Transwell permeable supports with 8 μm pore (Corning, New York City, USA) and 24‐well plates were used to conduct migration and invasion assays.
For invasion assay, the upper chambers were coated using diluted Matrigel (Corning) at 37°C for 4 h before seeding cells. For the migration assay, the upper chambers were not coated. An appropriate number of cells were seeded with an FBS‐free medium in the upper chamber of the Transwell permeable support. For DU145, we seeded 6 × 104 cells/well for “NC versus circSOBP” groups and 3 × 104 cells/well for “si‐NC versus si‐circSOBP” groups, respectively. For PC‐3, we seeded 8 × 104 cells/well for “NC versus circSOBP” groups and 6 × 104 cells/well for “si‐NC versus si‐circSOBP” groups, respectively. The lower chamber was filled with 400 μL complete medium supplied with 100 μL FBS. Appropriate subsequent culture time varies from cell lines (24 h for DU145 and 48 h for PC‐3). The migrated cells were fixed using 4% PFA followed by staining using 1% crystal violet solution. We counted the migrated cells from three random fields.
For invasion assay, the upper chambers were coated using diluted Matrigel (Corning) at 37°C for 4 h before seeding cells. For the migration assay, the upper chambers were not coated. An appropriate number of cells were seeded with an FBS‐free medium in the upper chamber of the Transwell permeable support. For DU145, we seeded 6 × 104 cells/well for “NC versus circSOBP” groups and 3 × 104 cells/well for “si‐NC versus si‐circSOBP” groups, respectively. For PC‐3, we seeded 8 × 104 cells/well for “NC versus circSOBP” groups and 6 × 104 cells/well for “si‐NC versus si‐circSOBP” groups, respectively. The lower chamber was filled with 400 μL complete medium supplied with 100 μL FBS. Appropriate subsequent culture time varies from cell lines (24 h for DU145 and 48 h for PC‐3). The migrated cells were fixed using 4% PFA followed by staining using 1% crystal violet solution. We counted the migrated cells from three random fields.