| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Original Studies |
Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, and the Department of Medicine (Z.K., J.M.A., V.J.C., K.G., A.V.S.), Section of Gynecologic Oncology, Tulane Cancer Center (W.R.R.), Tulane University School of Medicine, New Orleans, Louisiana 70112; and the Department of Medicine, University of Illinois (R.D.K.), Chicago, Illinois 60612
Address all correspondence and requests for reprints to: Dr. Andrew V. Schally, Veterans Administration Medical Center, 1601 Perdido Street, New Orleans, Louisiana 70112-1262.
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
GHRH exerts important biological actions on germ cell maturation and hormone production in ovary and testis. GHRH gene expression (14), GHRH peptide production (15, 16), and functional receptors for GHRH have been demonstrated in these organs (17, 18). These data implicate GHRH as an intragonadal regulatory factor. Gene expression for both GHRH and GHRH receptor was detected in various rat tissues using the RT-PCR method (19).
Frohman and Szabo were the first to demonstrate ectopic production of GHRH by carcinoid and pancreatic cell tumors in 1981 (reviewed in Ref. 20). Subsequently, two groups isolated GHRH from human pancreatic tumors that caused symptomatic acromegaly (21, 22). Since 1981, GHRH has been demonstrated in many tumors arising from and composed of peptide hormone-producing endocrine cells. Carcinoid tumors, tumors of the gut, pancreatic islet cell tumors, medullary cancers of the thyroid, pheochromocytomas, and even some small cell lung carcinomas can produce GHRH, which sometimes significantly contributes to elevated serum bioactive GHRH levels resulting in GH overproduction (7, 20). In addition, endometrial cancers have been shown to exhibit a significant amount of GHRH immunoreactivity in the absence of clinical acromegaly (20). A set of malignant tumors of various origins contained detectable levels of immunoreactive GHRH, leading to the conclusion that although they may produce large amounts of GHRH, this does not always lead to acromegaly (9). Studies of GHRH mRNA expression and GHRH production in normal human breast tissues and cancer samples showed that normal and tumoral tissues can express the peptide and also release it in a significant amount (23). These observations raise the question of whether tumors produce a biologically active form of GHRH.
In the present study, to clarify the pathophysiological significance of GHRH in tumors, we investigated the expression of the GHRH gene in human breast, ovarian, and endometrial cancers obtained after surgery or grown in nude mice and determined whether biologically and immunologically active GHRH was present.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Twenty-two endometrial cancer specimens and 22 ovarian cancer specimens were collected at the time of initial surgical treatment at Tulane Medical Center and Medical Center of Louisiana (New Orleans, LA). The local institutional (Tulane and Louisiana State University) review board has approved the collection and use of these specimens for the current analysis. The uterine specimens were taken from the surgical field after resection and were opened with a scalpel to expose the endometrial cavity, and grossly visible endometrial tumor samples approximately 1 cm3 in size were excised with the scalpel. Samples of similar size were obtained from primary ovarian malignant tumors in the surgical field by sharp excision. All samples were flash-frozen in liquid nitrogen and stored at -70 C until analysis was performed. Histological sections of each sample were examined to confirm the presence of malignant tumor with minimal admixed nonmalignant tissue. Samples with significant amounts of nonmalignant tissue were not used. All histological slides were examined by Tulane pathologists and reviewed by one of us (W.R.R.) to confirm the diagnosis.
