Influence of Freeze-Thaw Cycles on RNA Integrity of Gastrointestinal Cancer and Matched Adjacent Tissues.
BACKGROUND
Comparative analysis of RNA expression profiles between cancer and adjacent noncancerous tissues is an important part of cancer research. High-quality RNA is essential for consistent, reliable results, especially for identification of cancer biomarkers. However, the impact of freeze-thaw cycles on the quality of RNA both in gastrointestinal cancer and paired adjacent tissues is still unclear.


OBJECTIVE
To investigate the influence of freeze-thaw cycles on RNA integrity and overall histomorphology of gastrointestinal cancer and paired adjacent noncancerous tissues.


METHODS
Gastrointestinal cancer and matched adjacent noncancerous tissues were frozen and thawed twice before extracting RNA. Total RNA in each sample was extracted with TRIzol reagents and the RNA integrity was assessed by RNA integrity number (RIN) on an Agilent Bioanalyzer. Light microscopy was then used to assess tissue composition and morphology.


RESULTS
RIN values for all samples tended to decrease in correlation with the frequency of freeze-thawing. With an RIN cutoff value of 6, RNA extracted from pancreatic cancer tissues was not qualified after the first freeze-thaw cycle. Moreover, all RNA extracted from adjacent noncancerous tissues had nonqualifying RIN scores after the first freeze-thaw cycle, except for liver tissues. Microscopically, all samples displayed qualified tissue morphology regardless of freeze-thaw cycle frequency.


CONCLUSIONS
Freeze-thawing affects the RNA integrity, but not the tissue morphology of gastrointestinal cancer and paired adjacent noncancerous tissues. Furthermore, the RNA extracted from adjacent noncancerous tissues is more easily degraded than that in cancer tissues.
1 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of BioBank, Peking University Cancer Hospital and Institute , Beijing, China .
Ying
Y
Hu
1 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of BioBank, Peking University Cancer Hospital and Institute , Beijing, China .
Haibo
H
Han
1 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of BioBank, Peking University Cancer Hospital and Institute , Beijing, China .
Yixue
Y
Wang
1 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of BioBank, Peking University Cancer Hospital and Institute , Beijing, China .
Lijie
L
Song
2 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Division of Gastrointestinal Cancer Translational Research Laboratory, Peking University Cancer Hospital and Institute , Beijing, China .
Xiaojing
X
Cheng
2 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Division of Gastrointestinal Cancer Translational Research Laboratory, Peking University Cancer Hospital and Institute , Beijing, China .
Xiaofang
X
Xing
3 Department of Pathology, Peking University Cancer Hospital and Institute , Beijing, China .
Bin
B
Dong
1 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of BioBank, Peking University Cancer Hospital and Institute , Beijing, China .
Xiaohong
X
Wang
1 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of BioBank, Peking University Cancer Hospital and Institute , Beijing, China .
Meng
M
Chen
4 Department of Gastrointestinal Surgery, Peking University Cancer Hospital and Institute , Beijing, China .
Lianhai
L
Zhang
1 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of BioBank, Peking University Cancer Hospital and Institute , Beijing, China .|4 Department of Gastrointestinal Surgery, Peking University Cancer Hospital and Institute , Beijing, China .
Jiafu
J
Ji
D015925:Cryopreservation / Q000592:standards*; D005770:Gastrointestinal Neoplasms / Q000473:pathology*; D006801:Humans; D008853:Microscopy; D012313:RNA / Q000737:chemistry* / Q000592:standards*; D013696:Temperature; D059467:Transcriptome
D012313:RNA
RNA integrity number (RIN); freeze-thaw cycles