Pitfalls in spontaneous in vitro transformation of human mesenchymal stem cells

Spontaneous in vitro transformation of human primary cells was, and continues to be, a scarcely described phenomenon. Only the description of the generation of the HaCAT cell line [1] is a canonical example, worldwide accepted. More recent examples included the emergence of tumorogenic populations upon in vitro culture of fetal human mesenchymal stem cells (hMSC), induced by GM-CSF and IL-4, [2] and bone marrow hMSC [3]. Other examples have also been reported after very long-term in vitro culture of telomerized hMSCTerT [4]. In this scenario, our previous results [5-7] were only a new observation to be added to this list. Only very recently similar results have been published [8], reporting spontaneous malignant transformation in 46 % of bone marrow–derived hMSC long-term cultures (5–106 weeks). However, other authors reported opposite results.S

A variant t(14;17) in acute promyelocytic leukemia. Positive response to retinoic acid treatment

We present a case of acute promyelocytic leukemia (APL) carrying an atypical translocation involving chromosomes 14 and 17. This translocation could be considered a variant of the APL-specific t(15;17). Positive response to retinoic acid treatment suggests molecular rearrangement of retinoic acid receptor alpha

A recurrent translocation, t(3;11)(q21;q13), found in two distinct cases of acute myeloid leukemia

We report two cases of acute myeloid leukemia (M1 and M5B subtypes) with a similar translocation, t(3;11)(q21;q13). We discuss the involvement of these breakpoints in acute leukemia and their putative clinical implications

Epigenetic signatures associated with different levels of differentiation potential in human stem cells

BACKGROUND: The therapeutic use of multipotent stem cells depends on their differentiation potential, which has been shown to be variable for different populations. These differences are likely to be the result of key changes in their epigenetic profiles. METHODOLOGY/PRINCIPAL FINDINGS: to address this issue, we have investigated the levels of epigenetic regulation in well characterized populations of pluripotent embryonic stem cells (ESC) and multipotent adult stem cells (ASC) at the trancriptome, methylome, histone modification and microRNA levels. Differences in gene expression profiles allowed classification of stem cells into three separate populations including ESC, multipotent adult progenitor cells (MAPC) and mesenchymal stromal cells (MSC). The analysis of the PcG repressive marks, histone modifications and gene promoter methylation of differentiation and pluripotency genes demonstrated that stem cell populations with a wider differentiation potential (ESC and MAPC) showed stronger representation of epigenetic repressive marks in differentiation genes and that this epigenetic signature was progressively lost with restriction of stem cell potential. Our analysis of microRNA established specific microRNA signatures suggesting specific microRNAs involved in regulation of pluripotent and differentiation genes. CONCLUSIONS/SIGNIFICANCE: Our study leads us to propose a model where the level of epigenetic regulation, as a combination of DNA methylation and histone modification marks, at differentiation genes defines degrees of differentiation potential from progenitor and multipotent stem cells to pluripotent stem cells

Multiple myeloma primary cells show a highly rearranged unbalanced genome with amplifications and homozygous deletions irrespective of the presence of immunoglobulin-related chromosome translocations

Background and Objectives Multiple myeloma (MM) is a malignant plasma cell neoplasia in which genetic studies have shown that genomic changes may affect almost all chromosomes, as shown by fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH). Our objective was the genomic characterization of CD 138 positive primary MM samples by means of a high resolution array CGH platform. Design and Methods For the first time, a high resolution array CGH with more than 40,000 probes, has been used to analyze 26 primary MM samples after the enrichment of CD138-positive plasma cells. Results This approach identified copy number imbalances in all cases. Bioinformatics strategies were optimized to perform data analysis allowing the segregation of hyperdiploid and non-hyperdiploid cases by array CGH. Additional analysis showed that structural chromosome rearrangements were more frequently seen in hyperdiploid cases. We also identified the same Xq21 duplication in nearly 20% of the cases, which originated through unbalanced chromosome translocations. High level amplifications and homozygous deletions were recurrently observed in our series and involved genes with meaningful function in cancer biology. Interpretation and Conclusions High resolution array CGH allowed us to identify copy number changes in 100% of the primary MM samples. We segregated different MM subgroups based on their genomic profiles which made it possible to identify homozygous deletions and amplifications of great genetic relevance in MM

A comprehensive microarray-based DNA methylation study of 367 hematological neoplasms

Background: Alterations in the DNA methylation pattern are a hallmark of leukemias and lymphomas. However, most epigenetic studies in hematologic neoplasms (HNs) have focused either on the analysis of few candidate genes or many genes and few HN entities, and comprehensive studies are required. Methodology/Principal Findings: Here, we report for the first time a microarray-based DNA methylation study of 767 genes in 367 HNs diagnosed with 16 of the most representative B-cell (n = 203), T-cell (n = 30), and myeloid (n = 134) neoplasias, as well as 37 samples from different cell types of the hematopoietic system. Using appropriate controls of B-, T-, or myeloid cellular origin, we identified a total of 220 genes hypermethylated in at least one HN entity. In general, promoter hypermethylation was more frequent in lymphoid malignancies than in myeloid malignancies, being germinal center mature B-cell lymphomas as well as B and T precursor lymphoid neoplasias those entities with highest frequency of gene-associated DNA hypermethylation. We also observed a significant correlation between the number of hypermethylated and hypomethylated genes in several mature B-cell neoplasias, but not in precursor B- and T-cell leukemias. Most of the genes becoming hypermethylated contained promoters with high CpG content, and a significant fraction of them are targets of the polycomb repressor complex. Interestingly, T-cell prolymphocytic leukemias show low levels of DNA hypermethylation and a comparatively large number of hypomethylated genes, many of them showing an increased gene expression. Conclusions/Significance: We have characterized the DNA methylation profile of a wide range of different HNs entities. As well as identifying genes showing aberrant DNA methylation in certain HN subtypes, we also detected six genes—DBC1, DIO3, FZD9, HS3ST2, MOS, and MYOD1—that were significantly hypermethylated in B-cell, T-cell, and myeloid malignancies. These might therefore play an important role in the development of different HNs

Release of hypoacetylated and trimethylated histone H4 is an epigenetic marker of early apoptosis

Nuclear events such as chromatin condensation, DNA cleavage at internucleosomal sites, and histone release from chromatin are recognized as hallmarks of apoptosis. However, there is no complete understanding of the molecular events underlying these changes. It is likely that epigenetic changes such as DNA methylation and histone modifications that are involved in chromatin dynamics and structure are also involved in the nuclear events described. In this report we have shown that apoptosis is associated with global DNA hypomethylation and histone deacetylation events in leukemia cells. Most importantly, we have observed a particular epigenetic signature for early apoptosis defined by a release of hypoacetylated and trimethylated histone H4 and internucleosomal fragmented DNA that is hypermethylated and originates from perinuclear heterochromatin. These findings provide one of the first links between apoptotic nuclear events and epigenetic markers