Profiling and discovery of novel miRNAs from formalin-fixed, paraffin-embedded melanoma and nodal specimens

Area of Science:

• Oncology
• Molecular Biology
• Biotechnology

Background:

• Archived formalin-fixed, paraffin-embedded (FFPE) human tumors are valuable resources for research.
• MicroRNAs (miRNAs) in FFPE tissues hold potential for cancer prognostication and treatment response prediction.
• Existing methods for miRNA analysis are limited, especially for older or FFPE samples like those from malignant melanoma.

Purpose of the Study:

• To develop and validate a robust methodology for extracting and sequencing small RNAs, specifically miRNAs, from archived FFPE human cancer specimens.
• To enable miRNA discovery and expression profiling from FFPE tissues where fresh-frozen samples are unavailable.

Main Methods:

• A simple RNA extraction protocol optimized for small RNA recovery from various FFPE tissues was applied.
• A "poison primer" strategy was employed to block ribosomal RNA amplification, facilitating miRNA sequencing.
• Sequencing identified novel and known miRNAs from 10-year-old archived skin, melanoma, and lymph node samples.

Main Results:

• The protocol successfully recovered and sequenced 17 novel and 53 known miRNAs from aged FFPE samples.
• miRNA expression levels were estimated by cloning incidence and validated using Northern analysis and quantitative real-time polymerase chain reaction.
• The methodology proved effective for analyzing miRNA content in FFPE tissues, including those from malignant melanoma.

Conclusions:

• A reliable and robust method for miRNA extraction and sequencing from archived FFPE human cancers has been established.
• This technique facilitates miRNA discovery and analysis in valuable, long-term stored tissue samples.
• The developed methodology can significantly aid in understanding miRNA roles in cancer and improve patient prognostication and treatment strategies.