Abstract 5279: Sequential treatment with PARPi and WEE1i minimizes T cell DNA damage and enhances its immune response
Authors: Jiao Xiaofei , Liu Jiahao , Mu Wei , Zhu Li , Zhao Xuejiao , Mills Gordon B. , Gao Qinglei , Fang Yong 
Published: March 2024

Abstract
Background: DNA damage response (DDR) targeted therapy, like PARP inhibitors (PARPi) and WEE1 inhibitors (WEE1i), have demonstrated potent anti-cancer activity and are pronounced to activate the cytosolic immunity pathway. Our previous work showed that sequential inhibition of PARP and WEE1 could kill tumor cells as effective as their concurrent application, with ameliorated toxicity to normal cells, suggesting high clinical translational potential of this regimen. However, the effect of sequential treatment on T lymphocytes and anti-cancer immunity remains largely unknown.
Methods and results: T cells were treated with 25 μM olaparib, or 250 nM AZD1775, or olaparib combined with AZD1775 (concurrent group) for 48h, or olaparib for 24h followed by AZD1775 for 24h (sequential group) in vitro. AZD1775 and concurrent treatment reduced the T cell viability to 19% and 14.3%, while sequential treatment maintained the viability to 58.6%, closed to olaparib monotherapy (61.6%). And the most potent proliferation capacity accompanied with the lowest apoptosis level were both recorded after sequential treatment, manifested by the increasing of Ki67 and EdU and the decreasing of cleaved caspase-3. Reverse-phase protein arrays (RPPA) analyses identified relieved DNA damage in T cells receiving sequential treatment. Alkaline comet assay and detecting of γH2AX further confirmed that the T cell DNA damage caused by PARPi and WEE1i was obviously alleviated after sequential therapy. Furthermore, sequential treatment activated cGAS-STING pathway effectively and upregulated the production of CCL5, CXCL10 and IFNβ of downstream type I interferon response compared with monotherapy and concurrent treatment in ovarian cancer cell lines (SKOV3, OVCAR8, A2780). We also evaluated an ID8 intraperitoneal syngeneic immunocompetent mouse model. T cells isolated from tumors, ascites, spleen and peripheral blood in sequential group were presented with the highest proliferation potential and the lowest level of DNA damage. And the tumor burden of mice in sequential group was obviously subsided, which was comparable to that in concurrent group.
Conclusions: This study demonstrated that targeting PARP and/or WEE1 impaired the T cell viability and led to DNA damage. However, administrating PARPi and WEE1i sequentially diminished this inhibitory effect on T cells on the premise of ensuring their anti-tumor effect. These data provide strong rational for the further investigation on exploring the clinical significance of sequential treatment with PARPi and WEE1i.
Citation Format: Xiaofei Jiao, Jiahao Liu, Wei Mu, Li Zhu, Xuejiao Zhao, Gordon B. Mills, Qinglei Gao, Yong Fang. Sequential treatment with PARPi and WEE1i minimizes T cell DNA damage and enhances its immune response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5279.