Abstract
Tryptase is a serine protease that is expressed in leukemic cells of chronic myeloid leukemia (CML) patients and in blasts of acute myeloid leukemia (AML) patients. Tryptase may be useful for diagnosis, assessment of severity of disease (leukemic cell burden), monitoring minimal residual disease and prognosis of AML and CML patients. The main objective of this study was to assess the serum levels of tryptase activity among CML and AML patients and to compare the serum levels of tryptase activity of acute and chronic myeloid leukemia patients with each other and with those of healthy controls. To meet this objective, a hospital-based comparative cross-sectional study was conducted among CML and AML patients from February 2016 up to December 2016. Serum samples were obtained from 24 AML, 60 CML and 35 healthy controls. Fluorogenic assays for serum tryptase activity using aminomethylcoumarin (AMC) peptide derivative were carried out. Statistical analysis was done by using SPSS version 20. Descriptive statistics, Paired Samples T-test, Wilcoxon Signed Rank test and Spearman’s rho test were used to investigate any correlation among different parameters. The minimum level of statistical significance was set at p-value <0.05. Accordingly, the mean and median serum levels of tryptase activity were significantly higher in patients with AML and CML than in the healthy controls (P-value < 0.05). CML patients in chronic phase (CP) and secondary AML patients had significantly higher mean and median serum levels of tryptase activity than CML patients in accelerated/blast phase (AP/BP) and de novo AML patients (p-value < 0.05). These elevated mean and median levels of serum tryptase activities were due to a subset of individuals with elevated serum tryptase levels (41.7 % of AML & 30 % of CML); the remaining leukemic individuals (58.3 % AML & 70 % of CML) had normal serum levels of tryptase activity. Finally, it was concluded that the serum tryptase level might be a useful diagnostic and prognostic marker in a subset of patients with CML and AML. However, further studies that incorporate other protocols such as tryptase immunoassay are warranted to exclude contaminant non-tryptase proteases from the serum samples.
Highlights
This study focused on serum level of tryptase activity thatmay solve the problems of feasibility, sensitivity and constant positivity related to the potential diagnostic markers of Acute myeloid leukemia (AML) and Chronic myeloid leukemia (CML) used a day
It was found that the mean level of serum tryptase activity was significantly lower in healthy controls than in CML patients and AML
It was found that the median level of serum tryptase activity was significantly lower in healthy controls (241.5 pM/sec) than in CML patients (266 pM/sec) and AML patients (273.5 pM/sec) (Wilcoxan Signed Rank test, % CI = 95, p-value = 0.00) (Table 2)
Summary
Tryptase is a 134 kDa neutral serine protease [3], [11] which is highly expressed in mast cells and to a lesser extent in peripheral blood basophils [10], [24], and in leukemic cells of CML patients [25] and in blasts of AML patients [26]. Peripheral blood basophils express 500-fold less tryptase than mast cells in tissue [28]. Tryptase derives its name from its characteristic trypsin-like substrate specificity in which it cleaves peptide or protein substrates preferentially on the carboxyl side of lysine (K) or arginine (R) residues [3], [24]. Tryptase cleaves a scissile peptide bond in a protein or peptide or amide bond in a synthetic peptidyl chromogenic or fluorigenic substrate. Substrate amino acids that are on the amino (N) side of the scissile bond are numbered P1, P2, and P3, and so on (called P sites) with the one closest to the scissile bond numbered P1, and those that are on the carboxyl (C) side of the scissile bond are numbered as P1', P2', P3’ and so on (called P’ sites).Their corresponding binding sites on the protease are labeled with S(S1, S2, and S3...) and S’ (S1’, S2’ and S3’..., respectively (as shown in Figure 1) [30], [31]
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