GAPDH and endometrial cancer: In earlier qRT-PCR studies of endometrial cancer, normalisation was done using reference genes, such as β-actin (ACTB)21,22, glyceraldehyde-3-phosphate dehydrogenase (GAPDH)23,24, or 18S RNA ribosomal unit 1 (18S rRNA)25, chosen without rigorous testing.