Nesfatin-1 is an inhibitor of the growth hormone-insulin-like growth factor axis in goldfish (Carassius auratus)

Nesfatin-1, an 82 amino acid peptide cleaved from the N-terminal of its precursor nucleobindin-2 (NUCB2), is emerging as a multifunctional peptide in fish. The present study aimed to determine whether nesfatin-1 plays a role in fish somatic growth by modulating the growth hormone (GH)/insulin-like growth factor (IGF) axis, using a representative teleost model, the goldfish (Carassius auratus). The results demonstrated that a single i.p. injection of synthetic goldfish nesfatin-1 significantly decreased the expression of hypothalamic pacap (approximately 90%) and pituitary Gh (approximately 90%) mRNAs at 15 minutes post-injection. Serum GH levels were also reduced as a result of nesfatin-1 administration, by approximately 45% and 55% at 15 and 30 minutes post-injection, respectively. Likewise, in vitro treatment of goldfish dispersed pituitary cells with nesfatin-1 reduced Gh secretion, suggesting that nesfatin-1 acts directly on pituitary somatotrophs to inhibit Gh release. Exposure of cultured liver fragments to nesfatin-1 (0.1, 1 and 10 nmol L^-1 ) led to a significant reduction in igf-1 mRNA at 120 minutes and of igf-II mRNA at 30 and 60 minutes post-incubation. Collectively, these results indicate a suppressive role for nesfatin-1 on the goldfish GH/IGF axis. Immunohistochemical studies demonstrated that NUCB2/nesfatin-1-like immunoreactivity, although present in the goldfish pituitary, is not colocalised with GH in goldfish somatotrophs. Thus, nesfatin-1 does not appear to act in an autocrine manner to regulate GH secretion. Taken together, this research found that the pituitary gland is an important source of endogenous NUCB2/nesfatin-1 and also that nesfatin-1 directly suppresses the Gh/IGF axis in goldfish.

Curcumin suppresses renal carcinoma tumorigenesis by regulating circ-FNDC3B/miR-138-5p/IGF2 axis

Curcumin has a vital role in the development of renal carcinoma. Nevertheless, the mechanism of curcumin in renal carcinoma tumorigenesis remains largely unknown. Thirty renal carcinoma patients were recruited. Renal carcinoma cell lines CAKI-1 and ACHN were exposed to curcumin. The levels of circular RNA fibronectin type III domain-containing protein 3B (circ-FNDC3B), microRNA (miR)-138-5p and insulin-like growth factor 2 (IGF2) were detected via quantitative reverse transcription PCR or western blot. Cell proliferation and apoptosis were investigated via 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide, colony formation analysis, flow cytometry and western blot. Target association between miR-138-5p and circ-FNDC3B or IGF2 was analyzed via dual-luciferase reporter analysis. The function of curcumin in vivo was assessed via a xenograft model. circ-FNDC3B level was enhanced and miR-138-5p abundance was declined in renal carcinoma tissues and cells. Curcumin restrained renal carcinoma cell proliferation and promoted apoptosis. circ-FNDC3B overexpression or miR-138-5p knockdown weakened the influence of curcumin. circ-FNDC3B knockdown hindered cell proliferation and promoted apoptosis by increasing miR-138-5p. IGF2 was targeted via miR-138-5p and positively regulated via circ-FNDC3B. Curcumin decreased xenograft tumor growth via reducing circ-FNDC3B in vivo. Curcumin suppressed renal carcinoma tumorigenesis in vitro and in vivo via regulating circ-FNDC3B/miR-138-5p/IGF2 axis, proposing new insight into renal carcinoma tumorigenesis.

Estrogen Receptor-β Up-Regulates IGF1R Expression and Activity to Inhibit Apoptosis and Increase Growth of Medulloblastoma

Medulloblastoma (Med) is the most common malignant brain tumor in children. The role of ESR2 [estrogen receptor (ER)-β] in promoting Med growth was comprehensively examined in three in vivo models and human cell lines. In a novel Med ERβ-null knockout model developed by crossing Esr2(-/-) mice with cerebellar granule cell precursor specific Ptch1 conditional knockout mice, the tumor growth rate was significantly decreased in males and females. The absence of Esr2 resulted in increased apoptosis, decreased B-cell lymphoma 2 (BCL2), and IGF-1 receptor (IGF1R) expression, and decreased levels of active MAPKs (ERK1/2) and protein kinase B (AKT). Treatment of Med in Ptch1(+/-) Trp53(-/-) mice with the antiestrogen chemotherapeutic drug Faslodex significantly increased symptom-free survival, which was associated with increased apoptosis and decreased BCL2 and IGF1R expression and signaling. Similar effects were also observed in nude mice bearing D283Med xenografts. In vitro studies in human D283Med cells metabolically stressed by glutamine withdrawal found that 17β-estradiol and the ERβ selective agonist 2,3-bis(4-hydroxyphenyl)-propionitrile dose dependently protected Med cells from caspase-3-dependent cell death. Those effects were associated with increased phosphorylation of IGF1R, long-term increases in ERK1/2 and AKT signaling, and increased expression of IGF-1, IGF1R, and BCL2. Results of pharmacological experiments revealed that the cytoprotective actions of estradiol were dependent on ERβ and IGF1R receptor tyrosine kinase activity and independent of ERα and G protein-coupled estrogen receptor 1 (G protein coupled receptor 30). The presented results demonstrate that estrogen promotes Med growth through ERβ-mediated increases in IGF1R expression and activity, which induce cytoprotective mechanisms that decrease apoptosis.

