Background: The effects of preanalytical variables in tissue processing and storage periods on RNA quality of tissues have been well documented in each type of cancer. However, few studies have been performed on a comparative assessment of the impacts across different cancer tissues, even though it is well known that RNase activity is highly variable in various tissue types and RNase-rich tissues have been found to yield low-quality RNA.
Methods: We investigated the impacts of cold ischemia times and long-term storage on RNA integrity in various types of cancer tissue, which had been fresh-frozen and collected at the Samsung Medical Center Biobank. RNA quality was also evaluated with regard to histopathological variables. We analyzed RNA integrity number (RIN) data, which had been obtained from our quality control (QC) processes over the last 7 years. Approximately 2% of samples were randomly selected and processed to measure RIN quarterly and after 6 years of storage for QC purposes.
Results: Fresh-frozen tumor tissues yielded high-quality RNA regardless of tumor type and histopathological features. Up to 1-hour cold ischemia times and up to 6-year storage times did not adversely influence RNA integrity. Only 3 samples showed RIN of <7 out of a total of 396 analyzed tumor tissues.
Conclusions: Tissue quality was not adversely affected by long-term storage or limited variations of cold ischemia times. The low-quality samples could be correlated with the structural composition or intratumoral heterogeneity of tissues. The strict application of standardized protocols for tissue collection is the key for high-quality biobanking.
Keywords: RNA integrity; biobanking; tissue quality; tumor tissue.