Clinicopathological data (Tables 1
and 2) were compared to GHRH mRNA levels
determined by the RT-PCR method. Statistical analysis was performed
using Student’s t test.
|
|
Estrogen-independent human breast cancer cell lines MDA-MB-231 and MDA-MB-468, estrogen-dependent human breast cancer cell lines ZR-75–1 and T-47-D, human endometrial cancer cell line HEC-1-A, and human ovarian cancer cell line OV-1063 were obtained from the American Type Culture Collection (Manassas, VA). The estrogen-independent, but sensitive, human mammary cancer cell line MCF-7-MIII was provided by Dr. R. Clarke (Georgetown University Medical Center, Washington DC). Tumors were initiated by sc injection of the respective cell line into the flanks of female athymic (NCR/c nu/nu) nude mice obtained from the NCI (Frederick, MD) and were maintained by transplantation. Hormone-independent doxorubicin-resistant human mammary cancer xenograft MX-1 originating from surgical explant (NCI-Frederick Cancer and Development Center, Frederick, MD) was grown in nude mice. Tumors weighing 0.4–0.6 g were removed, immediately snap-frozen in liquid nitrogen, and stored at -70 C until use.
RT-PCR and Southern blot
Total RNA was extracted from tissues using the RNA Isolation Kit (Stratagene, La Jolla, CA) and was quantified spectrophotometrically at 260 nm. Three micrograms of total RNA were reverse transcribed with 200 U Superscript II ribonuclease H- reverse transcriptase (Life Technologies, Grand Island, NY) according to the manufacturer’s instructions. PCR for GHRH was carried out in a final volume of 100 µL containing 20 mmol/L Tris-HCl (pH 8.8), 10 mmol/L KCl, 10 mmol/L (NH4)2SO4, 2 mmol/L MgSO4, 1% Triton X-100, 1 mg/mL nuclease-free BSA, 2.5 U Taq Extender PCR Additive (Stratagene), 200 µmol/L of each deoxy-NTP (Stratagene), and primers at a concentration of 0.3 µmol/L each, and 2.5 U Taq 2000 (Stratagene) were added after 5 min of denaturation at 94 C in a thermal cycler (Stratagene). Primers were designed according to the sequence of the human GHRH (hGHRH) gene (24) as follows: sense, 5'-ATT TGA GCA GTG CCT CGG AG (nucleotides 30–49); and antisense, 5'-TTT GTT CTG CCC ACA TGC TG (nucleotides 331–350). Then, 40 cycles of PCR were performed using the following step program: 94 C for 30 s, 60 C for 30 s, and 72 C for 1 min, with a final 7-min extension at 72 C. PCR products were separated by electrophoresis on 1.5% agarose gel and visualized by ethidium bromide staining on an UV transilluminator.
RNA from liver tissue of MT-hGHRH transgenic mice developed as previously described (1) served as a positive control. RT without reverse transcriptase and PCR without complementary DNA (cDNA) were performed to test the possibilities of genomic DNA contamination and cross-contamination of the samples, respectively.
Determination of the expression of the ß-actin gene served as an internal control for the amount of RNA template in each RT-PCR aliquot. For the detection of human or mouse ß-actin, mRNA primers and conditions were used as previously described (25, 26).
GHRH PCR products were transferred to a nylon membrane (Hybond N+, Amersham, Arlington Heights, IL), and the DNA was linked onto it by baking. Blots were prehybridized in a buffer containing 4 x SSC (standard saline citrate) buffer, 2.5 x Denhardt’s solution (Sigma Chemical Co., St. Louis, MO), 0.1% SDS, 5 mmol/L ethylenediamine tetraacetate, and 0.1 mg/mL denatured salmon sperm DNA (Sigma Chemical Co.) at 50 C for 4 h. Blots were hybridized with 100 ng 32P 5'-end-labeled oligonucleotide probe specific for GHRH at 50 C for 16 h in a hybridization buffer containing 5 x SSC, 0.5 x Denhardt’s solution, 0.02 mol/L Tris-HCl, and 0.1 mg/mL sonicated salmon sperm DNA. The probe was designed according to the sequence of the hGHRH cDNA (24) as follows: 5'-GAC CCT CAG GAT GCG GCG GTA TGC AGA TGC (nucleotides 166–195). It was radiolabeled in a reaction mixture of 200 ng oligonucleotide DNA, 8 µL [32P]ATP 3000 Ci/mL, 10 mCi/mmol, and 10 U T4 polynucleotide kinase (Amersham). After incubation at 37 C for 1 h, the reaction was terminated by adding 2 µL 0.5 mol/L ethylenediamine tetraacetate. Unincorporated radioactivity was separated using a Nuctrap column (Stratagene). After hybridization, blots were washed under stringent conditions and were exposed to Biomax MS Kodak film (Eastman Kodak Co., Rochester, NY) for exposure times of 2 h to 3 days at -70 C.