Hippocampal Gene Expression Is Highly Responsive to Estradiol Replacement in Middle-Aged Female Rats

In the hippocampus, estrogens are powerful modulators of neurotransmission, synaptic plasticity and neurogenesis. In women, menopause is associated with increased risk of memory disturbances, which can be attenuated by timely estrogen therapy. In animal models of menopause, 17β-estradiol (E2) replacement improves hippocampus-dependent spatial memory. Here, we explored the effect of E2 replacement on hippocampal gene expression in a rat menopause model. Middle-aged ovariectomized female rats were treated continuously for 29 days with E2, and then, the hippocampal transcriptome was investigated with Affymetrix expression arrays. Microarray data were analyzed by Bioconductor packages and web-based softwares, and verified with quantitative PCR. At standard fold change selection criterion, 156 genes responded to E2. All alterations but 4 were transcriptional activation. Robust activation (fold change > 10) occurred in the case of transthyretin, klotho, claudin 2, prolactin receptor, ectodin, coagulation factor V, Igf2, Igfbp2, and sodium/sulfate symporter. Classification of the 156 genes revealed major groups, including signaling (35 genes), metabolism (31 genes), extracellular matrix (17 genes), and transcription (16 genes). We selected 33 genes for further studies, and all changes were confirmed by real-time PCR. The results suggest that E2 promotes retinoid, growth factor, homeoprotein, neurohormone, and neurotransmitter signaling, changes metabolism, extracellular matrix composition, and transcription, and induces protective mechanisms via genomic effects. We propose that these mechanisms contribute to effects of E2 on neurogenesis, neural plasticity, and memory functions. Our findings provide further support for the rationale to develop safe estrogen receptor ligands for the maintenance of cognitive performance in postmenopausal women.

Changes in insulin like growth factors, myostatin and vascular endothelial growth factor in rat musculus latissimus dorsi by poly-3-hydroxybutyrate implants

The present study aimed at researching the synergistic effect between an ectopic bone substitute and surrounding muscle tissue. To describe this effect, changes of insulin like growth factors (IGF1, IGF2), myostatin (GDF8) and vascular endothelial growth factor (VEGF) mRNA content of 12 Wistar-King rats musculus latissimus dorsi with implanted poly-3-hydroxybutyrate (PHB) scaffold were examined after 6 and 12 weeks. At each time interval six rats were killed and implants and surrounding tissues prepared for genetic evaluation. Eight rats without any implants served as controls. RNA was extracted from homogenized muscle tissue and reverse transcribed. Changes in mRNA content were measured by Real-Time PCR using specific primers for IGF1, IGF2, GDF8 and VEGF. Comparing the level of VEGF mRNA in muscle after 6 and 12 weeks to the controls, we could assess a significant increase of VEGF gene expression (p<0.05) whereas the level of mRNA expression was higher after 6 than after 12 weeks of treatment. Expression of IGF1 gene was also significantly increased as compared to the controls over the observed period of time (p<0.05). In the case of the IGF2 gene, the expression was significantly elevated after 6 weeks (p<0.05), but not significantly increased after 12 weeks (p>0.05). We observed a significantly decreased GDF8 gene expression (p<0.05) both after retrieval of implants after 6 as well as after 12 weeks. Moreover, mRNA level of GDF8 after 6 and 12 weeks were comparable the same. Our results show that PHB implants in rat musculus latissimus dorsi interact with the surrounding muscle tissue. This interaction works itself on growth potential of the muscle.

Role of nonessential amino acids on porcine embryos produced by parthenogenesis or somatic cell nuclear transfer

Amino acids play a multitude of roles during early embryonic development and have been demonstrated to facilitate improved development of in vivo or in vitro fertilized and parthenogenetic embryos in several species. However, review of emerging literatures, shows that culture milieu of cloned embryos might be different from those of in vitro fertilized embryos. This study therefore, evaluated the effect of nonessential amino acids (NEAA) on yield and quality of porcine embryos produced by somatic cell nuclear transfer (SCNT) and compared them with parthenogenetic embryos as control. Analysis showed that, supplementation of NEAA to culture medium significantly improved the blastocyst rate of parthenogenetic (38.9 +/- 8.8 vs. 27.5 +/- 9.0%) as well as SCNT (22.5 +/- 2.2 vs. 13.8 +/- 3.4%) embryos although cleavage rates were not different (P < 0.05). These blastocysts also had higher hatching ability and contained higher cell number than control blastocysts (P < 0.05). TUNEL labeling revealed that blastocysts cultured in the presence of NEAA were less predisposed to biochemical apoptosis and showed lower indices of TUNEL, fragmentation, and total apoptosis than those cultured in the absence of NEAA (P < 0.05). Real-time qRT-PCR analysis further revealed that NEAA decreased the expression ratio of BAX:BCL-xL and enhanced the relative abundance of IGF2 transcripts. Therefore, our study suggests that NEAA improves the yield and quality of cloned porcine embryos by enhancing blastocyst expansion, hatching, and total cell number and decreasing the apoptosis by positively modulating the expression of embryo survival related genes, similar to those reported for in vivo or in vitro fertilized embryos. Nonessential amino acids improve the yield and quality of cloned and parthenogenetic porcine embryos and modulate the expression of embryo survival related genes.

