PPIA and endometrial cancer: Peptidylpropyl isomerase A (Ppia), Importin 8 (Ipo8) and Mitochondrial ribosomal protein L19 (Mrpl19) have been described to be the most stable genes when comparing normal and endometrial cancer cells12, while Ppia and Gapdh were found to be more stable HKG when comparing normal with endometriotic endometrium20.