NEUROTENSIN RECEPTOR EXPRESSION IN PROSTATE-CANCER CELL-LINE AND GROWTH EFFECT OF NT AT PHYSIOLOGICAL CONCENTRATIONS

BACKGROUND. Neurotensin (NT), a neuroendocrine peptide, exerts trophic effects in vivo and stimulates growth of some tumor cells in vitro. A ndrogen-sensitive prostate cells derived from lymph node carcinoma of the prostate (LNCaP) secrete NT and exhibit growth responses to NT. Th is study examines NT secretion, NT receptor and NT-growth responses in androgen-independent prostatic carcinoma (PC3) cells derived from pro state adenocarcinoma metastatic to bone. METHODS. Binding of I-125-NT to PC3 membranes was studied by filtration. NT was measured by RIA. Re verse transcriptase polymerase chain reaction (RT-PCR) was used for NT and NT receptor mRNA. Growth was measured as H-3-thymidine incorporat ion into DNA. RESULTS. Scatchard analyses gave two binding components (K-d1 = 40 pM and K-d2 = 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. Glutaral dehyde crosslinking labeled two substances (M-r of 23 and 46 kDa). RT- PCR indicated robust expression of authentic NT receptor but little fo r 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 m itogenic effect with bell-shaped dose-response and maximum at 100 pM N T. CONCLUSIONS. PC3 cells expressed genuine NT receptors and generated growth responses to physiologic levels of NT which were blocked by SR 48692. If NT contributes to the survival of prostate tumor cells upon androgen deprivation therapy, NT antagonists might be useful agents in further treatment. (C) 1997 Wiley-Liss, Inc.