The expression of kappa-opioid receptor promotes the migration of breast cancer cells in vitro.

Background: Opioid receptors are implicated in cell proliferation and cancer migration. However, the effects and underlying mechanisms of opioid receptor κ (OPRK1) in breast cancer remain unknown.

Methods: Small interfering RNA (siRNAs) was used to knockdown the expression of OPRK1. Western blot was used to determine the protein expression and reverse transcription-quantitative PCR (RT-qPCR) determined the genes transcription. Cell viability was detected by MTT assay and cell death rates were determined by Annexin V/PI and flow cytometry. Cell migration and invasion were detected by wound healing analysis and transwell assay, respectively.

Results: Our research demonstrated that OPRK1 was overexpressed in breast cancer cells compared with the normal human mammary epithelial cells. OPRK1 knockdown could inhibited cell viability and migration in cancer cells, accompanied with the decreased proteins and genes expression of N-cadherin, Snail, MMP2 and Vimentin, while the E-cadherin expression was increased. Additionally, OPRK1 knockdown also promoted PI3K/AKT signaling inactivation. Activation of AKT reversed the OPRK1 knockdown-induced cell viability inhibition and migration suppression, while inhibition of AKT reduced cell viability and promoted cell death.

Conclusions: Our findings illustrated the role of OPRK1 played on promoting migration in vitro, and we also provided the therapeutic research of OPRK1 knockdown combined with AKT inhibition.