The diverse expression of the WT1 gene in patients with acquired bone marrow failure syndromes

Clinical significance of the increased expression of the WT1 gene in peripheral blood of patients with acquired aplastic anemia

To determine the significance of increased Wilms tumor 1 (WT1) gene expression in the peripheral blood of patients with acquired aplastic anemia (AA), we analyzed serial changes in WT1 mRNA copy number (WT1cn) in 63 patients with AA as well as in five patients with myelodysplastic syndromes (MDS) and seven patients with paroxysmal nocturnal hemoglobinuria (PNH). WT1cn was higher than the cut-off (≥50 copies/μg RNA) at the time of the first measurement in 41% of untreated (60-190 copies/μg RNA [median 130]) and 59% of treated (59-520 copies/μg RNA [median 150]) AA patients. Although WT1cns gradually increased in most AA patients during the 2-105 months follow-up period, they did not lead to clonal evolution except in three patients in whom the maximum change ratio of WT1cn (WT1cn-change max), defined as the ratio of WT1cn at the first examination to that of the maximum value, exceeded 20.0 and who developed MDS at 2, 46, and 105 months. Increased WT1 gene expression was enriched in granulocytes rather than in mononuclear cells in most WT1-positive AA patients and did not correlate with mutations of genes associated with myeloid malignancy. WT1cns were high at 690-5700 (median 2000) in MDS patients and remained high thereafter, while WT1cns in PNH patients (77-200; median 96) were similar to those in AA. Thus, moderate increases in WT1cns up to 600 are common in AA patients in stable remission. An increase in the WT1cn-change max over 20.0 may portend transformation from AA to MDS.

Impaired immunosuppressive role of myeloid-derived suppressor cells in acquired aplastic anemia

Myeloid-derived suppressor cells (MDSC) are a group of heterogeneous immature myeloid cells and display immunosuppressive function. In this study, MDSC populations were evaluated in acquired aplastic anemia (AA) (n=65) in which aberrant immune mechanisms contributed to bone marrow destruction. Our data demonstrate that both the proportion and immunosuppressive function of MDSC are impaired in AA patients. Decreased percentage of MDSC, especially monocytic MDSC, in the blood of AA patients (n=15) is positively correlated with the frequency of T-regulatory cells, bone marrow level of WT1 and decreased plasma level of arginase-1. RNA sequencing analyses reveal that multiple pathways including DNA damage, interleukin 4, apoptosis, and Jak kinase singnal transducer and activator of transcription are upregulated, whereas transcription, IL-6, IL-18, glycolysis, transforming growth factor and reactive oxygen species are downregulated in MDSC of AA (n=4), compared with that of healthy donors (n=3). These data suggest that AA MDSC are defective. Administration of rapamycin significantly increases the absolute number of MDSC and levels of intracellular enzymes, including arginase-1 and inducible nitric-oxide synthase. Moreover, rapamycin inhibits MDSC from differentiating into mature myeloid cells. These findings reveal that impaired MDSC are involved in the immunopathogenesis of AA. Pharmacologically targeting of MDSC by rapamycin might provide a promising therapeutic strategy for AA.

[Changes of WT1 mRNA expression level in patients with myelodysplastic syndromes after hypomethylating agents and its prognostic significance]

Objective: To monitor the WT1 mRNA level and its dynamic changes in patients with myelodysplastic syndromes (MDS) after hypomethylating agents (HMA) , as well as to assess the significance of WT1 mRNA levels and its dynamic changes in evaluating the efficacy of HMA and distinguishing the disease status of heterogeneous patients with stable disease (SD) . Methods: Bone marrow or peripheral blood samples of 56 patients with MDS who underwent hypomethylating agents (≥4 cycles) from November 2009 to March 2018 were tested by real-time quantitative polymerase chain reaction (PCR) to detect the expression of WT1 mRNA, and to observe the correlation between the dynamic changes of WT1 mRNA expression and clinical efficacy and prognosis of patients. Results: WT1 mRNA expression levels of MDS patients decreased significantly after 3 cycles of hypomethylating agent treatment. Besides, the WT1 mRNA expression levels of patients increased significantly after diseases progression. According to the dynamic changes of WT1 mRNA expression levels during SD, 45 cases could be further divided into increased group and non-increased group. In those SD patients with increased WT1 mRNA expression level, the ratio of suffering disease progression or transformation to AML was 95.65% (22/23) , whereas the ratio turned to be 9.09% (2/22) for the non-increased group (χ(2)=33.852, P<0.001) . Compared with those SD patients reporting no increase in WT1 mRNA expression level, the overall survival[17 (95%CI 11-23) months vs not reached, P<0.001] and progression-free survival [13 (95%CI 8-18) months vs not reached, P<0.001] of those SD patients reporting increase in WT1 mRNA expression level were significantly shorter. Conclusion: WT1 mRNA expression level is a useful indicator to assess the efficacy of hypomethylating agents in MDS patients. Especially in patients with SD, detection of the changes in WT1 mRNA expression level is able to predict disease progression and help to make clinical decision.