The circROBO1/KLF5/FUS feedback loop regulates the liver metastasis of breast cancer by inhibiting the selective autophagy of afadin

Mol Cancer. 2022 Jan 24;21(1):29. doi: 10.1186/s12943-022-01498-9.

Abstract

Background: Metastasis causes the majority of cancer-related deaths worldwide. Increasing studies have revealed that circRNAs are associated with the carcinogenesis and metastasis of many cancers. Nevertheless, the biological mechanisms of circRNAs in breast cancer (BC) liver metastasis remain extremely ambiguous.

Methods: In this study, we identified circROBO1 from three pairs of primary BC and metastatic liver sites by RNA sequencing. FISH assays and RT-qPCR were conducted to validate the existence and expression of circROBO1. The oncogenic role of circROBO1 was demonstrated both in vitro and in vivo. Western blot, ChIP, RIP, RNA pull-down, and dual-luciferase reporter assays were used to confirm the interaction of the feedback loop among circROBO1, miR-217-5p, KLF5, and FUS. Meanwhile, the regulation of selective autophagy was investigated by immunofluorescence, CoIP, and western blot.

Results: In this study, upregulated expression of circROBO1 was found in BC-derived liver metastases and was correlated with poor prognosis. Knockdown of circROBO1 strikingly inhibited the proliferation, migration, and invasion of BC cells, whereas overexpression of circROBO1 showed the opposite effects. Moreover, overexpression of circROBO1 promoted tumor growth and liver metastasis in vivo. Further research revealed that circROBO1 could upregulate KLF5 by sponging miR-217-5p, allowing KLF5 to activate the transcription of FUS, which would promote the back splicing of circROBO1. Therefore, a positive feedback loop comprising circROBO1/KLF5/FUS was formed. More importantly, we found that circROBO1 inhibited selective autophagy of afadin by upregulating KLF5.

Conclusions: Our results demonstrated that circROBO1 facilitates the carcinogenesis and liver metastasis of BC through the circROBO1/KLF5/FUS feedback loop, which inhibits the selective autophagy of afadin by suppressing the transcription of BECN1. Therefore, circROBO1 could be used not only as a potential prognostic marker but also as a therapeutic target in BC.

Keywords: Afadin; Autophagy; BC; BECN1; FUS; KLF5; Metastasis; circROBO1; miR-217.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions
  • Animals
  • Autophagy
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / pathology*
  • Cell Line, Tumor
  • Disease Models, Animal
  • Female
  • Gene Expression Regulation, Neoplastic
  • Gene Regulatory Networks
  • Humans
  • Kruppel-Like Transcription Factors / genetics*
  • Liver Neoplasms / genetics*
  • Liver Neoplasms / secondary*
  • Mice
  • MicroRNAs / genetics
  • Microfilament Proteins
  • Models, Biological
  • Nerve Tissue Proteins / genetics*
  • RNA Interference
  • RNA, Circular*
  • RNA-Binding Protein FUS / genetics*
  • Receptors, Immunologic / genetics*
  • Roundabout Proteins
  • Signal Transduction
  • Xenograft Model Antitumor Assays

Substances

  • 3' Untranslated Regions
  • FUS protein, human
  • KLF5 protein, human
  • Kruppel-Like Transcription Factors
  • MIRN217 microRNA, human
  • MicroRNAs
  • Microfilament Proteins
  • Nerve Tissue Proteins
  • RNA, Circular
  • RNA-Binding Protein FUS
  • Receptors, Immunologic
  • afadin