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Chasing non-existent "microRNAs" in cancer

Ayla Orang1, Nicholas I Warnock1,2, Melodie Migault1

  • 1Centre for Cancer Biology, an alliance of SA Pathology and University of South Australia, Adelaide, South Australia, Australia.

Oncogenesis
|April 18, 2025
PubMed

Insights

Many reported microRNAs (miRNAs) in cancer and Epithelial-Mesenchymal Transition (EMT) studies may not be functional. Researchers developed criteria to distinguish true miRNAs from RNA fragments, ensuring accurate gene regulation research.

Area of Science:

  • Molecular Biology
  • Genomics
  • Cancer Research

Background:

  • MicroRNAs (miRNAs) regulate gene expression and are implicated in cancer and Epithelial-Mesenchymal Transition (EMT).
  • Controversy exists regarding the number of functional miRNAs and the misidentification of RNA degradation products as miRNAs.
  • Functional miRNAs associate with Argonaute (AGO) proteins to form the RNA-Induced Silencing Complex (RISC) for target mRNA suppression.

Purpose of the Study:

  • To investigate the functional relevance of reported miRNAs in cancer and EMT contexts.
  • To differentiate genuine miRNAs from non-functional RNA fragments.
  • To establish criteria for identifying functional miRNAs within the RISC complex.

Main Methods:

  • Biochemical assays to assess miRNA incorporation into RISC.
  • Bioinformatic analyses to identify characteristics of functional miRNAs.
  • Comparison of endogenous miRNA activity versus artificial miRNA mimics.

Main Results:

  • Numerous "miRNAs" previously linked to EMT and cancer lack RISC incorporation and endogenous silencing capability.
  • Apparent functions of some "miRNAs" may stem from artificial mimics, not endogenous regulation.
  • Biochemical and bioinformatic criteria were developed to distinguish functional miRNAs from RNA fragments.

Conclusions:

  • Many purported miRNAs in cancer and EMT research may be non-functional RNA fragments.
  • The study provides a framework to re-evaluate existing miRNA data in these fields.
  • Accurate identification of functional miRNAs is crucial for understanding gene regulation and developing therapeutic strategies.

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