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Determine the Impact of Novel BRCA1 Translation Start Sites on Therapy Resistance in Ovarian Cancer

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Technical Report,01 Jul 2015,30 Jun 2017

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Institute for Cancer Research Philadelphia United States

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Purpose Recently, PARP inhibitors have emerged as promising agents for the treatment of BRCA1 mutant ovarian cancers. However, similar to platinum, drug resistance is a major clinical hurdle. Scope In this proposal, we aimed to characterize N-terminal deficient BRCA1 proteins contribution to DNA damage repair and their ability to confer resistance to ovarian cancer therapeutics, as well as identify novel small molecules that specifically kill N-terminal deficient BRCA1 protein expressing cells. Major findings We expressed a number of BRCA1 proteins produced from downstream translation start sites that were truncated at the N-terminal region and lacked the RING domain. We show that RING deficient-BRCA1 proteins were hypomorphic, contributing to RAD51 loading, PARPi and cisplatin resistance. The mechanism we describe may not be limited to cancers with BRCA1185delAG mutations and could be relevant to multiple frameshifting 5 located BRCA1 mutations. However, mutations located after Met-297 c.891 are unlikely to develop resistance through this mechanism, as we show that the next downstream translation start site at Met-531 c.1593 produced a functionless protein. Additionally, we identified three new small molecules that could be developed as drugs to specifically target PARP inhibitor resistant cancers that express N-terminal deficient BRCA1 proteins.

Subject Categories:

  • Medicine and Medical Research
  • Genetic Engineering and Molecular Biology
  • Biochemistry

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