WT1 Gene Expression Research Articles

Minimal Residual Disease Evaluation By Real-Time Quantitative Polymerase Chain Reaction for Wilms Tumor 1 Gene Expression and Multicolour Flow Cytometry, in Pediatric B Lineage Acute Lymphoblastic Leukemia

Introduction: Minimal residual disease (MRD) determination involves the measurement of very low levels of leukemia using sensitive techniques which at present are complex, time consuming and require expertise for performance and interpretation. A ''panleukemic''marker such as Wilm's tumor 1 gene (WT1) which is frequently over expressed in acute leukemia could simplify MRD detection and serve as a useful prognostic marker.Aim of study: To evaluate the usefulness of WT1 gene expression, as a marker for MRD in B-lineage acute lymphoblastic leukemia (B-ALL).Method and Material: Flow cytometric immunophenotyping (FCMI) and real time-polymerase chain reaction (RQ-PCR) for WT1 gene expression were performed usingbone marrow at diagnosis and at day 15 (mid-induction). Of the 23 patients recruited, day 15 MRD analyses by both these methods was performed on 11 bone marrow samples of patients who showed WT1 over expression at day 0.Results:WT1 over expression at diagnosis was found in 69.5% cases (16/23). MRD was detectable in 54.5% cases by WT1 RQ-PCR and by FCM in 72% cases. A statistically significant correlation was seen between WT1 normalized copy number (NCN) at diagnosis with MRD levels detected by FCM.Conclusion:WT1 represents a candidate MRD and prognostic marker. The significant correlation between WT1 over expression at diagnosis and MRD positivity by flow cytometry at day 15 (mid induction) of chemotherapy suggests that high WT1 expression could correlate with unfavourable outcome in childhood ALL.However, as not all patients of B-ALL over-express WT1 at diagnosis, quantitative assessment of WT1 transcripts can be used as useful molecular marker for MRD detection, but only in a subset of patients. DisclosuresNo relevant conflicts of interest to declare.

High Prognostic Value of a 3-Genes Molecular Score in Non-High Risk Acute Promyelocytic Leukemia Treated with AIDA 2000 Protocol: A Retrospective Study from a Regional Register

BACKGROUND AND AIMSNon high risk acute promyelocytic leukemia (APL) patients, as defined by WBC count at diagnosis, have nowadays a very good prognosis when treated with ATRA plus chemotherapy based protocols, with high rate of complete molecular remission after consolidation therapy. However, a small proportion of patients (roughly 10-15%) will eventually relapse, despite the achievement of molecular CR.In the past years, some groups showed that relapse risk could be predicted by testing for some gene alterations, such as FLT3-ITD, or by break point cluster region (BCR) analysis. However, those results were not confirmed in prospective trials.We retrospectively applied a simple 3 gene based molecular panel to low-intermediate risk acute promyelocytic patients, alongside with BCR analysis, in order to develop a risk score.MATERIALS AND METHODSFifty-nine low/intermediate risk APL patients, treated with the Italian age-adapted AIDA protocol from January 1st 2004 to December 31st 2014 in our center were retrospectively included in this study. Median age was 47 years (range 19-88), 16 patients were older than 60 years (27%).BCR analysis was available in all patients, 41 patients showed BCR1/2, whereas 18 patients had BCR3 (30%).Molecular profile included determination of FLT3-ITD mutation, WT1 and BAALC gene expression levels and was available in 38/59 patients (64%); bone marrow sample of diagnosis is available for all other 21 patients for further analysis. Cut-off values for WT1 (20000/abl x 104) and BAALC (450/abl x 104) were arbitrarily chosen after pre-analysis and comparison with our published data.Five patients had FLT3-ITD mutation (13%), 18 (45%) patients had higher WT1 expression levels and BAALC was overexpressed in 9 (24%) patients.Pre-analysis showed that FLT3-ITD, low WT1 levels, high BAALC levels but not the presence of BCR3 were associated with higher relapse risk. A molecular score including those 3 genes was built: 16 patients had no risk factors (42%), 17 patients had one risk factor (45%), 5 had two risk factors (13%).RESULTSFifty-four patients survived induction, all of them achieved CR, in 52 PML/RARα transcript was undetectable after last consolidation therapy. The two patients with molecular persistence of disease received further therapy and then achieved molecular CR. Nine patients (15%) relapsed after a median follow-up of 56 months, 45 patients are alive at the time of analysis (76%). Relapse risk was influenced only by the presence of at least one molecular risk factor (p<0.05), whereas age at diagnosis older than 60 years had only a borderline impact (p=0.105); none of the molecular alterations reached statistical significance if taken alone.Disease free survival (DFS) duration was significantly higher in patients who had none of the molecular risk factor, when compared to patients with at least one (3-years DFS of 100% and 70.8%, respectively, p<0.05, Figure 1). Younger patients had also a longer DFS, with a 3-years DFS of 90.7% and 72% for patients younger or older than 60 years, respectively (p<0.03).Overall survival (OS) analysis led to similar results: patients with no molecular risk factors had a very good outcome when compared to patients with at least one alteration (3-years OS of 100% and 71.5%, respectively, p<0.03). Survival was also influenced by age at diagnosis, as younger patients did significantly better, with 3-years OS of 90% (p<0.05).Again, none of the molecular alterations, if taken alone, had a significant impact on DFS or OS.CONCLUSIONSEven in our small cohort, molecular profile could identify a subset of low-intermediate APL patients at higher risk of relapse, who may take benefit from an intensified consolidation therapy, as it is currently applied to high risk patients defined by WBC at diagnosis. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

