Centre for Stem Cell Research, Faculty of Medicine and Health Sciences, Universiti Tunku Abdul Rahman, Selangor, Malaysia.
Postgraduate Program, Faculty of Medicine and Health Sciences, Universiti Tunku Abdul Rahman, Selangor, Malaysia.
Int J Med Sci. 2021 Feb 18;18(8):1798-1809. doi: 10.7150/ijms.50871. eCollection 2021.
Cell migration and invasion are modulated by epithelial-to-mesenchymal transition (EMT) and the reverse MET process. Despite the detection of microRNA-362 (miR-362, both the miR-362-5p and -3p species) in cancers, none of the identified miR-362 targets is a mesenchymal or epithelial factor to link miR-362 with EMT/MET and metastasis. Focusing on the TGF-β/SMAD signaling pathway in this work, luciferase assays and western blot data showed that miR-362 targeted and negatively regulated expression of SMAD4 and E-cadherin, but not SNAI1, which is regulated by SMAD4. However, miR-362 knockdown also down-regulated SMAD4 and SNAI1, but up-regulated E-cadherin expression. Wound-healing and transwell assays further showed that miR-362 knockdown suppressed cell migration and invasion, effects which were reversed by over-expressing SMAD4 or SNAI1, or by knocking down E-cadherin in the miR-362 knockdown cells. In orthotopic mice, miR-362 knockdown inhibited metastasis, and displayed the same SMAD4 and E-cadherin expression profiles in the tumors as in the studies. A scheme is proposed to integrate miR-362 negative regulation via SMAD4, and to explain miR-362 positive regulation of SMAD4 via miR-362 targeting of known SMAD4 suppressors, BRK and DACH1, which would have resulted in SMAD4 depletion and annulment of subsequent involvement in TGF-β signaling actions. Hence, miR-362 both negatively and positively regulates SMAD4 expression in TGF-β/SMAD signaling pathway to suppress cell motility and invasiveness and metastasis, and may explain the reported clinical association of anti-miR-362 with suppressed metastasis in various cancers. MiR-362 knockdown in miR-362-positive cancer cells may be used as a therapeutic strategy to suppress metastasis.
细胞迁移和侵袭受到上皮间质转化 (EMT) 和反向 MET 过程的调节。尽管在癌症中检测到 microRNA-362 (miR-362，包括 miR-362-5p 和 -3p 两种物种)，但尚未确定的 miR-362 靶标是连接 miR-362 与 EMT/MET 和转移的间质或上皮因子。本研究聚焦于 TGF-β/SMAD 信号通路，荧光素酶检测和 Western blot 数据表明，miR-362 靶向并负调控 SMAD4 和 E-cadherin 的表达，而不是 SNAI1，后者受 SMAD4 调控。然而，miR-362 敲低也下调了 SMAD4 和 SNAI1，但上调了 E-cadherin 的表达。划痕愈合和 Transwell 实验进一步表明，miR-362 敲低抑制细胞迁移和侵袭，过表达 SMAD4 或 SNAI1，或敲低 miR-362 敲低细胞中的 E-cadherin，可逆转这种作用。在原位小鼠模型中，miR-362 敲低抑制转移，且在肿瘤中表现出与研究中相同的 SMAD4 和 E-cadherin 表达谱。提出了一个方案来整合 miR-362 通过 SMAD4 的负调控，并解释 miR-362 通过靶向已知的 SMAD4 抑制剂 BRK 和 DACH1 对 SMAD4 的正调控，这将导致 SMAD4 耗竭，并取消随后参与 TGF-β 信号转导的作用。因此，miR-362 在 TGF-β/SMAD 信号通路中对 SMAD4 表达进行负调控和正调控，以抑制细胞迁移和侵袭及转移，这可能解释了在各种癌症中报道的抗 miR-362 与转移抑制的临床关联。在 miR-362 阳性癌细胞中敲低 miR-362 可能被用作抑制转移的治疗策略。
