Androgen receptor expression in androgen independent prostate cancer cell lines

BACKGROUND. Almost all attempts at establishing prostate carcinoma cell lin es have resulted in generation of cells that are androgen-independent, incl uding commonly used LNCaP which expresses androgen receptor (AR) and AR-neg ative Du145 and PC-3. We attempted to clarify the mechanism(s) responsible for the failure to respond to androgen. METHODS. Cell lines LNCaP, CWR22R, PC-3, Du145, and CA7T2CL were used to ex amine the AR promoter function with a reporter gene assay and its methylati on status by Southern blot, PCR of bisulfite-converted DNA, and 5-aza-2 ' - deoxycytidine treatment. Structural abnormalities of the AR were identified by sequencing of reverse-transcribed mRNA. RESULTS. All tested AR-positive prostate carcinoma cells were capable of AR transcription at a significantly higher level than PC-3 and Du145, thus su ggesting relative deficiency of the transcription factors in the AR-negativ e cells, further associated with methylation. Examination of CWR22R cells, which express the AR but are androgen-independent, identified an in-frame d uplication of exon 3, which resulted in insertion of 39 amino acids in the DNA-binding domain. CONCLUSIONS. Relative deficiency of transcription factors associated with m ethylation is responsible for the lack of AR promoter function in most of A R-negative cell lines. Mutations in the AR gene are present in the cells th at express the AR but are androgen-independent. Prostate 47:66-75, 2001. (C ) 2001 Wiley-Liss, Inc.