RIA for GHRH
Three different human cancer xenografts (ZR-75–1, MX-1, and MCF-7-MIII) and three human endometrial cancer specimens were used for studying GHRH contents by RIA. Tissues were homogenized in 2 mol/L acetic acid supplemented with protease inhibitors (1 mg/100 mL phenylmethylsulfonylfluoride, 200 µg/100 mL Trasylol, and 200 µg/100 mL pepstatin) with an Ultra-Turrax tissue homogenizer (IKA, SE, Wilmington, NC) on ice. The homogenates were placed in a boiling water bath for 10 min and then centrifuged at 10,000 x g for 10 min. The supernatants were lyophilized and subsequently dissolved in RIA buffer.
GHRH was measured using [125I]GHRH-(1–40) (Bachem, Torrance, CA) as labeled hormone and anti-GHRH-(1–40) (SV-95) antibody generated in our laboratory in a final dilution of 1:70,000, which cross-reacts 100% with GHRH-(1–29) as described previously (27). GHRH(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)NH2 was used as a standard. The range of the standard curve was 0.025–50 ng/tube (bound/free ratio, 23%; nonspecific binding, 4.3%). The inter- and intraassay coefficients of variation were 11.5% and 7.8%, respectively.
In vitro GHRH bioactivity of tumor extracts
For studying GHRH bioactivity, three human breast cancer ZR-75–1 xenografts, weighing a total of 1.4 g, were minced while frozen and placed immediately in boiling water for 10 min to inactivate the proteases. Acetic acid was then added to a final concentration of 2 mol/L, and the tissue was homogenized and stirred for 30 min at 4 C. The homogenate was centrifuged at 10,000 x g for 10 min. The supernatant was passed through a Mega Bond ElutR C8 cartridge (12 cc, 2 g; Varian, Walnut Creek, CA) previously equilibrated with 2 mol/L acetic acid. Thereafter, the column was washed with 2 mol/L acetic acid and eluted with 70% aqueous acetonitrile. Acetonitrile was evaporated, and the aqueous solution was lyophilized.
The purified extract of ZR-75–1 cells was tested for GHRH bioactivity in a dispersed rat pituitary superfusion system. The details of this method have been described previously (28). Briefly, anterior pituitary fragments from young male Sprague-Dawley rats (150–250 g BW) were digested with collagenase for 50 min followed by gentle mechanical dispersion. The cell clusters were mixed with Sephadex G-10 and loaded on superfusion columns. Medium 199 supplemented with 0.1% BSA, 50 mg/L penicillin G, and 87 mg/L gentamicin was perfused through the columns at a speed of 20 mL/h. After an overnight recovery period, the cells were exposed periodically to test compounds dissolved in fresh medium immediately before application. Three-minute stimulations were performed with 0.2, 0.5, and 1 nmol/L GHRH-(1–29)NH2 (DOB-2–048-1, synthesized in our laboratory); a mixture of 1 nmol/L GHRH-(1–29) and 20 nmol/L somatostatin (SS-14), and 25 mmol/L KCl. One-milliliter fractions were collected from the effluent medium for subsequent GH assay. In a separate experiment, stimulations with 1 nmol/L GHRH-(1–29), 1 nmol/L vasoactive intestinal peptide (VIP; California Peptide Research, Inc., Napa, CA), and the mixture of 1 nmol/L GHRH-(1–29) and 1 nmol/L VIP were performed in a set-up similar to that described above.
