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, Gábor; Artavanis‐Tsakonas, Spyros; Varga, József

doi:10.1073/pnas.012590999

Cited by 74 publications

(65 citation statements)

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“…However, in vitro and in vivo findings indicate that the principal action of GHRH antagonists is direct and based on the suppression of the autocrine and͞or paracrine production of insulin-like growth factors I and II in tumors and͞or to the blockade of the stimulatory action of tumoral GHRH. The direct actions of GHRH antagonists are mediated by specific tumoral receptors, which are different from the pituitary form of receptors (2,16,17,26). mRNAs for four of these SVs of the GHRH-R were found in many cancers, SV 1 being more prevalent than the other forms (16,17).…”

Section: Discussionmentioning

confidence: 99%

“…High affinity of the antagonists to the tumoral receptor facilitates their selective uptake from the circulation onto the tumor tissue (17,24). In addition, GHRH increased the proliferation of NIH 3T3 mouse fibroblasts transfected with the plasmid expressing the mRNA for SV 1 , and this effect was inhibited by the GHRH antagonist JV-1-38 in a dose-dependent manner (26).…”

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confidence: 90%

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Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

Toller

Horváth

Schally

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Antagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of various human cancers by multiple mechanisms, which include direct effects on tumor cells through the splice variants (SV) of the GHRH receptor. Our findings suggest that the tumoral protein encoded by SV 1 (SV 1) is a likely functional receptor. The aim of this study was to develop a polyclonal antiserum against a polypeptide analog of segment 1-25 of the putative SV 1 receptor protein. Rabbits were immunized with [Ala-23]SV 1 (1-25)-Tyr-26-Cys-27-NH2 as a hapten, conjugated to BSA or keyhole limpet hemocyanin. The antisera thus generated were evaluated by RIA for binding to the radiolabeled hapten. The specificity and sensitivity of the antisera were studied on xenografts of RL and HT human non-Hodgkin's lymphomas. The sera raised against keyhole limpet hemocyanin-SV 1 hapten, showed binding values of 50 -75% at a 1:56,000 dilution. In Western blot analyses, the purified polyclonal antibody recognized a specific signal with a molecular mass of Ϸ40 kDa in RL and HT lymphomas. This band corresponds to the estimated molecular mass of the GHRH receptor isoform encoded by SV 1. RT-PCR and ligand binding studies also revealed the expression of SV 1 and the presence of high-affinity binding sites for GHRH on RL and HT tumors. Because the antiserum developed recognizes the tumoral GHRH receptor protein encoded by SV 1, it should be of value in various investigations.splice variant ͉ growth hormone-releasing hormone receptor ͉ polyclonal antibody ͉ non-Hodgkin's lymphoma A ntagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of experimental human cancer cell lines xenografted into nude mice or cultured in vitro and are being developed for cancer therapy (1-4). To design still more potent antagonists, we have to fully understand their mechanism of action. GHRH antagonists suppress tumor growth through indirect and direct pathways. The indirect mechanism operates through a suppression of the growth hormone release from the pituitary and the resulting inhibition of the production of insulin-like growth factor I in the liver (1-11). However, the principal action of GHRH antagonists is probably exerted directly on tumors and appears to be mediated by specific receptors for GHRH antagonists on cancer cells (1-9, 11-13). Although the mRNA for GHRH and immunologically active GHRH were demonstrated in various human tumor cells, the mRNA for human pituitary GHRH receptor (GHRH-R) has not been detected on these tumor cells or any of the other cancer models (11,14,15).Because of the structural similarities between GHRH and vasoactive intestinal peptide (VIP), the receptors for VIP could be a target for the GHRH antagonists, but GHRH antagonists inhibit the proliferation of MiaPaCa-2 human pancreatic tumor cells, which do not express the receptors for VIP (13). Moreover, in LNCaP human prostatic carcinoma cells, which are positive for the VIP receptors, GHRH antagonists inhibit tumor growth more powerfully than the antagonists of VIP (1...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 90%

Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

Toller

Horváth

Schally

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…This method consisted of two consecutive PCR reactions that could accomplish the amplification of cDNA for all four SVs at the sizes of 720, 566, 390, and 335 bp corresponding to SV1, SV2, SV3, and SV4, respectively (18,22,23). Even though SV1 is the only SV of GHRH-R that was proven to respond physiologically to GHRH binding (31,32), we recently established a protocol that could detect the expression of each SV separately, without using the method of nested PCR. Nonetheless, our main objective was to determine whether the mRNA and protein for the pGHRH-R could be expressed in some tumor tissues.…”

Section: Discussionmentioning

confidence: 99%

The expression of the pituitary growth hormone-releasing hormone receptor and its splice variants in normal and neoplastic human tissues

Havt

Schally

Halmos

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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Various attempts to detect human pituitary growth hormonereleasing hormone receptor (pGHRH-R) in neoplastic extrapituitary tissues have thus far failed. Recently, four splice variants (SVs) of GHRH-R have been described, of which SV1 has the highest structural homology to pGHRH-R and likely plays a role in tumor growth. The aim of this study was to reinvestigate whether human tumors and normal human extrapituitary tissues express the pGHRH-R and to corroborate our previous findings on its SVs. Thus, we developed a real-time PCR method for the detection of the mRNA for the pGHRH-R, its SVs, and the GHRH peptide. Using real-time PCR, Western blotting, and radioligand-binding assays, we detected the mRNA for pGHRH-R and pGHRH-R protein in various human cancer cell lines grown in nude mice and in surgical specimens of human lung cancers. The expression of mRNA for SVs of pGHRH-R and GHRH was likewise found in xenografts of human non-Hodgkin's lymphomas, pancreatic cancer, glioblastoma, smallcell lung carcinomas, and in human nonmalignant prostate, liver, lung, kidney, and pituitary. Western blots showed that these normal and malignant human tissues contain SV1 protein and immunoreactive GHRH. Our results demonstrate that some normal human tissues and tumors express mRNA and protein for the pGHRH-R and its splice variants. These findings confirm and extend the concept that GHRH and its receptors play an important role in the pathophysiology of human cancers.

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“…mRNAs encoding four splice variants (SV) of GHRH receptors and specific high affinity binding sites for GHRH and its antagonistic analogs have been identified in diverse cell lines and specimens of human cancers [19,20,24,25,28,29,31,[33][34][35][36]. These findings suggest that the direct antiproliferative action of GHRH antagonists could be exerted through the disruption of an autocrine/paracrine stimulatory loop formed by tumoral GHRH and its receptors on tumors [14,19,20,28,29,35,37,38].…”

Section: Introductionmentioning

confidence: 99%

Triple-negative breast cancers express receptors for growth hormone-releasing hormone (GHRH) and respond to GHRH antagonists with growth inhibition

Köster

Engel

Schally

et al. 2008

Breast Cancer Res Treat

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

Cited by 74 publications

References 34 publications

Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

The expression of the pituitary growth hormone-releasing hormone receptor and its splice variants in normal and neoplastic human tissues

Triple-negative breast cancers express receptors for growth hormone-releasing hormone (GHRH) and respond to GHRH antagonists with growth inhibition

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