Biologic and clinical significance of CD7 expression in acute myeloid leukemia

CAR-T Cells in Acute Myeloid Leukemia: Where Do We Stand?

Despite recent advances, the prognosis of acute myeloid leukemia (AML) remains unsatisfactory due to disease recurrence and the development of resistance to both conventional and novel therapies. Engineered T cells expressing chimeric antigen receptors (CARs) on their cellular surface represent one of the most promising anticancer agents. CAR-T cells are increasingly used in patients with B cell malignancies, with remarkable clinical results despite some immune-related toxicities. However, at present, the role of CAR-T cells in myeloid neoplasms, including AML, is extremely limited, as specific molecular targets for immune cells are generally lacking on AML blasts. Besides the paucity of dispensable targets, as myeloid antigens are often co-expressed on normal hematopoietic stem and progenitor cells with potentially intolerable myeloablation, the AML microenvironment is hostile to T cell proliferation due to inhibitory soluble factors. In addition, the rapidly progressive nature of the disease further complicates the use of CAR-T in AML. This review discusses the current state of CAR-T cell therapy in AML, including the still scanty clinical evidence and the potential approaches to overcome its limitations, including genetic modifications and combinatorial strategies, to make CAR-T cell therapy an effective option for AML patients.

Recent advances in CAR-T cell therapy for acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a fatal and refractory haematologic cancer that primarily affects adults. It interferes with bone marrow cell proliferation. Patients have a 5 years survival rate of less than 30% despite the availability of several treatments, including chemotherapy, allogeneic haematopoietic stem cell transplantation (Allo-HSCT), and receptor antagonist drugs. Allo-HSCT is the mainstay of acute myeloid leukaemia treatment. Although it does work, there are severe side effects, such as graft-versus-host disease (GVHD). In recent years, chimeric antigen receptor (CAR)-T cell therapies have made significant progress in the treatment of cancer. These engineered T cells can locate and recognize tumour cells in vivo and release a large number of effectors through immune action to effectively kill tumour cells. CAR-T cells are among the most effective cancer treatments because of this property. CAR-T cells have demonstrated positive therapeutic results in the treatment of acute myeloid leukaemia, according to numerous clinical investigations. This review highlights recent progress in new targets for AML immunotherapy, and the limitations, and difficulties of CAR-T therapy for AML.

CD7-positive leukemic blasts with DNMT3A mutations predict poor prognosis in patients with acute myeloid leukemia

Background

DNMT3A mutations can be detected in premalignant hematopoietic stem cells and are primarily associated with clonal hematopoiesis of indeterminate potential; however, current evidence does not support assigning them to a distinct European Leukemia Net (ELN) prognostic risk stratification. CD7 is a lymphoid antigen expressed on blasts in approximately 30% of acute myeloid leukemia (AML), and its role in AML remains unclear and depends on subgroup evaluation. This study investigated the prognostic value of DNMT3A mutation combined with CD7 expression in AML.

Methods

We retrospectively analyzed the clinical data of 297 newly diagnosed non-M3 AML patients. According to the DNMT3A mutation and CD7 expression in AML cells, patients were divided into the DNMT3A-mutated/CD7-positive (CD7+), DNMT3A-mutated/CD7-negative (CD7-), DNMT3A-wild-type/CD7+, and DNMT3A-wild-type/CD7- groups.

Results

The DNMT3A-mutated/CD7+ group had lower complete remission rates and higher relapse rates. Importantly, these patients had significantly shorter overall survival (OS) and relapse-free survival (RFS). Furthermore, multivariate analysis showed that CD7+ with DNMT3A mutation was an independent risk factor for OS and RFS.

Conclusion

CD7+ with DNMT3A mutation predicts a poor prognosis in AML patients, and the immunophenotype combined with molecular genetic markers can help to further refine the current risk stratification of AML.

Chimeric Antigen Receptor T-Cell Therapy in Acute Myeloid Leukemia: State of the Art and Recent Advances

Chimeric antigen receptors (CAR)-T-cell therapy represents the most important innovation in onco-hematology in recent years. The progress achieved in the management of complications and the latest generations of CAR-T-cells have made it possible to anticipate in second-line the indication of this type of treatment in large B-cell lymphoma. While some types of B-cell lymphomas and B-cell acute lymphoid leukemia have shown extremely promising results, the same cannot be said for myeloid leukemias-in particular, acute myeloid leukemia (AML), which would require innovative therapies more than any other blood disease. The heterogeneities of AML cells and the immunological complexity of the interactions between the bone marrow microenvironment and leukemia cells have been found to be major obstacles to the clinical development of CAR-T in AML. In this review, we report on the main results obtained in AML clinical trials, the preclinical studies testing potential CAR-T constructs, and future perspectives.

Acute myeloid leukemia: from NGS, through scRNA-seq, to CAR-T. dissect cancer heterogeneity and tailor the treatment

Acute myeloid leukemia (AML) is a malignant blood cancer with marked cellular heterogeneity due to altered maturation and differentiation of myeloid blasts, the possible causes of which are transcriptional or epigenetic alterations, impaired apoptosis, and excessive cell proliferation. This neoplasm has a high rate of resistance to anticancer therapies and thus a high risk of relapse and mortality because of both the biological diversity of the patient and intratumoral heterogeneity due to the acquisition of new somatic changes. For more than 40 years, the old gold standard "one size fits all" treatment approach included intensive chemotherapy treatment with anthracyclines and cytarabine.The manuscript first traces the evolution of the understanding of the pathology from the 1970s to the present. The enormous strides made in its categorization prove to be crucial for risk stratification, enabling an increasingly personalized diagnosis and treatment approach.Subsequently, we highlight how, over the past 15 years, technological advances enabling single cell RNA sequencing and T-cell modification based on the genomic tools are affecting the classification and treatment of AML. At the dawn of the new millennium, the advent of high-throughput next-generation sequencing technologies has enabled the profiling of patients evidencing different facets of the same disease, stratifying risk, and identifying new possible therapeutic targets that have subsequently been validated. Currently, the possibility of investigating tumor heterogeneity at the single cell level, profiling the tumor at the time of diagnosis or after treatments exist. This would allow the identification of underrepresented cellular subclones or clones resistant to therapeutic approaches and thus responsible for post-treatment relapse that would otherwise be difficult to detect with bulk investigations on the tumor biopsy. Single-cell investigation will then allow even greater personalization of therapy to the genetic and transcriptional profile of the tumor, saving valuable time and dangerous side effects. The era of personalized medicine will take a huge step forward through the disclosure of each individual piece of the complex puzzle that is cancer pathology, to implement a "tailored" therapeutic approach based also on engineered CAR-T cells.

