Relaxin's effect on motility is RXFP1-mediated. RXFP1 relaxin receptor was down-regulated with 150 nM siRNA against RXFP1 (LGR7) in MDA-MB-231 cells. Cells treated with the vehicle Lipofectamine 2000 only or transfected with 150 nM non-silencing small interfering (si) RNA were used as controls. (a) Semi-quantitative PCR analysis was performed with specific primers for RXFP1, shown here for 48 hours after transfection. (b) Motility of MDA-MB-231 cells seeded at 1 × 104 cells was assessed after RXFP1 knock-down with RXFP1 siRNA. The results of three independent experiments are shown in the graph as mean ± SEM, a two-way ANOVA analysis was performed with the SPSS software package and a p < 0.05 was considered significant at the 95% confidence level as shown by the asterisks (**).