Xenograft Model

All animal experiments were performed under approval by the Experimental Animal Care Commission of Cancer Hospital of China Medical University. For xenograft model of VCaP cells: 6-week-old male BALB/c nude mice were housed under standard conditions and cared for according to protocols. 2 × 10⁶ VCaP cells with circFMN2 overexpressed vector or control vector were suspended in 200 μL serum-free RPMI-1640 and subcutaneously injected into the right flank of each mouse. The volumes of tumors were measured from 14 days after injecting. After 31 days the mice were sacrificed. For xenograft model of PC3 cells: 2 × 10⁶ PC3 cells were subcutaneously injected into a single flank of each mouse (12 mice in total). 2 weeks later, mice with palpable tumors were randomly divided into two groups (six mice per group), 50 nmol cholesterol-conjugated si-NC or si-circFMN2 was intratumorally injected into the two groups three times per week for 2 weeks. Tumor growth was examined every 4 days. After mice were sacrificed, tumors were weighed and processed for further histological analysis. Tumor volume was calculated as follows: V (volume) = (length × width2)/2.