Papillary Thyroid Carcinoma: Differential Stability of MicroRNAs and Endogenous Control Genes
Posted: Monday, January 11, 2021
The microRNA quantitation technique real-time quantitative polymerase chain reaction with relative gene expression is widely popular and requires an endogenous control gene for data normalization. However, selection criteria for suitable endogenous controls for microRNA expression studies are not adequate for many cancer types, including papillary thyroid cancer. A study, published in Molecular Medicine, indicated that the levels of microRNA expression appeared to be different in tissue samples of different ages.
“It is important to select endogenous controls not only stable in the tissue of interest but also with similar stability to target microRNA, especially when working with samples of different age,” reported Aurelija Zvirbliene, MS, PhD, of Vilnius University, Lithuania, and colleagues.
The research team used real-time quantitative polymerase chain reaction to determine expression levels of five microRNAs: miR-146b, miR-222, miR-21, miR-221, and miR-181b. To normalize the data, three different endogenous controls were used: RNU48, let-7a, and miR-16. Overall, 400 formalin-fixed, paraffin-embedded papillary thyroid cancer tissue samples were analyzed; the samples had been stored between 1 and 15 years.
The results indicated that two commonly used endogenous controls, RNU48 and let-7a, had significantly different degradation rates than target microRNAs in formalin-fixed, paraffin-embedded papillary thyroid cancer tissues. According to the researchers, the differences in degradation rates affect the detected microRNA levels and the differences between study groups when working with samples of different ages. Several factors may affect the individual degradation rates of microRNAs and endogenous control genes, such as differences in length, their primary sequence, function, placement in the cell, or association with proteins. Thus, when working with tissue samples of different ages, researchers should consider the differential storage-dependent transcript degradation.
“We expect that this study will be helpful for researchers searching for proper endogenous controls, which would assure the most accurate data for microRNA expression studies,” the study team concluded.
Disclosure: The authors reported no conflicts of interest.