Exosomal and intracellular miR-320b promotes lymphatic metastasis in esophageal squamous cell carcinoma

Abstract

Cancer-cell-released exosomal microRNAs (miRNAs) are important mediators of cell-cell communication in the tumor microenvironment. In this study, we sequenced serum exosome miRNAs from esophageal squamous cell carcinoma (ESCC) patients and identified high expression of miR-320b to be closely associated with peritumoral lymphangiogenesis and lymph node (LN) metastasis. Functionally, miR-320b could be enriched and transferred by ESCC-released exosomes directly to human lymphatic endothelial cells (HLECs), promoting tube formation and migration in vitro and facilitating lymphangiogenesis and LN metastasis in vivo as assessed by gain- and loss-of-function experiments. Furthermore, we found programmed cell death 4 (PDCD4) as a direct target of miR-320b through bioinformatic prediction and luciferase reporter assay. Re-expression of PDCD4 could rescue the effects induced by exosomal miR-320b. Notably, the miR-320b-PDCD4 axis activates the AKT pathway in HLECs independent of vascular endothelial growth factor-C (VEGF-C). Moreover, overexpression of miR-320b promotes the proliferation, migration, invasion, and epithelial-mesenchymal transition progression of ESCC cells. Finally, we demonstrate that METTL3 could interact with DGCR8 protein and positively modulate pri-miR-320b maturation process in an N6-methyladenosine (m6A)-dependent manner. Therefore, our findings uncover a VEGF-C-independent mechanism of exosomal and intracellular miR-320b-mediated LN metastasis and identify miR-320b as a novel predictive marker and therapeutic target for LN metastasis in ESCC.

The Role of Tumor Microenvironment in Invasion and Metastasis of Esophageal Squamous Cell Carcinoma

“…Recently, it has been shown that exosomes play important roles in ESCC invasion and metastasis ( 115 ). It is reported that exosomes released by ESCC can enrich miR-320b and promote ESCC lymph node metastasis via programmed cell death 4 (PDCD4) through the AKT signaling pathway ( 116 ). Exosome-shuttling miR-21 has been shown to promote ESCC invasion and metastasis by targeting PDCD4 via the c-Jun N-terminal kinase (JNK) signaling pathway ( 117 ).…”

The Regulation of Lymph Node Pre-Metastatic Niche Formation in Head and Neck Squamous Cell Carcinoma

“…Liu et al. found that overexpression of miR-320b is closely linked to peritumoral lymphangiogenesis and LN metastasis, and it is also worth mentioning that the miR-320b–PDCD4 axis activates the Akt pathway independent of VEGF-C ( 110 ). The anti-lymphangiogenesis strategy applying in the clinical treatment of HNSCC, however, not common so far.…”

The Role and Interactions of Programmed Cell Death 4 and its Regulation by microRNA in Transformed Cells of the Gastrointestinal Tract

“…Next generation sequencing used to analyse exosomes of oesophageal squamous cell carcinomas (ESCC) revealed that miRNA-320b was highly expressed in many ESCCs and correlates with lymph node metastasis ( 209 ). Exosomes purified from KYSE150 and EC9706 ESCC cell lines were found to be enriched with this miRNA and co-incubation of these exosomes with human lymphatic endothelial cells (HLECs) stimulated tube formation and migration, processes which occur in lymphangiogenesis during lymph node metastasis.…”