The Public Repository of Xenografts enables discovery and randomized phase II-like trials in mice

More than 90% of drugs with preclinical activity fail in human trials, largely due to insufficient efficacy. We hypothesized that adequately powered trials of patient-derived xenografts (PDX) in mice could efficiently define therapeutic activity across heterogeneous tumors. To address this hypothesis, we established a large, publicly available repository of well-characterized leukemia and lymphoma PDXs that undergo orthotopic engraftment, called the Public Repository of Xenografts (PRoXe). PRoXe includes all de-identified information relevant to the primary specimens and the PDXs derived from them. Using this repository, we demonstrate that large studies of acute leukemia PDXs that mimic human randomized clinical trials can characterize drug efficacy and generate transcriptional, functional, and proteomic biomarkers in both treatment-naive and relapsed/refractory disease

Tribbles homolog 2 inactivates C/EBPα and causes acute myelogenous leukemia

SummaryTribbles homolog 2 (Trib2) was identified as a downregulated transcript in leukemic cells undergoing growth arrest. To investigate the effects of Trib2 in hematopoietic progenitors, mice were reconstituted with hematopoietic stem cells retrovirally expressing Trib2. Trib2-transduced bone marrow cells exhibited a growth advantage ex vivo and readily established factor-dependent cell lines. In vivo, Trib2-reconstituted mice uniformly developed fatal transplantable acute myelogenous leukemia (AML). In mechanistic studies, we found that Trib2 associated with and inhibited C/EBPα. Furthermore, Trib2 expression was elevated in a subset of human AML patient samples. Together, our data identify Trib2 as an oncogene that induces AML through a mechanism involving inactivation of C/EBPα

High-level expression of Mastermind-like 2 contributes to aberrant activation of the NOTCH signaling pathway in human lymphomas.

Inappropriate activation of the NOTCH signaling pathway, for example, by activating mutations, contributes to the pathogenesis of various human malignancies. Here, we demonstrate that aberrant expression of an essential NOTCH coactivator of the Mastermind-like (MAML) family provides an alternative mechanism to activate NOTCH signaling in human lymphoma cells. We detected high-level MAML2 expression in several B cell-derived lymphoma types, including classical Hodgkin lymphoma (cHL) cells, relative to normal B cells. Inhibition of MAML-protein activity by a dominant negative form of MAML or by small hairpin RNAs targeting MAML2 in cHL cells resulted in downregulation of the NOTCH target genes HES7 and HEY1, which we identified as overexpressed in cHL cells, and in reduced proliferation. Furthermore, a NOTCH gene-expression signature in cHL cells confirmed their cell-autonomous NOTCH activity. Finally, in line with the essential role of MAML proteins for assembly and activity of the NOTCH transcriptional complex (NTC), we show that MAML-derived small-peptide constructs block NOTCH activity and disrupt NTC formation in vitro. These data strongly suggest direct targeting of the NTC as treatment strategy for NOTCH-dependent malignancies

Evolution morphogénique des Pyrénées orientales vue par les datations cosmogéniques de systèmes karstiques étagés.

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Pharmacological disruption of the Notch transcription factor complex.

Notch pathway signaling is implicated in several human cancers. Aberrant activation and mutations of Notch signaling components are linked to tumor initiation, maintenance, and resistance to cancer therapy. Several strategies, such as monoclonal antibodies against Notch ligands and receptors, as well as small-molecule γ-secretase inhibitors (GSIs), have been developed to interfere with Notch receptor activation at proximal points in the pathway. However, the use of drug-like small molecules to target the downstream mediators of Notch signaling, the Notch transcription activation complex, remains largely unexplored. Here, we report the discovery of an orally active small-molecule inhibitor (termed CB-103) of the Notch transcription activation complex. We show that CB-103 inhibits Notch signaling in primary human T cell acute lymphoblastic leukemia and other Notch-dependent human tumor cell lines, and concomitantly induces cell cycle arrest and apoptosis, thereby impairing proliferation, including in GSI-resistant human tumor cell lines with chromosomal translocations and rearrangements in Notch genes. CB-103 produces Notch loss-of-function phenotypes in flies and mice and inhibits the growth of human breast cancer and leukemia xenografts, notably without causing the dose-limiting intestinal toxicity associated with other Notch inhibitors. Thus, we describe a pharmacological strategy that interferes with Notch signaling by disrupting the Notch transcription complex and shows therapeutic potential for treating Notch-driven cancers