Biologic study of the effects of octreotide-LAR on growth hormone in unresectable and metastatic hepatocellular carcinoma

BACKGROUND

Animal models suggest that growth hormone participates in hepatocarcinogenesis.

OBJECTIVE

To correlate the effect of octreotide long-acting release (LAR) on insulin-like growth factor-I (IGF-I) and -II (IGF-II) with response and survival in patients with unresectable and metastatic hepatocellular carcinoma.

METHODS

We conducted a phase II, single-institution trial of octreotide-LAR (30 mg intramuscularly every 4 weeks) in 15 patients while monitoring serum IGF-I and -II levels.

RESULTS

Patients (median CLIP score 2, Okuda stage II, and ECOG performance status 1) were treated for a median of 2.0 cycles. No responses occurred. Median overall survival was 116 days (range, 27-937 days) and median progression-free survival was 60 days (range, 27-444 days). One patient had prolonged stable disease (16 months). There were no grade 4 and four grade 3 toxicities: abdominal cramping, elevated creatinine, diarrhea, and dyspnea. Median serum IGF-I decreased from baseline (42.2 ng/mL; range, 14.2-109 ng/mL) to day 29 (27.9 ng/mL; range, 5.7-71.1 ng/mL), and median serum IGF-II decreased from baseline (25,000 ng/mL; range, 12,400-93,600 ng/mL) to day 29 (18,400 ng/mL; range, 4,061-79,400 ng/mL; 2-sided P<.006 and P<.04, respectively; Wilcoxon signed rank test). This suppression did not correlate with clinical activity. Baseline serum IGF-I >30 ng/mL was associated with greater progression-free survival and overall survival (P=.0005 and P=.0173, respectively; 2-sided log-rank test).

CONCLUSIONS

Octreotide-LAR lowered serum IGF-I and -II levels; however, this lowering did not correlate with clinical activity. There were no responses, and progression-free survival and overall survival were similar to historical patients not on treatment. Baseline serum IGF-I predicted prognosis.

Complex Interactions Between Hypoxia Inducible Factors, Insulin-Like Growth Factor-II and Oxygen in Early Murine Trophoblasts

The human first trimester placenta experiences a low oxygen environment. The hypoxia inducible factors (HIFs) mediate the response to low oxygen, inducing genes such as insulin-like growth factor (IGF)-II. Interestingly, IGF-II has been shown to promote placental growth and function. Currently, the interaction between oxygen, IGF-II and HIFs in the regulation of trophoblast behaviour are unclear. Murine implantation sites from days 5.5-10.5 were collected for immunohistochemical analyses. Use of the hypoxia marker pimonidazole indicated that the early mouse implantation site is exposed to low oxygen levels similar to those seen in the early human placenta. HIF-1alpha protein immunostaining was also observed in the implantation site. Culturing murine ectoplacental cones in decreasing oxygen concentrations (20%, 5% and 1% O(2)), either with or without the addition of IGF-II, induced complex responses by trophoblasts in terms of their migration and differentiation. Following 3 days exposure to low oxygen there was reduced EPC outgrowth, reduced Igf2 and increased Tpbp mRNA levels, suggesting commitment to the spongiotrophoblast lineage. In addition, Hif-1alpha mRNA levels were decreased, whilst Hif-2alpha mRNA was unchanged. This decrease in Hif-1alpha may be due to the observed increase in antisense (as) Hif-1alpha mRNA levels in 1% cultures. Furthermore, expression of Hif-2alpha and the HIF target genes: asHif-1alpha, Vegf and Slc2a1 were reduced under low oxygen with the addition of IGF-II. In conclusion, Hif-1alpha and Hif-2alpha are differentially regulated by oxygen and IGF-II in cultured trophoblast cells and asHif-1alpha may mediate the response to prolonged hypoxia in murine trophoblasts.

Protective effects of mycosporine-like amino acids of Synechocystis sp. PCC 6803 and their partial characterization

In this work, mycosporine-like amino acids (MAAs) of Synechocystis sp. PCC 6803 were characterized and were investigated on UV induction and protective ability. High performance liquid chromatographic (HPLC) studies revealed three major compounds in the MAAs. By UV absorption and mass spectra analysis, one of the compounds was tentatively identified as mycosporine-tau (M-tau). One novel compound similar to usujirene was tentatively named as dehydroxylusujirene, and the other novel compound was named as M-343 according to its absorption maximum. In vivo experiments indicated that M-tau was induced by both UV-A and UV-B, while dehydroxylusujirene and M-343 were only induced by UV-A, suggesting that different chromophores were involved in MAAs synthesis in Synechocystis sp. PCC 6803. It was also indicated that M-343 could be photochemically synthesized from some precursors. Under both UV and oxidation stresses, M-343 was more stable than dehydroxylusujirene and M-tau. Considering the reaction with H2O2, M-tau and dehydroxylusujirene might be potential antioxidants in reaction with physiological reactive oxygen species in vivo. In protection experiments, the MAAs exhibited efficient protective ability towards UV-B and H2O2 stresses, with maximal protection rates of 30% and 21.5%, respectively. These results indicate that the MAAs in Synechocystis sp. PCC 6803 act as both UV-screen and antioxidant.

Growth factors, glucose and insulin kinetics after low dose growth hormone therapy in HIV-lipodystrophy

OBJECTIVES

Low-dose growth hormone (GH) administration has been suggested as a treatment for HIV-lipodystrophy.

