patients with chronic myeloid leukemia (CML) might eliminate residual CML cells after therapy with imatinib or chemotherapy and might enhance a specific graft-versus-leukemia effect after allogeneic stem cell transplantation. Here, we investigated the mRNA expression and T-cell recognition of tumor-associated antigens or leukemia-associated antigens (LAAs) in 34 patients with CML. Several LAAs are expressed in CML and therefore are candidate structures for specific immunotherapies: bcr-abl (100%), G250 (24%), hTERT (53%), MPP11 (91%), NEWREN60 (94%), PRAME (62%), Proteinase3 (71%), RHAMM/CD168 (83%), and WT1 (53%), but not BAGE, MAGE-A1, SSX2, or NY-ESO-1. The frequency of mRNA expression of RHAMM/CD168, Proteinase3, and PRAME was higher in acceleration phase and blast crisis. In flow cytometry, CD34+ progenitor cells typed positive for HLA molecules but were deficient for CD40, CD80, CD83, and CD86. However, RHAMM/CD168 R3-peptide (ILSLELMKL)-specific T-cell responses in CML patients were demonstrated by ELISPOT analysis and specific lysis of RHAMM/CD168 R3-pulsed T2 cells and CD34+ CML cells in chromium-51 release assays. RHAMM-R3-specific T cells could be phenotyped as CD8+R3*tetramer+CD45RA+CCR7-CD27- early effector T cells by tetramer staining. Therefore, vaccination strategies inducing such RHAMM-R3-directed effector T cells might be a promising approach to enhance specific immune responses against CML cells.     

Leukemia-associated antigens as target structures for a specific immunotherapy in chronic myeloid leukemia

Specific immunotherapies for CML patients targeting T cell antigens might eliminate residual CML cells after chemotherapy, in combination with imatinib or other tyrosine kinase inhibitors, and might enhance a specific graft versus leukemia effect after allogeneic stem cell transplantation without aggravating the graft versus host disease. For an effective specific immunotherapy in CML, the use of leukemia-associated antigens (LAAs) with an optimal expression pattern is required. In this work, we review known LAAs which are able to induce specific CD8 positive T cell responses and which are appropriate target structures for immunological targeting of CML cells. Moreover, an overview on LAA-targeted immunotherapeutic approaches for CML patients are given.     

Novel targeted and immunotherapeutic strategies in chronic myeloid leukemia

The advanced understanding of the molecular biology and immunology of chronic myeloid leukemia (CML) has led to novel therapeutic strategies unique to this disease. CML responds to immune-mediated therapies, including stem cell transplantation, donor lymphocyte infusion (DLI), and interferon alfa. T cells and other immune effectors are implicated in the mechanisms of action of these immune therapies. Recently, clinical observations supported by laboratory data have demonstrated the presence of CML-specific T cells in patients. Several proteins may potentially act as leukemia-specific antigens for major histocompatibility complex (MHC)-restricted cytotoxicity in CML, and active specific therapies (vaccines) are in development. Antigens under investigation include bcr-abl, PR1, Wilms tumor protein (WT1), minor histocompatibility antigens (mH), CML-66, CML-28, and survivin. Other strategies target vascular endothelial growth factor (VEGF) and heat shock protein 90 (Hsp90) inhibitors or make use of CML-derived dendritic cells (DC).     

Expression of lymphoid-associated cell surface antigens by childhood acute myeloid leukemia cells lacks prognostic significance.

The prognostic significance of cell surface antigens associated with lymphoid and myeloid lineage differentiation on the blasts of children with acute myeloid leukemia (AML) was evaluated. Leukemic blasts from 176 patients enrolled on Childrens Cancer Study Group Protocol 213 determined to have AML by standard morphologic and cytochemical criteria were immunophenotyped. Cell surface antigens associated with myeloid differentiation were found on blasts from 88.1% of patients (CD15, 44%; CD33, 65%; CD36, 53%; glycoprotein Ib, 9.3%). However, blasts from 30.7% of patients expressed surface antigens thought to be specific for lymphoid lineage differentiation (CD2, 9.4%; CD5, 2.7%; CD19, 34.5%; CD20, 0.8%). In addition, CD34, a glycoprotein found on immature cells of both myeloid and lymphoid lineages, was expressed on the blast cells of 48.2% of patients. With the exception of the lymphoid lineage nonspecific antigen CD4, no correlation was found between white blood cell count at diagnosis, age, and French-American-British morphology, and the expression of any of the lymphoid- or myeloid-associated cell surface antigens studied. Nor was the expression of these antigens prognostically significant with respect to response to induction therapy, death during induction, survival, event-free survival, or survival/event-free survival following remission induction. Multivariate analysis showed that CD4 expression was not an independent predictor of outcome. Thus, this prospective study suggests that expression of lymphoid-associated cell surface antigens as well as myeloid-associated antigens by childhood AML blasts lacks prognostic significance.     

