Abstract
Background and Purpose :
Materials and Methods :
We Transduced the SCLC cell-line SBC5 with a custom CRISPR sgRNA library focused on druggable gene targets and treated cells with RT . Cells collected at multiple timepoints were subjected to next-generation sequencing . We determined radiosensitization both in vitro with cell-lines assessed by short-term viability and clonogenic assays, and in vivo mouse models by tumour growth delay . Pharmacodynamic effects of AZD1390 were quantified by ATM-Ser1981 phosphorylation, and RT-induced DNA damage by comet assay .
Results :
Using a CRISPR dropout screen, we identified multiple radiosensitizing genes for SCLC at various timepoints with ATM as a top determinant gene for Radiosensitivity . Validation by ATM knockout (KO) demonstrated increased radiosensitivity by short-term viability assay (dose modification factor [DMF]50 = 3.25-3.73 in SBC5 ATM-KO) and clonogenic assays (DMF37 1.25-1.65 in SBC5 ATM-KO) . ATM inhibition by AZD1390 effectively abrogated ATM Ser1981 phosphorylation in SCLC cell-lines and increased RT-induced DNA damage . AZD1390 synergistically increased the radiosensitivity of SCLC cell-lines (cell viability assay: SBC5 DMF37=2.19, SHP77 DMF37=1.56, H446 DMF37= 3.27, KP1 DMF37= 1.65 at 100nM; clonogenic assay : SBC5 DMF37=4.23, H1048 DMF37=1.91), and in vivo murine syngeneic, KP1, and patient-derived xenograft (PDX) models, JHU-LX108 and JHU-LX33 .
Conclusion :
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