Background

Dexmedetomidine (DEX), a highly selective α2-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-231 were treated with DEX and scratch assay was performed. Expressions of TMPRSS2, α2-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 α2-adrenergic receptor. Nuclear phospho-STAT3 Tyr705 was increased dramatically following DEX treatment, and TMPRSS2 upregulation was significantly suppressed by the STAT3 inhibitor WP1066. 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-positive 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 α2-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.