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In GBM, Cox-2-derived PGE2 induces Id1 via EP4-dependent activation of MAPK signaling and the Egr1 transcription factor. PGE2-mediated induction of Id1 is required for optimal tumor cell self-renewal and radiation resistance. Collectively, these findings identify Id1 as a key mediator of PGE2-dependent modulation of radiation response and lend insight into the mechanisms underlying radiation resistance in GBM patients.

The widespread application of high-throughput sequencing methods is resulting in the identification of a rapidly growing number of novel gene fusions caused by tumour-specific chromosomal rearrangements, whose oncogenic potential remains unknown. Here we describe a strategy that builds upon recent advances in genome editing and combines ex vivo and in vivo chromosomal engineering to rapidly and effectively interrogate the oncogenic potential of genomic rearrangements identified in human brain cancers. We show that one such rearrangement, an microdeletion resulting in a fusion between Brevican (BCAN) and Neurotrophic Receptor Tyrosine Kinase 1 (NTRK1), is a potent oncogenic driver of high-grade gliomas and confers sensitivity to the experimental TRK inhibitor entrectinib. This work demonstrates that BCAN-NTRK1 is a bona fide human glioma driver and describes a general strategy to define the oncogenic potential of novel glioma-associated genomic rearrangements and to generate accurate preclinical models of this lethal human cancer.

Summary The mitotic checkpoint ensures proper segregation of chromosomes by delaying anaphase until all kinetochores are bound to microtubules. This inhibitory signal is composed of a complex containing Mad2, which inhibits anaphase progression. The complex can be disassembled by p31comet and TRIP13; however, TRIP13 knockdown has been shown to cause only a mild mitotic delay. Overexpression of checkpoint genes, as well as TRIP13, is correlated with chromosomal instability (CIN) in cancer, but the initial effects of Mad2 overexpression are prolonged mitosis and decreased proliferation. Here we show that TRIP13 overexpression significantly reduced, and TRIP13 reduction significantly exacerbated, the mitotic delay associated with Mad2 overexpression but not that induced by microtubule depolymerization. The combination of Mad2 overexpression and TRIP13 loss reduced the ability of checkpoint complexes to disassemble and significantly inhibited the proliferation of cells in culture and tumor xenografts. These results identify an unexpected dependency on TRIP13 in cells overexpressing Mad2.

Whole chromosome gains or losses (aneuploidy) are a hallmark of ~70% of human tumors. Modeling the consequences of aneuploidy has relied on perturbing spindle assembly checkpoint (SAC) components, but interpretations of these experiments are clouded by the multiple functions of these proteins. Here, we used a Cre recombinase-mediated chromosome loss strategy to individually delete mouse chromosomes 9, 10, 12, or 14 in tetraploid immortalized murine embryonic fibroblasts. This methodology also involves the generation of a dicentric chromosome intermediate, which subsequently undergoes a series of breakage-fusion-bridge (BFB) cycles. While the aneuploid cells generally display a growth disadvantage , they grow significantly better in low adherence sphere-forming conditions and three of the four lines are transformed, forming large and invasive tumors in immunocompromised mice. The aneuploid cells display increased chromosomal instability and DNA damage, a mutator phenotype associated with tumorigenesis Thus, these studies demonstrate a causative role for whole chromosome loss and the associated BFB-mediated instability in tumorigenesis and may shed light on the early consequences of aneuploidy in mammalian cells.

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Nature Communications 8: Article number: 15987 (2017); Published: 11 July 2017; Updated: 13 March 2018 In the original version of this Article, financial support was not fully acknowledged. The PDF and HTML versions of the Article have now been corrected to include the following: ‘This work was supported by grant I10-0095 from the STARR foundation.

was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.