The rat GH (rGH) content of the collected fractions was determined by RIA using materials provided by Dr. A. F. Parlow, National Hormone and Pituitary Program, NIDDK (Torrance, CA; rGH-RP-2/AFP/3190B, rGH I-6/AFP-5676B, and anti rGH-RIA-5/AFP-411S). RIA results were analyzed as previously described (28).
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
RT of RNA from liver tissue of MT-hGHRH transgenic mice, followed
by PCR amplification with specific primers for GHRH, produced a
fragment of the expected size of 322 bp as seen under UV light after
ethidium bromide staining. A PCR product of the same size could be
observed in 15 of 22 endometrial cancers (Fig. 1A), 12 of 22 ovarian cancers (Fig. 2A), 5 of 6 human breast cancer xenografts,
and also in OV-1063 ovarian cancer and HEC-1-A endometrial cancer
xenografts (Fig. 3A). Southern blotting with
a specific radiolabeled oligonucleotide probe demonstrated that the
322-bp fragment was the genuine transcript of the GHRH gene. Southern
blotting also revealed additional tumors that expressed GHRH. Sixteen
of 22 endometrial (Fig. 1B) and 16 of 22 ovarian cancer samples (Fig. 2B) could be demonstrated to contain GHRH mRNA after 3 h of film
exposure time. Longer film exposure (3 days) revealed an additional
endometrial and an ovarian cancer sample with a positive GHRH signal
(not shown). GHRH message could not be detected in 5 endometrial and 5
ovarian cancer specimens even after extended exposure times. All of the
human cancer xenografts investigated expressed the GHRH gene. Human
breast cancer xenograft ZR-75–1 had the strongest GHRH signal (Fig. 3). In the case of MCF-7-MIII tumor, a GHRH signal could only be
verified after 3 days of exposure (not shown).
|
|
|
GHRH RIA
RIA was performed on acid extracts of three human breast cancer
xenografts and three endometrial cancer specimens. All samples
contained variable, but measurable, amounts of immunoreactive GHRH
(Table 3). No cross-reactivity was
observed with VIP, eliminating the possibility that the
immunoreactivity was due to this peptide related to GHRH.
|
Dispersed rat pituitary cells were stimulated with KCl,
GHRH-(1–29), a combination of GHRH-(1–29) and SS, and the purified
extract of ZR-75–1 breast cancer xenografts (dissolved in 2.5 mL
medium) in the superfusion system. Pulsatile stimulation with the
tissue extract induced a significant, transitory elevation of GH in the
effluent medium similar in shape to that following the stimulation with
GHRH-(1–29). Based on the size of the net integral response (area
under the curve above the baseline), the GH-releasing potency of the
extract was similar to that of 2–3 nmol/L GHRH-(1–29). GHRH
immunoreactivity in this extract and in the 2 nmol/L standard were the
same, as determined by RIA. During the infusion of the tumor extract
(Fig. 4, black column), there was
a significant increase in GH release in contrast to the absence of
effects observed during simultaneous GHRH and SS-14 infusion,
indicating that a significant quantity of SS-14 was not contained in
the tumor extract (Fig. 4). In our system, stimulation with 1 nmol/L
VIP evoked a GH response amounting to 1/10th that induced by equimolar
concentration of GHRH-(1–29), and when VIP was added together with
GHRH, there was an additive effect on the GH response.
|
No significant correlation was found between GHRH mRNA levels in human cancer specimens and the clinicopathological data, such as histological grade of the tumor, tumor stage, and clinical outcome of the disease (Tables 1 and 2).
