BMC Research Notes (Nov 2018)

Proteinase K treatment improves RNA recovery from thyroid cells fixed with liquid-based cytology solution

  • Tomoo Jikuzono,
  • Aya Horikawa,
  • Tomoko Ishikawa,
  • Mitsuyoshi Hirokawa,
  • Iwao Sugitani,
  • Takashi Inui,
  • Osamu Ishibashi

DOI
https://doi.org/10.1186/s13104-018-3914-4
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 6

Abstract

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Abstract Objective Fine-needle aspiration biopsy (FNAB), an important diagnostic tool given its simplicity, safety, and cost-effectiveness, is fast becoming a popular procedure in the diagnosis of thyroid diseases. Generally, cells isolated from biopsies are transferred directly to microscope slides to prepare smears for cytopathological examination; however, the technical difficulties of this procedure often cause poor reproducibility, which limits the accuracy of diagnostic results. Liquid-based cytology (LBC), in which isolated cells are collected in a fixative solution, is advantageous in that it facilitates the preparation of homogenous cytological specimens. However, LBC has not been applied to molecular diagnoses, such as RNA expression-based diagnosis, mainly because of difficulties in cell recovery and RNA isolation. This study was aimed to improve RNA extraction from papillary cancer-derived K1 cells and thyroid FNAB specimens suspended in LBC solutions. Results K1 cells suspended in CytoRich-Red and CytoRich-Blue, fixatives for LBC, were efficiently recovered by trapping to glass-fiber filters. Importantly, subsequent Proteinase K treatment was essential for efficient RNA extraction from the fixed cells. This finding was also applicable to RNA extraction from CytoRich-Red-fixed thyroid FNAB specimens processed in the same way. Consistently, U6 small nuclear RNA was detected in these RNA samples by reverse transcription-polymerase chain reaction.

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