Cancer-secreted exosomal miRNAs are emerging mediators of cancer-stromal cross-talk in the tumor environment. Our previous miRNAs array of cervical squamous cell carcinoma (CSCC) clinical specimens identified upregulation of miR-221-3p. Here, we show that miR-221-3p is closely correlated with peritumoral lymphangiogenesis and lymph node (LN) metastasis in CSCC. More importantly, miR-221-3p is characteristically enriched in and transferred by CSCC-secreted exosomes into human lymphatic endothelial cells (HLECs) to promote HLECs migration and tube formation in vitro, and facilitate lymphangiogenesis and LN metastasis in vivo according to both gain-of-function and loss-of-function experiments. Furthermore, we identify vasohibin-1 (VASH1) as a novel direct target of miR-221-3p through bioinformatic target prediction and luciferase reporter assay. Re-expression and knockdown of VASH1 could respectively rescue and simulate the effects induced by exosomal miR-221-3p. Importantly, the miR-221-3p-VASH1 axis activates the ERK/AKT pathway in HLECs independent of VEGF-C. Finally, circulating exosomal miR-221-3p levels also have biological function in promoting HLECs sprouting in vitro and are closely associated with tumor miR-221-3p expression, lymphatic VASH1 expression, lymphangiogenesis, and LN metastasis in CSCC patients. In conclusion, CSCC-secreted exosomal miR-221-3p transfers into HLECs to promote lymphangiogenesis and lymphatic metastasis via downregulation of VASH1 and may represent a novel diagnostic biomarker and therapeutic target for metastatic CSCC patients in early stages.

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To explore the mechanisms through which hypoxic tumor microenvironment (TME) modulates the transition of tumor‐associated macrophages (TAMs). The migration ability of RAW264.7 macrophages was determined by transwell assay. Flow cytometric, western blot and immunofluorescence analyses of CD206 further validated the M2 polarization of macrophages. Immunofluorescence, western blot and qRT‐PCR were performed to detect the expression of neuropilin‐1 (Nrp‐1) and carbonic anhydrase IX (CAIX). An intermittent hypobaric hypoxia (IH) animal model was established to evaluate the role of hypoxia in activating M2‐like TAMs in vivo. We also used immunohistochemistry to analyze the association between CAIX, CD163+ macrophages and Nrp‐1 in a series of 72 human cervical cancer specimens. We found that the hypoxic cervical TME educated the recruited macrophages to transform into the M2 phenotype. Nrp‐1 expression was significantly increased in hypoxia‐primed cervical cancer cells. Blocking Nrp‐1 expression prevented hypoxic cells from recruiting and polarizing macrophages towards the M2 phenotype. Hypoxia exposure significantly increased the expression of Nrp‐1 as well as the infiltration of macrophages in vivo. Consistently, immunochemical staining in serial tissue sections of cervical cancer revealed upregulated levels of Nrp‐1 in CAIX‐positive hypoxic regions along with a concurrent significant elevation of M2 macrophages. Nrp‐1 and M2‐like TAMs were related to the malignant properties of cervical cancer, such as the FIGO stage and lymph node metastasis. Nrp‐1 plays critical roles in hypoxic TME‐induced activation and pro‐tumoral effects of TAMs in cervical cancer. Interfering with Nrp‐1 may be a potential therapeutic strategy in treating cervical cancer.