New Insight Towards Prognosis in Pediatric Acute Myeloid Leukemia: Comparative Study.

Wilms tumor gene (WT1) is a reliable marker for minimal residual disease assessment in acute leukemia children. This study was designed to demonstrate the potential use of WT1 to establish quality of remission in acute leukemia children for early identification of children at high risk of relapse. This study based on a quantitative Real–Time polymerase chain reaction (PCR) (TaqMan) assay in bone marrow samples collected from 45 acute myeloid leukemia children at diagnosis and during follow-up was established. Our results revealed, there was no significant association between WT1expression,at diagnosis, and either of gender, organomegally, total leucocytic count (TLC), French-AmericanBritish system (FAB) subtypes, CD34 expression, cytogenetic studies, percentage of blast infiltration or response to induction therapy. By comparing the results obtained at day 14 and those obtained at day 28, we cannot depend on WT1gene expression or MRD detection at day14 in predicting resistance to treatment or predicting mortality (p= 0.12). In contrast WT1 gene expression or MRD detection values after induction therapy (at day28) is an independent prognostic risk factor of relapse (p= 0.001) and death (p= 0.001). The blast percentage was significantly correlated to the WT1expression levels at day 28.The presence of MRD or WT1gene expression at the end of induction therapy is an extremely powerful adverse prognostic factor.WT1 at presentation has no prognostic significance whereas a high WT1 expression after induction therapy is a predictor for poor outcome. A rise inWT1expression during treatment is a predictor for relapse. WT1 expression is a valuable and important tool for MRD study in AML and the presence of MRD value at the end of induction therapy is an extremely powerful adverse prognostic factor despite of achievement of morphological remission.

WT1 expression is inversely correlated with MYCN amplification or expression and associated with poor survival in non-MYCN-amplified neuroblastoma

Neuroblastoma (NB) is the most common extra cranial solid tumor in childhood and the most frequently diagnosed neoplasm during infancy. A striking feature of this tumor is its clinical heterogeneity. Several tumor progression markers have been delineated so far, among which MYCN amplification, which occurs in about 25% of total NB cases, with the percentage increasing to 30% in advanced stage NB. Although MYCN amplification is strongly correlated with NB of poor outcome, the MYCN status cannot alone predict all cases of poor survival in NB. Indeed NB without MYCN amplification (about 70–80% of NB) are not always favorable. WT1 was initially identified as a tumor suppressor gene involved in the development of a pediatric renal tumor (Wilms' tumor). Here, we describe an inverse correlation between WT1 expression and MYCN amplification and expression. However and most notably, our results show that WT1 gene expression is associated with a poor outcome for patients showing non-MYCN-amplified tumors. Thus WT1 expression is clinically significant in NB and may be a prognostic marker for better risk stratification and for an optimized therapeutic management of NB.

Combined assessment of WT1 and BAALC gene expression at diagnosis may improve leukemia-free survival prediction in patients with myelodysplastic syndromes

Several genes with relevant pathogenetic and prognostic value have been identified in patients with myelodysplastic syndromes. Overexpression of WT1 at diagnosis has been associated with increased progression to acute myeloid leukemia and reduced leukemia free survival. Conversely, few data are available on the prognostic value of BAALC gene overexpression in AML and MDS patients. We evaluated the prognostic value of the combined expression of WT1 and BAALC genes at diagnosis in 86 MDS patients who had been stratified according to IPSS and R-IPSS scoring systems. Our results suggest that in the whole group of patients, low levels of both WT1 and BAALC were associated with a favorable outcome (3-year LFS 74.5%, median not reached), whereas patients presenting high expression levels of both genes had the worst prognosis (3-year LFS 0%, median 12 months, p<0.001). More specifically, molecular profiling was especially useful for intermediate 1 and intermediate-2/high risk groups. This study suggests that evaluating WT1 and BAALC gene expression at diagnosis may improve standard risk stratification and possibly refine the therapeutic approach for MDS patients.