Biomarkers as targets for CAR-T/NK cell therapy in AML

The most common kind of acute leukemia in adults is acute myeloid leukemia (AML), which is often treated with induction chemotherapy regimens followed by consolidation or allogeneic hematopoietic stem cell transplantation (HSCT). However, some patients continue to develop relapsed or refractory AML (R/R-AML). Small molecular targeted drugs require long-time administration. Not all the patients hold molecular targets. Novel medicines are therefore needed to enhance treatment outcomes. T cells and natural killer (NK) cells engineered with chimeric antigen receptors (CARs) that target antigens associated with AML have recently been produced and are currently being tested in both pre-clinical and clinical settings. This review provides an overview of CAR-T/NK treatments for AML.

The Black Hole: CAR T Cell Therapy in AML

Despite exhaustive studies, researchers have made little progress in the field of adoptive cellular therapies for relapsed/refractory acute myeloid leukemia (AML), unlike the notable uptake for B cell malignancies. Various single antigen-targeting chimeric antigen receptor (CAR) T cell Phase I trials have been established worldwide and have recruited approximately 100 patients. The high heterogeneity at the genetic and molecular levels within and between AML patients resembles a black hole: a great gravitational field that sucks in everything. One must consider the fact that only around 30% of patients show a response; there are, however, consequential off-tumor effects. It is obvious that a new point of view is needed to achieve more promising results. This review first introduces the unique therapeutic challenges of not only CAR T cells but also other adoptive cellular therapies in AML. Next, recent single-cell sequencing data for AML to assess somatically acquired alterations at the DNA, epigenetic, RNA, and protein levels are discussed to give a perspective on cellular heterogeneity, intercellular hierarchies, and the cellular ecosystem. Finally, promising novel strategies are summarized, including more sophisticated next-generation CAR T, TCR-T, and CAR NK therapies; the approaches with which to tailor the microenvironment and target neoantigens; and allogeneic approaches.

Immunophenotypic characterization of acute leukemias in Bahia, Brazil

OBJECTIVE

To characterize the immunophenotypic profile of acute leukemias in the population of the state of Bahia, Brazil.

METHODS

This is a descriptive, retrospective study. From 2014 to 2018, 796 new cases of acute leukemia were evaluated. The data were obtained from analysis of reports and records of tests performed by flow cytometry immunophenotyping. All individuals of all age groups diagnosed as acute lymphoblastic leukemia or acute myeloid leukemia were included in the study. Demographic variables and expression of leukemia antigens were evaluated.

RESULTS

Most cases were diagnosed as acute myeloid leukemia and 42.7% as acute lymphoblastic leukemia. Significant differences were found in expression of markers in acute leukemias when age groups were compared, as well as in demographic characteristics. B-cell acute lymphoblastic leukemia was more prevalent than cases of T-cell origin. Assessing the aberrant markers in acute myeloid leukemias, the non-acute promyelocytic leukemia group presented expression of CD7 and CD56 as the most frequent ones. In B-cell acute lymphoblastic leukemia, the most frequent aberrant markers were CD66c, CD13 and CD33.

CONCLUSION

Significant differences were found as to several antigens when comparing adults and children, and these findings may contribute to future studies correlating the phenotypic profile to genetic characteristics and therapeutic response, including specific antigen therapies, which may be better targeted.

Naturally selected CD7 CAR-T therapy without genetic editing demonstrates significant antitumour efficacy against relapsed and refractory acute myeloid leukaemia (R/R-AML)

Background

The survival rate for patients with relapsed and refractory acute myeloid leukaemia (R/R-AML) remains poor, and treatment is challenging. Chimeric antigen receptor T cells (CAR-T cells) have been widely used for haematologic malignancies. Current CAR-T therapies for acute myeloid leukaemia mostly target myeloid-lineage antigens, such as CD123 and CD33, which may be associated with potential haematopoietic toxicity. As a lineage-specific receptor, CD7 is expressed in acute myeloid leukaemia cells and T cells but is not expressed in myeloid cells. Therefore, the use of CD7 CAR-T cells for R/R-AML needs to be further explored.

Methods

In this report, immunohistochemistry and flow cytometry were used to analyse CD7 expression in clinical samples from R/R-AML patients and healthy donors (HDs). We designed naturally selected CD7 CAR-T cells to analyse various functions and in vitro antileukaemic efficacy based on flow cytometry, and xenograft models were used to validate in vivo tumour dynamics.

Results

We calculated the percentage of cells with CD7 expression in R/R-AML patients with minimal residual disease (MRD) (5/16, 31.25%) from our institution and assessed CD7 expression in myeloid and lymphoid lineage cells of R/R-AML patients, concluding that CD7 is expressed in T cells but not in myeloid cells. Subsequently, we designed and constructed naturally selected CD7 CAR-T cells (CD7 CAR). We did not perform CD7 antigen knockdown on CD7 CAR-T cells because CD7 molecule expression is naturally eliminated at Day 12 post transduction. We then evaluated the ability to target and kill CD7+ acute myeloid leukaemia cells in vitro and in vivo. Naturally selected CD7 CAR-T cells efficiently killed CD7+ acute myeloid leukaemia cells and CD7+ primary blasts of R/R-AML patients in vitro and significantly inhibited leukaemia cell growth in a xenograft mouse model.

