Usefulness of anti-CD117 in the flow cytometric analysis of acute leukemia

DNA-Based Nanomaterials as Drug Delivery Platforms for Increasing the Effect of Drugs in Tumors

DNA nanotechnology has significantly advanced and might be used in biomedical applications, drug delivery, and cancer treatment during the past few decades. DNA nanomaterials are widely used in biomedical research involving biosensing, bioimaging, and drug delivery since they are remarkably addressable and biocompatible. Gradually, modified nucleic acids have begun to be employed to construct multifunctional DNA nanostructures with a variety of architectural designs. Aptamers are single-stranded nucleic acids (both DNAs and RNAs) capable of self-pairing to acquire secondary structure and of specifically binding with the target. Diagnosis and tumor therapy are prospective fields in which aptamers can be applied. Many DNA nanomaterials with three-dimensional structures have been studied as drug delivery systems for different anticancer medications or gene therapy agents. Different chemical alterations can be employed to construct a wide range of modified DNA nanostructures. Chemically altered DNA-based nanomaterials are useful for drug delivery because of their improved stability and inclusion of functional groups. In this work, the most common oligonucleotide nanomaterials were reviewed as modern drug delivery systems in tumor cells.

The Research Advances of Aptamers in Hematologic Malignancies

Currently, research for hematological malignancies is very intensive, with many breakthroughs. Among them, aptamer-based targeted therapies could be counted. Aptamer is a targeting tool with many unique advantages (easy synthesis, low toxicity, easy modification, low immunogenicity, nano size, long stability, etc.), therefore many experts screened corresponding aptamers in various hematological malignancies for diagnosis and treatment. In this review, we try to summarize and provide the recent progress of aptamer research in the diagnosis and treatment of hematologic malignancies. Until now, 29 aptamer studies were reported in hematologic malignancies, of which 12 aptamers were tested in vivo and the remaining 17 aptamers were only tested in vitro. In this case, 11 aptamers were combined with chemotherapeutic drugs for the treatment of hematologic malignancies, 4 aptamers were used in combination with nanomaterials for the diagnosis and treatment of hematologic malignancies, and some studies used aptamers for the targeted transportation of siRNA and miRNA for targeted therapeutic effects. Their research provides multiple approaches to achieve more targeted goals. These findings show promising and encouraging future for both hematological malignancies basic and clinical trials research.

Aptamers: Potential Diagnostic and Therapeutic Agents for Blood Diseases

Aptamers are RNA/DNA oligonucleotide molecules that specifically bind to a targeted complementary molecule. As potential recognition elements with promising diagnostic and therapeutic applications, aptamers, such as monoclonal antibodies, could provide many treatment and diagnostic options for blood diseases. Aptamers present several superior features over antibodies, including a simple in vitro selection and production, ease of modification and conjugation, high stability, and low immunogenicity. Emerging as promising alternatives to antibodies, aptamers could overcome the present limitations of monoclonal antibody therapy to provide novel diagnostic, therapeutic, and preventive treatments for blood diseases. Researchers in several biomedical areas, such as biomarker detection, diagnosis, imaging, and targeted therapy, have widely investigated aptamers, and several aptamers have been developed over the past two decades. One of these is the pegaptanib sodium injection, an aptamer-based therapeutic that functions as an anti-angiogenic medicine, and it is the first aptamer approved by the U.S. Food and Drug Administration (FDA) for therapeutic use. Several other aptamers are now in clinical trials. In this review, we highlight the current state of aptamers in the clinical trial program and introduce some promising aptamers currently in pre-clinical development for blood diseases.

