Project description:Preclinical data support the investigation of PARP inhibitors in other neoplasms exhibiting homologous recombination deficiency (HRD) as monotherapy as well as in combination with chemotherapy. However,in colorectal cancer (CRC), the role of HRD alterations is mostly unknown. This study aims to explore the the Efficacy and Safety of Fluzoparib combined with Irinotecan in the Second-line treatment of HRD alterations metastatic colorectal cancer.
Project description:Brca1 is required for DNA repair by homologous recombination (HR) and normal embryonic development. Here we report that deletion of the DNA damage responsefactor 53BP1 overcomes embryonic lethality in Brca1-nullizygous mice, and rescues HR deficiency, as measured by hypersensitivity to PARP (polyADPribose polymerase) inhibition. However, Brca1,53BP1 double-deficient cells are hypersensitive to DNA interstrand crosslinks (ICLs), indicating that BRCA1 has an additional role in DNA cross-link repair that is distinct from HR. Disruption of the non-homologous end-joining (NHEJ) factor, Ku, promotes DNA repair in Brca1-deficient cells; however deletion of either Ku or 53BP1 exacerbates genomic instability in cells lacking FANCD2, a mediator of the Fanconi Anemia pathway for ICL repair. Brca1 therefore has two separate roles in ICL repair, whereas FANCD2 provides a key activity that can not be bypassed by ablation of 53BP1 or Ku. B cells were stimulated to undergo class switch recombination in vitro. Chromatin from B cells was harvested 72 hours post-stimulation and used for RPA ChIP to study the extent of resection of DNA DSBs.
Project description:Genomic determination for Homologous Recombination Deficiency (HRD) by shallow Whole Genome Sequencing (sWGS) with shallowHRD (PMID : 32315385) on 55 triple-negative breast cancer Patient Derived-Xenograft (PDX) treated with platinum
Project description:The m6A reader IGF2BP2 and helicase DHX9 collaborate to remove DNA-RNA hybrids at DSB sites. This action facilitates RAD51 loading and homologous recombination, influencing cancer cell responses to DNA damage therapies.
Project description:The Saccharomyces cerevisae RAD3 gene is homolog of human XPD, an essential gene encoding a DNA helicase of the TFIIH complex involved in both nucleotide excision repair (NER) and transcription. Mutant alleles of RAD3 have been identified (rad3-101 and rad3-102) that have partial defects in DNA repair associated with a strong hyper-recombination (hyper-Rec) phenotype. Previous studies showed that the hyper-Rec phenotype associated with rad3-101 and rad3-102 can be explained as a consequence of persistent single-stranded DNA gaps that are converted to recombinogenic double-strand breaks (DSBs) by replication. We have further characterized these events using a system in which the reciprocal products of mitotic recombination between homologs are recovered as red and white sectored colonies. Both rad3-101 and rad3-102 elevate the frequency of sectored colonies about 100-fold. Subsequent mapping of these events shows that three-quarters of crossovers between homologs induced in hyper-Rec rad3 mutants reflect DSBs formed in at the same positions in both sister chromatids (double sister-chromatid breaks, DSCBs). The remainder reflects DSBs formed in single chromatids (single chromatid breaks, SCBs). The ratio of DSCBs to SCBs is similar to that observed for spontaneous recombination events in wild-type cells. In addition to examining crossovers on chromosome V, we mapped 216 unselected genomic alterations throughout the genome including crossovers, gene conversions, deletions, and duplications. We found a significant association between the location of these recombination events and regions with elevated gamma-H2AX. In addition, there was a hotspot for deletions and duplications at the IMA2 and HXT11 genes near the left end of chromosome XV. A comparison of these data with our previous analysis of spontaneous mitotic recombination events suggests that a sub-set of spontaneous events in wild-type cells may be initiated by incomplete NER reactions, and that DSCBs, which cannot be repaired by sister-chromatid recombination, are a major source of mitotic recombination between homologous chromosomes.