Abstract B070: Antitumor effect of AZD5305, a selective PARP1 inhibitor, in breast and gastric cancer cells

Abstract

Background: Poly (ADP-ribose) polymerase (PARP) 1 has multiple cellular functions including its crucial role in DNA damage response. PARP inhibitor (PARPi) blocks the synthesis of PAR polymers and traps PARP1 on the damage sites. Currently approved PARPis target both PARP1 and PARP2, but the inhibition of PARP2 can cause undesirable hematological toxicity. AZD5305 is a novel selective PARP1 inhibitor that can reduce the hematological toxicity by off-targeting of PARP2. We evaluated the anti-tumor effects and mechanism of action of AZD5305 in breast and gastric cancer cells in vitro.

Methods: To investigate the anti-tumor effects of AZD5305, we used 2 cell lines of breast cancer cells (HCC1395 and MCF7) and 3 cell lines of human gastric cancer cells (SNU-601, SNU-668 and KATO Ⅲ). The cytotoxicity of AZD5305 was evaluated by colony formation assay (CFA) for 14 days with increasing concentration of AZD5305 (doses range: 0-5nM). Cell cycle was analyzed by flow cytometry and apoptotic cell death was assessed by annexin-Ⅴ/PI staining. DNA damage was detected by comet assay and cell immunofluorescence assay.

Results: BRCA1/2 mutated HCC1395 and RAD51C deficient SNU-601 were sensitive to AZD5305 (IC50: 0.25 nM), and SNU-668 was moderately sensitive (IC50: 2.05nM), while MCF7 and KATO III were less-sensitive to AZD5305 (IC50 > 5 nM). AZD5305 induced the G2/M cell cycle arrest in a dose-dependent manner in HCC1395 and SNU-601, but not in MCF7 and KATO Ⅲ. Moreover, AZD5305 increased sub-G1 population in HCC1395 and SNU-601 cells indicating apoptotic cell death, which was also confirmed by annexin-V assay and the cleaved PARP and caspase-7. Phosphorylation of RPA, γH2AX, and the expression of molecules related to DNA damage response were increased in the sensitive cells. Moreover, comet tails which indicate fragmented DNA were observed in the sensitive cells, but not in insensitive cells.

Conclusions: AZD5305, a novel PARP1 selective inhibitor, shows cytotoxic effect in HR defective breast and gastric cancer cells in vitro. AZD5305 accumulates DNA damage which leads to apoptotic cell death in sensitive cell lines, but not in less-sensitive cell lines.

Citation Format: Sujin Ham, So Hyeon Kim, Hae Min Hwang, Minyoung Lee, Youlim Noh, Changyun Lee, Yu-Jin Kim, Jinyong Kim, Dae-Won Lee, Kyung-Hun Lee, Seock-Ah Im. Antitumor effect of AZD5305, a selective PARP1 inhibitor, in breast and gastric cancer cells [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B070.