Rapid and highly specific screening for NPM1 mutations in acute myeloid leukemia

NPM1 mutations, the most frequent molecular alterations in acute myeloid leukemia (AML), have become important for risk stratification and treatment decisions for patients with normal karyotype AML. Rapid screening for NPM1 mutations should be available shortly after diagnosis. Several methods for detecting NPM1 mutations have been described, most of which are technically challenging and require additional laboratory equipment. We developed and validated an assay that allows specific, rapid, and simple screening for NPM1 mutations. FAST PCR spanning exons 8 to 12 of the NPM1 gene was performed on 284 diagnostic AML samples. PCR products were visualized on a 2 % agarose E-gel and verified by direct sequencing. The FAST PCR screening method showed a specificity and sensitivity of 100 %, i.e., all mutated cases were detected, and none of negative cases carried mutations. The limit of detection was at 5–10 % of mutant alleles. We conclude that the FAST PCR assay is a highly specific, rapid (less than 2 h), and sensitive screening method for the detection of NPM1 mutations. Moreover, this method is inexpensive and can easily be integrated in the routine molecular diagnostic work-up of established risk factors in AML using standard laboratory equipment.     

Expression of normal myeloid-associated antigens by acute leukemia cells

Monoclonal antibodies that react with hematopoietic cells and their precursors in a stage and lineage restricted fashion were used in indirect immunofluorescence assays to examine leukemic cells from 105 pediatric age patients. The differentiative states of blasts from 42 patients with acute nonlymphocytic leukemia (ANLL) were defined by these antibodies. When these were compared to their morphologic and histochemical levels of differentiation as defined by the French-American-British (FAB) classification, no direct relationship was found. The reactivity of these antibodies with leukemic cells from 63 patients with acute lymphocytic leukemiA (ALL) was also investigated, and the usefulness of these antibodies in distinguishing leukemias of myeloid from those of lymphoid origin was demonstrated.     

Identification of tumor-associated antigens in chronic lymphocytic leukemia by SEREX

Chronic lymphocytic leukemia (CLL) is associated with a variety of immunologic disturbances. Hypogammaglobulinemia and autoimmune phenomena are both often present in this disease. In contrast, humoral or cellular antitumor responses are rarely observed. It has been previously shown that antigens detected in patients with malignant diseases can provide information regarding intracellular molecules engaged in the transformation process and can identify tumor antigens that may be useful for development of immunotherapeutic strategies. Serologic identification by recombinant expression cloning (SEREX) has been demonstrated to be a useful method to detect tumor and tumor-associated antigens in a variety of malignancies. Although this approach is complicated in CLL, we used a modified SEREX approach and identified 14 antigens (KW-1 to KW-14) using this methodology. Several clones showed a restricted expression pattern in normal tissues. Moreover, distinctive expression of splice variants and aberrant gene expression in malignant tissue were detected. In this study, 6 antigens were detected exclusively in patients with CLL. Eight antigens were detected also in lymphoma patients. Healthy donors showed antibody responses against only 3 of the identified antigens. T cells with specific cytotoxicity against peptides derived from the 2 antigens tested could be generated from healthy donors. These findings demonstrate that humoral and cellular immune responses against CLL-associated antigens can be detected. Ongoing experiments investigate their potential for the development of immunotherapeutic strategies.     

Antibody therapy for acute myeloid leukemia

Due to the high rate of relapse in younger patients and the overall poor outcome in older patients, novel therapies are needed for the treatment of acute myeloid leukemia (AML). Monoclonal antibodies have become an important treatment modality in cancer therapy. Gemtuzumab ozogamicin (GO), an anti-CD33 immunoconjugate, was approved by the US Food and Drug Administration (FDA) for the treatment of elderly patients with relapsed AML who are not candidates for standard chemotherapy. Single-agent GO and combinations with standard chemotherapeutics have been explored extensively in this disease. Hepatotoxicity and delayed myelosuppression have been dose-limiting. Its toxicity profile is reduced with decreased doses of GO and even by administering only a single infusion. In patients with acute promyelocytic leukemia (APL), the addition of GO can produce molecular remissions and is well tolerated. Targeted immunotherapy with GO for treatment of AML has produced remissions. In order to reduce toxicity and improve efficacy, its optimal dose and schedule and pairing with other standard chemotherapeutic agents need to be defined better in large clinical trials.     

