Hypoxic tumor-derived exosomal miR-31-5p promotes lung adenocarcinoma metastasis by negatively regulating SATB2-reversed EMT and activating MEK/ERK signaling.

Background: Exosomes have emerged as critical mediators of intercellular communication. Hypoxia is widely recognized as a key regulator of tumor aggressiveness, and significantly affects exosome release by tumor cells. However, the effects of exosomes derived from hypoxic lung adenocarcinoma (LUAD) cells are poorly understood.

Methods: Samples of miRNA isolated from hypoxic LUAD cell-derived exosomes (HExo) and normoxic LUAD cell-derived exosomes (NExo) were sequenced to identify miRNAs that might mediate tumor progression. Exosomal miRNA was co-cultured with LUAD cells to assess its biological effects on cell migration and metastasis both in vitro and in vivo. The cellular target of exosomal miRNA was confirmed by dual-luciferase assays. Western blot studies showed that exosomal miRNA regulated the related pathway. The availability of circulating exosomal miRNA derived from plasma was also evaluated.

Results: We found that HExo could significantly enhance the migration and invasion of normoxic LUAD cells. MiRNA sequencing results suggested that miR-31-5p was largely internalized within HExo and could be taken up by normoxic LUAD cells. Exosomal miR-31-5p was found to directly target Special AT-Rich Sequence-Binding Protein 2 (SATB2)-revered epithelial mesenchymal transition and significantly increase activation of MEK/ERK signaling, thereby contributing to tumor progression both in vitro and in vivo. Furthermore, higher levels of circulating exosomal miR-31-5p were detected in LUAD patients, especially in patients with metastatic disease.

Conclusions: Our findings demonstrate that exosomal miR-31-5p exerts a crucial role in LUAD progression, and could serve as a diagnostic biomarker for LUAD.