Establishing a correlation between RIN and A260/280 along with the multivariate evaluation of factors affecting the quality of RNA in cryopreserved cancer bio-specimen

Biomarkers are biological characteristic to measure and evaluate normal and pathological states. To define expression-based molecular biomarkers, high-quality tissue samples are a prerequisite for the preparation of standard RNA. It is already known that RIN number defines the RNA quality, however its relation with A(260/280) ratio and Ct value is not defined clearly; therefore, understanding an association will provide a reliable method for describing RNA quality. Multiple cryopreserved human tumor tissue types from ACTREC Biorepository and TMH-INTTR were analyzed for the effect of storage time on RNA quality. The RNA from tumor samples were isolated and analyzed by RIN, A(260/280) ratio, and Ct value to establish inter-relationships. Around 50% samples had a RIN of >= 6.9 and A(260/280) <= 2.04; 27% had a RIN >= 5 and A(260/280) <= 2.08, and remaining 23% displayed RIN < 5 and A(260/280) > 2.08. However, the RNA quality has no association with the storage period of tissue samples. Moreover, all samples which had A(260/280) <= 2.08 showed acceptable Ct values of 17-24. The data clearly suggests that the A(260/280) ratio is able to predict RNA quality. To the best of our knowledge, this is the first Indian report analyzing the labile nucleic acid-RNA quality from different cancer tissue types cryopreserved for diverse time periods. In conclusion, RIN and A(260/280) ratio can help in predicting the quality of RNA independently; however, both together provide better assurance for further downstream processing.