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The fact that the relative level of expression of mRNA for GHRH did not correlate with GHRH content is of interest. Although GHRH could be detected by RIA in all of the samples tested for protein translation, GHRH contents did not always reflect GHRH mRNA levels. These data are in accordance with the observation that GHRH secretion by human breast cancer samples in a perfusion system did not correspond to their GHRH contents (23). Moreover, higher release was inversely correlated to GHRH tissue contents (23). These apparent differences could be due to tumor heterogeneity, because we used different parts of the tumor in the case of human specimens and different individual tumors in the case of xenografts for molecular biology and biochemical determinations. Other possible explanations for this dichotomy could include tissue-specific rates of degradation of mRNA for GHRH and GHRH peptide or an asynchronism in gene expression and protein translation, which has been observed in other endocrine systems (30).
Superfusion studies revealed that the potency of the GHRH purified from ZR-75–1 human breast cancer xenografts was equivalent to 2–3 nmol/L GHRH-(1–29) in tests on GH release from dispersed rat pituitary cells. This result is in good correlation with the concentration of GHRH in the tissue extract determined by RIA. These findings indicate that most of the GHRH produced is bioactive. VIP has also been suggested to be an autocrine growth factor in breast cancer (31), raising the possibility that the presence of VIP could contribute to the response seen in our superfusion system. However, we found that equimolar concentrations of VIP evoked significantly lower GH release from rat pituitary cells, about 1 order of magnitude less than that caused by GHRH. This is consistent with a report on cultured bovine hypophysial cells, where VIP was much less potent in releasing GH than GHRH (32). These results taken together with the findings that VIP does not cross-react in our GHRH RIA and a good agreement between GHRH detected by RIA and superfusion indicate that VIP could only contribute to a minor degree, if at all, to the GH-releasing activity of tumor extracts. In addition, the purification procedure used makes it unlikely that small molecules such as monoamines and amino acids that are able to provoke a GH response were present in the purified fractions eluted with 70% acetonitrile that were used in our studies. Our work supports the view that GHRH mRNA detected in ZR-75–1 breast cancer xenografts could serve as a template for the synthesis of GHRH in the tumor, which we detected biologically in superfusion system and immunologically by RIA. Moreover, the size and specificity of the PCR product, the immunoreactivity of the peptide product, and its high bioactivity make it likely that GHRH detected in the cancer samples studied is similar or identical to GHRH of hypothalamic origin.
The human breast cancer cell line ZR-75–1 (33), human mammary tumors,
and normal tissues (23) have been shown to produce SS. SS is also
present in neuroendocrine tumors (29). As SS is a powerful inhibitor of
GHRH-induced GH release, the possibility existed that the actions of
GHRH in our superfusion system could have been antagonized by locally
produced SS. However, we have previously demonstrated that the
GH-releasing effect of GHRH is detected despite the presence of large
amounts of SS during stimulation (28), which may be explained by the
fact that in the superfusion system the inhibitory effect of SS
disappears immediately after exposure of cells to the test material is
stopped, whereas the effect of GHRH becomes evident. The response to
the ZR-75–1 tumor extract in Fig. 4
shows that the amounts of SS-like
bioactivity present in our purified extract were too low to affect our
results.
The types of cells in the tumor that produce GHRH have not been identified. It is known that lymphocytes can infiltrate the tumors, and lymphocytes have been reported to produce GHRH (12). However, we do not believe that the primary source of GHRH is immune cells, because mRNA for hGHRH and peptide were detected in human cancer xenografts in which stromal cells of human origin are not present, thus supporting the view that the GHRH-producing capability of these tumors originated within the cancer cells themselves.
