Activated FVII-Antithrombin Complex and Tissue Factor mRNA As Potential Markers of Severe Thrombo-Hemorrhagic Syndrome in APL Patients

Abstract

Abstract 1195▪▪This icon denotes a clinically relevant abstract Introduction:Tissue Factor (TF) expressed by acute promyelocytic leukemia (APL) cells may have an important role in the pathogenesis of the life-threatening coagulopathy typical of the onset of this disease. In APL patients, the remission induction differentiating therapy with all-trans-retinoic acid (ATRA) downregulates TF expression by APL blasts and produces a simultaneous correction of the hypercoagulation and thrombo-hemorrhagic syndrome (THS). However the rate of early deaths due to the THS is still relevant in this disease. Therefore characterizing the coagulopathy and identifying predictive markers remain a critical issue. Aim: In this study, in newly diagnosed APL patients, we prospectively evaluated the rate of hemorrhage and thrombosis, in the first month after diagnosis, in relation to the plasma levels of activated factor VII-antithrombin complex (FVIIa-AT), a new parameter which may reflect the degree of TF exposure and activity. TF mRNA in the peripheral blood APL cells was also evaluated as well as the plasma levels of thrombin-antithrombin complex (TAT) and D-dimer, as additional coagulation markers. Methods: Fifty-four consecutive APL patients receiving ATRA+Idarubicin for the remission induction (GIMEMA protocol AIDA2000) were enrolled. Blood samples from 26 of these patients (F/M= 10/16) were obtained at the onset (T0) of the disease, and on days 7, 14 and 28 (T7, T14, T28) of remission induction therapy. Twenty-five healthy subjects acted as a control group. Plasma FVIIa-AT, TAT, and D-dimer were measured by ELISA. TF mRNA expression by peripheral blood mononuclear cells (PBMC) was evaluated by real time-polymerase chain reaction. Results: At the disease onset 8/54 patients had early major hemorrhages (15%), including 3 (5.5%) fatal intracranial bleeding and 5 non-fatal major bleeding (9.2%); 3/54 had thrombosis (1 fatal Budd-Chiari syndrome, and 2 non-fatal events). Two more patients developed deep vein thrombosis at 7 and 14 days of induction therapy (3.7%), respectively. Of the 26 patients included in the laboratory study, 3 had thrombosis at the diagnosis of APL. At T0, before starting therapy, the levels of FVIIa-AT as well as those of TAT and D-dimer were significantly higher in APL patients compared to controls (p<0.05). However, while the levels of FVIIa-AT complex were lower in patients with thrombosis than in those without (120±50 vs 332±75 ng/ml), differently the levels of TAT and D-dimer were not different between two groups, indicating that the FVIIa-AT is more sensitive to the consumption coagulopathy compared to the other thrombotic markers. During ATRA therapy the levels of FVIIa-AT were progressively decreased at T7 and T14, and dropped significantly at T28 (p<0.05 vs T0); TAT and D-dimer levels were also decreased starting from T7 to T28 (p<0.05 vs T0). In addition, in APL PBMC from 9 patients, the levels of TF mRNA, initially elevated compared to healthy control PBMC (p<0.05), were significantly decreased by 68% and 90%, at T7 and T28, respectively. Conclusions: These results confirm a significant rate of early deaths in APL due to the coagulopathy. FVIIa-AT complex levels paralleled TF mRNA expression and may therefore be a useful surrogate tool for the TF activity measurement in the peripheral blood. In addition, the study shows that, among hypercoagulation markers, which are overall elevated at the onset of APL, the ‘low' levels of plasma FVIIa-AT complex is the only parameter able to distinguish patients at highest risk of severe THS. Although the small size of the study did not allow to calculate the predictive value of this marker, FVIIA-AT complex may be a promising simple candidate biomarker to test for the predictive risk of lethal/severe THS in large prospective studies of APL patients. Disclosures:No relevant conflicts of interest to declare.