Conclusion

Naturally selected CD7 CAR-T cells represent an effective treatment strategy for relapsed and refractory acute myeloid leukaemia patients in preclinical studies.

Novel CAR T therapy is a ray of hope in the treatment of seriously ill AML patients

Acute myeloid leukemia (AML) is a serious, life-threatening, and hardly curable hematological malignancy that affects the myeloid cell progenies and challenges patients of all ages but mostly occurs in adults. Although several therapies are available including chemotherapy, allogeneic hematopoietic stem cell transplantation (alloHSCT), and receptor-antagonist drugs, the 5-year survival of patients is quietly disappointing, less than 30%. alloHSCT is the major curative approach for AML with promising results but the treatment has severe adverse effects such as graft-versus-host disease (GVHD). Therefore, as an alternative, more efficient and less harmful immunotherapy-based approaches such as the adoptive transferring T cell therapy are in development for the treatment of AML. As such, chimeric antigen receptor (CAR) T cells are engineered T cells which have been developed in recent years as a breakthrough in cancer therapy. Interestingly, CAR T cells are effective against both solid tumors and hematological cancers such as AML. Gradually, CAR T cell therapy found its way into cancer therapy and was widely used for the treatment of hematologic malignancies with successful results particularly with somewhat better results in hematological cancer in comparison to solid tumors. The AML is generally fatal, therapy-resistant, and sometimes refractory disease with a disappointing low survival rate and weak prognosis. The 5-year survival rate for AML is only about 30%. However, the survival rate seems to be age-dependent. Novel CAR T cell therapy is a light at the end of the tunnel. The CD19 is an important target antigen in AML and lymphoma and the CAR T cells are engineered to target the CD19. In addition, a lot of research goes on the discovery of novel target antigens with therapeutic efficacy and utilizable for generating CAR T cells against various types of cancers. In recent years, many pieces of research on screening and identification of novel AML antigen targets with the goal of generation of effective anti-cancer CAR T cells have led to new therapies with strong cytotoxicity against cancerous cells and impressive clinical outcomes. Also, more recently, an improved version of CAR T cells which were called modified or smartly reprogrammed CAR T cells has been designed with less unwelcome effects, less toxicity against normal cells, more safety, more specificity, longer persistence, and proliferation capability. The purpose of this review is to discuss and explain the most recent advances in CAR T cell-based therapies targeting AML antigens and review the results of preclinical and clinical trials. Moreover, we will criticize the clinical challenges, side effects, and the different strategies for CAR T cell therapy.

Prognostic value of lymphoid marker CD7 expression in acute myeloid leukemia patients undergoing allogeneic hematopoietic cell transplantation in first morphological complete remission

Although defined as a lymphoid surface marker, CD7 is aberrantly expressed on a subtype of acute myeloid leukemia cells and appears to be associated with an inferior response to chemotherapy. Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative modality but no data has been reported in CD7-positive AML patients. We performed a retrospective analysis involving 141 AML patients who underwent allo-HCT in first morphological complete remission (CR1). The results showed that CD7-positive AML patients had a poor 2-year overall survival (64.5% vs 82.0%, P = 0.040), relapse-free survival (RFS) (56.5% vs 79.4%, P = 0.005), and higher cumulative incidence of relapse (27.0% vs 9.7%, P = 0.003) post-HCT. In addition, expression of CD7 was related to RAS and RUNX1 mutation, and high residual disease level pre-HCT. Multivariate analyses showed CD7 expression at diagnosis was an independent risk factor for RFS (P = 0.016, HR = 0.418) and relapse (P = 0.014, HR = 0.307). We concluded that for AML patients in CR1, CD7 is a negative predictor for allo-transplant outcomes.

--Immunophenotypic Aberrancies in Acute Leukemia: A Tertiary Care Centre Experience

Objectives

Acute leukemias (AL) are a heterogeneous group of hematological malignancies with the presence of 20% or more blasts in the peripheral blood or bone marrow. Malignant cells display characteristic patterns of surface antigenic expression. Aberrant phenotypes are defined as patterns of antigen expression on neoplastic cells different from the process of normal hematopoietic maturation. We sought to evaluate the occurrence of aberrant phenotypes in newly diagnosed cases of AL.

Methods

The study included 100 patients in whom both bone marrow aspiration and flow cytometry were performed. Patients with blasts > 20% of all ages were included in the study. Flow cytometric analysis was done using the monoclonal antibody panel of peripheral blood/bone marrow.

Results

Out of 100 cases, 53 were categorized as acute myeloid leukemia (AML), 43 as acute lymphoid leukemia (ALL), and four cases of mixed phenotypic acute leukemia (MPAL). ALL were subcategorized based on immunophenotyping into B-ALL and T-ALL, which comprised 88.4% and 11.6%, respectively, of total ALL (43.0%) cases. Cluster of differentiation 33 (CD33) and CD13 were the most commonly expressed antigens in AML, with CD7 being the most common aberrancy. CD19 was expressed in all B-ALL cases followed by cCD79a, CD10, Tdt (86.8%) with CD13 being the most common aberrancy. cCD3, CD7, and CD5 were expressed in all T-ALL cases with aberrant antigen expression in 80.0% of T-ALL cases. MPAL cases showed expression of B/myeloid antigens.

Conclusions

The diagnosis and classification of leukemia rely on the simultaneous application of cytomorphology, cytochemistry, flow cytometry, cytogenetics, and molecular techniques. Flow cytometry is of great help in the diagnosis of AL, particularly in ALL for lineage assignment and in classifying MPAL. It also helps in detecting aberrant antigen expression and assisting in minimal residual disease detection.

