Serine protease (TPS): A diagnostic and prognostic marker in pediatric patients with acute non-lymphoblastic leukemia

Abstract

The Serine protease, TPS (tryptase), is a specific marker for mast cells and mast cell-associated disorders. However, substantial amounts of TPS are also expressed in neoplastic myeloid, non-mast cell lineage. The aim of this study is determination and quantitation of TPS expression in patients with acute non-lymphoblastic leukemia (ANLL); to evaluate its prognostic value and its relevance as a genetic marker for detection of minimal residual blast cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect levels of TPS from 30 newly diagnosed ANLL children and 10 normal children served as controls. TPS levels for positive cases were reevaluated after induction chemotherapy; after onset of relapse or by the end of the study. Our results showed that the gene transcripts were detected in 56.7% of patients but were not expressed by normal controls. The highest frequency of TPS was recorded in patients with M4 showing significantly higher levels compared to other FAB (French– American–British Classification) subtypes. TPS levels were directly correlated to TLC, absolute blast counts in peripheral blood, levels of CD34 and CD117. After induction chemotherapy, levels of TPS decreased  significantly in those who achieved complete remission while it increased significantly in relapsed patients with a risk estimate of relapse six times higher in positive cases than TPS negative patients. 84.6% of the patients negative for TPS achieved complete remission with better disease free survival. In conclusion, TPS is expressed in a group of patients with ANLL thus serves as a disease related marker; it could be used as a prognostic indicator in evaluating remission status and early relapse as its elevated levels are associated with high risk of relapse; again, it is useful in predicting disease outcome.

Keywords: Serine protease; Tryptase (TPS); RT-PCR; ANLL; Prognosis; Outcome