Anti-human CD117 CAR T-cells efficiently eliminate healthy and malignant CD117-expressing hematopoietic cells

Acute myeloid leukemia (AML) initiating and sustaining cells maintain high cell-surface similarity with their cells-of-origin, i.e., hematopoietic stem and progenitor cells (HSPCs), and identification of truly distinguishing leukemia-private antigens has remained elusive to date. To nonetheless utilize surface antigen-directed immunotherapy in AML, we here propose targeting both, healthy and malignant human HSPC, by chimeric antigen receptor (CAR) T-cells with specificity against CD117, the cognate receptor for stem cell factor. This approach should spare most mature hematopoietic cells and would require CAR T termination followed by subsequent transplantation of healthy HSPCs to rescue hematopoiesis. We successfully generated anti-CD117 CAR T-cells from healthy donors and AML patients. Anti-CD117 CAR T-cells efficiently targeted healthy and leukemic CD117-positive cells in vitro. In mice xenografted with healthy human hematopoiesis, they eliminated CD117-expressing, but not CD117-negative human cells. Importantly, in mice xenografted with primary human CD117-positive AML, they eradicated disease in a therapeutic setting. Administration of ATG in combination with rituximab, which binds to the co-expressed CAR T-cell transduction/selection marker RQR8, led to CAR T-cell depletion. Thus, we here provide the first proof of concept for the generation and preclinical efficacy of CAR T-cells directed against CD117-expressing human hematopoietic cells.

Importance of CD117 in the Assignation of a Myeloid Lineage in Acute Leukemias

The correct classification of acute leukemias (AL) is an essential part in the evaluation of any patient with this disease. Historically, CD117 has been an important asset in the diagnosis of patients with mixed-phenotype acute leukemia (MPAL). In an attempt to simplify the diagnosis of MPAL with fewer and more lineage specific markers, the World Health Organization (WHO) proposed in 2008 a new criteria for the diagnosis of this type of AL, which excluded CD117 from the myeloid markers that are utilized to diagnose MPAL. In order to assess whether CD117 is necessary in the diagnosis of MPAL, we evaluated the sensitivity and specificity of CD117 for acute myeloid leukemia (AML) in 331 patients with AL. The calculated sensitivity of CD117 for AML was 85.88% (103/120), while the specificity was 83.9% (177/211). Besides myeloperoxidase (MPO), which was used as the gold standard in differentiating AML from other type of ALs, the most specific markers for AML in our study were CD14 and CD64 (99.5 and 95.6%). Although the specificity of CD117 in this study is not as high as CD14 and CD64, markers concomitantly used in this this study and in the WHO classification, based on the results of other researches (i.e. the specificity of CD117 for AML was 100% in one study) and due to the fact that its specificity for AML in this study is relatively high, we recommend the use CD117 in assigning a myeloid lineage in MPAL.

Aptamers in hematological malignancies and their potential therapeutic implications

Aptamers are short DNA/RNA oligonucleotides selected by the process called Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Due to their functional similarity to monoclonal antibodies with some superior characters, such as high specificity and affinity, flexible modification and stability, and lack of toxicity and immunogenicity, they are promising alternative and complementary targeted therapy for hematologic malignancies. The trends in aptamer technology including production, selection, modifications are briefly discussed in this review. The key aspect is to illustrate aptamers against cancer cells in hematologic malignancies especially those that have entered clinical trials. We also discuss some challenges remain in the application of aptamers.

Flowcytometric comparative analysis in acute leukemias between Indian and proposed minimal screening panel

BACKGROUND

Acute myeloid leukemia and acute lymphoid leukemia differ substantially in response to therapy and course, and accurate differentiation of the two is fundamental to therapeutic decisions. Immunophenotyping is used for this purpose, and various guidelines have been proposed regarding a minimal screening antibody panel. Most of them have been found inefficient.

METHODS

Eighty-two cases of consecutive acute leukemias reporting to this hospital over a period of two years were included in the study. Peripheral blood smear, bone marrow aspirate, and bone marrow biopsy were studied using morphology, cytochemical stains, and relevant immunohistochemical stains on selected biopsy specimens. Flowcytometry analysis was carried out using Indian consensus screening panel and our proposed minimal screening panel (PMSP) for comparison.

RESULT

Immunophenotyping using PMSP resulted in 95.12% accurate diagnosis versus Indian consensus minimal screening panel (ICMSP) with an accuracy of 92.68%. This result was statistically significant as per Chi Square tests.

