Abstract P029: CDC7 inhibitor-induced replication stress generates inflamed aneuploid cells to sensitize immune checkpoint inhibitors
Authors: Morita Tomoko Y. , Yu Jie , Kashima Yukie , Tanaka Kosuke , Hakozaki Yumi , Kageyama Shun-ichiro , Nakamura Akito , Lightcap Eric , Niu Huifeng , Kannan Karuppiah , Ohashi Akihiro 
Published: December 2021

Abstract
Background: Cell division cycle 7 (CDC7), a serine/threonine kinase, plays important roles in the initiation of DNA replication. We developed a highly specific CDC7 inhibitor, TAK-931, as a next-generation of replication stress (RS) inducer. In this study, we preclinically investigated novel aspects of TAK-931 on antitumor efficacy and immunity to evaluate the therapeutic potential of TAK-931 with immune checkpoint inhibitors (ICIs). Methods: TAK-931-treated HeLa cells were subjected to cell growth assay, senescence-associated galactosidase (SA-b-gal) activity assay, transcriptome analysis (RNA-seq), and single-cell RNA-seq (scRNA-seq). The flowcytometry (FCM)-based immune profiling panel studies in J558 allograft syngeneic mouse models were performed at Shanghai Medicilon Inc. In vivo efficacy studies in J558 allograft models in combination with anti-mPD-1, anti-mPD-L1, and anti-mCTLA-4 antibodies were performed at Shanghai Medicilon Inc. Results: TAK-931 intensively induced RS to consequently generates senescence-associated secretory phenotype (SASP) aneuploid cells, which highly expressed inflammatory cytokines and chemokines. In transcriptome analyses, inflammatory cytokine and chemokine hallmarks were also significantly and intensively enriched in the TAK-931-induced aneuploid cells; 5 out of top-6 enriched hallmarks were inflammatory related. The scRNA-seq analyses revealed that advanced aneuploidy was closely associated with activations in the inflammatory-related and SASP-associated pathways. The FCM-based immune profiling panel studies demonstrated that the tumor infiltrating immune cells (TIICs), such as CD8+ T cells, CD4+ T cells, PD-1+CD8+ T cells, and PD-1+CD4+ T cells, were significantly accumulated in TAK-931-treated J558 mouse allografts, while immune suppressive CD45+ myeloid derived suppressor cells (MDSCs) were significantly decreased. Single-agent treatment with TAK-931 exhibited significant antitumor efficacy and immunity in J558 syngeneic allografts, which confirmed by tumor re-challenging studies. We finally demonstrated that combination treatment with TAK-931 and ICIs (anti-mPD-1, anti-mPD-L1, and andti-mCTLA-4 antibodies) enhances antiproliferative activities in preclinical syngeneic mouse models. Conclusions: These preclinical findings suggest the therapeutic potential of TAK-931 in antitumor efficacy and immunity, which may improve clinical benefit of the currently-used immunotherapy by combination treatment.
Citation Format: Tomoko Y. Morita, Jie Yu, Yukie Kashima, Kosuke Tanaka, Yumi Hakozaki, Shun-ichiro Kageyama, Akito Nakamura, Eric Lightcap, Huifeng Niu, Karuppiah Kannan, Akihiro Ohashi. CDC7 inhibitor-induced replication stress generates inflamed aneuploid cells to sensitize immune checkpoint inhibitors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P029.