METHODS

Postglucose GH-secretion, kinetics of insulin-like growth factors (IGFs), insulin, and glucose metabolism were examined in six male HIV-infected lipodystrophic patients (two normal-weight patients with normal glucose-tolerance (NGT), two normal-weight with impaired glucose-tolerance (IGT), and two obese patients with diabetes (DM)) during a 16 weeks open-labelled pilot-study of low-dose GH, 0.7 mg/day.

RESULTS

DM, compared to NGT and IGT, displayed an impaired rebound of GH during a 5h oral glucose-tolerance test. Near lower normal limits in all patients before GH-therapy, total and free IGF-I increased between 87 and 152% during the GH-therapy (P<0.001), approaching upper normal limits in all patients with the highest incremental percentages shown in DM. A slight and temporary reduction in insulin sensitivity was caused by a reduction in non-oxidative glucose metabolism (n=5). GH-administration reduced hepatic extraction of insulin alleviating the demand for insulin secretion (n=5). No adverse effects of GH were detected.

CONCLUSIONS

As judged from effects on circulating IGF-I, glucose metabolism, and insulin kinetics, 0.7 mg/day of GH may be expedient for treatment of HIV-infected males with lipodystrophy. Whether the patients' glucose metabolic status matters for the IGF-response to low-dose GH-therapy awaits further investigation.

Tamoxifen modulation of etoposide cytotoxicity involves inhibition of protein kinase C activity and insulin-like growth factor II expression in brain tumor cells

Tamoxifen, a non-steroidal anti-estrogen widely used against breast cancer, is also useful for treatment of other malignancies, due to its sensitizing effect on other chemotherapeutic agents and radiation. We have investigated the advantages of combining tamoxifen with one of the commonly used cancer chemotherapeutic drug, etoposide (VP-16) in brain tumor cell lines. While tamoxifen (10 microM) increased etoposide cytotoxicity 8.3-fold in the human glioma cell line (HTB-14), it increased etoposide cytotoxicity 47.5- and 40-fold in two primary cell lines established from pediatric medulloblastoma patients (MCH-BT-31 and MCH-BT-39), respectively. Similarly, in the pediatric ependymoma cell lines (MCH-BT-30 and MCH-BT-52), tamoxifen enhanced etoposide cytotoxicity 6- and 2.68-fold, respectively. CalcuSyn analysis of cytotoxicity data showed that tamoxifen and etoposide combinations were synergistic with combination index values ranging from 0.243 to 0.369 at IC50 level among different pediatric brain tumor cell lines. Tamoxifen is also cytotoxic at higher concentrations (> 20 microM) in brain tumor cells. To understand the mechanism underlying the tamoxifen modulation of etoposide cytotoxicity, we analyzed expression of P-glycoprotein (P-gp), insulin-like growth factor-I receptor (IGF-IR), IGF-I, IGF-II and estrogen receptor as well as protein kinase C (PKC) activity. While P-gp, IGF-IR and IGF-I were not affected, enhanced inhibition of PKC, and IGF-II were observed in brain tumor cells treated with tamoxifen and etoposide combination as compared to cells treated with either drug alone. Tamoxifen at 10 microM when combined with etoposide at 0-100 microM concentrations reduced PKC activity 77% compared to only 58% without tamoxifen. IGF-II expression decreased to 48.6% of the untreated control in the combination treatment as compared to 31.2% for etoposide alone and 26.2% for tamoxifen alone treatments. These results suggest that inhibitory effect of tamoxifen on brain tumor cells manifest through different mechanisms involving inhibition of targets such as PKC and IGF-II.

Effects of colostrum feeding and dexamethasone treatment on mRNA levels of insulin-like growth factors (IGF)-I and -II, IGF binding proteins-2 and -3, and on receptors for growth hormone, IGF-I, IGF-II, and insulin in the gastrointestinal tract of neonatal calves

The somatotropic axis regulates growth of the gastrointestinal tract (GIT). In addition, colostrum feeding and glucocorticoids affect maturation of the GIT around birth in mammals. We have measured mRNA levels of members of the somatotropic axis to test the hypothesis that colostrum intake and dexamethasone treatment affect respective gene expression in the GIT. Calves were fed either colostrum or an isoenergetic milk-based formula, and in each feeding group, half of the calves were treated with dexamethasone (DEXA; 30 microg/kg body weight per day). Individual parameters of the somatotropic axis differed (P < 0.05) among different GIT sections and formula feeding increased (P < 0.05) mRNA levels of individual parameters at various sites of the GIT. Effects of DEXA on the somatotropic axis in the GIT partly depended on different feeding. In colostrum-fed calves, DEXA decreased (P < 0.05) mRNA levels of IGF-I (esophagus, fundus, duodenum, and ileum), IGF-II (fundus), IGFBP-2 (fundus), IGFBP-3 (fundus), IGF1R (esophagus, ileum, and colon), IGF2R (fundus), GHR (fundus), and InsR (esophagus, fundus), but in formula-fed calves DEXA increased mRNA levels of IGF-I (esophagus, rumen, jejunum, and colon). Furthermore, DEXA increased (P < 0.05) mRNA levels of IGF-II (pylorus), IGFBP-3 (duodenum), IGF2R (pylorus), and GHR (ileum), but decreased mRNA levels of IGFBP-2 (ileum), and IGF1R (fundus). Whereas formula feeding had stimulating effects, effects of DEXA treatment on the gene expression of parameters of the somatotropic axis varied among GIT sites and partly depended on feeding.

