Constitutive expression of the FK506 binding protein 51 (FKBP51) in bone marrow cells and megakaryocytes derived from idiopathic myelofibrosis and non-neoplastic haematopoiesis

The calcineurin-NFAT pathway negatively regulates megakaryopoiesis

The calcium regulated calcineurin-nuclear factor of activated T cells (NFAT) pathway modulates the physiology of numerous cell types, including hematopoietic. Upon activation, calcineurin dephosphorylates NFAT family transcription factors, triggering their nuclear entry and activation or repression of target genes. NFATc1 and c2 isoforms are expressed in megakaryocytes. Moreover, human chromosome 21 (Hsa21) encodes several negative regulators of calcineurin-NFAT, candidates in the pathogenesis of Down syndrome (trisomy 21)-associated transient myeloproliferative disorder and acute megakaryoblastic leukemia. To investigate the role of calcineurin-NFAT in megakaryopoiesis, we examined wild-type mice treated with the calcineurin inhibitor cyclosporin A and transgenic mice expressing a targeted single extra copy of Dscr1, an Hsa21-encoded calcineurin inhibitor. Both murine models exhibited thrombocytosis with increased megakaryocytes and megakaryocyte progenitors. Pharmacological or genetic inhibition of calcineurin in mice caused accumulation of megakaryocytes exhibiting enhanced 5-bromo-2'-deoxyuridine uptake and increased expression of messenger RNAs encoding CDK4 and G1 cyclins, which promote cell division. Additionally, human megakaryocytes with trisomy 21 show increased proliferation and decreased NFAT activation compared with euploid controls. Our data indicate that inhibition of calcineurin-NFAT drives proliferation of megakaryocyte precursors by de-repressing genes that drive cell division, providing insights into mechanisms of normal megakaryopoiesis and megakaryocytic abnormalities that accompany Down syndrome.

Immunohistochemical analysis of FKBP51 in human cancers

FKBP51 is a FK506-binding immunophilin involved in the regulation of several fundamental biological processes. A growing body of data indicates that this protein has also a role in the abnormal cell growth of cancers, and could be considered as a promising new marker of tumor progression and response to radio/chemotherapy. However, the data concerning the expression of FKBP51 in cancer are not conclusive, and partially contradictory. They delineate a very complex scenario, in which many molecular FKBP51-related pathways are variously intersected among different tumors. This review reports the available data concerning FKBP51 expression in normal tissues and human malignancies, outlining the role of the immunohistochemical analysis as a fundamental tool for better understanding the role of this immunophilin in cancer biology.

FKBP51 expressed by both normal epithelial cells and adenocarcinoma of colon suppresses proliferation of colorectal adenocarcinoma

It has been reported, as a result of Western blot analyses, that FKBP51 is expressed in various tissues, but that it is not expressed in the pancreas, lung, colon, stomach, or spleen. In this paper, we show, using Western blot analyses, reverse transcriptase polymerase chain reaction, and immunohistochemical analyses of samples from colon cancer patients, that both normal epithelial cells and adenocarcinoma in the human colon express FKBP51, and that there are no significant differences in the expressions of FKBP51 between them. We also show that FKBP51 suppresses the proliferation of colorectal adenocarcinoma, possibly due to the suppression of functions of the glucocorticoid receptors.

Quantitative analysis of messenger RNA abundance for ribosomal protein L-15, cyclophilin-A, phosphoglycerokinase, β-glucuronidase, glyceraldehyde 3-phosphate dehydrogenase, β-actin, and histone H2A during bovine oocyte maturation and early embryogenesis in vitro

Real-time reverse transcription PCR has greatly improved the ease and sensitivity of quantitative gene expression studies. However, measurement of gene expression generally requires selection of a valid reference (housekeeping gene) for data normalization to compensate for inherent variations. Given the dynamic nature of early embryonic development, application of this technology to studies of oocyte and early embryonic development is further complicated due to limited amounts of starting material and a paucity of information on constitutively expressed genes for data normalization. We have validated quantitative procedures for real-time reverse transcription polymerase chain reaction (RT-PCR) analysis of mRNA abundance during bovine meiotic maturation and early embryogenesis and utilized this technology to determine temporal changes in mRNA abundance for ribosomal protein L-15, cyclophilin-A, phosphoglycerokinase, beta-glucuronidase, glyceraldehyde-3-phosphate dehydrogenase, beta-actin, and histone H2A. Quantification of amounts of specific exogenous RNAs added to samples revealed acceptable rates of RNA recovery and efficiency of reverse transcription with minimal variation. Progression of bovine oocytes to metaphase II resulted in reduced abundance of polyadenylated, but not total transcripts for majority of above genes; however phosphoglycerokinase exhibited a significant decline in both RNA populations. Abundance of mRNAs for above genes in early embryos generally remained low until the blastocyst stage, but abundance of ribosomal protein L-15 mRNA was increased at the morula stage and histone H2A mRNA showed dynamic changes prior to embryonic genome activation. Results demonstrate a valid approach for quantitative analysis of mRNA abundance in oocytes and embryos, but do not support constitutive expression of above genes during early embryonic development.