Prognostic Significance of WT1 and PRAME Gene Expression in Bone Marrow Samples of MDS and AML Patients Treated with Azacytidine

Introduction: The Wilms’ tumor gene (WT1) and preferentially expressed antigen of melanoma (PRAME) gene are frequently overexpressed in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) Combined quantitation of PRAME and WT1 transcript levels could provide a powerful molecular marker in newly diagnosed MDS patients, enabling the early identification of relapse through minimal residual disease monitoring and also to enable alternate treatment strategies (Qin et al, 2012).In this study, we investigated the prognostic impact of WT1 and PRAME gene expression on MDS and AML patients treated with azacytidine.Methods:In this ethically approved, retrospective study, we studied WT1 and PRAME gene expression in the bone marrow of 20 patients with MDS and AML (unsuitable for more intensive chemotherapy) prior to starting epigenetic therapy with azacytidine (100mg/M2 sc for 5 days every 28 days). 20 patients with lymphoma not involving the bone marrow were used as a control group. Quantitative assessment of WT1 and PRAME transcript levels was performed on formalin fixed paraffin-embedded trephine biopsies, using the WT1 Ipsogen ProfileQuant and a ‘homebrew’ kit respectively. A control GADPH was used. Overall survival was extimated using the Kaplan-Meier method and compared using the log-rank test. The logistic regression model was used to correlate IPSS-R with WT-1 and PRAME gene expression levels.Results: The median age of the patient group was 71. 16 patients had MDS (RCMD: 3; RARS: 2; RAEB1: 2; RAEB2: 5; CMML: 4) and 4 had AML. Median age of the control group was 61. Median number of cycles of azacytidine was 4 (range 1-21). In 11 of the patient group and in all of the controls, neither PRAME nor WT1 gene expression was detected.. PRAME gene expression without WT1 gene expression was detected in 5 patients, whilst, in the remaining 4 patients, both PRAME and WT1 gene expression was detected. There was no significant difference in mean percentage of bone marrow blasts between patients with detectable PRAME +/- WT1 gene expression (16.67%) and those without (12.64%).Median gene expression levels of PRAME +/- WT1 significantly correlated with IPSS-R (p=0.003).Overall survival (OS) was significantly inferior in patients who were positive for PRAME +/- WT1 (p=0.0103). Median OS for patients positive for both PRAME and WT1 was 270 days and for patients who were PRAME positive and WT1 negative was 300 days, whilst patients negative for both had a median OS of 630 days (figure 1).Conclusions: Our study results show that patients who have detectable WT1 and PRAME expression in their bone marrow prior to azacytidine therapy have more advanced disease in terms of IPSS-R score and have a much inferior OS compared to patients without detectable WT1 and PRAME. Such patients should be considered for either additional or alternate therapy to single agent azacytidine. DisclosuresNo relevant conflicts of interest to declare.

Clinical Significance of Myelofibrotic (MF) Changes in Myelodysplastic Syndromes (MDS): A Prospective Evaluation Including Mutational Analysis By Next-Generation Sequencing (NGS)

