Selecting Optimal Housekeeping Genes for RT-qPCR in Endometrial Cancer Studies: A Narrative Review

Detailed analysis of gene expression by real time-quantitative polymerase chain reaction (RT-qPCR) has become a widespread method. To normalize the expression of target genes, this approach relies on constitutively expressed internal controls known as housekeeping genes (HKGs). Their proper selection is a critically important methodological step, since all the studied gene expression will be recalculated based on HKG expression. This concise review aims to discuss the selection of HKGs for endometrial cancer (EC) studies. We draw attention to the fact that the commonly used gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is unsuitable as a HKG for research on the normal endometrium, EC, as well as many other tissues. In contrast, accumulating evidence suggests that GAPDH is a pan-cancer marker and an EC marker. Work on GAPDH overexpression in EC in relation to overall and relapse-free survival is lacking. Both original research and overviews indicate that at least two HKGs should be used for target gene expression recalculations, a rarely applied technical aspect of final data processing. The insufficiently careful selection in many studies of only one HKG, e.g., GAPDH, can be held responsible for broad discrepancies in published results obtained by this RT-qPCR technique. We provide an account of the discrepancies reported for sex hormone receptors expression in EC. Achieving consensus on the selection and validation of HKGs for research on this cancer is of crucial importance. Ideally, this trusted gene combination should be universal for any EC histotype and grade, irrespective of the final anatomopathological result.