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

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.

Homoharringtonine combined with cytarabine to treat chronic myelogenous leukemia in myeloid blast crisis and its impact on bone marrow CD34+CD7+ cells

BACKGROUND

The therapeutic response of chronic myelogenous leukemia in myeloid blast crisis (CML-MBC) is very poor.

AIM

To explore the therapeutic effect of homoharringtonine (HHT) combined with cytarabine (HA regimen) on CML-MBC and its influence on bone marrow CD34+CD7+ cells.

RESULTS

Thirty-four patients with CML-MBC were treated with the HA regimen and bone marrow CD34+CD7+ cells were assayed prior to and after treatment. Among 33 evaluable patients, the overall hematological response (complete/ partial hematological response and hematological improvement) was 60.1%. Seven patients (21.2%) had a cytogenetic response 12 months after treatment. In the untreated CMLMBC patients, the proportion of bone marrow CD34+CD7+ cells was much higher than in the control group (19.4 ± 7.9 vs. 4.4 ± 1.5%, p < 0.05) and decreased to 14.1 ± 7.1% (p < 0.05) after treatment. Before treatment, the proportion of CD34+CD7+ cells was lower in the patients who had a hematological response to the HA regimen than in the patients who did not respond.

CONCLUSION

The HA regimen is an effective treatment for CML-MBC and CD34+CD7+ cells may be one of the valuable clinical parameters to assess treatment effectiveness.

Expression of the leukemic prognostic marker CD7 is linked to epigenetic modifications in chronic myeloid leukemia

Background

Expression levels of the cell surface glycoprotein, CD7, and the serine protease, elastase 2 (ELA2), in the leukemic cells of patients with chronic myeloid leukemia (CML) have been associated with clinical outcome. However, little is known about the mechanisms that underlie the variable expression of these genes in the leukemic cells.

Results

To address this question, we compared the level of their expression with the DNA methylation and histone acetylation status of 5' sequences of both genes in leukemic cell lines and primitive (lin^-CD34⁺) leukemic cells from chronic phase CML patients. DNA methylation of the ELA2 gene promoter did not correlate with its expression pattern in lin^-CD34⁺ cells from chronic phase CML patient samples even though there was clear differential DNA methylation of this locus in ELA2-expressing and non-expressing cell lines. In contrast, we found a strong relation between CD7 expression and transcription-permissive chromatin modifications, both at the level of DNA methylation and histone acetylation with evidence of hypomethylation of the CD7 promoter region in the lin^-CD34⁺ cells from CML patients with high CD7 expression.

Conclusion

These findings indicate a link between epigenetic modifications and CD7 expression in primitive CML cells.

High expression of CD7 on CD34+cells is not linked to deletion of derivative chromosome 9 or lack of dendritic cells in chronic myeloid leukaemia

OBJECTIVE

High expression of CD7 on CD34+ cells (>20 %) has been shown to be associated with inferior prognosis in chronic myeloid leukaemia (CML), but the reason has not been unravelled. We set out to investigate whether lack of dendritic cells or der(9)t(9;22)(q34;q11) deletions might be correlated with increased CD7 expression on CD34+ cells in CML.

MATERIAL AND METHODS

We identified 43 patients in our cohort of CML patients in the first chronic phase in whom we were able to assess the expression of CD7 on CD34+ cells. der(9)t(9;22) deletions were evaluated by FISH (fluorescent in situ hybridization) analyses and the proportions of plasmacytoid and myeloid dendritic cells were assessed by flow cytometry.

RESULTS

High and low expressions of CD7 on CD34+ cells were found in 19 and 24 patients, respectively. Two out of 20 patients examined had a der(9)t(9;22)(q34;11) deletion, one patient with high expression and one with low expression of CD7 on CD34+ cells. The proportions of plasmacytoid dendritic cells (PDCs) and myeloid dendritic cells (MDCs) were reduced in a majority of patients in our cohort, but no correlation was found between high or low expression of CD7 on CD34+ cells and the proportion of dendritic cells.

CONCLUSIONS

A high proportion of CD34+CD7+ cells in patients with CML is not associated with der(9)t(9;22)(q34;q11) deletions. Nor did we find any correlation between CD7 expression on CD34+ cells and lack of dendritic cells. High expressions of CD7 on CD34+ cells and der(9)t(9;22)(q34;q11) deletions seem to be independent prognostic markers in CML.

Diagnostic flow cytometry for low-grade myelodysplastic syndromes

It has long been considered that flow cytometry (FCM) has little role in clinical practice in the diagnosis of myelodysplastic syndromes (MDS). However, recent advances in the analytical method and knowledge of MDS FCM are changing this stereotype. This paper reviews the concept and current status of FCM in the diagnosis of low-grade MDS. The diagnosis of low-grade MDS in the absence of ringed sideroblasts and chromosomal aberration is not always straightforward, and a report from a recent international working conference has proposed FCM as an adjunctive diagnostic test for such cases. Currently, only a limited number of laboratories are applying FCM to the diagnosis of MDS. Furthermore, standard analytical methods in FCM for MDS have not been established, and no single FCM parameter is sufficiently sensitive and specific to make the diagnosis of MDS. To establish MDS FCM as a widely accepted, dependable diagnostic tool, prospective studies should increase flow parameters that can be analysed reproducibly and determine their sensitivity and specificity, either alone or in combination. CD34+ cell-related parameters that are applicable for diagnosing low-grade MDS in many laboratories are introduced here.

