Mechanism of RBBP8‐mediated homologous recombination repair in gastric cancer synthetic lethal

BACKGROUND: It is of great clinical significance to further explore new strategies and potential combined therapeutic targets for gastric cancer. This study aimed to investigate the synthetic lethal effect of RBBP8 molecular intervention combined with a poly ADP ribose polymerase (PARP) inhibitor in non‐BRCA mutant gastric cancer and clarify the mechanism by which RBBP8 regulates homologous recombination repair. METHODS: The role of RBBP8 in DNA damage repair was observed using bioinformatic analysis, western blot analysis, and immunofluorescence. The synthetic lethal effect was verified using 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium, inner salt (MTS)and flow cytometry apoptosis experiments. RESULTS: Among the patients with gastric cancer treated with chemotherapy, the prognosis of patients with high RBBP8 expression levels was worse (homologous recombination [HR] = 1.54, p = 0.028). RBBP8 knockdown induced DNA damage and had a synergistic effect with PARP inhibitor treatment on cell viability inhibition and cell apoptosis in AGS (generic code for human gastric adenocarcinoma cells) (t = 11.154, p < 0.001) and N87 (t = 6.362, p < 0.001) cells. RBBP8 knockdown inhibited RAD51 activation and DNA terminal excision in homologous recombination repair. CONCLUSION: RBBP8 is involved in homologous recombination repair, and molecular intervention into RBBP8 could achieve a synthetic lethal effect with PARP inhibitor treatment in gastric cancer cells.