title: Prostate cancer-derived cathelicidin-related antimicrobial peptide facilitates macrophage differentiation and polarization of immature myeloid progenitors to protumorigenic macrophages.
abstract: BACKGROUND
  A growing body of evidence indicates a positive correlation between expression of human antimicrobial peptide leucin leucin 37 (LL-37) and progression of epithelial cancers, including prostate cancer (PCa). Although the molecular mechanisms for this correlation has not yet been elucidated, the primary function of LL-37 as a chemotactic molecule for innate immune effector cells suggests its possible association in coordinating protumorigenic mechanisms, mediated by tumor-infiltrating immune cells.
  
  
  METHODS
  To investigate protumorigenic role(s) of cathelicidin-related antimicrobial peptide (CRAMP), a murine orthologue of LL-37, the present study compared tumor growth kinetics between mouse PCa cell lines with and without CRAMP expression (TRAMP-C1 and TRAMP-C1(CRAMP-sh) , respectively) in immunocompetent mice. CRAMP-mediated chemotaxis of different innate immune cell types to the tumor microenvironment (TME) was observed in vivo and confirmed by in vitro chemotaxis assay. The role of CRAMP in differentiation and polarization of immature myeloid progenitors (IMPs) to protumorigenic type 2 macrophages (M2) in TME was determined by adoptive transfer of IMPs into mice bearing CRAMP(+) and CRAMP(-) tumors. To differentiate protumorigenic events mediated by tumor-derived CRAMP from host immune cell-derived CRAMP, tumor challenge study was performed in CRAMP-deficient mice. To identify mechanisms of CRAMP function, macrophage colony stimulating factor (M-CSF) and monocyte chemoattractant protein 1 (MCP-1) gene expression was analyzed by QRT-PCR and STAT3 signaling was determined by immunoblotting.
  
  
  RESULTS
  Significantly delayed tumor growth was observed in wild-type (WT) mice implanted with TRAMP-C1(CRAMP-sh) cells compared to mice implanted with TRAMP-C1 cells. CRAMP(+) TME induced increased number of IMP differentiation into protumorigenic M2 macrophages compared to CRAMP(-) TME, indicating tumor-derived CRAMP facilitates differentiation and polarization of IMPs toward M2. Tumor challenge study in CRAMP deficient mice showed comparable tumor growth kinetics with WT mice, suggesting tumor-derived CRAMP plays a crucial role in PCa progression. In vitro study demonstrated that overexpressed M-CSF and MCP-1 in TRAMP-C1 cells through CRAMP-mediated autocrine signaling, involving p65, regulates IMP-to-M2 differentiation/polarization through STAT3 activation.
  
  
  CONCLUSIONS
  Altogether, the present study suggests that overexpressed CRAMP in prostate tumor initially chemoattracts IMPs to TME and mediates differentiation and polarization of early myeloid progenitors into protumorigenic M2 macrophages during PCa progression. Thus, selective downregulation of CRAMP in tumor cells in situ may benefit overcoming immunosuppressive mechanisms in PCa.
authors: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama.
authors: Ha-Ram
authors: HR
authors: Cha
authors: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama.
authors: Joo Hyoung
authors: JH
authors: Lee
authors: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama.
authors: Jonathan A
authors: JA
authors: Hensel
authors: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama.
authors: Anandi B
authors: AB
authors: Sawant
authors: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama.
authors: Brittney H
authors: BH
authors: Davis
authors: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama.
authors: Carnellia M
authors: CM
authors: Lee
authors: Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.
authors: Jessy S
authors: JS
authors: Deshane
authors: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama.
authors: Selvarangan
authors: S
authors: Ponnazhagan
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics*; D045744:Cell Line, Tumor; D016764:Cell Polarity / Q000235:genetics*; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D002633:Chemotaxis / Q000235:genetics*; D005786:Gene Expression Regulation; D016173:Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D023461:Myeloid Progenitor Cells / Q000378:metabolism* / Q000473:pathology; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D059016:Tumor Microenvironment; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D018932:Chemokine CCL2; D016173:Macrophage Colony-Stimulating Factor; D054804:Cathelicidins
keywords: CRAMP; LL-37; prostate cancer