Harnessing T Cells to Target Pediatric Acute Myeloid Leukemia: CARs, BiTEs, and Beyond

Outcomes for pediatric patients with acute myeloid leukemia (AML) remain poor, highlighting the need for improved targeted therapies. Building on the success of CD19-directed immune therapy for acute lymphocytic leukemia (ALL), efforts are ongoing to develop similar strategies for AML. Identifying target antigens for AML is challenging because of the high expression overlap in hematopoietic cells and normal tissues. Despite this, CD123 and CD33 antigen targeted therapies, among others, have emerged as promising candidates. In this review we focus on AML-specific T cell engaging bispecific antibodies and chimeric antigen receptor (CAR) T cells. We review antigens being explored for T cell-based immunotherapy in AML, describe the landscape of clinical trials upcoming for bispecific antibodies and CAR T cells, and highlight strategies to overcome additional challenges facing translation of T cell-based immunotherapy for AML.

CD7 CAR T Cells for the Therapy of Acute Myeloid Leukemia

Chimeric antigen receptor (CAR) T cell therapy for the treatment of acute myeloid leukemia (AML) has the risk of toxicity to normal myeloid cells. CD7 is expressed by the leukemic blasts and malignant progenitor cells of approximately 30% of AML patients but is absent on normal myeloid and erythroid cells. Since CD7 expression by malignant blasts is also linked with chemoresistance and poor outcomes, targeting this antigen may be beneficial for this subset of AML patients. Here, we show that expression of a CD7-directed CAR in CD7 gene-edited (CD7^KO) T cells effectively eliminates CD7⁺ AML cell lines, primary CD7⁺ AML, and colony-forming cells but spares myeloid and erythroid progenitor cells and their progeny. In a xenograft model, CD7 CAR T cells protect mice against systemic leukemia, prolonging survival. Our results support the feasibility of using CD7^KO CD7 CAR T cells for the non-myeloablative treatment of CD7⁺ AML.

The clinical importance of CD4+ CD7- in human diseases

The CD7 antigen is a member of the immunoglobulin superfamily that expresses on the surface of all thymocytes, a majority of mature T cells, and also natural killer cells. Interestingly, under physiological and different pathological conditions, the loss of CD7 antigen occurred in the subset of CD4⁺ memory T cells. Various functions have been proposed for CD7, including its role in the activation and intercellular adhesiveness of T cells. Several studies indicate that the number of CD4⁺ CD7^- T cells increases in diseases such as chronic inflammation and T-cell malignancies, these being skin inflammatory lesions. Therefore, this can be useful for the diagnosis of cancer cells, especially with reference to blood origin, treatment monitoring, and establishment of new therapies. Therefore, a comprehensive review could be useful to increase our knowledge about the clinical importance of these cells in human disease.

Complex measurements may be required to establish the prognostic impact of immunophenotypic markers in AML

OBJECTIVES

The prognostic impact of immunophenotypic markers in acute myeloid leukemia (AML) is controversial.

METHODS

We retrospectively analyzed the value of CD34, CD117, CD7, and CD123 expression in a consecutive series of 592 adult patients with de novo AML.

RESULTS

CD34+ measured as a percentage (≥2.88%) and CD34 mean fluorescence intensity (MFI) (≥146.79, arbitrary units [AU]) expression had a prognostic impact in terms of overall survival (OS; P = .005, P = .003), leukemia-free survival (LFS; P = .011, P < .001), and cumulative incidence of relapse (CIR; P = .014, P =. 001). The percentage of CD117+ cells (61.29%) was associated with shorter LFS (P =. 043), and CD117 MFI (≥284.01 AU) was associated with a shorter OS (P =. 033) and LFS (P =. 028). In the multivariate analysis, high CD34 MFI retained the independent value as predictor of LFS and CIR (P =. 012; hazard ratio [HR], 1.59; 95% confidence interval [CI], 1.11-2.28 and P =. 045; HR, 1.58; 95% CI, 1.01-2.46).

CONCLUSIONS

CD34 positivity threshold with prognostic relevance is low (3% positive cells). Immunophenotypic findings in AML probably could only be fully exploited after a complex analysis that takes into account unconventional thresholds and the MFI.

CD7 promotes extramedullary involvement of the B-cell acute lymphoblastic leukemia line Tanoue by enhancing integrin β2-dependent cell adhesiveness

Extramedullary involvement (EMI) is a factor that defines prognosis of acute lymphoblastic leukemia; however, the molecular mechanism(s) remain elusive. Here, we show that CD7 promotes EMI of the human B-cell acute lymphoblastic leukemia cell line Tanoue. The Tanoue cell line expressing firefly luciferase, Luc-Tanoue, was transplanted into non-obese diabetic/severe combined immunodeficient mice, and cells infiltrated into the brain were cultured ex vivo. This process was repeated 4 times to obtain the highly invasive line Luc-Tanoue-F4. Comparison of the global gene expression signatures of Luc-Tanoue-F4 and Luc-Tanoue indicated that the CD7 gene showed the largest increase in expression among EMI-related genes in Luc-Tanoue-F4 cells. Overexpression of CD7 in Tanoue enhanced cell invasiveness. Among cell migration, proliferation, adhesion and protease activity, only cell adhesiveness showed enhancement in Luc-Tanoue-F4. Expression of the intracellular domain, but not the extracellular domain, of CD7 enhanced cell adhesiveness. Luc-Tanoue-F4 showed a higher level of integrin β2 expression; overexpression of CD7 induced the expression of integrin β2 in Luc-Tanoue. These results show that CD7 induces integrin β2 and enhances cell adhesiveness and invasiveness in Tanoue cells. This study highlights the role of the CD7/integrin β2 axis as a critical pathway in the process of EMI of human B-cell acute lymphoblastic leukemia.

Clinical characteristics, biological profile, and outcome of biphenotypic acute leukemia: a case series

BACKGROUND

Biphenotypic acute leukemia (BAL) is a rare type of acute leukemia that presents with a high degree of heterogeneity and is not well defined.

METHODS

We identified 51 cases (3%) of BAL from 1,693 newly diagnosed acute leukemia patients according to the EGIL scoring system. The immunophenotyping, cytogenetics, treatment, and outcome of 39 BAL patients were retrospectively analyzed.