[Leukemia inhibitory factor (LIF) improves and prolongs the development of parthenogenetic mouse embryos]

We studied the effect of the growth factor LIF on the development of parthenogenetic mouse embryos (CBA x C57BL/6)F1. LIF was added to the culture medium at 10, 50, 100, and 250 ng/ml at the morula stage and parthenogenetic embryos were cultivated in vitro until the late blastocysts stage and then transplanted in the uterus of pseudopregnant females, which were then sacrificed on day 12 of pregnancy. All the LIF doses used improved the development of parthenogenetic mouse embryos at the preimplantation stages and increased the amount of blastocysts by 16%, on average, as compared to the control. LIF at 50 and 100 ng/ml increased approximately twice the number of embryos that reached the somatic stages. Some of them reached the stage of 32-45 somites and had fore and hind limb buds. No such embryos were found in the control. Well formed placenta was observed in 6% of the embryos treated with LIF and the most pronounced effect was recorded at 100 ng/ml. The data we obtained suggest that exogenous LIF can improve pre- and postimplantation development of parthenogenetic mouse embryos due, possibly, to increased survival rate of embryonic stem cells derived from the inner cell mass of blastocysts. LIF improves not only the development of the parthenogenetic embryo per se, but also the formation of its extraembryonic envelopes, which leads to the development of a larger placenta in LIF-treated parthenogenetic embryos, as compared to the control.

Alcohol-induced modulation of the insulin-like growth factor system in early chick embryo cranial tissue

BACKGROUND

Fetal alcohol exposure has been shown to reduce fetal/embryonic growth. The insulin-like growth factor (IGF) system plays a major role in normal growth and development of the embryo. The purpose of this study was to gain a better understanding of the effects of alcohol (ethanol, EtOH) exposure on the insulin-like growth factors, their binding proteins, and receptors during embryonic development.

METHODS

After the administration of either alcohol or chick Ringer's solution to individual eggs at the start of incubation, type-1 IGF receptors, IGF-binding proteins (IGFBPs) as well as IGF-1 and IGF-2 levels were measured in chick embryo craniums on days 5, 6, 7, and 8 of incubation.

RESULTS

Levels of the IGF-1 receptor protein were not significantly different between treatment groups on any day studied. In EtOH-treated embryos, the 30 kDa IGFBP levels were significantly higher than vehicle levels on days 5 and 6. On day 6, IGF-1 levels were significantly lower in the alcohol-treated embryos compared with levels in vehicle-treated embryos of the same age. By day 8 of incubation, IGF-1 levels were significantly higher and the 30 kDa IGFBP levels were significantly lower in the alcohol-treated group compared with vehicles. These results indicate an initial EtOH-associated reduction in the amount of IGF-1 available to bind to its receptor (bioavailability), followed by increased IGF-1 bioavailability by day 8.

CONCLUSIONS

The elevated IGFBP levels and reduced IGF-1 levels on days 5 and 6 of incubation are congruent with an overall reduction in the bioavailability of IGF-1 during this period and correlate with the decreased embryo weight observed in the alcohol-treated embryos. An increased bioavailability of IGF-1 observed by day 8 may represent a rebound effect and is associated with increases in ornithine decarboxylase activity, a marker of increased growth.

Human breast carcinoma desmoplasia is PDGF initiated

The desmoplastic response to human breast carcinoma is a host myofibroblast-mediated collagenous response exhibiting synergistic effects on tumor progression. Although many paracrine interactions between breast carcinoma cells and myofibroblasts have been characterized, the event(s) which initiate desmoplasia have remained undefined. Our studies utilized c-rasH transfected MCF-7 cells which overexpress ras p2l and which are weakly tumorigenic in ovariectomized nude mice. The xenografts are desmoplastic and comprised of 30% myofibroblasts and 60 mg/g of interstitial collagen. In situ hybridization studies of these xenografts reveal a stromal gene expression pattern (stromelysin-3, IGF-II and TIMP-1) identical to that observed in human tumor desmoplasia. 17-beta estradiol increases c-rasH MCF-7 growth but abolishes desmoplasia. c-rasH MCF-7 in vitro constitutively produce myofibroblast mitogenic activity which competes with PDGF in a receptor binding assay. This myofibroblast mitogenic activity is unaltered by 17-beta estradiol/tamoxifen pretreatment in vitro. Transfection of c-rasH MCF-7 with a PDGF-A dominant negative mutant, 1308, produced by site-directed mutagenesis (serine-->cysteine129) reduces both homo- and heterodimer secretion of PDGF by as much as 90% but does not interfere with the secretion of other growth factors. Clones with low PDGF, though tumorigenic, are non-desmoplastic. Our results suggest that breast carcinoma-secreted PDGF is the major initiator of tumor desmoplasia.