Under physiological conditions, GHRH in the hypophyseal portal blood may be in a high (nanomolar) range depending on its pulsatile release, whereas GHRH immunoreactivity in the peripheral plasma is low or undetectable (34, 35). Many factors contribute to the rapid clearance of GHRH. Firstly, GHRH produced in the hypothalamus and released into the portal circulation is diluted at least 100-fold after perfusing the pituitary (35). Secondly, GHRH is rapidly inactivated in the circulation due to proteolytic cleavage by plasma dipeptidylpeptidase IV. After bolus iv injection, a substantial portion of GHRH-(1–44) is converted to a biologically inactive form [GHRH-(3–44)] within 1 min while it remains fully immunoreactive (36). The findings reported in the literature together with our results indicate that GHRH expression could be quite common in cancer. A rapid breakdown of GHRH in the circulation also favors its exclusive local intratumoral role, which should be distinguished from the rare cases of clinical acromegaly caused by ectopic GHRH secretion.
Our laboratory has previously demonstrated that blockade of GHRH action by potent antagonistic analogs of GHRH can powerfully inhibit the growth of various human tumors xenografted into nude mice (reviewed in Ref. 37). Thus, administration of GHRH antagonists MZ-4–71 and/or MZ-5–156 suppressed the growth of Caki-I renal adenocarcinoma (38), SK-ES-1 and MNNG/HOS osteosarcomas (39), PC-3 and DU-145 prostate cancers (40), and H-69 small cell and H-157 nonsmall cell lung carcinomas (41). Our results also indicate that GHRH antagonists can also inhibit the proliferation of human colorectal, pancreatic, and mammary cancers xenografted into nude mice and MXT hormone-independent breast cancers in BDF mice (unpublished data). The antiproliferative effects of GHRH antagonists could be based on several mechanisms. By inhibiting GH release, GHRH antagonists decrease the secretion of insulin-like growth factor I (IGF-I) by the liver and other tissues, which may lead to tumor growth inhibition. GHRH antagonists also decrease the growth of IGF-I- and/or IGF-II-dependent cancers by lowering autocrine or paracrine IGF-I and IGF-II production in tumors (37). The inhibition of IGF-II production and growth of DU-145 prostate cancers in mice treated with MZ-5–156 was linked to a reduction in the expression of mRNA for IGF-II in tumors (42). GHRH antagonists could exert some of these effects directly by blocking the effects of locally produced GHRH. The relevance of the latter mechanism is supported by the study of Benlot et al. (23), who showed that although there is no significant difference in mRNA expression for GHRH or tissue GHRH content between normal breast tissue and breast cancer, tumor samples released significantly more GHRH than normal samples during both static incubation and perfusion. It was speculated from these data that GHRH hypersecretion might represent a major disorder in breast cancer, leading to enhanced epithelial proliferation (23). Thapar et al. found a large number of somatotroph pituitary tumors in which overexpression of the GHRH gene was associated with neoplastic progression and clinical aggressiveness, reflecting the undifferentiated nature of the tumor (43).
To prove the pathophysiological significance of GHRH in tumorigenesis, demonstration of its specific receptors on tumors is required. GHRH receptor mRNA identical to that in the pituitary is found in the placenta, testis, ovary, and kidney, all of which also express GHRH (16, 19, 44, 45). GHRH receptor gene expression was also found in many other extrapituitary organs, although at lower levels (19). At present, GHRH receptors in tumor tissue that mediate the response to GHRH are still unidentified. Alternately, other members of this receptor family, such as VIP and pituitary adenylate cyclase-activating peptide receptors, which have been found in tumors and are still able to bind and respond to GHRH, may mediate the actions of GHRH. This would be in accordance with the concept that there are multiple receptors for several peptides in this family, which, in addition to GHRH, includes glucagon, secretin, VIP, gastric inhibitory peptide, and pituitary adenylate cyclase-activating peptide. In fact, several members of the GHRH family and the simultaneous presence of their receptors mediating special paracrine functions have been shown in the testis (45).
In conclusion, this report demonstrates that human endometrial, ovarian, and breast cancers synthesize GHRH. These findings appear to provide a mechanistic basis for our previous observations that GHRH antagonists can inhibit the proliferation of various human cancers xenografted into nude mice. Collectively, these results suggest a possible pathophysiological role for GHRH and support the merit of further investigation of antagonistic analogs of GHRH as potential therapeutic agents.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 On leave of absence from the Department of Onkotherapy, A.