RESULTS

There were 23 (59%) cases of the myeloid and B-lymphoid phenotype, 14 (36%) cases of the myeloid and T-lymphoid phenotype, and 1 case (3%) of the trilineage phenotype or B/T phenotype. Abnormal karyotypes were detected in 76% of the 37 validated patients and displayed a high degree of heterogeneity. Combined regimens for both acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL), as well as ALL type regimens, appeared to achieve a better complete remission rate than AML type regimens (71 and 64 vs. 33%, respectively). BAL patients with complex karyotypes or a rearrangement of chromosome 11 had a significantly reduced survival rate in comparison to patients with normal, t(8; 21), or t(9; 22) karyotypes. The probability of overall survival and disease-free survival at 2 years was 26 and 18%, respectively.

CONCLUSIONS

Our findings indicate that BAL shows a high incidence of abnormal karyotypes and a poor prognosis. Combined-type regimens or ALL-based protocols are effective for the treatment of BAL.

CD19-positive acute myeloblastic leukemia with trisomy 21 as a sole acquired karyotypic abnormality

We report that a 63-year-old Chinese female had acute myeloblastic leukemia (AML) in which trisomy 21 (+21) was found as the sole acquired karyotypic abnormality. The blasts were positive for myeloperoxidase, and the immunophenotype was positive for cluster of differentiation 19 (CD19), CD33, CD34, and human leukocyte antigens (HLA)-DR. The chromosomal analysis of bone marrow showed 47,XX,+21[2]/46,XX[18]. Fluorescent in situ hybridization (FISH) showed that three copies of AML1 were situated in separate chromosomes, and that t(8;21) was negative. The patient did not have any features of Down syndrome. A diagnosis of CD19-positive AML-M5 was established with trisomy 21 as a sole acquired karyotypic abnormality. The patient did not respond well to chemotherapy and died three months after the diagnosis. This is the first reported case of CD19-positive AML with trisomy 21 as the sole cytogenetic abnormality. The possible prognostic significance of the finding in AML with +21 as the sole acquired karyotypic abnormality was discussed.

Cell viability of acute myeloid leukaemia blasts in culture correlates with treatment outcome

Despite the advances in understanding the pathophysiology of acute myeloid leukaemia (AML), the cure rate for acute myeloid leukaemia patients remains low. Cytogenetic abnormalities and age are the prognostic factors that guide treatment decisions. However, many AML patients still die. The biological factors that influence treatment outcome are largely unknown. Thus, the objective of our study was to use the in vitro viability test to correlate with treatment outcome. Acute myeloid leukaemia blasts demonstrated differing ability to survive in culture. Our examination of blast phenotype at various days in culture showed two possible growth directions. First, cells underwent maturation by increased expression of CD16 and down-regulated CD34 (a haemopoietic stem cell marker). These cells also appeared to have undergone apoptosis. Alternatively, cells continued to survive in culture and maintained high expression of CD34. An MTT assay was carried out to determine viability after three days of culture. Lower optical density values were obtained for samples that underwent apoptosis and higher values were obtained for samples that survived in culture. Apoptosis was measured by Annexin V/propidium iodide staining. A comparison between results of MTT assay and duration of disease free survival revealed that a higher viability in vitro correlated significantly with shorter survival duration in the patient (R -0.761, p=0.002, n=13). Thus, this study further supports the hypothesis that AML patients with poor survival may be related to having blasts with a biologically more immature or stem cell-like nature.

Trisomy 21 as a sole acquired abnormality in an adult Omani patient with CD7- and CD9-positive acute myeloid leukemia

We describe a case of acute myeloid leukemia (AML) in which trisomy 21 was the sole acquired cytogenetic abnormality. The immunophenotype showed positivity for CD7 and CD9 along with CD13, CD33, and CD34. The chromosomal analysis of bone marrow showed 47,XY +21 in all the metaphases analyzed. The constitutional karyotype was normal. The patient was an adult and did not have any features of Down's syndrome. The bone marrow morphology was AML-M2 as per the French-American-British (FAB) criteria. A final diagnosis of CD7- and CD9-positive AML-M2 was established with trisomy 21 as a sole cytogenetic abnormality. The patient responded remarkably well to chemotherapy and achieved complete clinical remission. This is the first case of CD7- and CD9-positive AML with trisomy 21 as a sole abnormality. A putative role for the co-expression of abnormal lymphoid markers in achieving quick remission is discussed.

CD7 expression predicts poor disease free survival and post-remission survival in patients with acute myeloid leukemia and normal karyotype

AML patients with normal karyotype comprise the largest subgroup ( approximately 50%) but have a highly heterogeneous clinical course. By multi-parameter flow cytometry we analyzed CD7 expression along with other phenotypic markers in 185 patients with normal-karyotype AML. CD7 was expressed in 68 (37%) patients. CD7 expression was associated with younger age (P=0.024) but not with sex, WBC count, or extramedullary disease. Patients expressing CD7 had significant shorter disease free (DFS) and post-remission survivals (PRS) than patients without CD7 (DFS of 12 months versus 42 months, P=0.005; PRS of 15 months versus 33 months, P=0.013). We also found that expression of CD34 or HLA-DR was associated with lower CR rate (P=0.0007 and P=0.019, respectively) but did not affect DFS or OS. Furthermore, as for all AML patients, we demonstrated that in the normal karyotypic subgroup, patients with higher WBC counts (>50) and older age (>60 years) had lower CR rate (P=0.003 and P=0.0157, respectively) and shorter OS (P</=0.001 and P=0.007, respectively). Multivariate analysis of age, WBC, CD34, HLA-DR and CD7 showed that CD7 expression was an independent risk factor for DFS (P=0.01) and PRS (P=0.02).

