Exosomal miR-373-3p Derived from Docetaxel-Resistant Lung Cancer Cells Targets PDCD4 to Promote Proliferation and Inhibit Apoptosis in Lung Cancer Cells

Background: Lung cancer ranks among the most common and deadly malignant tumors worldwide. Drug resistance is a critical factor hindering the effect of chemotherapy for lung cancer. Exosomes, as intercellular signaling molecule carriers, play an important role in carcinogenesis, metastasis and drug resistance. Our study was aimed at exploring the impact of exosomes derived from docetaxel (DTX)-resistant lung cancer cells on regulating biological behaviors of DTX-sensitive cells, further investigating the molecular mechanisms regarding exosome-mediated intercellular communication. Methods: We extracted and identified the exosomes derived from A549, A549/DTX, H1299 and H1299/DTX cells, and then analyzed the expression of exosomal miR-373-3p between DTX-sensitive and DTX-resistant cells. Cell proliferation and apoptosis experiments were verified using a CCK-8 assay, a colony formation assay, a TUNEL assay and flow cytometry. The molecular interaction between miR-373-3p and PDCD4 was evaluated using a dual-luciferase reporter assay. The function of miR-373-3p was further assessed using an in vivo mouse xenograft model. Results: We found that the exosomal miR-373-3p level from DTX-resistant A549/DTX or H1299/DTX cells significantly exceeded that from DTX-sensitive A549 or H1299 cells. In addition, both exosomes derived from DTX-resistant lung cancer cells and miR-373-3p mimics could promote the proliferation of DTX-sensitive cells and inhibit their apoptosis. Moreover, we identified PDCD4 as a key target gene of miR-373-3p, which could induce the malignant behaviors of DTX-sensitive cells by reducing PDCD4 expression. Conclusions: Our results demonstrated that DTX-resistant lung cancer cells could transfer miR-373-3p to DTX-sensitive cells through exosomes, where miR-373-3p could exert its carcinogenic effect via targeting PDCD4.