Cited by 248MicroRNA in disease regulationExtracellular vesicles in diseaseCancer-related molecular mechanisms research

The DOI matches its Crossref record; 82 of the 83 references it cites were found in a registry or an index; 10 of the 13 sources its claims cite were checked for support.

miR-21: a non‐specific biomarker of all maladies

Open access
Jenike, Ana E., Halushka, Marc K.·2021·Biomarker Research

Abstract

miRNA-21 is among the most abundant and highly conserved microRNAs (miRNAs) recognized. It is expressed in essentially all cells where it performs vital regulatory roles in health and disease. It is also frequently claimed to be a biomarker of diseases such as cancer and heart disease in bodily-fluid based miRNA studies. Here we dissociate its contributions to cellular physiology and pathology from its potential as a biomarker. We show how it has been claimed as a specific predictive or prognostic biomarker by at least 29 diseases. Thus, it has no specificity to any one disease. As a result, it should not be considered a viable candidate to be a biomarker, despite its continued evaluation as such. This theme of multiple assignments of a miRNA as a biomarker is shared with other common, ubiquitous miRNAs and should be concerning for them as well.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

miR-21 is a highly conserved, abundant miRNA with important regulatory roles, but it has been claimed as a predictive or prognostic biomarker for at least 29 diseases. Because it lacks specificity to any one disease, the authors argue it should not be pursued as a fluid-based biomarker.

Key findings

  • miR-21 is implicated as a biomarker in no less than 29 diseases or processes, with 45 publications spanning 2008–2020 and over 5,000 collective citations (median 68).
  • miR-21 expression is highest in macrophages, monocytes, and dendritic cells: median 137,021 RPM among 75 combined macrophage, monocyte, and dendritic cell samples versus 38,281 RPM among 470 other cells from a combined 75 cell types.
  • The authors argue that if miR-21 is elevated across many diseases—ranging from cardiovascular disease to cancer—it cannot be a specific biomarker for any one disease, and its use alongside other common miRNAs such as miR-155, miR-92a, and miR-122 further decreases specificity.
  • They conclude that miR-21 remains functionally important and may be therapeutically targetable, but it is not a useful fluid-based biomarker; future work should focus on more cell-type-specific miRNAs such as miR-371a-3p for testicular cancer or miR-122 for liver injury.

Methods

  • Narrative review/commentary dissociating miR-21’s cellular physiology and pathology from its potential as a biomarker.
  • Data include two tables of published biomarker studies: Table 1 lists a subset of 16 non-neoplastic diseases, and Table 2 lists 13 neoplasias, with sample sizes, fluid sources, additional miRNA biomarkers, and predictive/prognostic status.
  • Expression analysis uses the University of California, Santa Clara (UCSC) Genome Browser Human cellular microRNAome barCharts to compare miR-21 levels across cell types; no primary experimental data are reported.

Limitations

  • The paper does not state a formal limitations section.
  • Evident from the text: the biomarker tables are described as a “subset” of studies rather than a systematic or exhaustive review, and no primary validation or meta-analysis is performed.
  • The argument focuses on miR-21 but notes that other ubiquitous miRNAs, such as let-7 family, miR-10a, and miR-22, may share the same biomarker-specificity concern.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1186/s40364-021-00272-1

Cites

82 of 82 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Figures

Fig. 1 miR-21 expression across 78 cell types. While miR-21 is robustly expressed in most cell types, its highest expression levels appear in macrophages, monocytes, and dendritic cells. Image modified from the UCSC Genome Browser
Fig. 1 miR-21 expression across 78 cell types. While miR-21 is robustly expressed in most cell types, its highest expression levels appear in macrophages, monocytes, and dendritic cells. Image modified from the UCSC Genome BrowserCC BY · PubMed Central

Verification

Claims the paper makes

9 Own interpretation · 4 Partly supported · 4 No basis given · 2 Not checked yet · 2 Own result · 1 Supported so far · 1 Couldn’t confirm · accuracy not yet measured

Show all 15 claims

  • It may state two separate claims as one. 6
  • Probably not a substantial claim. 4
8 of 8
  • The paper relies on this without support.

    A biomarker must be specific to a single disease to be a viable candidate.

    “As a result, it should not be considered a viable candidate to be a biomarker, despite its continued evaluation as such.”
1 of 1

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Citations

Cites

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Cited by

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Metadata

Authors
Jenike, A. E., & Halushka, M. K.
Affiliations
Johns Hopkins University (US)
Corresponding author
Halushka, Marc K.
Venue
Biomarker Research
Published
2021-03-12
Volume
9
Issue
1
Pages
18-18
ISSN
2050-7771 (ISSN-L)
OpenAlex
W3133811159
Cited by
248
References
83
Citations by year
2026: 32 · 2025: 48 · 2024: 68 · 2023: 43 · 2022: 38 · 2021: 17
FWCI
13.66
Type
journal article
Language
en
Open access
Locations
  • Biomarker Research (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • National Institute of General Medical Sciences (R01GM130564)
  • National Heart, Lung, and Blood Institute (1R01HL137811)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › MicroRNA in disease regulation
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Extracellular vesicles in disease
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Cancer-related molecular mechanisms research
Keywords
miR-21, microRNA, biomarkers, biomarker specificity, disease biomarkers, cancer, heart disease, biological fluids, miRNA expression regulation

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