Androgen receptor gene mutations in hormone-refractory prostate cancer

Prostate cancer is considered to be one of the most hormone-dependent human malignancies. As a key mediator of hormonal response, the androgen receptor (AR) is believed to have an important role in the progression of prostate cancer. Mutations in the coding region of the AR gene have been found in both untreated and hormone-refractory prostate cancer, but the frequency of such mutations at different stages of the disease is poorly documented and even contradictory results have been published. In the present study, the frequency of AR gene mutations was determined in 30 locally recurrent and two metastatic hormone-refractory prostate tumours using the polymerase chain reaction (PCR), non-radioactive single strand conformation polymorphism (SSCP), and sequencing. The length of the polymorphic CAG repeat, which is inversely correlated with the ability of the AR to activate transcription, was also analysed as well as the GGC repeat. Twelve samples were known to contain an AR gene amplification. Altogether, one point mutation (Gly(674)-->Ala) and one microsatellite mutation (CAG(20)-->CAG(18)) were found, both in cancers containing the AR gene amplification. The mean lengths of the polymorphic CAG and GGC repeats were similar to those observed in the normal population. These results favour the view that mutations in the AR gene are rare in hormone-refractory prostate cancer and do not play an important role, at least, in local relapse. Instead, the amplification and consequent overexpression of the wild-type AR gene seem to be the most common alteration involving the AR in hormone-refractory prostate cancer.