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The RAS gene family is frequently mutated in human cancers, and the quest for compounds that bind to mutant RAS remains a major goal, as it also does for inhibitors of protein-protein interactions. We have refined crystallization conditions for KRAS169Q61H-yielding crystals suitable for soaking with compounds and exploited this to assess new RAS-binding compounds selected by screening a protein-protein interaction-focused compound library using surface plasmon resonance. Two compounds, referred to as PPIN-1 and PPIN-2, with related structures from 30 initial RAS binders showed binding to a pocket where compounds had been previously developed, including RAS effector protein-protein interaction inhibitors selected using an intracellular antibody fragment (called Abd compounds). Unlike the Abd series of RAS binders, PPIN-1 and PPIN-2 compounds were not competed by the inhibitory anti-RAS intracellular antibody fragment and did not show any RAS-effector inhibition properties. By fusing the common, anchoring part from the two new compounds with the inhibitory substituents of the Abd series, we have created a set of compounds that inhibit RAS-effector interactions with increased potency. These fused compounds add to the growing catalog of RAS protein-protein inhibitors and show that building a chemical series by crossing over two chemical series is a strategy to create RAS-binding small molecules. [ABSTRACT FROM AUTHOR]

Human cancers and some congenital traits are characterized by cytogenetic aberrations including translocations, amplifications, duplications or deletions that can involve gain or loss of genetic material. We have developed a simple method to precisely delineate such regions with known or cryptic genomic alterations. Molecular copy-number counting (MCC) uses PCR to interrogate miniscule amounts of genomic DNA and allows progressive delineation of DNA content to within a few hundred base pairs of a genomic alteration. As an example, we have located the junctions of a recurrent nonreciprocal translocation between chromosomes 3 and 5 in human renal cell carcinoma, facilitating cloning of the breakpoint without recourse to genomic libraries. The analysis also revealed additional cryptic chromosomal changes close to the translocation junction. MCC is a fast and flexible method for characterizing a wide range of chromosomal aberrations. [ABSTRACT FROM AUTHOR]

The EWS-ERG fusion protein is found in human sarcomas with the chromosomal translocation t(21;22)(q22;q12), where the translocation is considered to be an initiating event in sarcoma formation within uncommitted mesenchymal cells, probably long-lived progenitors capable of self renewal. The fusion protein may not therefore have an oncogenic capability beyond these progenitors. To assess whether EWS-ERG can be a tumour initiator in cells other than mesenchymal cells, we have analysed Ews-ERG fusion protein function in a cellular environment not typical of that found in human cancers, namely, committed lymphoid cells. We have used Ews-ERG invertor mice having an inverted ERG cDNA cassette flanked by loxP sites knocked in the Ews intron 8, crossed with mice expressing Cre recombinase under the control of the Rag1 gene to give conditional, lymphoid-specific expression of the fusion protein. Clonal T cell neoplasias arose in these mice. This conditional Ews gene fusion model of tumourigenesis shows that Ews-ERG can cause haematopoietic tumours and the precursor cells are committed cells. Thus, Ews-ERG can function in cells that do not have to be pluripotent progenitors or mesenchymal cells. [ABSTRACT FROM AUTHOR]

Lmo2 is an oncogenic transcription factor that is frequently overexpressed in T-cell acute lymphoblastic leukemia (T-ALL), including early T-cell precursor ALL (ETP-ALL) cases with poor prognosis. Lmo2 must be recruited to DNA by binding to the hematopoietic basic helix-loop-helix factors Scl/Tal1 or Lyl1. However, it is unknown which of these factors can mediate the leukemic activity of Lmo2. To address this, we have generated Lmo2-transgenic mice lacking either Scl or LyM in the thymus. We show that although Scl is dispensable for Lmo2-driven leukemia, Lyl1 is critical for all oncogenic functions of Lmo2, including upregulation of a stem cell-like gene signature, aberrant self-renewal of thymocytes, and subsequent generation of T-cell leukemia. LyM ex- pression is restricted to preleukemic and leukemic stem cell populations in this model, providing a molecular explanation for the stage-specific expression of the Lmo2-induced gene expression program. Moreover, LM02 and LYL1 are coexpressed in ETP-ALL patient samples, and LYL1 is required for growth of ETP-ALL cell lines. Thus, the LM02-LYL1 interaction is a promising therapeutic target for inhibiting self-renewing cancer stem cells in T-ALL, including poor-prognosis ETP-ALL cases. [ABSTRACT FROM AUTHOR]

The etiology of human tumors often involves chromosomal translocations. Models that emulate translocations are essential to understanding the determinants of frank malignancy, those dictating the restriction of translocations to specific lineages, and as a basis for development of rational therapeutic methods. We demonstrate that developmentally regulated Cre-loxP-mediated interchromosomal recombination between the Mll gene, whose human counterpart is involved in a spectrum of leukemias, and the Enl gene creates reciprocal chromosomal translocations that cause myeloid tumors. There is a rapid onset and high penetrance of leukemogenesis in these translocator mice, and high proportions of cells carrying chromosomal translocations can be found in bone marrow as early as 12 days after birth. This de novo strategy is a direct recapitulation of naturally occurring human cancer-associated translocations. [Copyright &y& Elsevier]

The expression of antibodies inside cells to ablate protein function has the potential for disease therapy and for target validation in functional genomics. However, due to inefficient expression or folding, only a few antibodies or antibody fragments, usually as single-chain Fv antibody fragments (scFv), bind their antigens in an intracellular environment. We have established a genetic-selection technology (intracellular antibody capture, IAC) to facilitate the isolation of functional intracellular scFv from a diverse repertoire. This approach comprises an in vitro library screen with scFv-expressing bacteriophage, employing bacterially expressed antigen, followed by a yeast in vivo antibody-antigen interaction screen of the sub-library of in vitro scFv antigen-binders. Accordingly, we have isolated panels of scFv that bind intracellularly to the BCR or the ABL parts of the BCR-ABL oncogenic protein. Sequence analysis of the intracellular antibody scFv panels revealed a sequence conservation indicating an intracellular antibody consensus for both VH and VL, which could form the basis for the de novo synthesis of intracellular antibody libraries to be used with intracellular antibody-capture technology. [Copyright &y& Elsevier]