title: Neurotensin receptor expression in prostate cancer cell line and growth effect of NT at physiological concentrations.
abstract: BACKGROUND
  Neurotensin (NT), a neuroendocrine peptide, exerts trophic effects in vivo and stimulates growth of some tumor cells in vitro. Androgen-sensitive prostate cells derived from lymph node carcinoma of the prostate (LNCaP) secrete NT and exhibit growth responses to NT. This study examines NT secretion, NT receptor and NT-growth responses in androgen-independent prostatic carcinoma (PC3) cells derived from prostate adenocarcinoma metastatic to bone.
  
  
  METHODS
  Binding of 125I-NT to PC3 membranes was studied by filtration. NT was measured by RIA. Reverse transcriptase polymerase chain reaction (RT-PCR) was used for NT and NT receptor mRNA. Growth was measured as 3H-thymidine incorporation into DNA.
  
  
  RESULTS
  Scatchard analyses gave two binding components (Kd1 = 40 pM and Kd2 = 300 pM) in equal amounts (15-30 x 10(3) sites/cell). The bioactive region of NT was essential and the specific, non-peptide NT antagonist, SR48692, inhibited (IC50 = 3 nM). GTP analogs, sodium ion and SH-directed alkylating agents also inhibited. Glutaraldehyde crosslinking labeled two substances (M(r) of 23 and 46 kDa). RT-PCR indicated robust expression of authentic NT receptor but little for NT precursor. NT was stable in PC3 cultures but it was not found in cells or conditioned media. Incubated with PC3 cells, NT exhibited a mitogenic effect with bell-shaped dose-response and maximum at 100 pM NT.
  
  
  CONCLUSIONS
  PC3 cells expressed genuine NT receptors and generated growth responses to physiologic levels of NT which were blocked by SR48692. If NT contributes to the survival of prostate tumor cells upon androgen deprivation therapy, NT antagonists might be useful agents in further treatment.
authors.affiliation: Department of Physiology, University of Massachusetts Medical Center, Worcester 01655, USA.
authors.forename: L
authors.initials: L
authors.lastname: Seethalakshmi
authors.forename: S P
authors.initials: SP
authors.lastname: Mitra
authors.forename: P R
authors.initials: PR
authors.lastname: Dobner
authors.forename: M
authors.initials: M
authors.lastname: Menon
authors.forename: R E
authors.initials: RE
authors.lastname: Carraway
mesh_terms: D002455:Cell Division / Q000187:drug effects; D004355:Drug Stability; D006801:Humans; D008297:Male; D009496:Neurotensin / Q000494:pharmacology*; D009994:Osmolar Concentration; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D018028:Receptors, Neurotensin / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D012333:RNA, Messenger; D018028:Receptors, Neurotensin; D009496:Neurotensin