EN2 and acute promyelocytic leukemia: RT-QPCR revealed that promyelocytic leukemia derived HL60, melanoma derived SKMEL5, and the prostate cancer-derived cell lines DU145, PC3, and LNCaP, all express high levels of EN2, whilst WPMY-1 (a cell line derived from normal prostate fibroblasts) showed only very low levels of expression (Fig. 1A).