1G6‐D7 Inhibits Homologous Recombination Repair by Targeting Extracellular HSP90α to Promote Apoptosis in Non–Small Cell Lung Cancer

ABSTRACT Despite recent advances in treatment, non–small cell lung cancer (NSCLC) continues to have a high mortality rate. Currently, NSCLC pathogenesis requires further investigation, and therapeutic drugs are still under development. Homologous recombination repair (HRR) repairs severe DNA double‐strand breaks. Homologous recombination repair deficiency (HRD) occurs when HRR is impaired and causes irreparable double‐strand DNA damage, leading to genomic instability and increasing the risk of cancer development. Poly(ADP‐ribose) polymerase (PARP) inhibitors can effectively treat HRD‐positive tumors. Extracellular heat shock protein 90α (eHSP90α) is highly expressed in hypoxic environments and inhibits apoptosis, thereby increasing cellular tolerance. Here, we investigated the relationship between eHSP90α and HRR in NSCLC. DNA damage models were established in NSCLC cell lines (A549 and H1299). The activation of DNA damage and HRR markers, apoptosis, proliferation, and migration were investigated. In vivo tumor models were established using BALB/c nude mice and A549 cells. We found that human recombinant HSP90α stimulation further activated HRR and reduced DNA damage extent; however, eHSP90α monoclonal antibody, 1G6‐D7, effectively inhibited HRR. HRR inhibition and increased apoptosis were observed after LRP1 knockdown; this effect could not be reversed with hrHSP90α addition. The combined use of 1G6‐D7 and olaparib caused significant apoptosis and HRR inhibition in vitro and demonstrated promising anti‐tumor effects in vivo. Extracellular HSP90α may be involved in HRR in NSCLC through LRP1. The combined use of 1G6‐D7 and PARP inhibitors may exert anti‐tumor effects by inhibiting DNA repair and further inducing apoptosis of NSCLC cells.