Cell-autonomous intracellular androgen receptor signaling drives the growth of human prostate cancer initiating cells.
BACKGROUND
The lethality of prostate cancer is due to the continuous growth of cancer initiating cells (CICs) which are often stimulated by androgen receptor (AR) signaling. However, the underlying molecular mechanism(s) for such AR-mediated growth stimulation are not fully understood. Such mechanisms may involve cancer cell-dependent induction of tumor stromal cells to produce paracrine growth factors or could involve cancer cell autonomous autocrine and/or intracellular AR signaling pathways.


METHODS
We utilized clinical samples, animal models and a series of AR-positive human prostate cancer cell lines to evaluate AR-mediated growth stimulation of prostate CICs.


RESULTS
The present studies document that stromal AR expression is not required for prostate cancer growth, since tumor stroma surrounding AR-positive human prostate cancer metastases (N = 127) are characteristically AR-negative. This lack of a requirement for AR expression in tumor stromal cells is also documented by the fact that human AR-positive prostate cancer cells grow equally well when xenografted in wild-type versus AR-null nude mice. AR-dependent growth stimulation was documented to involve secretion, extracellular binding, and signaling by autocrine growth factors. Orthotopic xenograft animal studies documented that the cellautonomous autocrine growth factors which stimulate prostate CIC growth are not the andromedins secreted by normal prostate stromal cells. Such cell autonomous and extracellular autocrine signaling is necessary but not sufficient for the optimal growth of prostate CICs based upon the response to anti-androgen plus/or minus preconditioned media.


CONCLUSIONS
AR-induced growth stimulation of human prostate CICs requires AR-dependent intracellular pathways. The identification of such AR-dependent intracellular pathways offers new leads for the development of effective therapies for prostate cancer.
Vander Griend
Donald J
DJ
Chemical Therapeutics Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
D'Antonio
Jason
J
Gurel
Bora
B
Antony
Lizamma
L
Demarzo
Angelo M
AM
Isaacs
John T
JT
D000818:Animals; D019898:Autocrine Communication / Q000502:physiology; D014408:Biomarkers, Tumor / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000378:metabolism* / Q000473:pathology; D005110:Extracellular Space / Q000378:metabolism / Q000502:physiology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism / Q000502:physiology; D007424:Intracellular Fluid / Q000502:physiology*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D011485:Protein Binding / Q000502:physiology; D011944:Receptors, Androgen / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D014408:Biomarkers, Tumor; D036341:Intercellular Signaling Peptides and Proteins; D011944:Receptors, Androgen