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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 41  |  Issue : 4  |  Page : 206-210

Dipeptidyl peptidase-4 (CD26): a prognostic marker in patients with B-cell chronic lymphocytic leukemia


1 Department of Clinical Pathology, Faculty of Medicine, Tanta University, Tanta, Egypt
2 Department of Internal Medicine, Faculty of Medicine, Tanta University, Tanta, Egypt

Date of Submission21-Aug-2016
Date of Acceptance30-Aug-2016
Date of Web Publication20-Jan-2017

Correspondence Address:
Hossam Hodeib
Department of Clinical Pathology, Faculty of Medicine, Tanta University, El Geish Street, Tanta, 31511
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-1067.198650

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  Abstract 

Introduction B-cell chronic lymphocytic leukemia (B-CLL) is an incurable disease; nevertheless, its prognosis varies widely among patients. CD26 is considered a cell adhesion molecule. It is suggested that CD26 expression is involved in tumor growth, invasion, and metastasis.
Aim The aim of this study was to assess the prognostic value of dipeptidyl peptidase-4 (CD26) in patients with B-CLL and its relation to the clinical and laboratory parameters.
Patients and methods This case–control study was carried out from April 2013 to April 2016, and it was performed on 75 newly diagnosed B-CLL patients admitted at Hematology and Oncology Unit, Department of Internal Medicine, Tanta University Hospital, Egypt; 30 apparently healthy individuals were involved in the study as the control group. Dipeptidyl peptidase-4 (CD26) expression was evaluated by flow cytometry.
Results The main finding in this study was that CD26 expression was increased in B-CLL patients in comparison with normal subjects. There was also a positive correlation between white blood cell count, absolute lymphocytosis, clinical staging of B-CLL patients, and CD26 expression. Overall survival (OS) and disease-free survival (DFS) were shorter in B-CLL patients with positive CD26 expression compared with patients with negative CD26 expression. Patients with positive CD26 expression had significantly shorter OS (16 vs. 20 months) and significantly lower DFS (6 vs. 16.5 months) at 24 months compared with those with negative CD26 expression.
Conclusion CD26 expression was significantly higher in B-CLL patients compared with healthy subjects, and its expression among B-CLL patients correlated with poor laboratory data, clinical staging, OS, and DFS, and thus it may play a role in prognosis of B-CLL. CD26 could be used as a prognostic marker either alone or in combination with other markers in assessment of B-CLL patients.

Keywords: CD26, chronic lymphocytic leukemia, dipeptidyl peptidase-4


How to cite this article:
Hodeib H, Shahbah A. Dipeptidyl peptidase-4 (CD26): a prognostic marker in patients with B-cell chronic lymphocytic leukemia. Egypt J Haematol 2016;41:206-10

How to cite this URL:
Hodeib H, Shahbah A. Dipeptidyl peptidase-4 (CD26): a prognostic marker in patients with B-cell chronic lymphocytic leukemia. Egypt J Haematol [serial online] 2016 [cited 2019 Dec 8];41:206-10. Available from: http://www.ehj.eg.net/text.asp?2016/41/4/206/198650


  Introduction Top


The accumulative rise of incompetently functional mature-looking bloodstream-circulating monoclonal B lymphocytes together within bone marrow, lymph nodes, and spleen/liver have always characterized B-cell chronic lymphocytic leukemia (B-CLL) [1]. The highest proportion of peripherally located B-CLL lymphocytes is either in the G0 or early G1 phase of the cell cycle. Defects in apoptosis have been linked to the summation of leukemic cells and the progression of the disease, and it is postulated to be responsible for resistance of the disease against chemotherapy [2]. B-CLL is an incurable disease; nevertheless, its prognosis varies widely among patients, as in some the disease may flare up swiftly regardless of the intensive treatment and result in patient mortality within 2–3 years, whereas other patient mortalities occur because of causes not linked to B-CLL [3]. Dipeptidyl peptidase-4 (CD26) (PPD-4) is a serine exopeptidase belonging to the S9B protein family, which breaks the X-proline dipeptides from the N terminus of polypeptides [4]. It is a type II transmembrane glycoprotein, expressed on the surface of many cell types. CD26 has many physiological roles, as it is responsible for immune regulation through T-cell activation [5],[6]. CD26 interacts with proteins of the extracellular matrix, such as fibronectin, and thus it is considered a cell adhesion molecule [7]. CD26 has been detected on the cell surface of different types of cancers such as cancer colon [8],[9],[10]. It is suggested that CD26 expression is involved in tumor growth, invasion, and metastasis [11],[12].

The aim of this study was to assess the prognostic value of dipeptidyl peptidase-4 (DPP4) (CD26) in B-CLL patients, and its relation to clinical and laboratory parameters.


