Androgen receptor expression in prostate cancer stem cells: is there a conundrum?

Androgen deprivation therapy (ADT) is standard frontline therapy for metastatic prostate cancer. However, prostate cancer progresses to a castrate-resistant state. The response of prostate cancer to androgen deprivation is mediated by the androgen receptor (AR). Castrate-resistant disease is marked by a gain-of-function in AR and AR reactivation. The stem cell hypothesis of cancer would therefore predict that AR should be expressed in the prostate cancer stem cell, since genetic selection for gain-of-function changes in AR, such as AR gene amplification, should occur at the level of the stem cell population. Initial reports characterizing prostate cancer stem cells suggest that AR is not expressed in this population, which is an apparent conundrum. Here, we examined the CD44+/24− LNCaP putative stem cell population by in-cell Western and show that AR is expressed at the protein level. Our findings suggest that at least a subset of prostate cancers express AR in the putative stem cell population.