MDS with MF is not recognized as a distinct entity in 2008 WHO classification, and the prognostic role of MF remains controversial after several retrospective evaluations (Della Porta, 2009; Greenberg, 2012). In order to minimize inter-observer variability, a European Consensus (EC) has been reached for MF grade assignation (Thiele, 2005). IHC analysis of p53 protein BM accumulation has been proposed as prognosticator in MDS (Ramos, 2002), and more specifically in MDS with isolated 5q- (Jädersten, 2011; Saft, 2014) where it correlates with TP53 mutations. Several gene mutations have a prognostic role in MDS (Bejar,2011; Papaemmanuil, 2013; Haferlach, 2014), mutTP53 ranking as the most potent molecular prognosticator. By contrast, CALRmut, common in MPN, seems rare in MDS (Klampfl, 2013; Nangalia, 2013) albeit a focused evaluation taking into consideration EC grading has not been performed so far.The aim of this study was to evaluate the events that underlie MF changes in MDS by studying 77 MDS patients (52M/ 25F; median age 76, range 31-88; WHO-2008: RCUD 2, RARS 4, RCMD 40, RAEB-1 15, RAEB-2 7, 5q- 7, MDS-U 2), that were recruited prospectively since June 2006 and followed up to June 2104 in 7 GESMD centers. Diagnosis and cytogenetic evaluation followed GESMD SOP’s (Schanz’s cytogenetic score: Very good 6, Good 51, Intermediate 12, Poor 5, Very Poor 5). The study was approved by the IRB at each study site and all patients gave written informed consent. Median follow-up was 3.0 years (0.1-7.7). During this time, 49 patients (63.6%) died and 2 (2.6%) were lost to follow-up, while 20 (21.6%) progressed into acute leukemia.MF was evaluated independently by 2 pathologists following EC guidelines (MF-0 29, MF-1 31, MF-2 15, MF-3 2). IHC accumulation of p53 protein was evaluated as described previously and soluble p53 protein was analyzed in plasma by ELISA. Serum levels of 9 cytokines and chemokines were analyzed using cytometric bead arrays and a FACScanto flow cytometer (Becton-Dickinson). WT1 gene expression was evaluated by RT-PCR in PB and calculated as the WT1/GUSratio. The presence of mutations was evaluated in 67 patients. Sequencing was performed on a MISEQ NGS (Illumina) system using a panel of 111 genes previously related to MDS or MF. Sequencing results were analyzed by using the VariantStudio software package (Illumina), the threshold for mutation calling was set to 5%. Descriptive statistics and nonparametric statistical procedures were performed as appropriate, and univariate and multivariate analysis were performed for OS prediction.MF grade showed a statistically significant nonparametric correlation with the proportion of bone marrow erythroid precursors in BMA (-0.408), Hb levels (-0.271), number of PRBC transfused in the first 16 wks (0.302), ferritin levels (0.294), EPO levels (0.331) and p53 IHC score (0.231), as well as the presence of ALIPs (0.358), WT1/GUSratio (0.264) and serum levels of MIG (-0.251), but not with other covariates.Mutation incidence was highest for genes involved in splicing machinery (38.8%) as well as ASXL1 (18%). Mutated SF3B1 was associated with the absence of fibrosis (MF-0 23.1%, MF-1 7.4%, MF-2/3 0%; p=0.024) while the opposite was true for mutated ETV6 (MF-0 and MF-1 no mutations, MF-2/3 14.3%; p=0.041). Only 1 patient harbored a mutation in CALR. In our series, p53 protein accumulation and mutTP53 were not statistically linked. Mutations in GATA1 and SMC3 were more frequent in patients with IPSS-R High/Very High (25.0% vs. 3.6%, p=0.037 and 25.0% vs. 0%, p=0.005, respectively), but no single mutation was linked to Schanz’s cytogenetic score (Very Good/Good vs. Intermediate vs. Poor/Very Poor) with this sample size.Survival analysis showed MF-2 or higher as a relevant predictor for OS (median OS for MF-0/1 4.0 years [CI95% 1.4-6.6] vs. 1.2 [0-3.3] for MF-2/3; HR 2.3, CI95% 1.2-4.3, p=0.008), that was independent of IPSS-R in multivariate analysis (IPSS-R HR 2.47 [1.3-4.7], p=0.006; MF HR 2.18 [1.2-4.1], p=0.013).In conclusion, MF changes observed in MDS patients are not linked to mutations in CALR, cytogenetic score or IPSS-R, but to erythroid failure. Mutations in SF3B1 and ETV6 seem to diverge on their influence over MF. MF grade 2 or higher seems relevant for OS and independent of IPSS-R. DisclosuresNo relevant conflicts of interest to declare.

Effect of decitabine on immune regulation in patients with acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation

Based on the representative articles in recent years, the different mechanisms of decitabine on immune regulation in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (HSCT) are summarized. Decitabine improves the expression of WT1 gene to stimulate specific cytotoxic T cells which can enhance graft versus leukemia effect (GVL) and improve the expression of FOXP3 gene to stimulate regulatory T cells so as to inhibit the acute graft versus host disease (GVHD). Through the above-mentimed mechanisms, decitabine can improve both therapeutic effect and quality of life in the patients with AML after allogeneic HSCT.

Abnormal WT1 gene expression in paroxysmal nocturnal hemoglobinuria

To explore the pathogenesis of abnormal WT1 expression in paroxysmal nocturnal hemoglobinuria (PNH). The expression of WT1 mRNA in CD59⁻ and CD59⁺ bone marrow mononuclear cells (BMMNC) were measured by semi-quantitative reverse transcription PCR. After WT1 gene silence by RNA interference (RNAi) technology, biological characteristics of BMMNC were investigated by flow cytometry. The relative expression of WT1 mRNA in PNH CD59⁻ BMMNC (1.06 ± 0.12) was significantly higher than that in PNH CD59⁺ BMMNC (0.90 ± 0.12) and normal BMMNC (0.86 ± 0.05, P<0.05), but there was no significant difference between PNH CD59⁺ BMMNC and normal BMMNC (P>0.05). WT1 mRNA expression in PNH was positively correlated with the proportion of CD59⁻ cells (r²=0.490, P=0.016), but had no relationship with the proportion of CD59⁺ cells. After WT1 gene silence by siRNA in PNH CD59⁻ BMMNC, WT1 mRNA expression was decreased. The proportions of G0/G1 phase in PNH CD59⁻ cell blank control group and siRNA-scr transfected group were (92.73 ± 3.71)% and (93.06 ± 4.14)%, and the proportions of S phase were (6.99 ± 3.61)% and (6.73 ± 4.08)%, respectively. The proportions of G0/G1 and S phase in siRNA-WT1 transfected group was (94.46 ± 3.71)% and (5.40 ± 3.55)%, respectively. There were significant differences in the proportions of G0/G1 phase and S phase among the controls, siRNA-WT1 transfected group and siRNA-scr transfected group (P<0.05). The rate of apoptosis in siRNA-WT1 transfected group [(35.91 ± 22.36)%] was significantly higher than those in controls [(26.12 ± 17.10)%] and siRNA-scr transfected group [(27.39 ± 18.99)%] (P<0.05). siRNA-WT1 could effectively suppress the WT1 gene expression of CD59⁻ clone in PNH patients, inhibit its proliferation, and promote its apoptosis. WT1 gene expression might contribute to PNH clone proliferation.

