sentence: The expression of thirteen candidate EC genes : B2M , HPRT , GAPDH , ACTB , PPIA , HCRT , SLC25A23 , DTX3 , APOC4 , RTDR1 , KRTAP12-3 , CHRNB4 and MRPL19 were analysed in a cohort of 64 colorectal tumours and tumour associated normal specimens .