CONCLUSION

PMSP can be used as a substitute for ICMSP, since it includes lineage-specific cytoplasmic antibodies, as well as lesser number of monoclonal antibodies, and enables us to diagnose mixed lineage leukemia. Fewer markers can be linked to a lower cost as well, which is relevant in a developing economy.

Oligonucleotide aptamer-drug conjugates for targeted therapy of acute myeloid leukemia

Oligonucleotide aptamers can specifically bind biomarkers on cancer cells and can be readily chemically modified with different functional molecules for personalized medicine. To target acute myeloid leukemia (AML) cells, we developed a single-strand DNA aptamer specific for the biomarker CD117, which is highly expressed on AML cells. Sequence alignment revealed that the aptamer contained a G-rich core region with a well-conserved functional G-quadruplex structure. Functional assays demonstrated that this synthetic aptamer was able to specifically precipitate CD117 proteins from cell lysates, selectively bound cultured and patient primary AML cells with high affinity (Kd < 5 nM), and was specifically internalized into CD117-expressing cells. For targeted AML treatment, aptamer-drug conjugates were fabricated by chemical synthesis of aptamer (Apt) with methotrexate (MTX), a central drug used in AML chemotherapy regimens. The formed Apt-MTX conjugates specifically inhibited AML cell growth, triggered cell apoptosis, and induced cell cycle arrest in G1 phase. Importantly, Apt-MTX had little effect on CD117-negative cells under the same treatment conditions. Moreover, exposure of patient marrow specimens to Apt-MTX resulted in selective growth inhibition of primary AML cells and had no toxicity to off-target background normal marrow cells within the same specimens. These findings indicate the potential clinical value of Apt-MTX for targeted AML therapy with minimal to no side effects in patients, and also open an avenue to chemical synthesis of new, targeted biotherapeutics.

Diagnosis and subclassification of acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a disseminated malignancy of B- or T-lymphoblasts which imposes a rapid and accurate diagnostic process to support an optimal risk-oriented therapy and thus increase the curability rate. The need for a precise diagnostic algorithm is underlined by the awareness that both ALL therapy and related success rates may vary greatly between ALL subsets, from standard chemotherapy in patients with standard-risk ALL, to allotransplantation (SCT) and targeted therapy in high-risk patients and cases expressing suitable biological targets, respectively. This review summarizes how best to identify ALL and the most relevant ALL subsets.

Diagnostic value of CD117 in differential diagnosis of acute leukemias

C-kit receptor (CD117) and its ligand, stem cell factor, play a key role in normal hematopoiesis. It has been demonstrated that its expression extremely increases in leukemias with myeloid commitment. We analyzed findings on CD117 expression together with other myeloid related markers in 203 de novo acute leukemias, referred to Iranian immunophenotyping centers: Iranian Blood Transfusion Organization (IBTO) and Baghiatallah Hospital (BH). All cases were characterized based on the French American British cooperative group (FAB) and European Group for Immunological Classification of Leukemias (EGIL). The cases comprised of 111 acute myeloblastic leukemia (AML), 86 acute lymphoblastic leukemia (ALL), and 6 acute undifferentiated leukemia (AUL). CD117 was positive in 75 % of AML and 50 % of AUL, whereas none of the ALL cases was positive for this marker. Although CD117 was positive in 100 % of M5a cases, no M5b positive was found (p = 0.036). The calculated specificity for myeloid involvement was 100 % for CD117 and CD33, and 98 % for CD13 and CD15 (p < 0.001). The calculated sensitivity for myeloid involvement was 83, 76, 64, and 41 % for CD13, CD117, CD33, and CD15, respectively (p < 0.001). We concluded that CD117 expression is a specific and rather sensitive marker for differential diagnosis between AML and ALL, and except for M5 subtypes, it fails to determine FAB subtypes; lack of expression in M5 can identify M5b. Therefore, it should be included in the routine primary panel for diagnosis of acute leukemias.

