Inappropriate activation of the androgen receptor by nonsteroids: involvement of the Src kinase pathway and its therapeutic implications.
The inappropriate activation of androgen receptor (AR) by nonsteroids is considered a potential mechanism in the emergence of hormone-refractory prostate tumors, but little is known about the properties of these "pseudoactivated" AR. Here, we present the first comprehensive analysis closely examining the properties of AR activated by the neuropeptide bombesin that distinguish it from androgen-activated AR. We show that bombesin-activated AR (a) is required for bombesin-induced growth of LNCaP cells, (b) has a transcriptional profile overlapping with, but not identical to, androgen-activated AR, (c) activates prostate-specific antigen by preferentially binding to its proximal promoter, and (d) assembles a distinct coactivator complex. Significantly, we found that Src kinase is critical for bombesin-induced AR-mediated activity and is required for translocation and transactivation of AR. Additionally, we identify c-Myc, a Src target gene, to be activated by bombesin and a potential coactivator of AR-mediated activity specific to bombesin-induced signaling. Because Src kinase is often activated by other nonsteroids, such as other neuropeptides, growth factors, chemokines, and cytokines, our findings have general applicability and provide rationale for investigating the efficacy of the Src kinase pathway as a target for the prevention of relapsed prostate cancers.
Desai
Sonal J
SJ
Department of Biological Chemistry and Cancer Center, University of California at Davis, Sacramento, California 95817, USA.
Ma
Ai-Hong
AH
Tepper
Clifford G
CG
Chen
Hong-Wu
HW
Kung
Hsing-Jien
HJ
D001839:Bombesin / Q000494:pharmacology* / Q000627:therapeutic use; D049109:Cell Proliferation / Q000187:drug effects; D019886:Gastrin-Releasing Peptide / Q000494:pharmacology; D006801:Humans; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D017430:Prostate-Specific Antigen / Q000235:genetics; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D021381:Protein Transport / Q000187:drug effects; D011944:Receptors, Androgen / Q000187:drug effects* / Q000502:physiology; D015398:Signal Transduction; D019061:src-Family Kinases / Q000502:physiology*
D011944:Receptors, Androgen; D019886:Gastrin-Releasing Peptide; D019061:src-Family Kinases; D017430:Prostate-Specific Antigen; D001839:Bombesin