Serum tryptase levels in acute leukemia at diagnosis: Correlation with CBF AML

Α and β tryptase genes cluster on the short arm of human chromosome 16 and encode lineage-associated serine proteases that are abundantly expressed in mast cells and, in trace amounts, in basophils. Under physiologic conditions no other myeloid cells express tryptases. However, in several myeloid leukemia cell lines and in AML blasts, the level of tryptase is elevated. In vitro, AML blasts are capable to produce and release the α-protryptase constitutively. Recently, elevated levels of serum tryptase have been detected in certain FAB subtypes of AML, particularly in AML-M4eo. In an attempt at correlating the levels of tryptase with FAB classification and cytogenetics, we have analyzed serum samples collected at diagnosis, from 103 AML and 57 ALL patients referred to our Institution. The total serum concentration was determined by UniCAP 100 and UniCAP Tryptase Fluorenzyme Immunoassay Kit (Pharmacia-Upjohn, Uppsala, Sweden). The median value of tryptase level in the control group (50 healthy people; mean age 35 y, range 20–50; M/F= 26/24) amounted to less than 5 ng/ml. We found elevated tryptase levels (more than 15 ng/ml) in 46 out of 103 AML-patients (44.6%) and in 1 out of 57 ALL-patients (1.75%) (p = <0.0001). In AML, the patients showing elevated tryptase levels resulted equally distributed among the FAB subtypes (M0, M1, M2, M3, M4, M4Eo, M5) (p = 0.269). In the group of 18 AML with t(8;21) or inv(16), we recorded the highest frequency (89%) of cases with tryptase more than 15 ng/ml (p =< 0.001) and the highest median serum tryptase levels (>89.3 ng/ml) (p = 0.0001), in comparison with other cytogenetic groups (diploid, n= 43; t(15;17), n=10; other, n=29). Our data suggest that elevated serum tryptase levels at diagnosis may play a role as a marker for CBF AML subtypes.