Lymphomas are heterogenous class of diseases characterized by proliferation of a malignant lymphocyte clone. MicroRNA miR-155 was found to be a key molecule in immune response, namely in inflammation and germinal reaction of B cells. On the other hand, miR-155 can drive lymphoproliferation in mouse and its levels were found to be elevated in certain lymphoma types in human. MiR-155 down-regulates expression of its target gene PU.1, a hematopoietic transcription factor important for B cell differentiation. Expression of the gene encoding miR-155, known as MIR155HG, is controled by several transcription factors, among them MYB, a member of an oncogenic E-box protein family. Levels of MYB itself are controled by microRNA miR-150. In this study, we measured levels of miR-155, PU.1, MYB and miR-150 in lymph nodes of patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (B-CLL/SLL, N=20), diffuse large B-cell lymphoma (DLBCL, N=24), follicular lymphoma (FL, N=29), Hodgkin lymphoma (HL, N=25), marginal zone lymphoma (MZL, N=13), and mantle cell lymphoma (MCL, N=10). We also measured levels of these molecules in lymph nodes with the finding of strong inflammation (N=4). We found that patients of all the diagnoses except of MCL display heterogeneously elevated levels of miR-155 and correspondingly...

Oncogenic microRNAs (miRNAs) are small RNA molecules that inhibit post-translational regulatory mechanisms at the epigenetic level. miRNAs are often deregulated in malignancies and due to their stability are detectable in non-cellular fractions of peripheral blood. In our laboratory, we have performed several studies that have investigated and utilized miRNAs as biomarkers for various hematological tumors (e.g., chronic lymphocytic leukemia, Hodgkin`s lymphoma) and solid tumors (e.g., breast cancer). The aim of these studies was to find the association of miRNAs with pathophysiological and clinical aspects of each disease. Here, we confirmed the importance of particular miRNA or its complex during disease monitoring. Combining clinical, molecular biological and statistical analyses, we were able to find miRNA sets that fulfilled not only a diagnostic role but also a prognostic role beyond expectations. The main focus of this thesis is on the investigation of microRNAs in the diagnosis of a hematological malignancy - primary cutaneous T-cell lymphoma (CTCL). Tumor specificity of some miRNAs has been demonstrated. Their aberrant expression in tissue samples of CTCL patients obtained from skin biopsies, correctly distinguished malignant disease from control samples of benign skin lesions. Here, we...