  Patients and methods Top


This case–control study was carried out from April 2013 to April 2016, and it was performed on 75 newly diagnosed B-CLL patients admitted at Hematology and Oncology Unit, Department of Internal Medicine, Tanta University Hospital, Egypt; 30 apparently healthy individuals were involved in the study as the control group after approval by the hospital ethical committee, and the study was conducted according to the principles of the declaration of Helsinki. A written informed consent of the patients was obtained.

Inclusion criteria were patients admitted to our hospital who were suffering from B-CLL. None of them had any evidence of neoplastic or other systemic diseases. According to modified RAI staging system of CLL, the B-CLL cases in the present study were categorized into three classes.

Exclusion criteria were patients suffering from any malignant diseases other than B-CLL.

All patients were asked to enter the study at the time of the admission, and they were observed for a period of 3 years or until death of the patients, which is the endpoint of the study.

Blood collection and laboratory assay

Laboratory assays were performed in blood obtained from B-CLL patients and the healthy control subjects. Liver function tests and kidney function tests were performed on fully automated chemistry analyzer (Konelab Prime 60i, Konelab; Vantaa, Finland). Complete blood count was performed on a fully automated cell counter (PCE 210 N; Erma Inc., Tokyo, Japan). Immunophenotyping was performed for all B-CLL patients.

All flow cytometric analyses were performed on an FACS Caliber flow cytometer (BD Biosciences, San Diego, California, USA). Monoclonal antibodies used were CD5-FITC, CD19-PE, CD20-APC, CD10-PE, CD2-FITC, CD23-PE, FMC-7-FITC, CD79b-PE, CD200-PE, CD38-FITC, ZAP-30-Percp, CD26 PE, Kappa-FITC, and Lambda-PE (Becton Dickinson, Mountain View, California, USA), including one tube for negative isotypic control. A volume of 100 μl of each sample was delivered in each tube, and 5 μl of each monoclonal antibody was added to the respective tubes. The tubes were vortexed and incubated in the dark at room temperature for 25 min. A volume of 1 ml of lysis solution was added to each tube. The tubes were vortexed and incubated for 20 min in the dark at room temperature. The tubes were centrifuged at 3000 rpm for 5 min and the supernatant was discarded. A volume of 0.5 ml of PBS as washing solution was added to each tube and mixed thoroughly. The tubes were centrifuged at 3000 rpm for 5 min, and the supernatant was discarded; this step was repeated. Cells were suspended in 300 μl of PBS and were ready for acquiring data by the flow cytometer. A total of 10 000 events (cells) were acquired, from which the lymphocytes were selectively gated (CD5+, CD19+ cells) for immunophenotyping analysis. The cutoff of positivity was 30% for all B-CLL markers except for ZAP-70, which was 20% [13] and CD26, which was 10% [14].

Statistical analysis

Data were analyzed using SPSS, version 16 (SPSS, version 23, Armonk, NY, USA). Quantitative data were expressed in the form of mean±SD, and qualitative data were described in the form of number and percentage. Differences between groups were evaluated with t-test and F-test. Disease-free survival (DFS) and overall survival (OS), measured from diagnosis, were detected by the Kaplan–Meier method, and comparisons between groups were performed by means of the log rank test [15].


  Results Top


A total of 105 subjects were included in the study, with 75 patients presenting with B-CLL, 28% female and 72% male, and 30 healthy subjects (control group), 30% female and 70% male. The mean of age (in years) of B-CLL patients and the healthy subjects was 62.626±7.508 and 62.066±6.71, respectively. In all, 76% of our patients presented with hepatosplenomegaly and 68% presented with lymphadenopathy. There were no significant differences between all groups regarding age and sex (P>0.05). There was a highly significant decrease in hemoglobin (Hb) levels and platelet count in B-CLL patients compared with healthy subjects (P<0.001). In addition, there was a highly significant increase in white blood cell (WBC) count and peripheral blood lymphocytes in B-CLL patients compared with healthy subjects (P<0.001) ([Table 1]). Interestingly, CD26 expression in B-CLL patients ranged from 2 to 60%, with a mean of 26.6±16.18, whereas healthy subjects showed negative expression of CD26, which ranged from 1 to 6% with a mean of 3.36±1.54 (P<0.001) ([Table 2]). In addition, there was a significant positive correlation between CD26 expression in B-CLL patients and WBCs, peripheral blood lymphocytosis, and ZAP-70, whereas there was a significant negative correlation between CD26 expression in B-CLL patients and Hb and platelet count and there was no correlation between CD26 expression in B-CLL patients and age and CD38 expression ([Table 3]). Furthermore, according to the modified RAI staging system, the B-CLL patients in the present study were categorized into three classes: the first class included 45 patients out of 75 (60%) patients with high risk, the second class included 15 (20%) patients with intermediate risk, and the third class included another 15 (20%) patients with low risk. In the present study, there was a statistically significant increase in CD26 percentage of expression in the high-risk group of patients in comparison with those with intermediate or low risk. In addition, there was a statistically significant increase in CD26 expression in the intermediate-risk group of patients in comparison with those with low risk − that is, these results indicated that there was a positive correlation between clinical staging and CD26 percentage of expression ([Table 4]). Interestingly, patients with positive CD26 expression had significantly shorter OS (16 vs. 20 months) and significantly lower DFS (6 vs. 16.5 months) at 24 months versus those with negative CD26 expression (P<0.001) ([Figure 1],[Figure 2],[Figure 3],[Figure 4]).
Table 1 Clinical and laboratory data of studied subjects

