LINE-1 Cargo and Reverse Transcriptase Activity Profiles in Extracellular Vesicles from Lung Cancer Cells and Human Plasma

Emma C. Bowers, Alexandre Motta, Ken Knox, Brian S. McKay, Kenneth Ramos

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Long Interspersed Element-1 (LINE-1) is an oncogenic human retrotransposon that ‘copies and pastes’ DNA into new locations via reverse transcription. Given that enzymatically active LINE-1 can be exported in extracellular vesicles (EVs), and that LINE-1 mRNA and its two encoded proteins, ORF1p and ORF2p, are required for retrotransposition, the present study examined LINE-1 EV loading patterns relative to reverse transcriptase (RT) activity in vivo and in vitro. Density gradient ultracentrifugation identified conserved patterns of LINE-1 mRNA and protein distribution in EVs, with RT activity readily detected in EV fractions containing both LINE-1 mRNA and protein. Unlike whole cell and tissue lysates, the ORF1p in EVs was detected as a dimer. EVs from ostensibly healthy plasma donors showed variable but consistent ORF1p profiles, with residual levels of LINE-1 mRNA measured in some but not all samples. EVs from cancer cell lines had elevated mean LINE-1 levels and 5–85 times greater RT activity than EVs from normal cells or healthy plasma. EV RT activity was associated with EV LINE-1 mRNA content and was highest in cell lines that also expressed an elevated expression of ORF1p and ORF2p. Given that LINE-1 activation is a hallmark of many cancer types, our findings suggest that an EV LINE-1 ‘liquid biopsy’ may be developed to monitor LINE-1 activity during the course of malignant progression.

Original languageEnglish (US)
Article number3461
JournalInternational journal of molecular sciences
Issue number7
StatePublished - Apr 1 2022


  • BaP
  • Benzo[a]pyrene
  • Exosomes
  • Extracellular vesicles
  • LINE-1
  • Liquid biopsy
  • Lung cancer
  • ORF1p
  • ORF2p
  • Retrotransposition
  • Retrotransposons
  • Reverse transcriptase

ASJC Scopus subject areas

  • Catalysis
  • Molecular Biology
  • Spectroscopy
  • Computer Science Applications
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry


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