<p>The expression of Annexin A3 (ANXA3) is thought to be associated with chemoresistance in lung cancer. However, the underlying molecular mechanisms of ANXA3-mediated cisplatin (DDP) resistance in lung cancer still need to be further explored. The levels of ANXA3, forkhead box D1 (FOXD1), and Annexin A4 (ANXA4) were examined by qRT-PCR or Western blot. The DDP resistance, viability, apoptosis, invasion, and migration were determined by CCK8 assay, MTT assay, flow cytometry, TUNEL staining, transwell assay, and wound healing assay. The interaction between FOXD1 and ANXA3 promoter was confirmed by dual-luciferase reporter assay and ChIP assay. Co-IP assay and immunofluorescence staining were used to verify ANXA3 and ANXA4 interaction. The effect of ANXA3 on the DDP resistance of tumor tissues was further confirmed by animal experiments. ANXA3 was highly expressed in lung cancer DDP-resistant tissues and cells. ANXA3 knockdown inhibited lung cancer cell growth and metastasis, thereby improving DDP sensitivity. FOXD1 bound to ANXA3 promoter region to activate its transcription. In rescue experiments, silencing of FOXD1 enhanced the DDP sensitivity of lung cancer cells, and this effect was abolished by ANXA3 overexpression. Moreover, ANXA3 interacted with ANXA4 to promote its expression, and ANXA4 overexpression could reverse the promoting effect of ANXA3 knockdown on DDP sensitivity of lung cancer cells. In addition, FOXD1 positively regulated ANXA4 expression by activating ANXA3. Also, ANXA3 silencing could reduce lung cancer tumorigenesis and enhance DDP sensitivity by decreasing ANXA4 expression in vivo. ANXA3, activated by FOXD1, might contribute to the DDP resistance of lung cancer via regulating ANXA4, providing new ideas for overcoming chemoresistance in lung cancer.</p> Graphical abstract <p></p>