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      Small molecule selected to disrupt oncogenic protein EWS-FLI1 interaction with RNA Helicase A inhibits Ewing's Sarcoma

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          Abstract

          Many sarcomas and leukemias carry non-random chromosomal translocations encoding mutant fusion transcription factors that are essential to their molecular pathogenesis. These novel, tumor-specific proteins provides a unique opportunity for the development of highly selective anticancer drugs that has yet to be exploited. A particularly clear example is provided by Ewing's Sarcoma Family Tumors (ESFT) which contain a characteristic t(11;22) translocation leading to expression of the oncogenic fusion protein EWS-FLI1. EWS-FLI1 is a disordered protein that precluded standard structure-based small molecule inhibitor design. Using surface plasmon resonance screening, we discovered a lead compound, NSC635437. A derivative compound, YK-4-279, blocks RHA binding to EWS-FLI1, induces apoptosis in ESFT cells, and reduces the growth of ESFT orthotopic xenografts. These findings provide proof of principle that inhibiting the interaction of mutant cancer-specific transcription factors with the normal cellular binding partners required for their oncogenic activity provides a promising strategy for the development of uniquely effective, tumor-specific anticancer agents.

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          Most cited references 38

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          Gene fusion with an ETS DNA-binding domain caused by chromosome translocation in human tumours.

          Ewing's sarcoma and related subtypes of primitive neuroectodermal tumours share a recurrent and specific t(11;22) (q24;q12) chromosome translocation, the breakpoints of which have recently been cloned. Phylogenetically conserved restriction fragments in the vicinity of EWSR1 and EWSR2, the genomic regions where the breakpoints of chromosome 22 and chromosome 11 are, respectively, have allowed identification of transcribed sequences from these regions and has indicated that a hybrid transcript might be generated by the translocation. Here we use these fragments to screen human complementary DNA libraries to show that the translocation alters the open reading frame of an expressed gene on chromosome 22 gene by substituting a sequence encoding a putative RNA-binding domain for that of the DNA-binding domain of the human homologue of murine Fli-1.
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            Control of apoptosis and mitotic spindle checkpoint by survivin.

            Progression of the cell cycle and control of apoptosis (programmed cell death) are thought to be intimately linked processes, acting to preserve homeostasis and developmental morphogenesis. Although proteins that regulate apoptosis have been implicated in restraining cell-cycle entry and controlling ploidy (chromosome number), the effector molecules at the interface between cell proliferation and cell survival have remained elusive. Here we show that a new inhibitor of apoptosis (IAP) protein, survivin, is expressed in the G2/M phase of the cell cycle in a cycle-regulated manner. At the beginning of mitosis, survivin associates with microtubules of the mitotic spindle in a specific and saturable reaction that is regulated by microtubule dynamics. Disruption of survivin-microtubule interactions results in loss of survivin's anti-apoptosis function and increased caspase-3 activity, a mechanism involved in cell death, during mitosis. These results indicate that survivin may counteract a default induction of apoptosis in G2/M phase. The overexpression of survivin in cancer may overcome this apoptotic checkpoint and favour aberrant progression of transformed cells through mitosis.
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              The Ewing family of tumors--a subgroup of small-round-cell tumors defined by specific chimeric transcripts.

              Precise diagnosis of small-round-cell tumors is often a challenge to the pathologist and the clinical oncologist. In Ewing's sarcomas and related peripheral primitive neuroectodermal tumors, a t(11;22) translocation or a (21,22) rearrangement is associated with hybrid transcripts of the EWS gene with the FLI1 or ERG gene. To investigate the diagnostic implication of this observation, we searched for these hybrid transcripts in tumors from patients with clinical and radiologic features of Ewing's sarcoma or peripheral primitive neuroectodermal tumors. Samples of RNA from 114 tumors were reverse transcribed and subjected to the polymerase chain reaction with primers designed to amplify the relevant chimeric transcripts. All amplified products were sequenced. In-frame hybrid transcripts were observed in 89 cases. A hybrid transcript was found in 83 of 87 cases (95 percent) of Ewing's sarcoma or peripheral primitive neuroectodermal tumors. Samples of RNA from all of 12 tumors that had been proved to be other than Ewing's sarcoma or neuroectodermal tumors had no hybrid transcript. However, 6 of 15 undifferentiated tumors whose type was ambiguous (nonsecreting, poorly differentiated neuroblastoma or undifferentiated sarcoma) contained a hybrid transcript, suggesting that they might have to be reclassified. A subgroup of small-round-cell tumors identified as belonging to the Ewing family of tumors can be defined according to a specific molecular genetic lesion that is detectable by a rapid, reliable, and efficient method. This approach can be applied to small specimens obtained by fine-needle biopsies.
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                Author and article information

                Journal
                9502015
                8791
                Nat Med
                Nature medicine
                1078-8956
                1546-170X
                18 May 2009
                5 July 2009
                July 2009
                5 January 2010
                : 15
                : 7
                : 750-756
                Author notes
                [* ]Corresponding author Jeffrey A Toretsky 3970 Reservoir Rd NW New Research Building W311 Washington DC, 20007 Phone: 202-687-8655 Fax: 202-687-1434 email: jat42@ 123456georgetown.edu
                Article
                nihpa116382
                10.1038/nm.1983
                2777681
                19584866
                Funding
                Funded by: National Cancer Institute : NCI
                Award ID: R01 CA138212-01 ||CA
                Funded by: National Cancer Institute : NCI
                Award ID: R01 CA133662-01A2 ||CA
                Funded by: National Cancer Institute : NCI
                Award ID: R01 CA088004-08 ||CA
                Categories
                Article

                Medicine

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