Activated leukemic oncogenes AML1-ETO and c-kit: role in development of acute myeloid leukemia and current approaches for their inhibition

Acute myeloid leukemia (AML) is a malignant blood disease caused by different mutations that enhance the proliferative activity and survival of blood cells and affect their differentiation and apoptosis. The most frequent disorders in AML are translocations between chromosomes 21 and 8 leading to production of a chimeric oncogene, AML1-ETO, and hyperexpression of the receptor tyrosine kinase KIT. Mutations in these genes often occur jointly. The presence in cells of two activated oncogenes is likely to trigger their malignization. The current approaches for treatment of oncologic diseases (bone marrow transplantation, radiotherapy, and chemotherapy) have significant shortcomings, and thus many laboratories are intensively developing new approaches against leukemias. Inhibiting expression of activated leukemic oncogenes based on the principle of RNA interference seems to be a promising approach in this field.

Targeting the c-kit receptor in the treatment of acute myelogenous leukemia

Acute myelogenous leukemia (AML) is a difficult disease to treat. Novel treatment strategies, including molecular targeted therapy, are being explored. The c-kit receptor represents a potential therapeutic target for AML. The receptor is expressed on more than 10% of blasts in 64% of patients with de novo AML and 95% of those with relapsed AML. It mediates proliferation and anti-apoptotic effects in AML. This review discusses the biology of c-kit in normal and malignant hematopoiesis and the recent clinical trials targeting c-kit in AML.

A Phase 1 study of imatinib mesylate in combination with cytarabine and daunorubicin for c-kit positive relapsed acute myeloid leukemia

The c-kit receptor is expressed in 95% of relapsed acute myeloid leukemias (AMLs) and mediates leukemic proliferation. We conducted a Phase 1 study of the c-kit inhibitor, imatinib mesylate (IM), in combination with cytarabine and daunorubicin (7+3) in c-kit+ relapsed AML. IM was dose escalated using a 3 by 3 design. Phosphorylated STAT5 was absent to minimally present in residual blasts on day 14 bone marrows. The maximum tolerated dose of IM was 300 mg. The dose-limiting toxicity was Grade 3-4 hepatic toxicity. The CR/CRp rate was 57%. Cytotoxic therapy that includes IM for relapsed AML is well-tolerated and effective.

AML1-ETO9a is correlated with C-KIT overexpression/mutations and indicates poor disease outcome in t(8;21) acute myeloid leukemia-M2

AML1-ETO fusion gene is generated from chromosomal translocation t(8;21) mainly in acute myeloid leukemia M2 subtype (AML-M2). Its spliced variant transcript, AML1-ETO9a, rapidly induces leukemia in murine model. To evaluate its clinical significance, AML1-ETO9a expression was assessed in 118 patients with t(8;21) AML-M2, using qualitative and nested quantitative reverse transcriptase (RT)-PCR methods. These cases were accordingly divided into the AML1-ETO9a-H group (n=86, positive for qualitative RT-PCR, with higher level of AML1-ETO9a by quantitative RT-PCR) and the AML1-ETO9a-L group (n=32, negative for qualitative RT-PCR, with lower but still detectable level of AML1-ETO9a by quantitative RT-PCR). C-KIT expression was significantly increased in the AML1-ETO9a-H group, as compared with the AML1-ETO9a-L group. Of the 36 patients harboring C-KIT mutations, 32 patients overexpressed AML1-ETO9a (P=0.0209). Clinically, AML1-ETO9a-H patients exhibited significantly elevated white blood cells count, less bone marrow aberrant myelocytes, increased CD56 but decreased CD19 expression (P=0.0451, P=0.0479, P=0.0149 and P=0.0298, respectively). Moreover, AML1-ETO9a overexpression was related to short event-free and overall survival time (P=0.0072 and P=0.0076, respectively). Taken together, these data suggest that AML1-ETO9a is correlated with C-KIT overexpression/mutations and indicates poor disease outcome in t(8;21) AML-M2.

