miR-33b-3p Suppresses Metastasis in Prostate Cancer by Targeting DOCK4

Purpose: Despite that androgen-deprivation therapy results in long-lasting responses, the disease inevitably progresses to metastatic castration-resistant prostate cancer. In this study, we identified miR-33b-3p as a suppressor of metastasis in prostate cancer. miR-33b-3p was significantly reduced in prostate cancer tissues, and the low expression of miR-33b-3p was correlated with poor overall survival of prostate cancer patients. Overexpression of miR-33b-3p inhibited both migration and invasion of highly metastatic prostate cancer cells whereas antagonizing miR-33b-3p promoted those processes in lowly metastatic cells. The in vivo results demonstrate that miR-33b-3p suppresses metastasis of tail vein inoculated prostate cancer cells to lung, liver, and lymph node in mice. DOCK4 was validated as the direct target of miR-33b-3p. miR-33b-3p decreased the expression of DOCK4 and restoration of DOCK4 could rescue miR-33b-3p inhibition on cell migration and invasion. Moreover, downregulation of miR-33b-3p was induced by bortezomib, the clinically used proteasome inhibitor, and overexpression of miR-33b-3p rescued the insufficient inhibition of bortezomib on migration and invasion in prostate cancer cells. Collectively, our findings demonstrate that miR-33b-3p suppresses metastasis by targeting DOCK4 in prostate cancer. Our results suggest that enhancing miR-33b-3p expression may provide a promising therapeutic strategy for overcoming that proteasome inhibitor’s poor efficacy against metastatic prostate cancer. Mimic-negative control (NC) and mimic-miR-33b-3p (3p) were generated by deep sequencing, using Illumina GAIIx.

研究背景：尽管雄激素剥夺疗法（androgen-deprivation therapy）可使前列腺癌患者获得持久的治疗应答，但该病仍会不可避免地进展为转移性去势抵抗性前列腺癌（metastatic castration-resistant prostate cancer）。本研究鉴定出miR-33b-3p（microRNA-33b-3p）为前列腺癌的转移抑制因子。miR-33b-3p在前列腺癌组织中显著低表达，其低表达与前列腺癌患者的不良总生存期显著相关。过表达miR-33b-3p可抑制高转移性前列腺癌细胞的迁移与侵袭能力，而拮抗miR-33b-3p则可促进低转移性细胞的上述过程。体内实验结果显示，miR-33b-3p可抑制经尾静脉接种的前列腺癌细胞向小鼠肺、肝及淋巴结的转移。DOCK4被验证为miR-33b-3p的直接靶基因。miR-33b-3p可下调DOCK4的表达，而恢复DOCK4的表达能够逆转miR-33b-3p对细胞迁移与侵袭的抑制作用。此外，临床使用的蛋白酶体抑制剂硼替佐米（bortezomib）可诱导miR-33b-3p的下调，而过表达miR-33b-3p可弥补硼替佐米对前列腺癌细胞迁移与侵袭抑制作用不足的缺陷。综上，本研究结果证实miR-33b-3p通过靶向DOCK4抑制前列腺癌的转移，提示增强miR-33b-3p的表达或可成为改善蛋白酶体抑制剂对转移性前列腺癌疗效不佳这一问题的潜在治疗策略。本研究通过Illumina GAIIx平台进行高通量测序，构建了模拟物阴性对照（NC）及miR-33b-3p模拟物（3p）样本。