title: Elevated circulating tissue inhibitor of metalloproteinase 1 (TIMP-1) levels are associated with neuroendocrine differentiation in castration resistant prostate cancer.
abstract: BACKGROUND
  Tissue inhibitor of metalloproteinase-1 (TIMP-1) is a 28.5 kDa secreted glycoprotein that inhibits matrix metalloproteinase (MMP) activity. Our group has previously shown that elevated plasma TIMP-1 levels predict poor survival in metastatic castration-resistant prostate cancer (CRPC) patients; however, the underlying source and impact of elevated circulating TIMP-1 protein is unknown.
  
  
  METHODS
  In this study, we used qRT-PCR, ELISA and immunohistochemistry to evaluate TIMP-1 expression in androgen-sensitive and resistant prostate cancer (PC) cell lines, tumor tissues and patient sera, and to correlate TIMP-1 levels to expression of chromogranin A (CGA), an established marker of neuroendocrine differentiation (NED). We also explored the relationship between TIMP-1 overexpression and induction of NED by overexpressing TIMP-1 in androgen-sensitive LNCaP cells, as well as by inducing NED of LNCaP cells with IL-6.
  
  
  RESULTS
  Patients with CRPC have significantly higher serum TIMP-1 levels compared to patients with hormone-sensitive disease. Although circulating TIMP-1 levels were increased, peripheral blood cells were not the source of elevation. Instead, elevated TIMP-1 expression was associated with higher expression of CGA in both blood and metastatic tumor tissue. We further show that androgen receptor (AR) and PSA non-expressing prostate cancer cell lines known to display NED phenotypes such as PC-3, PC-3M, and DU145 cells, expressed high levels of TIMP-1, in contrast to AR (+) and PSA (+) adenocarcinoma cell lines such as LNCaP, VCaP, and LAPC-4, which had barely detectable levels of TIMP-1. In addition, ectopic overexpression of TIMP-1 in LNCaP cells did not induce NED. However, TIMP-1 mRNA expression was elevated >10-fold during IL-6-induced NED of LNCaP cells, suggesting that TIMP-1 overexpression accompanies, but is not the driving force for NED. Finally, we show that conditioned media from androgen-resistant PC-3, PC-3M, and DU145 cells induced TIMP-1 mRNA expression in primary prostate stromal fibroblasts in an ERK and NF-κB dependent manner.
  
  
  CONCLUSIONS
  We provide in vitro and clinical evidence to support the association between NED and elevated circulating TIMP-1 expression in CRPC. Our observation supports further evaluation of TIMP-1 as a tissue and serum biomarker for NED in CRPC.
authors.affiliation: Division of Hematology and Medical Oncology, The Tisch Cancer Institute, Mount Sinai School of Medicine, New York, New York.
authors.forename: Yixuan
authors.initials: Y
authors.lastname: Gong
authors.forename: Uma D
authors.initials: UD
authors.lastname: Chippada-Venkata
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Galsky
authors.forename: Jiaoti
authors.initials: J
authors.lastname: Huang
authors.forename: William K
authors.initials: WK
authors.lastname: Oh
mesh_terms: D002454:Cell Differentiation; D045744:Cell Line, Tumor; D053379:Chromogranin A / Q000097:blood; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology; D016328:NF-kappa B / Q000502:physiology; D055099:Neuroendocrine Cells / Q000166:cytology*; D017430:Prostate-Specific Antigen / Q000097:blood; D064129:Prostatic Neoplasms, Castration-Resistant / Q000097:blood / Q000473:pathology*; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000097:blood*
chemical_list: D053379:Chromogranin A; D015850:Interleukin-6; D016328:NF-kappa B; C560822:TIMP1 protein, human; D019715:Tissue Inhibitor of Metalloproteinase-1; D020929:Mitogen-Activated Protein Kinase Kinases; D017430:Prostate-Specific Antigen
keywords: TIMP-1; castration resistance; neuroendocrine differentiation; prostate cancer