Cryptic 6p21.3 duplications and triplication involving HMGA1 partially masked by add 6p in four cases of myelodysplasia

Rearrangements of 6p are frequent in both myeloid and lymphoid malignant hematological disorders. High-mobility group AT-hook 2 (HMGA2) rearrangements have been described in myelofibrosis with myeloid metaplasia (MMM) and also in myelodysplasia. High-mobility group A proteins are nonhistone nuclear proteins that bind DNA and regulate the transcriptional activity of many genes. We used FISH, with bacterial artificial chromosome RP11-513I15 probe, to study 16 cases of myeloid malignancies with chromosome 6 short arm rearrangements, most of them following myeloproliferative disorders. Among these we found two 6p21.3 duplications and one 6p21.3 triplication involving HMGA1 in four cases of myelodysplasia with and without myelofibrosis. In these four cases, duplications and triplication were partially masked at the cytogenetic level by a derivative chromosome 6 resulting from translocation with another chromosome. HMGA1 proteins have been recently found overexpressed in human leukemias, but to our knowledge this is the first reported duplication of HMGA1.

Pathogenesis of myelofibrosis with myeloid metaplasia

The primary disease process in myelofibrosis with myeloid metaplasia (MMM) is clonal myeloproliferation with varying degrees of phenotypic differentiation. This is characteristically accompanied by secondary intramedullary collagen fibrosis, osteosclerosis, angiogenesis, and extramedullary hematopoiesis. Modern clonality studies have confirmed the multipotent stem-cell origin of the neoplastic process in MMM. The nature of the specific oncogenic mutation(s) is currently being unraveled with the recent discovery of an association between a somatic point mutation of JAK2 tyrosine kinase (V617F) and bcr/abl-negative myeloproliferative disorders, including MMM. The pathogenetic mechanisms that underlie the secondary bone marrow stromal changes in MMM are also incompletely understood. Mouse models of this latter disease aspect have been constructed by either in vivo overexpression of thrombopoietin (TPOhigh mice) or megakaryocyte lineage restricted underexpression of the transcription factor GATA-1 (GATA-1low mice). Gene knockout experiments using such animal models have suggested the essential role of hematopoietic cell-derived transforming growth factor beta1 in inducing bone marrow fibrosis and stromal cell-derived osteoprotegerin in promoting osteosclerosis. However, experimental myelofibrosis in mice does not recapitulate clonal myeloproliferation that is fundamental to human MMM. Other cytokines that are implicated in mediating myelofibrosis and angiogenesis in MMM include basic fibroblast, platelet-derived, and vascular endothelial growth factors. It is currently assumed that such cytokines are abnormally released from clonal megakaryocytes as a result of a pathologic interaction with neutrophils (eg, emperipolesis). This latter phenomenon, through neutrophil-derived elastase, could also underlie the abnormal peripheral-blood egress of myeloid progenitors in MMM.

Detection of Aberrant Gene Expression in CD34+Hematopoietic Stem Cells from Patients with Agnogenic Myeloid Metaplasia Using Oligonucleotide Microarrays

Agnogenic myeloid metaplasia (AMM) is a clonal stem cell disorder that leads to ineffective hematopoiesis, bone marrow fibrosis, and extramedullary hematopoiesis. The molecular mechanisms underlying the development of this syndrome are currently unknown. Therefore, the aim of this study was to characterize aberrant gene expression in CD34+ hematopoietic stem cells from patients with AMM. We used oligonucleotide microarrays to analyze gene expression profiles in CD34+ hematopoietic stem cells from patients with AMM compared with expression in CD34+ cells from healthy individuals. We identified 95 highly differentially expressed genes (48 upregulated and 47 down-regulated) that are potentially involved in regulating abnormal hematopoietic proliferation and differentiation and confirmed many of them by quantitative polymerase chain reaction. Using class membership prediction analysis, we identified 75 genes whose expression profiles can accurately differentiate AMM samples from the controls. Using these 75 genes, we were able to discriminate patients with AMM from the controls by hierarchical clustering (Spearman's confidence correlation). The predictive power of these genes was verified by applying the algorithm to an unknown test set containing expression data from eight additional CD34+ samples (four AMM, four control). Our results indicate that a subset of genes may be used to differentiate patients with AMM from healthy individuals. Furthermore, we identify 95 genes whose aberrant expression may be involved in AMM.