Different forms of pulmonary hypertension in a family with clinical and genetic evidence for hereditary hemorrhagic teleangectasia type 2.

Hereditary hemorrhagic telangiectasia (HTT) is an autosomal dominant disease, most frequently caused by a mutation in either ENG or ACVRL1, which can be associated with pulmonary arterial hypertension (PAH). In this report, we describe a new unpublished ACVRL1 mutation segregating in three members of the same family, showing three different types of pulmonary hypertension (PH) in the absence of BMPR2 mutations. The first patient has a form of heritable PAH (HPAH) in the absence of hepatic arteriovenous malformations (AVMs); the second one has a severe form of portopulmonary hypertension (PoPAH) associated with multiple hepatic AVMs; the third one has hepatopulmonary syndrome (HPS) with numerous hepatic arteriovenous fistulas and a form of post-capillary PH due to high cardiac output. In summary, a single mutation in the ACVRL1 gene can be associated, in the same family, with an extreme phenotypic variability regarding not only the clinical presentation of HHT but also the type of PH in the absence of BMPR2 mutations. More studies are needed to evaluate if this variability can be explained by the presence of additional variants in other genes relevant for the pathogenesis of HHT.

Multi-omic profiling of MYCN-amplified neuroblastoma cell-lines.

Neuroblastoma is the most common pediatric cancer, arising from the neural crest cells of the sympathetic nervous system. Its most aggressive subtype, characterized by the amplification of the MYCN oncogene, has a dismal prognosis and no effective treatment is available. Understanding the alterations induced by the tumor on the various layers of gene expression is therefore important for a complete characterization of this neuroblastoma subtype and for the discovery of new therapeutic opportunities. Here we describe the profiling of 13 MYCN-amplified neuroblastoma cell lines at the genome (copy number), transcriptome, translatome and miRome levels (GEO series GSE56654, GSE56552 and GSE56655). We provide detailed experimental and data analysis procedures by means of which we derived the results described in [1].

Translational compensation of genomic instability in neuroblastoma.

Cancer-associated gene expression imbalances are conventionally studied at the genomic, epigenomic and transcriptomic levels. Given the relevance of translational control in determining cell phenotypes, we evaluated the translatome, i.e., the transcriptome engaged in translation, as a descriptor of the effects of genetic instability in cancer. We performed this evaluation in high-risk neuroblastomas, which are characterized by a low frequency of point mutations or known cancer-driving genes and by the presence of several segmental chromosomal aberrations that produce gene-copy imbalances that guide aggressiveness. We thus integrated genome, transcriptome, translatome and miRome profiles in a representative panel of high-risk neuroblastoma cell lines. We identified a number of genes whose genomic imbalance was corrected by compensatory adaptations in translational efficiency. The transcriptomic level of these genes was predictive of poor prognosis in more than half of cases, and the genomic imbalances found in their loci were shared by 27 other tumor types. This homeostatic process is also not limited to copy number-altered genes, as we showed the translational stoichiometric rebalance of histone genes. We suggest that the translational buffering of fluctuations in these dose-sensitive transcripts is a potential driving process of neuroblastoma evolution.

Segmental chromosome aberrations converge on overexpression of mitotic spindle regulatory genes in high-risk neuroblastoma.

Integration of genome-wide profiles of DNA copy number alterations (CNAs) and gene expression variations (GEVs) could provide combined power to the identification of driver genes and gene networks in tumors. Here we merge matched genome and transcriptome microarray analyses from neuroblastoma samples to derive correlation patterns of CNAs and GEVs, irrespective of their genomic location. Neuroblastoma correlation patterns are strongly asymmetrical, being on average 10 CNAs linked to 1 GEV, and show the widespread prevalence of long range covariance. Functional enrichment and network analysis of the genes covarying with CNAs consistently point to a major cell function, the regulation of mitotic spindle assembly. Moreover, elevated expression of 14 key genes promoting this function is strongly associated to high-risk neuroblastomas with 1p loss and MYCN amplification in a set of 410 tumor samples (P < 0.00001). Independent CNA/GEV profiling on neuroblastoma cell lines shows that increased levels of expression of these genes are linked to 1p loss. By this approach, we reveal a convergence of clustered neuroblastoma CNAs toward increased expression of a group of prognostic and functionally cooperating genes. We therefore propose gain of function of the spindle assembly machinery as a lesion potentially offering new targets for therapy of high-risk neuroblastoma.

The vent-like homeobox gene VENTX promotes human myeloid differentiation and is highly expressed in acute myeloid leukemia.

Recent data indicate that a variety of regulatory molecules active in embryonic development may also play a role in the regulation of early hematopoiesis. Here we report that the human Vent-like homeobox gene VENTX, a putative homolog of the Xenopus xvent2 gene, is a unique regulatory hematopoietic gene that is aberrantly expressed in CD34(+) leukemic stem-cell candidates in human acute myeloid leukemia (AML). Quantitative RT-PCR documented expression of the gene in lineage positive hematopoietic subpopulations, with the highest expression in CD33(+) myeloid cells. Notably, expression levels of VENTX were negligible in normal CD34(+)/CD38(-) or CD34(+) human progenitor cells. In contrast to this, leukemic CD34(+)/CD38(-) cells from AML patients with translocation t(8,21) and normal karyotype displayed aberrantly high expression of VENTX. Gene expression and pathway analysis demonstrated that in normal CD34(+) cells enforced expression of VENTX initiates genes associated with myeloid development and down-regulates genes involved in early lymphoid development. Functional analyses confirmed that aberrant expression of VENTX in normal CD34(+) human progenitor cells perturbs normal hematopoietic development, promoting generation of myeloid cells and impairing generation of lymphoid cells in vitro and in vivo. Stable knockdown of VENTX expression inhibited the proliferation of human AML cell lines. Taken together, these data extend our insights into the function of embryonic mesodermal factors in human postnatal hematopoiesis and indicate a role for VENTX in normal and malignant myelopoiesis.