Standard induction chemotherapy followed by attenuated consolidation in elderly patients with acute myeloid leukemia

The benefits of intensive post-remission chemotherapy have not been verified in elderly patients with acute myeloid leukemia (AML). To reduce fatal complications caused by intensive post-remission therapy, we performed a prospective phase II multicenter trial of standard induction chemotherapy ('7+3' of cytarabine plus daunorubicin), followed by two cycles of attenuated consolidation therapy ('5+1' of cytarabine plus daunorubicin) for elderly patients with AML, excluding those with M3. Of the 41 patients enrolled in the study, 24 (58.5%) attained CR. Of these 24, 17 (70.8%) completed both planned cycles of consolidation therapy. After a median follow-up of 566 days (range, 63-1190 days) among surviving patients, 15 relapsed, with an actuarial 3-year disease-free survival rate of 22.5%. There were no fatal complications during consolidation therapy. Actuarial 3-year overall survival was 17.0%. These findings suggest that, when compared with previous findings using more intensive consolidation therapy, attenuated consolidation therapy does not compromise outcomes in elderly AML patients.

The immunophenotype of acute myeloid leukemia: is there a relationship with prognosis?

Immunophenotyping of acute myeloid leukemia has controversial implications with regards to prognosis. Many associations have been described between individual antigen expression on myeloid blasts and prognosis, however few are consistent. Markers with a consistent prognostic association that have been demonstrated in more than one study have been CD13, CD14, and CD15. The association of the expression of CD11b with poor prognosis appears definite, as does CD7 expression. When compared with the expression of a single antigen, a pattern of antigen expression is likely to have a more significant relationship to prognosis. This is exemplified by the panmyeloid phenotype (expression of 5 myeloid antigens) which appears to be associated with a good prognosis and may differentiate a subgroup within an otherwise intermediate prognosis group of patients. Further analysis with the inclusion of novel antibodies and the combination of multiple antibodies to create further subgroups such as the panmyeloid phenotype will continue to enhance knowledge in this area.

Aberrant expression of CD7, CD56, and CD79a antigens in acute myeloid leukemias

The prognostic significance of selected markers of leukemic cells is well known. CD7 and CD56 expression at diagnosis has been associated with low remission rates and biological aggressiveness in a significant proportion of acute leukemias. Among 46 patients with acute myeloid leukemia, we found CD7 expression in 15 cases (32.6%) and CD56 positivity in 10 patients (21.7%). Six of these myeloid leukemia cases (13%) showed expression of both CD7 and CD56. Four of 46 (8.7%) patients expressed CD79a. Among the 10 that were acute myeloblastic leukemia, 8 expressed CD7, 4 expressed CD56, and 4 were positive for CD79a. Thus, these markers were expressed early in hemopoietic ontogeny in the lesser-differentiated acute myeloid leukemia subtypes, including FAB M0, M1, and M2. Whereas CD7 and CD56 were each positive in 4 cases of acute myelomonocytic leukemia (FAB M4 subtype), there was no CD79a expression in the M4 cases. CD7 is expressed by mature T cells, NK cells, and an immature myeloid cell subset. NK cells and a T cell subset express CD56. By contrast, CD79a is a B cell marker that is assigned a high score of 2.0 in the differentiation of acute leukemias of ambiguous lineage in the WHO classification. The aberrant expression of CD7, CD56, and CD79a, representing the capacity of these leukemias for trilineal expression of leukocyte differentiation antigens, portends a poor prognosis.

Ajoene (natural garlic compound): a new anti-leukaemia agent for AML therapy

The reputation of garlic (Allium sativum) as an effective remedy for tumours extends back to the Egyptian Codex Ebers of 1550 b.c. Several garlic compounds including allicin and its corresponding sulfide inhibit the proliferation and induce apoptosis of several human non-leukaemia malignant cells including breast, bladder, colorectal, hepatic, prostate cancer, lymphoma and skin tumour cell lines. Ajoene (4,5,9-trithiadodeca-1,6,11-triene-9-oxide) is a garlic-derived compound produced most efficiently from pure allicin and has the advantage of a greater chemical stability than allicin. Several clinical trials and in vitro studies of ajoene have demonstrated its best-known anti-thrombosis, anti-microbial and cholesterol lowering activities. Recently, topic application of ajoene has produced significant clinical response in patients with skin basal cell carcinoma. Ajoene was shown to inhibit proliferation and induce apoptosis of several human leukaemia CD34-negative cells including HL-60, U937, HEL and OCIM-1. Also, ajoene induces 30% apoptosis in myeloblasts from chronic myeloid leukaemia patient in blast crisis. More significantly, ajoene profoundly enhanced the apoptotic effect of the two chemotherapeutic drugs: cytarabine and fludarabine in human CD34-positive resistant myeloid leukaemia cells through enhancing their bcl-2 inhibitory and caspase-3 activation activities. The two key anti-leukaemia biological actions of ajoene were the inhibition of proliferation and the induction of apoptosis. Studies have shown the anti-proliferation activity of ajoene to be associated with a block in the G2/M phase of cell cycle in human myeloid leukaemia cells. The apoptosis inducing activity of ajoene is via the mitochondria-dependent caspase cascade through a significant reduction of the anti-apoptotic bcl-2 that results in release of cytochrome c and the activation of caspase-3. Since acute myeloid leukaemia (AML) is a heterogeneous malignant disease in which disease progression at the level of CD34-positive cells has a major impact on resistance to chemotherapy and relapse and the inability to undergo apoptosis is a crucial mechanism of multi-drug resistance in AML patients. The recent findings of the potent enhancing activity of ajoene on chemotherapy-induced apoptosis in CD34-positive resistant human myeloid leukaemia cells suggest a novel promising role for the treatment of refractory and/or relapsed AML patients as well as elderly AML patients. Further studies are warranted to evaluate similar enhancing effect for ajoene in blast cells from AML patients in primary cultures before its introduction in pilot clinical study.