Calcitonin increases the concentration of insulin-like growth factors in serum-free cultures of human osteoblast-line cells

The current studies were intended to determine whether the anabolic effects of calcitonin (CT) on human osteoblast-line cells were (1) unique to osteosarcoma cells or also evident in osteoblast-line cells derived from normal human bone; and/or (2) associated with effects on several insulin-like growth factor (IGF) system components. Preliminary studies identified several osteoblastic cell lines, derived from normal human bone, which showed calcitonindependent increases in cell proliferation, alkaline phosphatase activity, and/or (45)Ca uptake (P < 0.05-P < 0.001). Two of these cell lines-(human vertebrae) HBV-155 and HBV-163-were included with the human osteosarcoma cell line, SaOS-2, in most of our subsequent studies of calcitonin effects on selected IGF system components: IGF-II, IGF-I, and IGF binding proteins -3, -4, and -5. The results of those studies revealed that a 48 hour exposure to salmon CT caused a dose-dependent (0.03-3 mU/ml) increase in the net extracellular level of IGF-II (r = 0.96, P < 0.01) in serum-free cultures of SaOS-2 cells, with a maximal 60% increase at the highest tested dose (P < 0.02). Similar effects were seen with HBV-163 cells (r = 0.90, P < 0.01) and HBV-155 cells (r = 0.55, P < 0.02). The effect of calcitonin on the extracellular level of IGF-II was biphasic with respect to time: it decreased at 6 hours (P < 0.005 and P < 0.001, for SaOS-2 cells and HBV-163 cells, respectively) and increased at 24 hours (P < 0.02 and P < 0.05). These calcitonin-dependent increases in the extracellular level of IGF-II were associated with parallel increases in IGF-I (P < 0.005 for SaOS-2 cells and P < 0.03 for HBV-163 cells), but calcitonin did not affect the extracellular level of transforming growth factor (TGF)-beta. The calcitonin-dependent changes in IGF-II were not associated with changes in the extracellular levels of IGF binding proteins -3, -4, or -5. Finally, our studies showed that two other members of the CT superfamily-CT gene-related peptide and amylin-did not mimic the effect of CT to increase the extracellular level of IGF-II. Together, these data demonstrate that human osteoblast-line cells derived from normal human bone can respond to CT, and that those responses can include CT dose- and time-dependent increases in the extracellular levels of IGF-I and IGF-II.</hea

Picroliv modulates the expression of insulin-like growth factor (IGF)-I, IGF-II and IGF-I receptor during hypoxia in rats

The insulin-like growth factors (IGFs), IGF-I and IGF-II, play important roles in normal growth and differentiation. In recent studies, IGFs have been implicated in tissue repair and regeneration after hypoxicischemic injury. The growth effects of these genes are exerted primarily through IGF-I receptor (IGF-IR). We have earlier shown that picroliv, obtained from the roots of Picrorhiza kurrooa, reduces cellular damage caused by hypoxia in vitro. We have now studied the modulation of IGF-I, IGF-II and IGF-IR in hypoxia and the ability of picroliv to modify their expression in vivo. Male Sprague-Dawley rats, placed in 10% oxygen for 4 days, were sacrificed, and the expression of IGF-I, IGF-II and IGF-IR was determined by immunohistochemistry, in situ hybridization and reverse transcriptase polymerase chain reaction (RT-PCR) in brain, liver and lung. One group of animals was pretreated with picroliv and the other served as control. IGF-I and IGF-IR were expressed in distinct regions of the brain but not in liver or lung. IGF-I was mainly expressed in the hippocampus and cerebellum, whereas IGF-IR expression was also observed in the cortex. A significant reduction in the messenger RNA (mRNA) level of these genes was observed in response to hypoxia. Pretreatment with picroliv not only prevented such downregulation but more importantly resulted in increased levels of IGF-I and IGF-IR. These observations correlated with reduced neuronal cell death observed in these animals. The mRNA of IGF-II was constitutively expressed and was not altered by hypoxia. Modulation of IGF-I and IGF-II expression by picroliv, a novel pharmacological agent, could benefit in similar clinical settings such as myocardial ischemia and certain cerebral injuries.

Normal growth despite GH, IGF-I and IGF-II deficiency

A 6.5-year-old male with normal linear growth, despite septo-optic dysplasia, panhypopituitarism and a deficient GH/IGF axis, is presented. In addition to measuring IGF-I, IGF-II and IGFBP-3, serum IGFBP-1, -2, -4 and -5 were measured. A human osteosarcoma cell line was used to assess growth-promoting activity in the patient's serum. The role of leptin in linear growth in this case was investigated. There was no evidence for hyperinsulinism or hyperandrogenism. GH was undetectable upon multiple stimulation. GHBP was elevated. Serum IGF-I (25 microg/l), IGF-II (194 microg/l), IGFBP-3 (0.4 mg/l), and IGFBP-5 (87 microg/l) levels were low compared to age-matched prepubertal children. Serum IGFBP-4 level was normal. Molecular size of IGF-II in the patient's serum was normal, suggesting normal IGF-II bioavailability. Human osteosarcoma cell proliferation in response to the patient's serum was similar to sera from age-matched normal controls. Leptin levels were markedly elevated. Osteoblast cell proliferation was not stimulated by leptin. The data demonstrate that normal growth and osteoblast cell proliferation in this patient is not mediated by GH, total IGFs, insulin, or leptin, and suggest the presence of a yet unidentified growth factor or mechanism. The case offers a detailed picture of binding proteins in a case of growth without GH. It introduces osteoblast cell proliferation as a method of assessing serum growth-promoting activity in such cases. It adds IGF-II and leptin to the list of excluded growth-promoting candidates in GH-independent growth, and further demonstrates our incomplete understanding of the phenomenon of growth.

