Gonadotropin-releasing hormone (
GnRH) is a
neuropeptide that plays a pivotal role in reproductive processes. In recent years, it has become clear that it is also an anti-proliferative agent.
GnRH analogs are now used clinically in the treatment of
prostate cancer as well as
endometriosis and
precocious puberty. The target cells of
GnRH include the gonadotropes of the anterior pituitary gland and the cells of various
hormone-dependent
tumors. Only a few target genes have been identified in these cells, however, and little is known concerning their regulation by
GnRH. Therefore, we used a quantitative microarray assay to identify the genes that are regulated by
GnRH in a murine gonadotrope tumor cell line (LbetaT2). Treatment of LbetaT2 cells with
GnRH agonist des-
gly(10),[D-Ala(6)]
GnRH (GnRHA) for 1 h resulted in alterations in the levels of expression of genes that ranged in magnitude from 1.3- to 159-fold, with a total of 232 genes exhibiting a twofold or greater alteration in expression compared to vehicle treated cells. Of these 232 genes, 149 were up-regulated and, surprisingly, 83 were down-regulated by GnRHA treatment. After 24 h of treatment, the expression of most of the genes that had exhibited altered expression after 1 h of treatment had returned to baseline levels. Moreover, a different profile was observed after 24 h of treatment with 208 genes exhibiting a twofold or greater alteration. Of these, 95 were up-regulated and 113 down-regulated. Most of the affected genes were not known to be responsive to
GnRH prior to this study. Treatment with GnRHA was found to affect the expression of a diverse range of genes, including oncogenes and those that encode
transcription factors,
ion channel proteins, and
cytoskeletal proteins as well as other
proteins that are involved in signal transduction, the cell cycle, cell proliferation and apoptosis. The altered expression of six of the genes that were found by microarray analysis to be regulated by GnRHA was confirmed by semiquantitative
reverse transcriptase-polymerase chain reaction. This is first application of the microarray technique in the study of the global profile of genes regulated by
GnRH, and should prove to be a powerful tool for future analysis of the mechanisms by which
GnRH regulates the expression of
gonadotropins and the growth of
tumor cells.