Quality control of nucleic acids and protein of freeze-preserving gastric cancer samples / 中国肿瘤临床

ABSTRACT

Objective:To explore the quality of inventory samples of a biobank stored in a deep freezer from 0 to over 10 years in Shanghai Ruijin Hospital. Methods:We extracted 24 pairs of stocked gastric cancer samples between 2003 and 2014. We used 1%aga-rose gel electrophoresis to analyze DNA and RNA purity and integrity while adding the RNA integrity number (RIN) for precise analysis. Bicinchonininc acid (BCA) assay was used for protein concentration evaluation. Coomassie brilliant blue method was used for protein integrity assay. Results: The samples were divided into four groups according to cryopreservation period (9 years). No significant difference in DNA integrity was found between the groups (P>0.05);however, DNA degradation in normal gastric mucosa was faster than that in gastric cancer tissue (P=0.023). The RIN significantly declined when the storage period was 6 years or longer (P=0.018). No significant difference in protein concentration was observed between different groups. Using Coo-massie brilliant blue method, we found significant differences in preserved proteins with different molecular weights. Proteins with varying molecular weights were detected in the groups with the following cryopreservation periods>9 years, a small number of low-molecular-weight (average 36.5 KD) proteins;6-8 years, medium-molecular-weight (average 65.63KD) proteins;3-5 years, high-molecu-lar-weight (average 127.5 KD) proteins;<2 years, high-molecular-weight (average 160 KD) proteins. Conclusion:Cryopreservation does not exert an obvious effect on DNA. If the cryopreservation period is more than 5 years, serious degradation of RNA should occur;like-wise, degradation of proteins with higher molecular weight should occur.