Lung cancer is a common malignancy and non-small cell lung cancer is more common in clinical practice.Heat shock protein 90?HSP90? is an important protein in body tissues, it is a molecular chaperone of many proteins as well as a potential tumor marker.Our group has long focused on the role of extracellular HSP90?eHSP90? in respiratory-related diseases and found that it is relevant in the development of a variety of diseases.Focusing on non-small cell lung cancer, this topic explores the effect of eHSP90 on tumors, further investigates how eHSP90 affects intracellular activities, attempts to illustrate the relationship between eHSP90 and DNA damage repair (especially homologous recombination repair), which in turn affects the immune microenvironment of tumors.The current findings show that bleomycin induces DNA damage. Replacing with new medium and continued incubation for 6 h, the homologous recombination repair key protein Rad51 was upregulated, suggesting that the homologous recombination repair process was activated. When the repair process was intervened with the eHSP90? mAb 1G6-D7, Rad51 expression levels were significantly reduced, while the gene expression levels of ATM, CHK1, and Rad51 were lower.Thus, our results tentatively suggest that the use of 1G6-D7 can regulate the level of DNA damage repair in A549 cells by inhibiting eHSP90?.On this basis, we will further explore how the effect arises and the downstream impact on tumor immunity.