Abstract B008: Targeting DNA damage responsive pathways in cancer therapy

Abstract DNA double strand breaks (DSBs) result in activation of several key DNA damage response (DDR) kinases including ATM, ATR, and DNA-PK. These protein kinases not only promote DNA damage-induced checkpoint control, but also facilitate DSB repair in humans. Thus, these DDR kinases have become promising drug targets for cancer therapy. However, the benefits of targeting DDR kinases remain to be realized, in part due to the lack of predictive biomarkers. By undertaking CRISPR screens with inhibitors targeting key DDR kinases, we obtained a global and unbiased view of genetic interactions with DDR inhibition. Additionally, we compared the synergistic effects of combining different DDR inhibitors and found that ATM and PARP inhibitors showed remarkable synergy, which depends on the dominant negative function of ATM inhibition. Moreover, to provide comprehensive and unbiased perspective of DDR signaling pathways, we performed 30 fluorescence-activated cell sorting–based genome-wide CRISPR screens with antibodies recognizing distinct endogenous DNA damage–signaling proteins to identify new regulators involved in DNA damage response (DDR). We discovered that proteasome-mediated processing is an early and prerequisite event for cells to trigger camptothecin- and etoposide-induced DDR signaling. Furthermore, we identified PRMT1 and PRMT5 as new modulators that regulate ATM protein level. Additionally, we discovered that GNB1L is a master regulator of DDR signaling via its role as a co-chaperone for PIKK proteins. Collectively, these screens offer a rich resource for further investigation of DDR, which may provide insight into strategies of targeting these DDR pathways to improve therapeutic outcomes. More recently, we have adopted dTAG technology for the investigation of many essential DDR and replication proteins, which provide mechanistic insights into the roles of these essential proteins in genome maintenance. Additionally, we have expanded FACS-based screens for the studies of other cancer-associated pathways and explored key biological processes critical for cancer progression in vivo. These studies will facilitate the development of better therapies for cancer patients. Citation Format: Junjie Chen. Targeting DNA damage responsive pathways in cancer therapy [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Functional and Genomic Precision Medicine in Cancer: Different Perspectives, Common Goals; 2025 Mar 11-13; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(5 Suppl):Abstract nr B008.