Nestin and WT1 expression in atheromathous plaque neovessels: association with vulnerability.

Neoangiogenesis is crucial for the progression and vulnerability of atheromasic lesions. Since adult vasa vasorum, which represent the neoangiogenetic burden of healthy arteries, constitutively express Nestin and Wilms Tumor (WT1), the aims of the present study are: i) to describe and quantify Nestin and WT1 in plaque neovessels; ii) to investigate the relationship between neovessel phenotype and plaque instability. We prospectively evaluated 49 consecutive carotid endarterectomy specimens. Histopathological characteristics were separately collected, particularly the intraplaque histological complications. Immunohistochemistry was carried out for CD34, Nestin and WT1; the density of positivity was evaluated for each marker. RT-PCR was performed to assess Nestin and WT1 mRNA levels on the first 10 plaques and on 10 control arteries. Six (12.2%) plaques showed no neoangiogenesis. In the others, the mean immunohistochemical densities of CD34, Nestin, and WT1-positive structures were 41.88, 28.84 and 17.68/mm2. Among the CD34+ neovessels, 68% and 42% expressed Nestin and WT1 respectively, i.e., nearly 36% of the neovessels resulted to be Nestin+/WT1-. Furthermore, complicated plaques (n=30) showed significantly more CD34 and Nestin-positive vessels than uncomplicated plaques (n=13; P=0.045 and P=0.009), while WT1 was not increased (P=0.139). RT-PCR confirmed that WT1 gene expression was 3-fold lower than Nestin gene in plaques (p=0.001). Plaque neoangiogenesis shows both a Nestin+/WT1- and a Nestin+/WT1+ phenotype. The Nestin+/WT1- neovessels are significantly more abundant in complicated (vulnerable) plaques. The identification of new transcription factors in plaque neoangiogenesis, and their possible regulation, can open new perspectives in the therapy of vulnerable plaques.

Expression of WT1 and PRAME gene in bone marrow and peripheral blood samples of patients with myelodysplastic syndrome

This study was aimed to explore the transcription level of WT1 and PRAME two genes in bone marrow and peripheral blood samples of patients with myelodysplastic syndrome(MDS) and their relationship with bone marrow dysplasia and karyotype. The quantitative expression of WT1 and PRAME transcripts detected by RQ-PCR in the bone marrow samples of 203 MDS patients and 19 aplastic anemia(AA), 6 other benign anemia(BA), 4 paroxysmal nocturnal hemoglobinuria(PNH) patients from July 2009 to June 2012 and 14 healthy donors, and in 92 peripheral blood samples. The results showed that WT1 and PRAME expression levels in both BM and PB samples of MDS group were higher than those in normal controls, AA, and BA patients (BM: WT1:P = 0.000, 0.000, 0.000, PRAME: P = 0.048, 0.000, 0.064; PB: WT1:P = 0.012, 0.000, 0.011, PRAME: P = 0.020, 0.004, 0.003). What is more, this expression in high risk MDS group (RAEB1, RAEB2, MDS-AML) were higher than those in low risk group (RCUD, RCMD, MDS-U) and AA and BA. The WT1 and PRAME mRNA expression levels in PB and BM were well correlated (WT1:r = 0.6028, P = 0.001; PRAME: r = 0.7628, P = 0.000), as well as the WT1 expression levels in BM samples with the Karyotype (P = 0.049). In addition, the same positive rate of WT1 or PRAME expression existed in BM and PB samples of MDS patients. It is concluded that the WT1 and PRAME gene expression levels in both BM and PB samples of MDS patients are higher than those in healthy controls, AA and other benign anemia patients, and increase with the progression of the disease. The WT1 and PRAME transcripts constitute good molecular markers for the clinical diagnosis and prognosis and monitoring minimal residual disease after treatment of MDS. What is more, when bone marrow is not so convenient to get, the transcript levels of PB samples can be detected.

WT1 expression increases with malignancy and indicates unfavourable outcome in astrocytoma

AimsThe zinc finger transcription factor WT1 is expressed in astrocytic neoplasms and therefore is a potential target of immunotherapy in brain tumours. Our aim was to further elucidate the role...

