Retrospective MicroRNA Sequencing: Complementary DNA Library Preparation Protocol Using Formalin-fixed...

Area of Science:

• Molecular Biology
• Genomics
• Cancer Research

Background:

• Archived formalin-fixed paraffin-embedded (FFPE) tissues are valuable for retrospective cancer studies.
• Nucleic acids from FFPE tissues are often degraded and chemically modified, complicating molecular analysis.
• MicroRNAs (miRNAs) are small RNA molecules that are relatively stable in FFPE samples.

Purpose of the Study:

• To develop and validate a robust library preparation protocol for analyzing small RNAs from long-term archived FFPE tissues.
• To enable the identification of early molecular alterations associated with cancer development using degraded RNA.
• To establish a reproducible method for multiplex analysis of compromised RNA samples for next-generation sequencing (NGS).

Main Methods:

• A 3' barcoded complementary DNA (cDNA) library preparation protocol was optimized for small RNA extraction from archived FFPE tissues.
• The protocol involves ligating individual 3' barcoded adapters to RNA samples, followed by pooling and enzymatic preparation.
• Purification is achieved via polyacrylamide gel electrophoresis (PAGE) for size-specific selection, and pilot PCR is used to determine optimal amplification cycles for NGS.

Main Results:

• The developed protocol demonstrated robustness and high reproducibility with archived clinical specimens stored for up to 35 years.
• The method is well-adapted for multiplex analysis of degraded RNA, accommodating up to 18 samples.
• The protocol efficiently handles minute RNA inputs and yields reproducible NGS data from compromised FFPE RNA.

Conclusions:

• This 3' barcoded cDNA library preparation protocol is effective for analyzing small RNAs from degraded FFPE tissues.
• The method facilitates the study of early molecular changes in cancer development using historical clinical samples.
• The protocol's reproducibility and adaptability to degraded RNA make it a valuable tool for retrospective genomic studies.