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:Homologous recombination deficiency (HRD) has emerged as a key vulnerability in selected cancer types and is associated with response to platinum and PARPi-based treatment strategies. However, additional biomarkers and targeted therapy options are needed to broaden the range of patients that could benefit from this therapeutic niche. Here, we show that the SARC-HRD signature, composed of ten genes of the homologous recombination repair pathway, stratifies a cohort of sarcoma patients, and associates with genomic biomarkers of HRD, with disease progression and with the CINSARC prognostic signature. Equivalently to CINSARC, high levels of SARC-HRD are associated with poor metastasis-free survival, underscoring the potential of SARC-HRD to predict disease outcome. By pharmacotyping patient-derived cell models, we identified promising drug targets within the DNA damage response for sarcoma with HRD traits. Inhibition of ATR, CHK1 and WEE1 elicited synthetic lethality in sarcoma cells with HRD, which concomitantly showed an upregulation of ATR signaling. Combinatorial drug testing further revealed synergistic drug combinations between ATRi, WEE1i, PARP1/2i and chemotherapeutic agents with potential clinical impact. Mechanistically, targeting ATR signaling at multiple levels induced a replication defect and apoptotic cell death. Taken together, our results demonstrate the therapeutic benefit of targeting DDR mechanisms in sarcoma with HRDness traits and their potential clinical utility for treating a broader spectrum of tumor types.
Project description:Mutational burdens and clonal compositions are established early and are maintained throughout recurrence. Using both next generation and ultra long read sequencing to analyze single nucleotide and structural variants (SVs) we discovered that although tumors from the same patient remained relatively stable, homologous recombination repair proficient (HRP) and homologous recombination repair deficient (HRD) tumors presented with distinct clonal profiles. SV signature analysis revealed three distinct classes: tumors defined by DNA losses, DNA gains, and copy number neutral changes. Each class displayed structural variation affecting distinct regions of the genome. Ultra long read sequencing validated most of the SVs identified in short read sequencing and identified additional SVs. A novel candidate driver gene from the HRP pathway, MDC1, was significantly mutated in patients with HRP tumors.
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: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.