急性髓性白血病的靶向治疗

目前,急性髓性白血病(AML)传统化疗的疗效已难以提高.在慢性粒细胞白血病确定了BCR-ABL可以作为有效的靶点,并合成了特异针对该靶点的药物伊马替尼,伊马替尼在临床上取得了非常好的疗效.通过研究AML的分子生物学、免疫表型和细胞生物学异常,从而确定有效的治疗靶点,合成特异的靶向治疗药物,可能会进一步提高白血病疗效.过去的十年,在AML的靶向治疗领域取得了巨大的进展,本文将对这些进展进行简述.     

Post-remission therapy for acute myeloid leukemia

Induction followed by post-remission therapy including intensive chemotherapy with high-dose cytarabine, autologous and allogeneic hematopoietic stem cell transplantation is recognized as the main road towards cure in acute myeloid leukemia. In recent years, also a renaissance of maintenance therapy after completion of intensive consolidation has been observed with the introduction of kinase inhibitors and demethylating agents in clinical trials. Greater insight into the genetic background of the disease fostered the extension of disease classification and pretreatment risk-categorization by gene mutations. In addition, the pre-treatment risk-defining parameters have been supplemented by markers evaluated at distinct time points during treatment and follow up. In this context, minimal residual disease assessment is increasingly used to dynamically fine tune treatment recommendations. Currently, the gold standard to counterbalance a higher risk of relapse by treatment strategies based on hematopoietic stem cell transplantation with grafts from matched related or unrelated donors is still valuable, whereas autologous hematopoietic stem cell transplantation showed promising results especially in patients categorized as low-risk. Nonetheless, more targeted approaches including kinase inhibitors and demethylating agents in combination with or sequentially before or after intensive chemotherapy are currently in clinical evaluation and may lead to more genotype- instead of purely risk-adapted treatment strategies.     

Venetoclax-based therapies for acute myeloid leukemia

The prognosis of adult acute myeloid leukemia (AML) remains poor, with the long-term survival rate less than 50%. However, the current paradigms of treatment are changing through a better understanding of the disease genetics and pathophysiology. Since 2017, eight new drugs have been approved by the U.S. Food and Drug Administration for the treatment of AML, including the FLT3 inhibitors midostaurin and gilteritinib, the IDH inhibitors ivosidenib and enasidenib, the anti-CD33 monoclonal antibody gemtuzumab ozogamicin, liposomal daunorubicin and cytarabine, the hedgehog pathway inhibitor glasdegib and the BCL-2 inhibitor venetoclax. Preclinical data demonstrated the anti-leukemic efficacy of venetoclax in AML and its synergy when combined with hypomethylating agents or chemotherapy agents. Clinical trials have demonstrated the clinical benefit of venetoclax-based therapies in newly diagnosed AML, leading to the recent FDA approval of venetoclax in combination with hypomethylating agents or low-dose cytarabine for older adults with newly diagnosed AML. Herein, we focus on the role of single-agent BCL-2 inhibition in AML and review the clinical studies of venetoclax-based combination regimens and the evolving mechanisms of resistance.     

Drug therapy for acute myeloid leukemia

Although improvement in outcomes has occurred in younger adults with acute myeloid leukemia (AML) during the past 4 decades, progress in older adults has been much less conspicuous, if at all. Approximately 50% to 75% of adults with AML achieve complete remission (CR) with cytarabine and an anthracycline such as daunorubicin or idarubicin or the anthracenedione mitoxantrone. However, only approximately 20% to 30% of the patients enjoy long-term disease survival. Various postremission strategies have been explored to eliminate minimal residual disease. The optimal dose, schedule, and number of cycles of postremission chemotherapy for most patients are not known. A variety of prognostic factors can predict outcome and include the karyotype of the leukemic cells and the presence of transmembrane transporter proteins, which extrude certain chemotherapy agents from the cell and confer multidrug resistance and mutations in or over expressions of specific genes such as WT1, CEBPA, BAX and the ratio of BCL2 to BAX, BAALC, EVI1, KIT, and FLT3. Most recently, insights into the molecular pathogenesis of AML have led to the development of more specific targeted agents and have ushered in an exciting new era of antileukemia therapy. Such agents include the immunoconjugate gemtuzumab ozogamicin, multidrug resistance inhibitors, farnesyl transferase inhibitors, histone deacetylase and proteosome inhibitors, antiangiogenesis agents, Fms-like tyrosine kinase 3 (FLT3) inhibitors, and apoptosis inhibitors.