Recent evidence suggests that
LHRH or a
LHRH-like peptide might be produced by human prostatic
tumor cells. To test this hypothesis, we have studied whether a
mRNA for
LHRH is expressed in the human
prostatic cancer cell line LNCaP, by means of the RT-PCR (reverse transcription-polymerase chain reaction) technique. For these experiments,
mRNA was extracted from LNCaP cells, from rat hypothalami and from rat pituitaries, reverse transcribed to
cDNA and amplified via the PCR utilizing a pair of
oligonucleotide primers complementary to the
LHRH cDNA. Following gel electrophoresis, a band of the expected size of 228 base pairs was found in LNCaP cells as well as in the rat hypothalamus, but not in the rat anterior pituitary. This 228 base pair band from LNCaP cells and from the rat hypothalamus specifically hybridized to a 32P-labeled
LHRH oligonucleotide probe. The
cDNA band obtained from LNCaP cells was subcloned into a plasmid vector, and the analysis of its sequence showed a complete match with the authentic human placental
LHRH cDNA. These observations clearly demonstrate that a
mRNA for
LHRH is expressed in human
prostatic cancer cells, and suggest that
LHRH or a
LHRH-like peptide may be produced by these cells. To test the hypothesis whether this material might act as a local growth regulating factor on
tumor cell proliferation, LNCaP cells, grown in a
steroid-free medium, were treated daily with a potent
LHRH antagonist. After 9, 12 and 15 days, the treatment resulted in a significant increase of
tumor cell proliferation. These data clearly suggest that the
LHRH mRNA expressed in LNCaP cells is possibly translated into
LHRH or a
LHRH-like peptide which probably functions as a local
growth inhibitory factor on prostatic
tumor cell proliferation, by acting on
LHRH receptors.