Evaluation of RNA and DNA extraction from liquid-based cytology specimens.

Molecular diagnosis using DNA and RNA derived from malignant tumors and molecular biological tools such as the quantitative polymerase-chain-reaction (qPCR) is a commonly used technique in clinical pathology. In this report, we compared the qualitative extraction of RNA and DNA from cancer cells fixed using several liquid-based cytology (LBC) kits. Ten to 1,000 cells from the T24 urinary bladder cancer cell line and SKG-II cervical cancer cell line were fixed with 55% methanol and three different methanol-based LBC solutions. The mRNA levels of CD44 in T24 cells and E7 in SKG-II cells and DNA levels of p53 in T24 cells and E7 in SKG-II cells were analyzed by qPCR. mRNA and DNA extracted from T24 and/or SKG-II cells fixed with methanol-based LBC solutions were efficiently detected, but to differing degrees, by qPCR. mRNA, and DNA from cells fixed with a formaldehyde-containing fixative liquid were detected at significantly low copy numbers by qPCR. Our results demonstrate that LBC systems are powerful tools for cytopathology and immunocytochemistry applications. However, the appropriate fixative must be selected for cell preservation when a small number of LBC samples is used for molecular testing, particularly in RNA-based molecular analyses. Diagn. Cytopathol. 2016;44:833-840.