Casein Kinase 2 (CK2): A Possible Therapeutic Target in Acute Myeloid Leukemia

The protein kinase CK2 (also known as casein kinase 2) is one of the main contributors to the human phosphoproteome. It is regarded as a possible therapeutic strategy in several malignant diseases, including acute myeloid leukemia (AML), which is an aggressive bone marrow malignancy. CK2 is an important regulator of intracellular signaling in AML cells, especially PI3K-Akt, Jak-Stat, NFκB, Wnt, and DNA repair signaling. High CK2 levels in AML cells at the first time of diagnosis are associated with decreased survival (i.e., increased risk of chemoresistant leukemia relapse) for patients receiving intensive and potentially curative antileukemic therapy. However, it is not known whether these high CK2 levels can be used as an independent prognostic biomarker because this has not been investigated in multivariate analyses. Several CK2 inhibitors have been developed, but CX-4945/silmitasertib is best characterized. This drug has antiproliferative and proapoptotic effects in primary human AML cells. The preliminary results from studies of silmitasertib in the treatment of other malignancies suggest that gastrointestinal and bone marrow toxicities are relatively common. However, clinical AML studies are not available. Taken together, the available experimental and clinical evidence suggests that the possible use of CK2 inhibition in the treatment of AML should be further investigated.

The Implementation of Mass Spectrometry-Based Proteomics Workflows in Clinical Routines of Acute Myeloid Leukemia: Applicability and Perspectives

With the current reproducibility of proteome preparation workflows along with the speed and sensitivity of the mass spectrometers, the transition of the mass spectrometry (MS)-based proteomics technology from biomarker discovery to clinical implementation is under appraisal in the biomedicine community. Therefore, this technology might be implemented soon to detect well-known biomarkers in cancers and other diseases. Acute myeloid leukemia (AML) is an aggressive heterogeneous malignancy that requires intensive treatment to cure the patient. Leukemia relapse is still a major challenge even for patients who have favorable genetic abnormalities. MS-based proteomics could be of great help to both describe the proteome changes of individual patients and identify biomarkers that might encourage specific treatments or clinical strategies. Herein, we will review the advances and availability of the MS-based proteomics strategies that could already be used in clinical proteomics. However, the heterogeneity of complex diseases as AML requires consensus to recognize AML biomarkers and to establish MS-based workflows that allow their unbiased identification and quantification. Although our literature review appears promising towards the utilization of MS-based proteomics in clinical AML in a near future, major efforts are required to validate AML biomarkers and agree on clinically approved workflows.

Therapeutic targeting of leukemic stem cells in acute myeloid leukemia - the biological background for possible strategies

INTRODUCTION

Acute myeloid leukemia (AML) is an aggressive malignancy, caused by the accumulation of immature leukemic blasts in blood and bone marrow. There is a relatively high risk of chemoresistant relapse even for the younger patients who can receive the most intensive antileukemic treatment. Treatment directed against the remaining leukemic and preleukemic stem cells will most likely reduce the risk of later relapse. Areas covered: Relevant publications were identified through literature searches. The authors searched for original articles and recent reviews describing (i) the characteristics of leukemic/preleukemic stem cells; (ii) the importance of the bone marrow stem cell niches in leukemogenesis; and (iii) possible therapeutic strategies to target the preleukemic/leukemic stem cells. Expert opinion: Leukemia relapse/progression seems to be derived from residual chemoresistant leukemic or preleukemic stem cells, and a more effective treatment directed against these cells will likely be important to improve survival both for patients receiving intensive treatment and leukemia-stabilizing therapy. Several possible strategies are now considered, including the targeting of the epigenetic regulation of gene expression, proapoptotic intracellular signaling, cell metabolism, telomere activity and the AML-supporting effects by neighboring stromal cells. Due to disease heterogeneity, the most effective stem cell-directed therapy will probably differ between individual patients.

Epigenetic assays for chemical biology and drug discovery

The implication of epigenetic abnormalities in many diseases and the approval of a number of compounds that modulate specific epigenetic targets in a therapeutically relevant manner in cancer specifically confirms that some of these targets are druggable by small molecules. Furthermore, a number of compounds are currently in clinical trials for other diseases including cardiovascular, neurological and metabolic disorders. Despite these advances, the approved treatments for cancer only extend progression-free survival for a relatively short time and being associated with significant side effects. The current clinical trials involving the next generation of epigenetic drugs may address the disadvantages of the currently approved epigenetic drugs.

The identification of chemical starting points of many drugs often makes use of screening in vitro assays against libraries of synthetic or natural products. These assays can be biochemical (using purified protein) or cell-based (using for example, genetically modified, cancer cell lines or primary cells) and performed in microtiter plates, thus enabling a large number of samples to be tested. A considerable number of such assays are available to monitor epigenetic target activity, and this review provides an overview of drug discovery and chemical biology and describes assays that monitor activities of histone deacetylase, lysine-specific demethylase, histone methyltransferase, histone acetyltransferase and bromodomain. It is of critical importance that an appropriate assay is developed and comprehensively validated for a given drug target prior to screening in order to improve the probability of the compound progressing in the drug discovery value chain.

Patients with acute myeloid leukemia can be subclassified based on the constitutive cytokine release of the leukemic cells; the possible clinical relevance and the importance of cellular iron metabolism

OBJECTIVE

Acute myeloid leukaemia (AML) is a heterogeneous malignancy; we studied how the constitutive cytokine release by the AML cells varies among patients.

METHODS

We investigated the constitutive release of 28 mediators during in vitro culture for 79 consecutive patients.

RESULTS

Constitutive cytokine release profiles differed among patients, and hierarchical clustering identified three subsets with high, intermediate and low release, respectively. The high-release subset showed high levels of most mediators, usually monocytic differentiation as well as altered mRNA expression of proteins involved in intracellular iron homeostasis and molecular trafficking; this subset also included 4 out of 6 patients with inv(16). Spontaneous in vitro apoptosis did not differ among the subsets. For the high-release patients, cytokines were released both by CD34⁺ and CD34^- cells. The mRNA and released protein levels showed statistically significant correlations only for eleven of the cytokines. The overall survival after intensive anti-leukemic therapy was significantly higher for high-release compared with low-release patients. Pharmacological targeting of iron metabolism (iron chelation, transferrin receptor blocking) altered the cytokine release profile.

CONCLUSIONS

Subclassification of AML patients based on the constitutive cytokine release may be clinically relevant and a part of a low-risk (i.e. chemosensitive) AML cell phenotype.

Acute myeloid leukemia: advancing clinical trials and promising therapeutics

Recent progress in understanding the biology of acute myeloid leukemia (AML) and the identification of targetable driver mutations, leukemia specific antigens and signal transduction pathways has ushered in a new era of therapy. In many circumstances the response rates with such targeted or antibody-based therapies are superior to those achieved with standard therapy and with decreased toxicity. In this review we discuss novel therapies in AML with a focus on two major areas of unmet need: (1) single agent and combination strategies to improve frontline therapy in elderly patients with AML and (2) molecularly targeted therapies in the frontline and salvage setting in all patients with AML.