Kelly Rachel, Albert Monique, de Ladurantaye Manon, Moore Melissa, Dokun Olusola, Bartlett John M S
1Ontario Tumour Bank, Ontario Institute for Cancer Research, Toronto, Canada.
2Diagnostic Development, Ontario Institute for Cancer Research, Toronto, Canada.
Biopreserv Biobank. 2019 Aug;17(4):282-287. doi: 10.1089/bio.2018.0095. Epub 2019 Feb 14.
It is widely assumed that the integrity of tissue specimens remains stable indefinitely if preserved at cryogenic temperatures. With biobanking reaching a level of maturity where samples are increasingly stored for 10 years and beyond, this assumption of prolonged stability should be tested. Data from such an assessment are critical to verify if samples stored for extended durations remain "fit for purpose" or if there is need to reconsider the utility of samples stored beyond a certain timeframe. The Ontario Tumour Bank has been collecting samples since 2004, and assesses a random selection of frozen samples each year for RNA and DNA integrity as a part of ongoing quality control (QC) practices. This historical quality assessment data provide a unique opportunity to assess the impact of extended storage on nucleic acid integrity using replicate samples that remain in the bank in the present day as comparators. To examine the stability of fresh-frozen tumor tissue stored at cryogenic temperatures, RNA was extracted and analyzed from 87 cases over 14 disease sites stored long term in vapor-phase liquid nitrogen (LN2) (approximately -180°C). Historical QC data were compared against new data after re-extraction of replicate samples to determine the effect of extended storage on RNA quality. In addition, DNA was extracted from a subselection of samples ( = 20) to determine the effect of prolonged storage on DNA integrity. No time-dependent decrease in tissue RNA or DNA quality, as measured by RNA integrity number (RIN) and DNA integrity number, was observed over an 11-year period. As a secondary observation, RNA integrity was not predictive of DNA integrity: DNA quality may still be very good, and as such RIN scores should not be used as a substitute indicator for evaluating DNA. Extended cryogenic storage beyond 2-11 years remains a viable option for maintaining the high quality of specimens in biobanks.
人们普遍认为，如果在低温下保存，组织样本的完整性会无限期保持稳定。随着生物样本库发展到成熟阶段，样本储存时间越来越长，可达10年及以上，这种长期稳定性的假设应该得到验证。此类评估的数据对于核实长期储存的样本是否仍“适用于研究目的”，或者是否需要重新考虑超过特定时间框架储存的样本的效用至关重要。安大略肿瘤库自2004年以来一直在收集样本，并作为持续质量控制（QC）措施的一部分，每年随机选择一批冷冻样本评估其RNA和DNA完整性。这些历史质量评估数据提供了一个独特的机会，可使用现今仍保存在样本库中的重复样本作为对照，来评估延长储存时间对核酸完整性的影响。为了研究保存在低温下的新鲜冷冻肿瘤组织的稳定性，从长期保存在气相液氮（LN2）（约-180°C）中的14个疾病部位的87例样本中提取并分析了RNA。在对重复样本进行重新提取后，将历史QC数据与新数据进行比较，以确定延长储存时间对RNA质量的影响。此外，从一部分样本（n = 20）中提取DNA，以确定延长储存时间对DNA完整性的影响。在11年的时间里，未观察到通过RNA完整性数值（RIN）和DNA完整性数值衡量的组织RNA或DNA质量随时间下降。作为次要观察结果，RNA完整性不能预测DNA完整性：DNA质量可能仍然非常好，因此RIN分数不应作为评估DNA的替代指标。在生物样本库中，超过2至11年的延长低温储存仍然是维持样本高质量的可行选择。
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