Wilms’ tumor gene 1 (WT1) is a zinc finger transcriptional regulator with crucial functions in embryonic development. Originally WT1 was described as a tumor suppressor gene, but later studies have shown oncogenic properties of WT1 in a variety of tumors. Because of its dual functions in tumorigenesis, WT1 has been described as a chameleon gene. In this thesis, the significance of WT1 as a biomarker was investigated in acute myeloid leukemia (AML), clear cell renal cell carcinoma (ccRCC), ovarian carcinoma (OC) and childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Previous studies have suggested that expression of WT1 is a potential marker for detection of minimal residual disease (MRD) in AML. We aimed to define expression of WT1 as an MRD marker in AML. In adult AML patients, we found that a reduction of WT1 expression in bone marrow (≥ 1-log) detected less than 1 month after diagnosis was associated with an improved overall survival (OS) and freedom from relapse (FFR). In peripheral blood, a reduction of WT1 expression (≥ 2-log) detected between 1 and 6 months after treatment initiation was associated with an improved OS and FFR. WT1 harbor pathogenic genetic variants in a considerable proportion of AML and T-lymphoblastic leukemia (T-ALL), but mutations have not been reported in BCP-ALL. We aimed to evaluate the clinical impact of WT1 mutations and single nucleotide polymorphisms (SNPs) in BCP-ALL. Pathogenic mutations in the WT1 gene were rarely seen in childhood BCP-ALL. However, five WT1 SNPs were identified. In survival analyses, WT1 SNP rs1799925 was found to be associated with worse OS, indicating that WT1 SNP rs1799925 may be a useful marker for clinical outcome in childhood BCP-ALL. We also explored whether WT1 mutations and SNPs in ccRCC could be used as biomarkers for risk and treatment stratification. We therefore examined whether SNPs or mutations in WT1 were associated with WT1 expression and clinical outcome. Sequencing analysis revealed that none of the previously reported WT1 mutations were found in ccRCC; however, we identified six different WT1 SNPs. Our data suggest that pathogenic WT1 mutations are not involved in ccRCC, and the prognostic significance of WT1 SNPs in ccRCC is considerably weak. However, a favorable OS and disease-specific survival were found in the few cases harboring the homozygous minor allele. OC has a poor prognosis, and early effective screening markers are lacking. Serous OCs are known to express the WT1 protein. Overexpressed oncogenic proteins can be considered potential candidate antigens for cancer vaccines and T-cell therapy. It was therefore of great interest to investigate whether anti-WT1 IgG antibody (Ab) measurements in plasma could serve as biomarkers of anti-OC response. We found limited prognostic impact, but the results indicated that anti-WT1 IgG Ab measurements in plasma and WT1 staining in tissue specimens could be potential biomarkers for patient outcome in the high-risk subtypes of OCs. In conclusion, the results of this thesis indicate that WT1 gene expression can provide information about MRD of patients with AML, and WT1 SNP rs1799925 may be used as a biomarker for predicting clinical outcome in childhood BCP-ALL. In ccRCC, the prognostic significance of WT1 SNPs is weak and limited to the subgroup of patients that are homozygous for the minor allele. In OCs anti-WT1 IgG Ab measurement in plasma and WT1 staining in tissue specimens could possibly be used as biomarkers for predicting patient outcome in the high-risk subtypes of OCs.

Myeloid leukemias include malignant diseases characterized by clonal expansion of the myeloid cell lineage. While in case of chronic myeloid leukemia (CML), the main cause of the disease has already been identified - t(9;22) and the aktivity of the fusion product of the translocation BCR-ABL, acute myeloid leukemia (AML) has been associated with plenty of different translocations and mutations. The aim of this work was to contribute to the improvement of monitoring of patients with myeloid leukemias via detailed study of the panleukemic marker Wilms tumor gene 1 (wt1) expression. Prognostic value of wt1 expression has been proved for AML patients, however, it has not yet been confirmed for CML patients. Expression of different wt1 variants (more then 36 protein products) is known very poorly in both, AML and CML as well as in normal hematopoiesis. Most of the study is focused on CML, only limited parts are dedicated to AML. In the first part of the work, we clearly proved prognostic value of total wt1 mRNA expression for CML patients. Statistical evaluations revealed critical wt1 values which enable to specify prognosis of patients responding non-optimally to imatinib. Bcr-abl looses much of its prognostic value in these patients. Further, we have designed and optimized PCRs for selected wt1...

61 Summary Wilms' tumor gene 1 (WT1) is highly expressed in acute leukemia and other hematological malignancies. It has been therefore suggested as a potential universal marker of minimal residual disease (MRD), particularly in patients with acute myeloid leukemia (AML). Due to controversial results of some of the studies, the role of WT1 in MRD follow-up and WT1 prognostic significance remain unclear. WT1 protein is produced in more than 36 different isoforms. These variants have distinct, partially overlapping functions and their ratio is supposed to influence the final effect of WT1. However, despite the increasing number of studies, the clinical impact of WT1 and its isoforms in acute leukemia have not yet been elucidated. We established a unique qPCR method to assess the expression pattern of the main 4 WT1 isoforms. Using this method, we determined the ratio of WT1 variants in the samples of patients with AML, myelodysplastic syndrome (MDS) and healthy controls. Our data showed that this pattern can distinguish among particular hematological malignancies, but lacks a prognostic significance. Within our international study group we determined the prognostic significance of total WT1 expression in childhood AML. Based on our results of a large cohort of patients we can conclude that WT1 expression at...

Testicular germinal tumors (TGCT) are relatively rare solid tumors in adults. Even so, they affect more than 700 men a year in the Czech Republic, mostly young patients aged 18- 45 years. A large number of patients are curable by a combination of surgery and chemotherapy, yet about 50 men a year in the Czech Republic succumb to this tumor, in the vast majority of cases due to the development of resistance to chemotherapy containing cisplatin. The rare occurrence and high curability are probably the cause of infrequent molecular and clinical studies carried out in these tumors, and our understanding of the biological processes leading to primary tumor development and the development of cisplatin resistance (CDDP) is still limited. At present, no specific molecular markers that could be used as prognostic or predictive factors and improve patient stratification or treatment tailoring are available in TGCT management. In this work, we studied the molecular-genetic background of TGCT development and CDDP resistance at several levels. To comprehensively study the development of cisplatin resistance, we prepared and analyzed CDDP-exposed TGCT cell lines. Long-term exposure to CDDP increased resistance 10-fold in the NCCIT cell line, while no significant resistance was achieved with Tera-2. The...