Szent-Györgyi University Medical School (Szeged, Hungary).
3 On leave of absence from the Department of Anatomy, University
Medical School (Pécs, Hungary).
Received July 15, 1998.
Revised November 2, 1998.
Accepted November 6, 1998.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
 |
|
 |
|
  V. Pandey, J. K. Perry, K. M. Mohankumar, X.-J. Kong, S.-M. Liu, Z.-S. Wu, M. D. Mitchell, T. Zhu, and P. E. Lobie Autocrine Human Growth Hormone Stimulates Oncogenicity of Endometrial Carcinoma Cells Endocrinology, August 1, 2008; 149(8): 3909 - 3919. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Buchholz, A. V. Schally, J. B. Engel, F. Hohla, E. Heinrich, F. Koester, J. L. Varga, and G. Halmos Potentiation of mammary cancer inhibition by combination of antagonists of growth hormone-releasing hormone with docetaxel PNAS, February 6, 2007; 104(6): 1943 - 1946. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Siriwardana, A. Bradford, D. Coy, and P. Zeitler Autocrine/Paracrine Regulation of Breast Cancer Cell Proliferation by Growth Hormone Releasing Hormone via Ras, Raf, and Mitogen-Activated Protein Kinase Mol. Endocrinol., September 1, 2006; 20(9): 2010 - 2019. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Havt, A. V. Schally, G. Halmos, J. L. Varga, G. L. Toller, J. E. Horvath, K. Szepeshazi, F. Koster, K. Kovitz, K. Groot, et al. The expression of the pituitary growth hormone-releasing hormone receptor and its splice variants in normal and neoplastic human tissues PNAS, November 29, 2005; 102(48): 17424 - 17429. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Keller, A. V. Schally, K. Groot, G. L. Toller, A. Havt, F. Koster, P. Armatis, G. Halmos, M. Zarandi, J. L. Varga, et al. Effective treatment of experimental human non-Hodgkin's lymphomas with antagonists of growth hormone-releasing hormone PNAS, July 26, 2005; 102(30): 10628 - 10633. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. B. Engel, G. Keller, A. V. Schally, G. L. Toller, K. Groot, A. Havt, P. Armatis, M. Zarandi, J. L. Varga, and G. Halmos Inhibition of Growth of Experimental Human Endometrial Cancer by an Antagonist of Growth Hormone-Releasing Hormone J. Clin. Endocrinol. Metab., June 1, 2005; 90(6): 3614 - 3621. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Szereday, A. V. Schally, J. L. Varga, C. A. Kanashiro, F. Hebert, P. Armatis, K. Groot, K. Szepeshazi, G. Halmos, and R. Busto Antagonists of Growth Hormone-Releasing Hormone Inhibit the Proliferation of Experimental Non-Small Cell Lung Carcinoma Cancer Res., November 15, 2003; 63(22): 7913 - 7919. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Kiaris, I. Chatzistamou, A. V. Schally, G. Halmos, J. L. Varga, H. Koutselini, and A. Kalofoutis Ligand-dependent and -independent effects of splice variant 1 of growth hormone-releasing hormone receptor PNAS, August 5, 2003; 100(16): 9512 - 9517. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Halmos, A. V. Schally, T. Czompoly, M. Krupa, J. L. Varga, and Z. Rekasi Expression of Growth Hormone-Releasing Hormone and Its Receptor Splice Variants in Human Prostate Cancer J. Clin. Endocrinol. Metab., October 1, 2002; 87(10): 4707 - 4714. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Busto, A. V. Schally, J. L. Varga, M. O. Garcia-Fernandez, K. Groot, P. Armatis, and K. Szepeshazi The expression of growth hormone-releasing hormone (GHRH) and splice variants of its receptor in human gastroenteropancreatic carcinomas PNAS, September 3, 2002; 99(18): 11866 - 11871. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Kiaris, A. V. Schally, R. Busto, G. Halmos, S. Artavanis-Tsakonas, and J. L. Varga Expression of a splice variant of the receptor for GHRH in 3T3 fibroblasts activates cell proliferation responses to GHRH analogs PNAS, January 1, 2002; (2002) 12590999. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Szepeshazi, A. V. Schally, P. Armatis, K. Groot, F. Hebert, A. Feil, J. L. Varga, and G. Halmos Antagonists of GHRH Decrease Production of GH and IGF-I in MXT Mouse Mammary Cancers and Inhibit Tumor Growth Endocrinology, October 1, 2001; 142(10): 4371 - 4378. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. Khorram, M. Garthwaite, and T. Golos The Influence of Aging and Sex Hormones on Expression of Growth Hormone-Releasing Hormone in the Human Immune System J. Clin. Endocrinol. Metab., July 1, 2001; 86(7): 3157 - 3161. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Chatzistamou, A. V. Schally, J. L. Varga, K. Groot, P. Armatis, R. Busto, and G. Halmos Antagonists of Growth Hormone-Releasing Hormone and Somatostatin Analog RC-160 Inhibit the Growth of the OV-1063 Human Epithelial Ovarian Cancer Cell Line Xenografted into Nude Mice J. Clin. Endocrinol. Metab., May 1, 2001; 86(5): 2144 - 2152. [Abstract] [Full Text]
|
|
|
|
|
|
P. Cassoni, M. Papotti, C. Ghè, F. Catapano, A. Sapino, A. Graziani, R. Deghenghi, T. Reissmann, E. Ghigo, and G. Muccioli Identification, Characterization, and Biological Activity of Specific Receptors for Natural (Ghrelin) and Synthetic Growth Hormone Secretagogues and Analogs in Human Breast Carcinomas and Cell Lines J. Clin. Endocrinol. Metab., April 1, 2001; 86(4): 1738 - 1745. [Abstract] [Full Text]
|
|
|
|
 |
|
 F. Beuschlein, C. J. Strasburger, V. Siegerstetter, D. Moradpour, P. Lichter, M. Bidlingmaier, H. E. Blum, and M. Reincke Acromegaly Caused by Secretion of Growth Hormone by a Non-Hodgkin's Lymphoma N. Engl. J. Med., June 22, 2000; 342(25): 1871 - 1876. [Full Text] [PDF]
|
|
|
|
|
|
R. D. Kineman Antitumorigenic actions of growth hormone-releasing hormone antagonists PNAS, January 18, 2000; 97(2): 532 - 534. [Full Text] [PDF]
|
|
|
|
|
|
H. Kiaris, A. V. Schally, J. L. Varga, K. Groot, and P. Armatis From the Cover: Growth hormone-releasing hormone: An autocrine growth factor for small cell lung carcinoma PNAS, December 21, 1999; 96(26): 14894 - 14898. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. J. Csernus, A. V. Schally, H. Kiaris, and P. Armatis Inhibition of growth, production of insulin-like growth factor-II (IGF-II), and expression of IGF-II mRNA of human cancer cell lines by antagonistic analogs of growth hormone-releasing hormone in vitro PNAS, March 16, 1999; 96(6): 3098 - 3103. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Kiaris, A. V. Schally, R. Busto, G. Halmos, S. Artavanis-Tsakonas, and J. L. Varga Expression of a splice variant of the receptor for GHRH in 3T3 fibroblasts activates cell proliferation responses to GHRH analogs PNAS, January 8, 2002; 99(1): 196 - 200. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z. Rekasi, T. Czompoly, A. V. Schally, and G. Halmos Isolation and sequencing of cDNAs for splice variants of growth hormone-releasing hormone receptors from human cancers PNAS, September 12, 2000; 97(19): 10561 - 10566. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