A correlation study of immunophenotypic, cytogenetic, and clinical features of 180 AML patients in China

New WHO classification has been widely applied in the diagnosis of leukemia. To elucidate the immunophenotype of acute myeloid leukemia (AML) and characterize the correlation among morphological, immunological, cytogenetic, and clinical features, we studied the bone marrow immunophenotypes of 180 AML patients in China by flow cytometry. The results showed that CD34, CD2, CD14, CD19, CD56, and HLA-DR were correlated with FAB subtypes. Amongst the 180 patients enrolled in this study, 122 cases were also subjected to karyotype analysis by G-banding technology and abnormal karyotypes were detected in 69 out of 122 patients. Correlation assay showed that t(8;21) was only present in 16 AML-M2 patients, and strongly associated with the individual or combinational expressions of CD15/CD19/CD34/CD56. As to M3, although lymphoid lineage antigens were observed in a considerable number of patients, they were never detected in t(15;17) positive patients. The expressions of CD22, CD56, and TdT showed significant correlation with the overall presence of abnormal karyotype. Additionally, the expressions of CD4, CD7, CD14, CD56, and TdT were positively correlated with clinical features such as white blood cell count, platelet count, and patient's age. In conclusion, immunophenotype analysis was useful for AML diagnosis and classification. At the same time, the data also suggested that the karyotype abnormalities and clinical features were tightly linked with abnormal antigen expression characteristics in AML patients. As one of the largest correlative study performed in China, the results highlighted the importance of a morphological, immunological, and cytogenetic classification of AML that might constitute a working basis for future studies aimed at a better definition of clinicopathological features and optimal treatment strategy for these leukemias.

Adult acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) in adults is a relatively rare neoplasm with a curability rate around 30% at 5 years. This consideration makes it imperative to dissect further the biological mechanisms of disease, in order to selectively implement an hitherto unsatisfactory success rate. The recognition of discrete ALL subtypes (some of which deserve specific therapeutic approaches, like T-lineage ALL (T-ALL) and mature B-lineage ALL (B-ALL)) is possible through an accurate combination of cytomorphology, immunophenotytpe and cytogenetic assays and has been a major result of clinical research studies conducted over the past 20 years. Two-three major prognostic groups are now easily identifiable, with a survival probability ranging from <10 to 20% (Philadelphia-positive ALL) to about 50-60% (low-risk T-ALL and selected patients with B-lineage ALL). These issues are extensively reviewed and form the basis of current knowledge. The second major point relates to the emerging importance of studies that reveal a dysregulated gene activity and its clinical counterpart. It is now clear that prognostication is a complex matter ranging from patient-related issues to cytogenetics to molecular biology, including the evaluation of minimal residual disease (MRD) and possibly gene array tests. On these bases, the role of a correct, highly personalised therapeutic choice will soon become fundamental. Therapeutic progress may be obtainable through a careful integration of chemotherapy, stem cell transplantation, and the new targeted treatments with highly specific metabolic inhibitors and humanised monoclonal antibodies.

Importance of CD117 in the evaluation of acute leukemias by flow cytometry

BACKGROUND

The issue of which specific antibodies need to be used when evaluating acute leukemias by flow cytometry is controversial.

METHODS

Recent studies have suggested that antibodies against CD117 or c-kit are not essential for the assignment of blast lineage by flow cytometry, even though CD117 appears to be a very specific marker for myeloid lineage acute leukemias. We report a case of acute myeloid leukemia M2 subtype with an 8:21 translocation, where the leukemic blasts expressed CD117, CD19, and CD15 but did not show definitive expression of the myeloid markers CD13 or CD33.

RESULTS AND CONCLUSIONS

This study highlights the importance of CD117 when evaluating acute leukemias by flow cytometry, which was necessary in this case to suggest that the blasts were phenotypically abnormal myeloblasts. In addition, this case presented an unusual acute myeloid leukemia phenotype that will likely be encountered by others and could be difficult to interpret.