HPRT1 and cancer: Some of the common housekeeping genes are de-regulated in several cancers,18 so the extent of variation in the level of expression of five housekeeping genes (Gusb, Hprt1, Hsp90ab1, Gapdh and Actb) in tumour tissues (compared with spleens and TDLN) was examined to assess their potential as internal controls for normalizing specific chemokine mRNA expression.