T-cell acute lymphoblastic leukemia with add(1)(p36) and del(12)(p11) following acute myelocytic leukemia with partial deletion of 9p

We describe the case of a 40-year-old man whose disease was initially diagnosed as acute myelocytic leukemia. The patient achieved remission with chemotherapy, but relapsed shortly afterwards with an acute T-cell lymphoblastic leukemia. He died of intracranial bleeding. Karyotyping analysis showed a del(9p?) as a common abnormality in the leukemic cells at onset and relapse. Fluorescence in situ hybridization analysis demonstrated allelic loss of the CDKN2A gene in cells from both stages of the disease. At relapse the leukemia cells had additional abnormalities such as add(1)(p36) and del(12)(p11). We postulate that the loss of CDKN2A is involved in leukemogenesis but does not determine the lineage of the leukemic cells. Instead, abnormalities of genes at 1p36, 12p11, or both may be involved in driving a lymphoid phenotype.

The importance of CD7 and CD56 antigens in acute leukaemias

The prognostic significance of immunophenotypical properties of leukaemic cells is well known. However, the biological and clinical significance of CD7 and CD56 antigen expression in acute leukaemias are not clearly established. In patients with acute leukaemias, we identified CD7 and CD56 expression and analysed their associations with markers expressed early in haemopoietic ontogeny and clinical parameters. Among 22 patients with acute leukaemia [12 acute myeloblastic leukaemia (AML), 10 acute lymphoblastic leukaemia (ALL)], we found CD7 positivity in 15 of 22 patients (68%) and CD56 positivity in four patients (18%). CD7 positivity was observed in seven patients (58%) with AML and in eight patients (80%) with ALL. CD56 positivity was observed in three patients (25%) with AML and one patient (10%) with ALL. Lymphadenopathy was present in five patients and associated with hepatosplenomegaly in three patients with ALL. Splenomegaly and hepatomegaly were present in three patients with AML. Central nervous system involvement was seen in one patient with ALL. Complete remission was achieved in nine patients (41%) (five ALL and four AML). Our data showed that CD7 and CD56 positivity at diagnosis associated with low remission rate and biological aggressiveness in a significant proportion of patients. We suggest the evaluation of CD7 and CD56 in all patients with acute leukaemias at the time of diagnosis in view of poor clinical outcome.

CD7 expression by CD34+ cells in CML patients, of prognostic significance?

The purpose of the study was to identify a unique immunophenotype of normal or Philadelphia chromosome positive (Ph+) CD34+ cells that might be used to purify normal CD34+ cells from chronic myelogenous leukemia (CML) patients. An immunophenotypical study of CD34+ bone marrow cells of 20 patients with CML at diagnosis and during hydroxyurea treatment, and 39 controls were performed. All patients were Ph+, two patients had variant translocations and three patients displayed cytogenetic signs of clonal evolution. The immature progenitor cell compartment (CD34+ HLA-DR- and CD34+ CD38- cells) was comparable. The CD34+ AC133+ progenitor cell compartment was decreased in CML patients. We found no difference for any of the adhesion molecules examined except for CD62L, where the percentage of CD34+ CD62L+ cells was decreased in CML patients. The number of myeloid progenitors (CD34+ CD33+) was increased at the expense of B-lymphoid progenitors (CD34+ CD10+ and CD34+ CD19+) in CML patients indicating that B-lymphopoiesis is inhibited in CML. The megakaryocytic (CD34+ CD61+) and erythroid (CD34+ CD71+) progenitors were increased in CML patients. The number of CD34+ CD7+ cells was also significantly increased (mean 25.3% vs. 4.9%). However, the level of CD7 expression was quite heterogeneous, and the patients could be separated into two populations according to CD7 expression (more or less than 20% CD7+ CD34+ cells). The Sokal and Hasford risk scores did not differ between CD34+ CD7- CML and CD34+ CD7+ CML, but all patients with signs of disease progression clustered in the CD34+ CD7+ population indicating that the level of CD7 expression on CD34+ cells may be of prognostic importance in CML.

Biphenotypic acute leukemia with coexpression of CD79a and markers of myeloid lineage

Acute leukemias demonstrating immunophenotypic features of more than 1 cell lineage are referred to as acute leukemias of ambiguous lineage in the new World Health Organization classification system. A subtype of leukemia of ambiguous lineage is biphenotypic acute leukemia in which the malignant cell population expresses markers of 2 different lineages, most commonly myeloid and either B- or T-lymphoid lineages. This entity has been defined by a scoring system proposed by the European Group for the Immunological Characterization of Acute Leukemias (EGIL), with various markers assigned a score of 2, 1, or 0.5 depending on their specificity for myeloid or lymphoid lineage. Those cases having a score greater than 2 for the myeloid and either the B- or T-lymphoid lineages are biphenotypic acute leukemia in this system. One marker, CD79a, has been so clearly associated with acute lymphoblastic leukemia (ALL) by some researchers that its expression in the presence of blast markers is considered indicative of B-ALL. We describe an unusual case of acute leukemia meeting the criteria for biphenotypic acute leukemia in which CD79a expression was observed in the blast population.

Immunological classification of acute myeloblastic leukemias: relevance to patient outcome

Immunophenotyping is a major tool to assign acute leukemia blast cells to the myeloid lineage. However, because of the large heterogeneity of myeloid-related lineages, no clinically relevant immunological classification of acute myeloblastic leukemia (AML) has been devised so far. To attempt at formulating such a classification, we analyzed the pattern of expression of selected antigens, on blast cells collected at AML diagnosis. Patients were eligible if they had a first diagnosis of de novo AML and a sufficient number of blast cells for proper immunophenotyping. The relative expression of CD7, CD13, CD14, CD15, CD33, CD34, CD35, CD36, CD65, CD117, and HLA-DR were analyzed by cytometry in a test series of 176 consecutive AML cases. Statistical tools of clusterization allowed to remove antigens with overlapping distribution, leading us to propose an AML classification that was validated in a second AML cohort of 733 patients. We identified five AML subsets (MA to ME) based on the expression of seven antigens within four groups (CD13/CD33/CD117, CD7, CD35/CD36, CD15).-MA and MB-AML have exclusively myeloid features with seldom extramedullary disease and rare expression of lymphoid antigens. No cases of acute promyelocytic leukemia (APL) were observed within MB AML. MC AML have either myeloid or erythroblastic features. MD AML have more frequently high WBC counts than other subsets, which were related to the expression of CD35/CD36 and CD14 and to monoblastic differentiation. ME AML lack CD13, CD33, and CD117 but display signs of terminal myeloid differentiation. Specific independent prognostic factors were related to poor overall survival in each immunological subset: CD34+ (P<3 x 10(-4)) in MA AML, CD7+ in MB AML, non-APL cases (P<0.03) in MC AML, CD34+ (P<0.002) and CD14+ (P<0.03) in MD AML, CD14+ in ME AML (P<0.01). The inclusion of seven key markers in the immunophenotyping of AML allows a stratification into clinically relevant subsets with individual prognostic factors, which should be considered to define high-risk AML populations.

