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

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• Long Interspersed Element-1 (LINE-1) are human retrotransposons capable of DNA replication and insertion.
• Active LINE-1 elements can be exported via extracellular vesicles (EVs).
• LINE-1 retrotransposition requires its mRNA and two proteins, ORF1p and ORF2p.

Purpose of the Study:

• To investigate the patterns of LINE-1 mRNA and protein loading into EVs.
• To correlate LINE-1 EV content with reverse transcriptase (RT) activity.
• To assess the potential of EV-associated LINE-1 as a cancer biomarker.

Main Methods:

• Density gradient ultracentrifugation to isolate and analyze EV components.
• Detection and quantification of LINE-1 mRNA and proteins (ORF1p, ORF2p) within EVs.
• Measurement of reverse transcriptase (RT) activity in EV fractions.
• Comparison of LINE-1 profiles in EVs from cancer cell lines versus healthy plasma donors.

Main Results:

• Conserved patterns of LINE-1 mRNA and protein distribution were observed in EVs.
• RT activity was detected in EV fractions containing LINE-1 mRNA and protein.
• ORF1p in EVs was predominantly found as a dimer, unlike in cell lysates.
• EVs from cancer cell lines exhibited significantly higher LINE-1 levels and RT activity compared to those from healthy donors.
• EV RT activity correlated positively with LINE-1 mRNA content and ORF1p/ORF2p expression.

Conclusions:

• Extracellular vesicles efficiently package and export active LINE-1 elements.
• EV-associated LINE-1 activity is significantly elevated in cancer.
• EV LINE-1 profiles, including RT activity, may serve as a non-invasive 'liquid biopsy' for monitoring cancer progression.