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Table 2 CD26 expression in the studied subjects

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Table 3 CD26 expression in studied patients and other laboratory data

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Table 4 CD26 expression and staging of studied B-CLL patients

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Figure 1 Kaplan–Meier procedure of CD26 expression and overall survival in B-cell chronic lymphocytic leukemia (B-CLL) patients.

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Figure 2 Kaplan–Meier procedure of CD26 expression and disease-free survival in B-cell chronic lymphocytic leukemia (B-CLL) patients.

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Figure 3 Negative CD26 expression.

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Figure 4 Positive CD26 expression.

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  Discussion Top


Indolent course has always characterized B-CLL, which is characterized by progressive splenic and lymph node enlargement associated with peripheral blood lymphocytosis. This disease is related to the accumulation of monoclonal B cells with the morphology of small mature lymphocytes. B-CLL patients follow heterogeneous clinical courses. Some survive for a long time without therapy, whereas others die rapidly despite aggressive treatment [16]. CD26 is a 110-kDa surface glycoprotein that is expressed on many different types of cell and has various biological functions. DPP4 acts as a regulatory protein in tumor development and progression by changing the effect of biologically active peptides; it also causes extracellular matrix degradation [17]. In the present study and according to modified RAI staging system, B-CLL patients were categorized into three classes − low risk (15 patients), intermediate risk (15 patients), and high risk (45 patients) − and most patients were included in the high-risk group with lymphocytosis together with anemia or thrombocytopenia. This was in contrast with the study by Zwiebel and Cheson [18], who reported that most B-CLL cases were low risk. It may be attributed to the delay in seeking medical advice in the present work; thus, there was a delay in diagnosis of the disease and hence the majority of patients were classified as the higher-risk group. The main finding in the present study was that there was a statistically significant increase in the percentage of CD26 expression in the high-risk group of patients in comparison with those with intermediate or low risk. In addition, there was a statistically significant increase in CD26 expression in the intermediate-risk group of patients in comparison with those at low risk; that is, these results indicated that there was a positive correlation between clinical staging and CD26 expression. These results were in accordance with those reported by Cro et al. [14], who reported a correlation between CD26 expression and clinical course in B-CLL patients. In the present study, no significant association was detected between CD26 expression and both age and sex, which was in agreement with that reported by Molica et al. [19], who found no association between both age, sex, and CD26 expression. In the present study, there was a negative correlation between Hb level and platelet count and CD26 expression. On the other hand, there was a positive correlation between WBC counts, peripheral blood lymphocytes, and CD26 expression. These results were in accordance with results reported by Cro et al. [14], and Ibrahim et al. [20]. There was also a positive correlation between ZAP-70 expression and CD26 expression, which was in an agreement with the studies by Cro et al. [14], and Ibrahim et al. [20]. There was no correlation between CD38 expression and CD26 expression. These results were in contrast to those reported by Ibrahim et al. [20], who reported that CD38 expression correlated with CD26 expression. Patients with positive CD26 expression had significantly shorter OS (16 vs. 20 months) and significantly lower DFS (6 vs. 16 months) at 24 months versus those with negative CD26 expression (P<0.001). These results were in accordance with those found by Cro et al. [14], and Ibrahim et al. [20]. Ultimately, CD26 has enzymatic activity and interacts with other molecules. The substrates of CD26 are neuropeptides, growth factors, chemokines, and vasoactive peptides. DPP4 plays an essential role in regulation of immunity, signal transduction, and apoptosis. Furthermore, CD26 appears to play an important role in tumor progression [17].


  Conclusion Top


CD26 expression was significantly higher in B-CLL patients compared with healthy subjects, and its expression among B-CLL patients correlated with poor laboratory data, clinical staging, OS, and DFS, and thus it may play a role in prognosis of B-CLL. CD26 could be used as a prognostic marker either alone or in combination with other markers in assessment of B-CLL patients.

Acknowledgements

The authors thank the nurses at Internal Medicine and Clinical Pathology departments, Tanta University Hospital, for their assistance in conducting the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]


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