Long-Term Preservation at Room Temperature of Freeze-Dried Human Tumor Samples Dedicated to Nucleic Acids Analyses

Abstract

Tumor banks are the only means for researchers to study in situ human lesions in a reproducible manner. Large amounts of money are spent at national and international levels for proper collection, in respect of both quality control and ethics, most importantly for shared use of the human samples. Preservation as whole tissue, and not simply as extracted DNA or RNA, allows additional scientific use of the samples. However, economic issues influence long-term development of biobanks since low-temperature cryopreservation with long-term storage of numerous samples and transfers avoiding RNA degradation are particularly costly. We optimized freeze-drying protocols for tumor samples dedicated to molecular analyses in our biobank using directly snap-frozen samples as references. We then compared different long-term storage conditions for preservation of nucleic acids in tumor samples to corresponding normal tissues and human cell lines. When stored for 1 year at room temperature with dessicant and no light, cell and tissue samples allowed for the extraction of nucleic acids, retaining their initial quality and suitable for quantitative molecular analyses. An extended use of the freeze-drying process in tumor banks could favor a larger scientific use of the samples and the standardization of preanalytical methods in molecular biology while reducing the cost of safe long-term preservation and transfers.