Dexmedetomidine promotes breast cancer cell migration through Rab11-mediated secretion of exosomal TMPRSS2

Background: Dexmedetomidine (DEX), a highly selective alpha 2-adrenergic receptor agonist, has been reported to increase the malignancy of breast cancer cells in vitro and stimulate tumor growth in mice. Transmembrane protease serine 2 (TMPRSS2) demonstrates proteolytic activity, resulting in degradation of the extracellular matrix (ECM). This study investigated whether and how TMPRSS2 regulates migration of DEX-treated breast cancer cells. Methods: Breast cancer cell lines MCF-7 and MDA-MB-23 I were treated with DEX and scratch assay was performed. Expressions of TMPRSS2, alpha 2-adrenergic receptor, phospho-STAT3(Tyr705), Rab11, and ECM components were assessed using real-time polymerase chain reaction (real-time PCR), Western blotting, and immunofluorescence staining. ELISA and ultracentrifugation were used to quantify secreted exosomal proteins. Knockdown assay was used to inhibit the expression of TMPRSS2 and Rab11. Results: DEX significantly increased the migration of MCF-7 and MDA-MB-231, which was accompanied by the upregulation and colocalization of TMPRSS2 and alpha 2-adrenergic receptor. Nuclear phospho-STAT3(Tyr705) was increased dramatically following DEX treatment, and TMPRSS2 upregulation was significantly suppressed by the STAT3 inhibitor WP 1066. Meanwhile, TMPRSS2 knockdown decreased DEX-induced cellular migration. TMPRSS2 and Rab11 were significantly detected in the media and the isolated exosomes from DEX-treated cells, and their colocalization was also revealed. Rab11 knockdown prevented exosomal TMPRSS2 from increasing in DEX-treated cells. In normal cultured MDA-MB-231, migration was increased by Rab11-positive exosomes isolated from DEX-treated MCF-7. Moreover, transmission electron microscopy showed that Rab11-pasitive exosomes enriched more components than Rab11-negative exosomes. Additionally, a reduction in ECM components fibronectin, collagen IV, matrix metallopeptidase 16, and Tenascin C was detected after DEX treatment, but was prohibited when TMPRSS2 or Rab11 were knocked down. Conclusions: This study provides evidence that DEX upregulates TMPRSS2 expression via the activation of alpha 2-adrenergic receptor/STAT3 signaling and promotes TMPRSS2 secretion in exosomes through Rab11, thus resulting in degradation of the ECM, which is responsible for DEX-induced migration of breast cancer cells.