Therapy-related CD7+ acute myeloid leukemia with trisomy 8 following acute monocytic leukemia

We report a patient who developed CD7+ therapy-related acute myeloid leukemia (t-AML) with trisomy 8 after chemotherapy for AML.

Trisomy 21 as the sole acquired karyotypic abnormality in an adult patient with CD7-positive acute myeloid leukemia

We report a unique case of acute myeloid leukemia (AML) in which trisomy 21 was the sole acquired karyotypic abnormality. The blasts were positive for myeloperoxidase, and phenotypic analysis of peripheral blood cells by flow cytometry demonstrated positivity for CD7, CD13, CD33, and CD34. chromosomal analysis of peripheral blood and bone marrow cells showed trisomy 21; however, that of the buccal mucosal membrane revealed a normal karyotype. A diagnosis of CD7+AML (M2) with trisomy 21 was diagnosed and the patient achieved complete remission following treatment with Japan Adult Leukemia Study Group-AML97 protocol. This is the first reported case of CD7+AML with trisomy 21 as the sole cytogenetic abnormality.

Isolation and characterization of human CD34−Lin− and CD34+Lin− hematopoietic stem cells using cell surface markers AC133 and CD7

Recent evidence indicates that human hematopoietic stem cell properties can be found among cells lacking CD34 and lineage commitment markers (CD34−Lin−). A major barrier in the further characterization of human CD34− stem cells is the inability to detect this population using in vitro assays because these cells only demonstrate hematopoietic activity in vivo. Using cell surface markers AC133 and CD7, subfractions were isolated within CD34−CD38−Lin− and CD34+CD38−Lin− cells derived from human cord blood. Although the majority of CD34−CD38−Lin− cells lack AC133 and express CD7, an extremely rare population of AC133+CD7− cells was identified at a frequency of 0.2%. Surprisingly, these AC133+CD7− cells were highly enriched for progenitor activity at a frequency equivalent to purified fractions of CD34+ stem cells, and they were the only subset among the CD34−CD38−Lin− population capable of giving rise to CD34+ cells in defined liquid cultures. Human cells were detected in the bone marrow of non-obese/severe combined immunodeficiency (NOD/SCID) mice 8 weeks after transplantation of ex vivo–cultured AC133+CD7− cells isolated from the CD34−CD38−Lin− population, whereas 400-fold greater numbers of the AC133−CD7− subset had no engraftment ability. These studies provide novel insights into the hierarchical relationship of the human stem cell compartment by identifying a rare population of primitive human CD34− cells that are detectable after transplantation in vivo, enriched for in vitro clonogenic capacity, and capable of differentiation into CD34+ cells.

Effect of all-trans retinoic acid on chemotherapy induced apoptosis and down-regulation of Bcl-2 in human myeloid leukaemia CD34 positive cells

Acute myeloid leukaemia (AML) is a heterogeneous malignant disease in which disease progression at the level of CD34 positive cells has a major impact in drug resistance and relapse. The multi-drug resistance (MDR1) gene product, P-glycoprotein is expressed mainly in CD34 positive AML cells and Bcl-2 is expressed simultaneously with several putative drug resistance parameters in these cells. Bcl-2 over-expression is associated with CD34 positivity, poor response to chemotherapy and reduced overall survival in AML patients. Recently, all-trans retinoic acid (RA) has been reported to enhance cytarabine-induced apoptosis and downregulate Bcl-2 in several human myeloid leukaemia CD34 negative cells. The two CD34 positive human myeloid leukaemia cell lines: KG1 and KGla have the unique feature of expressing significant functional P-glycoprotein. Thus, the efficacy of RA in enhancing cytrabine- and fludarabine-induced apoptosis and overcoming the resistance was examined in both KG1 (CD34+CD7-) and KGla (CD34+CD7+) human myeloid leukaemia cells in the present study. Both cytarabine and fludarabine induced a dose dependent increase in the number of apoptotic cells in both CD34 positive cell types. Interestingly, the cytarabine-induced apoptosis was significantly more than fludarabine-induced apoptosis in both cell types. All-trans RA alone failed to induce apoptosis or inhibit proliferation of either of the two human CD34 positive leukaemia cell types. However, RA enhanced cytarabine- or fludarabine-induced apoptosis and inhibition of proliferation in KG1 CD34+CD7- but not in KGla CD34+CD7+ myeloid leukaemia cells. As single agents, RA, cytarabine and fludarabine reduced Bcl-2 expression in a dose dependent manner in both cell types. Using a quantitative ELISA assay, the Bcl-2 protein concentration was reduced by 86 or 100%, after 72 h of treatment with 10 microM cytarabine or fludarabine, respectively, in both CD34 positive leukaemia cell types. The addition of RA to cytarabine enhanced its induced reduction of Bcl-2 in KG1 CD34+CD7- but not in KGla CD34+CD7+ human myeloid leukaemia cells. Meanwhile, RA failed to augment fludarabine-induced reduction of Bcl-2 in both cell types. In conclusion, the present results suggest a potential role for the combination of RA and cytarabine in the treatment of refractory and/or relapsed AML patients with CD34+CD7- but not CD34+CD7+ blast cells.