Juvenile myelo-monocytic leukemia (JMML): No effect of granulocyte monocyte-colony stimulating factor (GM-CSF) on Wilms Tumor gene (&lt;i&gt;WT&lt;/i&gt;1) by nested Polymerase Chain Reaction (nPCR) and flow cytometry

This study was to determine whether GM-CSF induced WT1 gene expression and to establish an association with markers of proliferation CD71+CD34+ using nPCR and flow cytometry respectively, in samples obtained from 5 newly diagnosed JMML patients. Overtime (day 0 to day 14) there was an insignificant difference in WT1 gene expression and CD71+CD34+ in JMML samples when compared to peripheral blood of normal volunteers (n = 3). Our study suggests that there is a correlation between WT1 gene expression and cellular proliferation and that GMCSF in vitro does not create a significant difference in JMML samples.

Derivation of lung mesenchymal lineages from the fetal mesothelium requires hedgehog signaling for mesothelial cell entry

Recent studies have shown that mesothelial progenitors contribute to mesenchymal lineages of developing organs. To what extent the overlying mesothelium contributes to lung development remains unknown. To rigorously address this question, we employed Wt1(CreERT2/+) mice for high-fidelity lineage tracing after confirming that Cre recombinase was mesothelial specific and faithfully recapitulated endogenous Wilms' tumor 1 (Wt1) gene expression. We visualized WT1(+) mesothelial cell entry into the lung by live imaging and identified their progenies in subpopulations of bronchial smooth muscle cells, vascular smooth muscle cells and desmin(+) fibroblasts by lineage tagging. Derivation of these lineages was only observed with Cre recombinase activation during early lung development. Using loss-of-function assays in organ cultures, and targeted mesothelial-restricted hedgehog loss-of-function mice, we demonstrated that mesothelial cell movement into the lung requires the direct action of hedgehog signaling. By contrast, hedgehog signaling was not required for fetal mesothelial heart entry. These findings further support a paradigm wherein the mesothelium is a source of progenitors for mesenchymal lineages during organogenesis and indicate that signals controlling mesothelial cell entry are organ specific.

Integrating post induction WT1 quantification and flow-cytometry results improves minimal residual disease stratification in acute myeloid leukemia

Fifty uniformly treated adult AML patients were analyzed with respect to pre-treatment and post-induction risk factors. Forty-two patients achieving complete hematological remission were assessed for minimal residual disease (MRD) by WT1 gene expression; 34 by flow-cytometry (flow-MRD). Patients who were flow-MRD negative had a better 3-year disease-free (DFS; 79.5% vs. 27.3%; p=.032) compared with patients who were still positive after induction. Interestingly, DFS of flow-MRD positive patients was not related to the amount of flow-detected clone population (≥ or <1%, p=.41) but to WT1 reduction (ΔWT1, 3-year DFS; 46.2% vs. 0% if ΔWT1 was ≥ or < of 1.5 log, p=.001). In AML, combining MRD results provided by WT1 quantification and flow-cytometry improves the reliability of MRD-based prognostic stratification. Similar analyses by further larger studies should be advocated.

Hsf-1 affects podocyte markers NPHS1, NPHS2 and WT1 in a transgenic mouse model of TTRVal30Met-related amyloidosis

Introduction: Familial amyloid polyneuropathy is characterized by transthyretin (TTR) deposition in various tissues, including the kidneys. While deposition induces organ dysfunction, renal involvement in TTR-related amyloidosis could manifest from proteinuria to end-stage kidney failure. As proteinuria is considered result of glomerular filtration barrier injury we investigated whether TTR deposition affects either glomerular basement membrane (GBM) or podocytes.Materials and methods: Immunohistochemistry, immunoblot and gene expression studies for nephrin, podocin and WT1 were run on renal tissue from human-TTRV30M transgenic mice hemizygous or homozygous for heat shock factor one (Hsf-1). Transmission electron microscopy was used for evaluation of podocyte foot process width (PFW) and GBM thickness in Hsf-1 hemizygous mice with or without TTRV30M or amyloid deposition.Results: Glomeruli of hsf-1 hemizygous transgenic mice showed lower nephrin and podocin protein levels but an increased podocyte number when compared to Hsf-1 homozygous transgenic mice. Nephrin, podocin and WT1 gene expression levels were unaffected by the Hsf-1 carrier status. TTRV30M deposition was associated with increased PFW and GBM thickness.Conclusions: Under the effect of Hsf-1 hemizygosity, TTRV30M deposition has deleterious effects on GBM thickness, PFW and slit diaphragm composition, without affecting nephrin and podocin gene expression.