Hematopoietic stem cells and progenitors of chronic myeloid leukemia express leukemia-associated antigens: implications for the graft-versus-leukemia effect and peptide vaccine-based immunotherapy

The cure of chronic myeloid leukemia (CML) patients following allogeneic stem cell transplantation (SCT) is attributed to graft-versus-leukemia (GVL) effects targeting alloantigens and/or leukemia-associated antigens (LAA) on leukemia cells. To assess the potential of LAA-peptide vaccines in eliminating leukemia in CML patients, we measured WT1, PR3, ELA2 and PRAME expression in CD34+ progenitor subpopulations in CML patients and compared them with minor histocompatibility antigens (mHAgs) HA1 and SMCY. All CD34+ subpopulations expressed similar levels of mHAgs irrespective of disease phase, suggesting that in the SCT setting, mHAgs are the best target for GVL. Furthermore, WT1 was consistently overexpressed in advanced phase (AdP) CML in all CD34+ subpopulations, and mature progenitors of chronic phase (CP) CML compared to healthy individuals. PRAME overexpression was limited to more mature AdP-CML progenitors only. Conversely, only CP-CML progenitors had PR3 overexpression, suggesting that PR1-peptide vaccines are only appropriate in CP-CML. Surface expression of WT1 protein in the most primitive hematopoietic stem cells in AdP-CML suggest that they could be targets for WT1 peptide-based vaccines, which in combination with PRAME, could additionally improve targeting differentiated progeny, and benefit patients responding suboptimally to tyrosine kinase inhibitors, or enhance GVL effects in SCT patients.

Flow cytometry in myelodysplastic syndromes: Report from a working conference

Since new therapeutic strategies are emerging in myelodysplastic syndromes (MDS), a refined diagnostic procedure of the several subgroups of MDS is of increased importance. Multidimensional flow cytometry may add significantly to a more detailed analysis of the hematopoietic lineages with respect to qualification and quantification of bone marrow cells and is described in detail. Clearly defined aberrancies on myeloid immature and maturing cells are now identified with possible impact on diagnosis, classification and prognostication in the near feature.

Molecular profiling of CD34+ cells identifies low expression of CD7, along with high expression of proteinase 3 or elastase, as predictors of longer survival in patients with CML

Although most patients with chronic myeloid leukemia (CML) have the same initial molecular abnormality, the BCR-ABL fusion gene, the duration of chronic phase (CP) varies widely. To identify the possible molecular basis of this heterogeneity, we studied CD34+ cells collected at diagnosis from 68 patients with CML-CP. By using oligonucleotide microarray screening, we performed gene-expression profiling on 2 subsets of patients, one comprising patients with an “aggressive disease” who developed blastic transformation (BT) within 3 years of diagnosis (n = 10) and, at the other extreme, patients with an “indolent disease” whose BT occurred 7 or more years from diagnosis (n = 9). This screening revealed 20 genes differentially expressed in patients with aggressive and indolent disease, which were validated by quantitative reverse transcriptase/polymerase chain reaction (Q-RT/PCR). A multivariate Cox regression model identified the combination of low CD7 expression with high expression of proteinase 3 or elastase as associated with longer survival in the complete cohort of 68 patients. This differential pattern of gene expression probably reflects the intrinsic heterogeneity of the disease; if so, assessing expression levels of selected genes at diagnosis may be valuable in predicting duration of survival in patients treated with imatinib and the newer tyrosine kinase inhibitors.

CD34+CD7+ Leukemic Progenitor Cells May Be Involved in Maintenance and Clonal Evolution of Chronic Myeloid Leukemia

Purpose: We analyzed CD34+ cells coexpressing CD7 in chronic myeloid leukemia (CML) in chronic phase (CP) or accelerated phase (AP) to clarify their role in progression or regression of the disease during treatment.

Experimental Design: Enumeration of CD34+CD7+ cells was done on bone marrow nucleated cells from normal donors and CML patients. Fluorescence in situ hybridization analysis was done on sorted CD34+CD7+ and CD34+CD7− cells to examine the occupancy rate of each fraction by BCR-ABL+ cells with or without additional cytogenetic abnormalities.

Results: The proportion of CD34+CD7+ cells was significantly affected by the treatment outcome and/or the disease status as follows: 20.5 ± 10.4% in normal donors (n = 22), 18.1 ± 10.2% in CP with major cytogenetic response (n = 14), 53.0 ± 12.9% in CP at diagnosis (n = 18), 55.0 ± 15.8% in CP with minor or no cytogenetic response (n = 28), and 70.2 ± 18.1% in AP (n = 6). The proportion of CD34+CD7+ cells decreased in parallel with cytogenetic improvement in individual patients. In six untreated CP patients, the ratio of BCR-ABL+ cells was comparable between each fraction. In three patients with major cytogenetic response, the ratio of BCR-ABL+ cells was remarkably lower in CD34+CD7− cells than in CD34+CD7+ cells. In three AP patients with additional cytogenetic abnormalities, extra signals were detected at a much higher rate in CD34+CD7+ cells than in CD34+CD7− cells.

Conclusions: Our results suggest that CD34+CD7+ cells may be involved in maintenance and clonal evolution of BCR-ABL+ cells in CML.