Expression of a splice variant of the receptor for GHRH in 3T3 fibroblasts activates cell proliferation responses to GHRH analogs

Hippokratis Kiaris, Andrew V Schally, Rebeca Busto, Gabor Halmos, Spyros Artavanis-Tsakonas, Jozsef L. Varga

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

The stimulatory effects of growth hormone-releasing hormone (GHRH) and the antiproliferative action of GHRH antagonists have been demonstrated in various cancers, but the receptors that mediate these responses are not clearly identified. Recently, we reported that human cancer cell lines express splice variants (SVs) of the receptors for GHRH. SV1 exhibits the greatest similarity to the pituitary GHRH receptor and is most likely to be functional. To ascertain whether SV1 mediates mitogenic effects on nonpituitary tissues, we expressed SV1 in 3T3 mouse fibroblasts and studied the properties of the transfected cells. Radioligand binding assays with 125l-labeled GHRH antagonist JV-1-42 detected high affinity (Kd = 0.58 ± 0.17 nM) binding sites for GHRH with a maximal binding capacity (Bmax) of 103 ± 17.4 fmol/mg of membrane protein in 3T3 cells transfected with pcDNA3-SV1, whereas the control cells transfected with the empty vector did not show any GHRH binding. Cell proliferation studies showed that cells expressing SV1 are much more sensitive to GHRH analogs than the pcDNA3 controls. Thus, the expression of SV1 augments the stimulatory responses to GHRH(1-29)NH2 or GHRH agonist JI-38 and inhibitory responses to GHRH antagonist JV-1-38 as compared with pcDNA3 controls. The stimulation of SV1-expressing cells by GHRH or JI-38 is followed by an increase in cAMP production, but no GH release occurs. Vasoactive intestinal peptide had no effect, and its antagonist JV-1-53 did not inhibit the proliferation of SV1-expressing cells stimulated by GHRH. Our results suggest that SV1 could mediate responses of nonpituitary cells and various tumors to GHRH and GHRH antagonists. The presence of SV1 in several human cancer cell lines provides a rationale for antitumor therapy based on the blockade of this receptor by specific GHRH antagonists.

Original languageEnglish
Pages (from-to)196-200
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume99
Issue number1
DOIs
StatePublished - Jan 8 2002
Externally publishedYes

Fingerprint

Growth Hormone-Releasing Hormone
Fibroblasts
Cell Proliferation
Hormone Antagonists
somatotropin releasing hormone receptor
Pituitary Hormone-Regulating Hormone Receptors
Neoplasms
Somatotropin Receptors
Cell Line
3T3 Cells
Radioligand Assay
Vasoactive Intestinal Peptide
Growth Hormone

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

Expression of a splice variant of the receptor for GHRH in 3T3 fibroblasts activates cell proliferation responses to GHRH analogs. / Kiaris, Hippokratis; Schally, Andrew V; Busto, Rebeca; Halmos, Gabor; Artavanis-Tsakonas, Spyros; Varga, Jozsef L.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 99, No. 1, 08.01.2002, p. 196-200.

Research output: Contribution to journalArticle

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