Interaction of Human Genes WT1 and CML28 in Leukemic Cells

The molecular pathogenesis of leukemia is poorly understood. Earlier studies have shown both Wilms' tumor 1 suppressor gene (WT1) and CML28 abnormally expressed in malignant diseases of the hematopoietic system and WT1 played an important role in leukemogenesis. However, the relationship between molecular CML28 and WT1 has not been reported. Here we described the use of small interfering RNA (siRNA) against WT1 and CML28 in leukemic cell line K562 to examine the interaction between CML28 and WT1. WT1 and CML28 gene expression in transfected K562 cells was detected by using RQ-PCR and Western blotting. K562 cells transfected with WT1-siRNA could greatly decrease both mRNA and protein expression levels of WT1 and CML28. In contrast, CML28-siRNA did not exert effect on WT1. Further, subcellular co-localization assay showed that the two proteins could co-localize in the cytoplasm of K562 cells, but WT1/CML28 complexes were not detected by using immunoprecipitation. It was suggested that there exists the relationship between CML28 and WT1. CML28 may be a downstream target molecule of WT1 and regulated by WT1, which will provide important clues for further study on the role of CML28 and WT1 in leukemic cells.

Minimal residual disease detectable by quantitative assessment of WT1 gene before allogeneic stem cell transplantation in patients in first remission of acute myeloid leukemia has an impact on their future prognosis

Overall 42 patients (pts) transplanted in hematological CR1 were retrospectively analyzed. Median follow-up was 15 months (range 2-77). The expression of WT1 gene was measured according to the European Leukaemia Net recommendations. At the time of allogeneic stem cell transplantation (allo-SCT) 29 pts were WT1-negative and 13 pts were WT1-positive. In the univariate analysis, significantly better results were observed in the group of WT1 neg in terms of progression-free survival (in three yr 77% vs. 27%, p = 0.001). In multivariate analysis, the only significant feature in terms of better OS was WT1 negativity (p = 0.029). Our results show that minimal residual disease status measured by quantitative assessment of WT1 gene in acute myeloid leukemia pts in CR1 significantly affects their future prognosis after allo-SCT.

Aberrant Expression of the MLL5, BAALC, ID1, and WT1 Genes Is Associated with Higher Induction Mortality and Poorer Overall Survival in Acute Promyelocytic Leukemia Patients Treated with ATRA and Anthracycline-Based Chemotherapy: An International Consortium On Acute Promyelocytic Leukemia Study

AbstractAbstract 1407▪▪This icon denotes a clinically relevant abstract Background:Aberrant expression of MLL5, BAALC, ID1, and WT1 genes is frequently associated with inferior outcome in cytogenetically normal acute myeloid leukemia patients (Damm et al. Blood 2011; 117(17):4561–8). The expression levels of these genes vary in patients with acute promyelocytic leukemia (APL), but the clinical significance of these findings remains unclear. Objective:(1) to determine if the gene expression levels of MLL5, BAALC, ID1, and WT1 are associated with clinical outcome of APL patients treated with ATRA and anthracycline-based chemotherapy, (2) to generate an integrative score (IS) based on these potential prognostic factors and clinical parameters and (3) to use this score for outcome prediction in APL. Design and Methods:One hundred and fifty APL patients (age, 15–73y) from seven different Brazilian institutions and treated according to the IC-APL protocol were included. The treatment schedule was identical to the PETHEMA-LPA 2005, except for the replacement of idarubicin by daunorubicin; ATRA treatment was initiated immediately in all cases in which the diagnosis of APL was suspected based on morphology. Gene expression profile was analyzed by Real-time PCR. Integer weights for the IS were derived from Cox proportional hazard model, using overall survival (OS) as outcome parameter. Hazard ratios (HR) for OS were calculated for each variable separately (Table 1). Variables with P<0.05 in univariate analyses were included in the model. Variables considered for the model inclusion consisted in 2 clinical (WBC counts, albumin levels) and 5 molecular markers (FLT3-ITD status and gene expression levels of MLL5, BAALC, ID1, and WT1). Other candidates, such as age, platelet count, gender, ECOG performance status, PML breakpoint and FAB subtype were not significant and not included in the score. The HR were converted to integer weights according to the following: variables with HR < 1 were excluded from analyses; variables with HR 3 1 and < 1.5 were assigned a weight of 1; variables with HR 3 1.5 and < 2.5 were assigned a weight of 2; variables with HR 3 2.5 were assigned a weight of 3. The final score was the sum of these integer weights. Based on maximally selected rank statistics, the scores were grouped into 3 risk-groups: 0–5 (low-IS), 6–9 (intermediate-IS), and > 9 (high-IS). Results:The integrative weights of variables analyzed are summarized in Table 1. The IS was modeled in 137 patients (median score: 6; range, 1–17). According to PETHEMA-GIMEMA relapse risk criteria, 22%, 23% and 70% of patients assigned in the low-IS (n=46), intermediate-IS (n=57) and high-IS (n=34) groups were deemed high-risk of relapse (P<0.001). Overall, 118 (86%) patients achieved CR; the remaining 19 patients (14%) experienced early death due to hemorrhage (n=12), therapy-related infection (n=6) and differentiation syndrome (n=1). Induction mortality was significantly higher in the high-IS group (low: 2%; intermediate: 15%; high: 26%) (P=0.001). CR was achieved in the low-, intermediate-, and high-IS group in 98%, 84%, and 73% of the patients, respectively (P=0.007). With a follow-up of 24 months among survivors, patients assigned in the high-IS group had a lower 2-y OS rate (63%) compared with those in the intermediate- (80%) and low-IS groups (97%; P<0.001). Eight relapses were recorded. The IS was not predictive of relapses (P=0.351). Conclusions:Our results suggest that MLL5, BAALC, ID1, and WT1 expression levels are associated with clinical outcome and that the IS may become a useful tool for outcome prediction in APL.Table 1Variables used for the determination of the Integrated Score (IS).Log-rank test, p-valueHR (95%CI); p-valueInteger weight**WBC counts (<=10×109/L vs >10×109/L)p = 0.0272.32 (1.1-5.02); 0.0322Albumin levels (<= 3.5 vs >3.5)p = 0.0030.24 (0.09-0.65); 0.0053FLT3-ITD status (FLT3-ITDnegativevs FLT3-ITD positive)p = 0.0132.72 (1.19-6.24); 0.0173MLL5 gene expression (> 25th percentile*)p = 0.0190.42 (0.14-0.72); 0.0062ID1 gene expression (>75th percentile*)p = 0.0053.22 (1.34-7.76); 0.0093BAALC gene expression (>50th percentile*)p = 0.0193.13 (1.13-8.62); 0.0273WT1 gene expression (>25th percentile*)p = 0.0336.91 (0.92-51.6); 0.053*Calculated using the values obtained in whole cohort of patients;**Integer weights for the risk score were derived from Cox proportional hazard model, using overall survival (OS) as outcome parameter. Disclosures:Lo-Coco:Cephalon: Speakers Bureau; Boehringer Ingelheim: Membership on an entity’s Board of Directors or advisory committees. Löwenberg:Skyline Diagnostics: Membership on an entity’s Board of Directors or advisory committees.

