title: Transforming growth factor-β signaling induced during prostate cancer cell death and neuroendocrine differentiation is mediated by bone marrow stromal cells.
abstract: BACKGROUND
  Prostate cancer that has metastasized to bone undergoes critical interactions with bone marrow stromal cells (BMSCs), ultimately promoting tumor survival. Previous studies have shown that BMSCs secrete factors that promote prostate cancer apoptosis or neuroendocrine differentiation. Because of the significance of transforming growth factor-β (TGF-β) family cytokines in cytostasis and bone metastasis, the role of TGF-β signaling in the context of prostate cancer-BMSC interactions was investigated.
  
  
  METHODS
  The role of TGF-β family signaling in BMSC-induced apoptosis of lineage-related prostate cancer cells was investigated in live/dead assays. SMAD phosphorylation or activity during apoptosis and neuroendocrine differentiation was investigated using immunofluorescence, Western blotting, and luciferase reporter assays, along with the ALK-4, -5, -7 kinase inhibitor, SB-431542.
  
  
  RESULTS
  Treatment of castration-resistant prostate cancer cells with SB-431542 resulted in significant reduction of apoptosis mediated by HS-5 BMSCs, supporting the involvement of TGF-β/SMAD signaling during this event. Interestingly, however, pre-treatment of BMSCs with TGF-β1 (5 ng/mL) yielded a conditioned medium that elicited a marked reduction in prostate cancer death. Phosphorylated-SMAD2 (P-SMAD2) was activated in BMSC-triggered transdifferentiated prostate cancer cells, as demonstrated through immunoblotting and luciferase reporter assays. However, SB-431542 did not restore androgen receptor and prostate specific antigen levels down-regulated by BMSC-secreted factors. Prostate cancer cells induced to undergo neuroendocrine differentiation in a BMSC-independent mechanism also showed elevated levels of P-SMAD2.
  
  
  CONCLUSIONS
  Collectively, our findings indicate that: (1) TGF-β family cytokines or regulated factors secreted from BMSCs are involved in prostate cancer apoptosis; (2) TGF-β signaling in prostate cancer cells is induced during neuroendocrine differentiation; and (3) TGF-β1 stimulation of BMSCs alters paracrine signaling to create a permissive environment for prostate cancer survival, suggesting a mechanism for prostate cancer-mediated colonization of bone.
  
  
  CONCLUSIONS
  TGF-β signaling resulting in activation of SMAD2 in prostate cancer may be an indicator of cellular stress in the presence of toxic paracrine factors released from the bone marrow stroma, ultimately fostering prostate cancer colonization of bone.
authors.affiliation: Laboratory for Cancer Ontogeny and Therapeutics, University of Delaware, Newark, Delaware.|Department of Biological Sciences, Center for Translational Cancer Research, University of Delaware, Newark, Delaware.|Department of Epidemiology, Fielding School of Public Health, University of California-Los Angeles, Los Angeles, California.
authors.forename: Fayth L
authors.initials: FL
authors.lastname: Miles
authors.affiliation: Laboratory for Cancer Ontogeny and Therapeutics, University of Delaware, Newark, Delaware.|Department of Biological Sciences, Center for Translational Cancer Research, University of Delaware, Newark, Delaware.
authors.forename: Senem
authors.initials: S
authors.lastname: Kurtoglu
authors.affiliation: Laboratory for Cancer Ontogeny and Therapeutics, University of Delaware, Newark, Delaware.
authors.forename: Chris
authors.initials: C
authors.lastname: Ahmer
authors.affiliation: Laboratory for Cancer Ontogeny and Therapeutics, University of Delaware, Newark, Delaware.
authors.forename: Mehrnoosh
authors.initials: M
authors.lastname: Soori
authors.affiliation: Laboratory for Cancer Ontogeny and Therapeutics, University of Delaware, Newark, Delaware.
authors.forename: John S
authors.initials: JS
authors.lastname: Favate
authors.affiliation: Laboratory for Cancer Ontogeny and Therapeutics, University of Delaware, Newark, Delaware.|Department of Biological Sciences, Center for Translational Cancer Research, University of Delaware, Newark, Delaware.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Sikes
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001549:Benzamides / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D004149:Dioxoles / Q000494:pharmacology; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D064129:Prostatic Neoplasms, Castration-Resistant / Q000378:metabolism* / Q000473:pathology; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects*; D053773:Transforming Growth Factor beta1 / Q000187:drug effects / Q000378:metabolism*
chemical_list: C459179:4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-yl-1H-imidazol-2-yl)benzamide; D001549:Benzamides; D004149:Dioxoles; D018125:Receptors, Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1
keywords: apoptosis; bone marrow stroma; neuroendocrine; prostate cancer; transforming growth factor‐β