AP-2 may contribute to IGF-II overexpression in rhabdomyosarcoma

The human insulin-like growth factor II gene is regulated in a development-dependent manner and is not expressed in most adult tissues. However, high levels of insulin-like growth factor II mRNA are detected in many human tumors including rhabdomyosarcoma, an embryonal tumor of skeletal muscle origin. In this study, we demonstrate that the developmentally regulated transcription factor AP-2 is expressed at higher levels in human fetal skeletal muscle and rhabdomyosarcoma cells compared to human adult skeletal muscle. Endogenous insulin-like growth factor II mRNA derived from the P3 as well as transfected P3 promoter activity were modestly and consistently increased to the same extent following treatment of the rhabdomyosarcoma cell line RD with forskolin, a compound implicated in AP-2 transactivation. This effect of AP-2 on increased transcriptional activity was confirmed by nuclear run-on assays. Expression of AP-2B, a dominant-negative inhibitor of AP-2, suppressed the P3 promoter activity in AP-2 expressing RD cells. Furthermore, five AP-2 protected regions corresponding to six AP-2 specific binding sites were detected in the insulin-like growth factor II P3 promoter. These data together suggest that AP-2 may contribute to the high expression of IGF-II in rhabdomyosarcoma cells.

Estrogen effects on insulin-like growth factor gene expression in a human osteoblastic cell line with high levels of estrogen receptor

Insulin-like growth factors (IGF)-I and IGF-II are produced by osteoblasts and are important paracrine/autocrine regulators of osteoblast proliferation and differentiation. Estrogen has been reported to increase gene expression of IGF-I in rodent osteoblasts. However, because species differences have been demonstrated in expression of various aspects of the IGF system in bone cells, it is not known whether this action also occurs in human osteoblasts. Thus, we assessed the effects of estrogen treatment on IGF-I and IGF-II gene expression in vitro in a recently developed human fetal osteoblast cell line that has high levels of estrogen receptors. As assessed by a quantitative reverse transcriptase-polymerase chain reaction method, treatment of hFOB/ER9 cells with 17beta-estradiol (E2) increased steady state levels of IGF-I mRNA in a time- and dose- dependent fashion with a maximal increase of 319% +/- 33% (P < 0.01) of control occurring after treatment with 10(-7) M E2 for 48 hours. In contrast, E2 did not alter steady state levels of IGF-II mRNA. The pure (type 2) antiestrogens ICI 182,780 (10(-7) M) and ICI 164,384 (10(-6) M) blocked the E2- induced increase in IGF-I mRNA levels. Interestingly, 4-hydroxytamoxifen (10(-7) M), a documented pure antiestrogen in reproductive tissues, also increased IGF-I mRNA to levels similar to those observed in E2-treated cells. Since E2 was shown to mediate its effects on some target genes through a cAMP-dependent pathway, we studied the interaction between E2 and agents that are known to increase intracellular cAMP. Forskolin (10(-8) M) and dibutyryl cAMP (10(-3) M) increased IGF-I mRNA levels sixfold, and cotreatment with E2 did not affect these changes, consistent with a possible mediation of the estrogen effect on IGF-I gene expression by cAMP. We conclude that in human osteoblastic cells, the IGF-I gene is a target for estrogen action, suggesting that IGF-I may mediate part of the effects of estrogen in human bone.

Modulation of Igf2 genomic imprinting in mice induced by 5-azacytidine, an inhibitor of DNA methylation

The adjacent genes, insulin-like growth factor 2 (Igf2) and H19, are imprinted in both mouse and human. While Igf2 is expressed from the paternal allele, H19 is transcribed exclusively from the maternal allele. To explore the underlying mechanism of Igf2 and H19 imprinting, we studied the effect of DNA demethylation on allelic expression by injecting mice with the demethylating agent 5-azacytidine (5-aza-C). We observed a > or = 2-fold increase in the abundance of Igf2 mRNA in liver from treated mice compared with that of control mice. There was no significant change in Igf2 or H19 expression in brain. In the 5-aza-C-treated mice, there was dramatic modulation of Igf2 imprinting. In some tissues, Igf2 was expressed biallelically, while in other tissues, the paternal allele was silenced and the normally imprinted maternal allele was expressed, an example of allelic switching. There was no change in the normal biallelic pattern of Igf2 expression in brain. H19, on the other hand, remained imprinted in all tissues in mice treated with 5-aza-C. These results provide the first example of a pharmacological manipulation of genomic imprinting of an endogenous gene in vivo and further implicate DNA methylation as an important factor in maintaining the differential allelic expression of the Igf2 gene.

Modulation of Igf2 genomic imprinting in mice induced by 5-azacytidine, an inhibitor of DNA methylation

The adjacent genes, insulin-like growth factor 2 (Igf2) and H19, are imprinted in both mouse and human. While Igf2 is expressed from the paternal allele, H19 is transcribed exclusively from the maternal allele. To explore the underlying mechanism of Igf2 and H19 imprinting, we studied the effect of DNA demethylation on allelic expression by injecting mice with the demethylating agent 5-azacytidine (5-aza-C). We observed a > or = 2-fold increase in the abundance of Igf2 mRNA in liver from treated mice compared with that of control mice. There was no significant change in Igf2 or H19 expression in brain. In the 5-aza-C-treated mice, there was dramatic modulation of Igf2 imprinting. In some tissues, Igf2 was expressed biallelically, while in other tissues, the paternal allele was silenced and the normally imprinted maternal allele was expressed, an example of allelic switching. There was no change in the normal biallelic pattern of Igf2 expression in brain. H19, on the other hand, remained imprinted in all tissues in mice treated with 5-aza-C. These results provide the first example of a pharmacological manipulation of genomic imprinting of an endogenous gene in vivo and further implicate DNA methylation as an important factor in maintaining the differential allelic expression of the Igf2 gene.