Normal Blood and Bone Marrow Wt1 Expression Level in Extramedullary Relapse in AML Patient

AbstractAbstract 4825Wilms' tumor gene 1 (WT1) that encodes a transcription factor has elevated expression in 90% of AML. High level of WT1 gene expression in bone marrow and peripheral blood of patients with AML indicates the presence of leukemia tumor burden. Thus, quantifying assessment of the level of WT1 could predict relapse. It is important to monitor a universal marker in the absence of target molecular genetic abnormalities in the disease onset. There are few data related to extramedullary relapses. Here we describe the patient with extramedullary relapse without concomitant elevation of WT1 expression.The patient is 22 year old male with the first early bone marrow and CNS relapse of AML. Cytogenetics- (45XY, t (3, 5) (q29; q15), −7, der (7), add (11) (p15)). Blast cells immunophenotype was CD45 + CD34 + CD38 + CD117 +. There was high blast count with high expression of WT1 level (Tabl 1). And there was no expression of other molecular genetic prognostic markers. Therapy with high dose of cytarabine with intrathecal administration of cytotoxic drugs was conducted. The complete hematological and cytogenetic remission was achieved after the first induction. Also there was no any blast cell in the CSF, WT1 expression decreased by 1,87 log (WT1 level became normal). Consolidation of remission with three similar courses with high doses of cytarabine was conducted. Extramedullary relapse during bone marrow and CNS remission with unilateral lesion of the lacrimal gland and the periorbital area( 2.8 × 3.4×4.6 cm )was diagnosed in 6 month. Relapse was confirmed by histological and immunochemical study of the left lacrimal gland biopsy, blasts phenotype was similar to the phenotype of bone marrow blasts at AML onset. WT1 level in bone marrow and peripheral blood remained within normal limits: 15.5 WT1/104 ABL copies and 13.4 WT1/104 ABL copies respectively. Therapy with high dose cytarabine and mitoxantrone was used as an induction. After this therapy a local remission was diagnosed according to MRI. Consolidation courses were followed by a course of radiotherapy to the area of the left orbit. Bone marrow remission and low-level expression of WT1 remained to be normal. Thereafter the patient has undergone unrelated allogeneic bone marrow transplantation. Conclusion.We have described isolated AML relapse without elevation of WT1. A possible reason for normal level of expression of WT1 in patients with extramedullary relapse may be a small amount of the extramedullary formation, its location and features of blood supply of the body area.Table 1Blast count in bone marrowWT1/104 ABL copies in bone marrowAt the diagnosis58%3560,6After the induction1%50,8After the first consolidation course1,4%26,7After the second consolidation course0,4%9,6After the third consolidation course0,4%3,04Follow-up2,4%14,3Follow-up1,4%17,7Extramedullary relapse1,4%15,5Day 14 of ≪HDAC≫3,4%29,4After ≪HiDAC≫6%49,2Follow-up before radiotherapy1,6%15Follow-up after radiotherapy32 [Display omitted] Disclosures:No relevant conflicts of interest to declare.