HES5 and neoplasm: In prostate cancer cells, de-repression of HES5 with the demethylating agent 5-aza-2′-deoxycytidine resulted in a delayed downregulation of HES6 (Fig. 3c), consistent with HES5 repression of HES6. We also observed an inverse relationship between HES5 and HES6 expression in a series of primary tumours compared with benign prostate samples, where HES5 expression decreased and HES6 expression increased in tumour vs benign prostate samples (Fig. 3d and e).