Purpose: To investigate the role of microRNA-21 (miR21) in radiofrequency (RF) ablation-induced tumor growth and whether miR21 inhibition suppresses tumorigenesis.Material and Methods: Standardized liver RF ablation was applied to 35 C57/BL6 mice. miR21 and target proteins pSTAT3, PDCD4, and PTEN were assayed 3 hours, 24 hours, and 3 days after ablation. Next, 53 Balb/c and 44 C57BL/6 mice received Antago-miR21 or scrambled Antago-nc control, followed by intrasplenic injection of 10,000 CT26 or MC38 colorectal tumor cells, respectively. Hepatic RF ablation or sham ablation was performed 24 hours later. Metastases were quantified and tumor microvascular density (MVD) and cellular proliferation were assessed at 14 or 21 days after the procedures, respectively.Results: RF ablation significantly increased miR21 levels in plasma and hepatic tissue at 3 and 24 hours as well as target proteins at 3 days after ablation (P < .05, all comparisons). RF ablation nearly doubled tumor growth (CT26, 2.0 SD +/- 1.0 fold change [fc]; MC38, 1.9 SD +/- 0.9 fc) and increased MVD (CT26, 1.9 SD +/- 1.0 fc; MC38, 1.5 +/- 0.5 fc) and cellular proliferation (CT26, 1.7 SD +/- 0.7 fc; MC38, 1.4 SD +/- 0.5 fc) compared with sham ablation (P < .05, all comparisons). RF ablation-induced tumor growth was suppressed when Antago-miR21 was administered (CT26, 1.0 SD +/- 0.7 fc; MC38, 0.9 SD +/- 0.4 fc) (P < .01, both comparisons). Likewise, Antago-miR21 decreased MVD (CT26, 1.0 SD +/- 0.3 fc; MC38, 1.0 SD +/- 0.2 fc) and cellular proliferation (CT26, 0.9 SD +/- 0.3 fc; MC38, 0.8 SD +/- 0.3 fc) compared with baseline (P < .05, all comparisons).Conclusions: RF ablation upregulates protumorigenic miR21, which subsequently influences downstream tumor promoting protein pathways. This effect can potentially be suppressed by specific inhibition of miR21, rendering this microRNA a pivotal and targetable driver of tumorigenesis after hepatic thermal ablation.