A novel role for Lef-1, a central transcription mediator of Wnt signaling, in leukemogenesis.

Canonical Wnt signaling is critically involved in normal hematopoietic development and the self-renewal process of hematopoietic stem cells (HSCs). Deregulation of this pathway has been linked to a large variety of cancers, including different subtypes of leukemia. Lef-1 is a major transcription factor of this pathway and plays a pivotal role in lymphoid differentiation as well as in granulopoiesis. Here, we demonstrate Lef-1 expression in murine HSCs as well as its expression in human leukemia. Mice transplanted with bone marrow retrovirally transduced to express Lef-1 or a constitutive active Lef-1 mutant showed a severe disturbance of normal hematopoietic differentiation and finally developed B lymphoblastic and acute myeloid leukemia (AML). Lef-1-induced AMLs were characterized by immunoglobulin (Ig) DH-JH rearrangements and a promiscuous expression of lymphoid and myeloid regulatory factors. Furthermore, single cell experiments and limiting dilution transplantation assays demonstrated that Lef-1-induced AML was propagated by a leukemic stem cell with lymphoid characteristics displaying Ig DH-JH rearrangements and a B220(+) myeloid marker(-) immunophenotype. These data indicate a thus far unknown role of Lef-1 in the biology of acute leukemia, pointing to the necessity of balanced Lef-1 expression for an ordered hematopoietic development.

Constitutive expression of the ATP-binding cassette transporter ABCG2 enhances the growth potential of early human hematopoietic progenitors.

The ATP-binding cassette transporter, ABCG2, is a molecular determinant of the side population phenotype, which is enriched for stem and progenitor cells in various nonhematopoietic and hematopoietic tissues. ABCG2 is highly expressed in hematopoietic progenitors and silenced in differentiated hematopoietic cells, suggesting a role of ABCG2 in early hematopoiesis. To test whether ABCG2 is involved in human hematopoietic development, we retrovirally transduced umbilical cord blood-derived early hematopoietic cells and analyzed hematopoiesis in vitro and in vivo. ABCG2 increased the number of clonogenic progenitors in vitro, including the most primitive colony-forming unit-granulocyte, erythroid, macrophage, megakaryocyte, by twofold (n = 14; p < .0005). Furthermore, ABCG2 induced a threefold increase in the replating capacity of primary colonies (n = 9; p < .01). In addition, ABCG2 impaired the development of CD19+ lymphoid cells in vitro. In transplanted NOD/SCID mice, the ATP-binding cassette transporter decreased the number of human B-lymphoid cells, resulting in an inversion of the lymphoid/myeloid ratio. ABCG2 enhanced the proportion of CD34+ progenitor cells in vivo (n = 4; p < .05) and enhanced the most primitive human progenitor pool, as determined by limiting dilution competitive repopulating unit assay (p < .034). Our data characterize ABCG2 as a regulatory protein of early human hematopoietic development.

Overexpression of CDX2 perturbs HOX gene expression in murine progenitors depending on its N-terminal domain and is closely correlated with deregulated HOX gene expression in human acute myeloid leukemia.

The mechanisms underlying deregulation of HOX gene expression in AML are poorly understood. The ParaHox gene CDX2 was shown to act as positive upstream regulator of several HOX genes. In this study, constitutive expression of Cdx2 caused perturbation of leukemogenic Hox genes such as Hoxa10 and Hoxb8 in murine hematopoietic progenitors. Deletion of the N-terminal domain of Cdx2 abrogated its ability to perturb Hox gene expression and to cause acute myeloid leukemia (AML) in mice. In contrast inactivation of the putative Pbx interacting site of Cdx2 did not change the leukemogenic potential of the gene. In an analysis of 115 patients with AML, expression levels of CDX2 were closely correlated with deregulated HOX gene expression. Patients with normal karyotype showed a 14-fold higher expression of CDX2 and deregulated HOX gene expression compared with patients with chromosomal translocations such as t(8:21) or t(15;17). All patients with AML with normal karyotype tested were negative for CDX1 and CDX4 expression. These data link the leukemogenic potential of Cdx2 to its ability to dysregulate Hox genes. They furthermore correlate the level of CDX2 expression with HOX gene expression in human AML and support a potential role of CDX2 in the development of human AML with aberrant Hox gene expression.

Effects of the protein tyrosine kinase inhibitor, SU5614, on leukemic and normal stem cells.

FLT3 activating mutations are the most frequent single genetic abnormality in patients with acute myeloid leukemia. Thus targeting the FLT3 activated kinase is a promising treatment approach. We wanted to test whether the protein tyrosine kinase inhibitor SU5614 selectively eliminates leukemic stem cells while sparing their normal counterparts.