Androgen receptor expression in androgen-independent prostate cancer cell lines

BACKGROUND Almost all attempts at establishing prostate carcinoma cell lines have resulted in generation of cells that are androgen‐independent, including commonly used LNCaP which expresses androgen receptor (AR) and AR‐negative 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 examine the AR promoter function with a reporter gene assay and its methylation 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 suggesting relative deficiency of the transcription factors in the AR‐negative cells, further associated with methylation. Examination of CWR22R cells, which express the AR but are androgen‐independent, identified an in‐frame duplication of exon 3, which resulted in insertion of 39 amino acids in the DNA‐binding domain. CONCLUSIONS Relative deficiency of transcription factors associated with methylation is responsible for the lack of AR promoter function in most of AR‐negative cell lines. Mutations in the AR gene are present in the cells that express the AR but are androgen‐independent. Prostate 47:66–75, 2001. © 2001 Wiley‐Liss, Inc.