Bioactivity of a 29-kilodalton insulin-like growth factor binding protein-3 fragment present in excess in chronic renal failure serum

Children with chronic renal failure (CRF) have normal or high serum levels of GH, IGF-I, and IGF-II. Despite this, the serum of CRF patients has low IGF bioactivity, which may contribute to CRF growth failure. Recent studies suggest that excess IGF binding proteins (IGFBPs) in the approximately 35-kD fractions of CRF serum contribute to this low IGF bioactivity. This report characterizes a 29-kD form of IGFBP-3, IGFBP-3(29), which accumulates in the approximately 35-kD fractions of CRF serum and peritoneal dialysate. Deglycosylation and [125I]IGF ligand blot studies show that IGFBP-3(29) is a glycosylated IGFBP-3 fragment with low affinity for IGF peptides. Using an IGFBP-3 antibody column, IGFBP-3(29) was purified to homogeneity from the approximately 35-kD fractions of peritoneal dialysate from children with CRF. Compared with native IGFBP-3, pure IGFBP-3(29) has a 4-10-fold lower affinity for IGF-II and a 200-fold lower affinity for IGF-I. Consistent with the binding data, IGFBP-3(29) inhibited IGF-II-stimulated thymidine incorporation in chondrosarcoma cells, but was a less potent inhibitor than native IGFBP-3; also, native IGFBP-3 clearly inhibited IGF-I-stimulated thymidine incorporation in chondrosarcoma cells and potentiated IGF-I-stimulated aminoisobutyric acid uptake in bovine fibroblasts, but higher concentrations of IGFBP-3(29) had no effect on these IGF-I actions. Thus, the 29-kD IGFBP-3 form that accumulates in CRF serum and extravascular spaces is an IGFBP-3 fragment that may modulate IGF-II, but not IGF-I, effects on target tissues. Whether IGFBP-3(29) plays any role in the growth failure of children with CRF remains to be determined.

mRNA expression of insulin-like growth factor-I (IGF-I) is suppressed and those of IGF-II and IGF-binding protein-1 are constantly expressed in the endometrium during use of an intrauterine levonorgestrel system

Insulin-like growth factors (IGF-I and IGF-II) are believed to mediate and modulate steroid hormone actions in the endometrium. In this study we determined the effects of an intrauterine system (IUS), releasing 20 microg levonorgestrel (LNG) daily, on endometrial expression of mRNAs encoding IGFs and insulin-like growth factor binding protein (IGFBP)-1. In Northern blotting, IGF-I mRNA was undetectable in all endometrial specimens from women with an LNG-IUS (n = 11) and in pregnancy decidua, whereas several transcripts of 0.6-7.6 kb were detected in proliferative and secretory phase endometria. In contrast, mRNAs encoding IGF-II and IGFBP-1 were strongly expressed in pregnancy and in all endometrial samples from women with an LNG-IUS, but were undetectable in proliferative or early to mid-secretory phase endometria. Using the more sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) method, IGF-I and IGF-II mRNAs were detectable in all cycling endometria, in early pregnancy decidua and in LNG-exposed endometrium. IGFBP-1 mRNA was constantly expressed in LNG-exposed endometrium, in early pregnancy decidua and in premenstrual endometrium, but was undetectable in all specimens from proliferative or early to mid-secretory endometrium. Our data demonstrate that progestin treatment can affect the gene expression of endometrial growth factors in vivo. The consistent expression of mRNAs encoding IGF-II and IGFBP-1, with suppression of IGF-I mRNA in endometria exposed to LNG, suggests that this mode of hormone treatment can inhibit IGF-I action in the endometrium. If IGF-I mediates and modulates oestrogen action, suppression of IGF-I mRNA may be one of the molecular mechanisms which accounts for the antiproliferative effects of progestogens on oestrogen-primed endometrium and the atrophy of endometrial epithelium resulting from use of an LNG-IUS.

Ontogeny of insulin-like growth factors (IGF-I and IGF-II) and IGF-binding proteins in the chicken following hatching

The present study examined plasma concentrations of insulin-like growth factor (IGF)-I, IGF-II and IGF-binding proteins (IGFBPs) during posthatch growth and development in chickens. Three distinct proteins which bound 125I-IGF-I were observed irrespective of age or sex, these having apparent molecular weights of 22, 28, and 36 kDa. The major IGFBP present during much of the growth and development period was the 28-kDa form followed by the 36-kDa form. Plasma concentrations of IGF-II and of the 22-kDa IGFBP showed little ontogenic variation with the exception of elevated levels of the 22 kDa IGFBP in 1-day-old chicks. The circulating concentrations of IGF-I and of the 28-kDa IGFBP increased progressively between the time of hatching to reach a maximum at 6 weeks of age and subsequently declined to lower levels in adults. Somewhat similarly, the 36-kDa IGFBP increased during early pre- and posthatching growth to a maximum at 6 weeks of age. There were marked sex differences in circulating concentrations of IGF-I in young (4 week) and adult chickens and in the 36-kDa IGFBP in the adult, both being lower in females. Estrogen treatment of adult male chickens decreased the circulating concentrations of IGF-I together with the level of both the 28- and 36-kDa IGFBPs. Testosterone treatment had no effect on the circulating concentrations of either IGF-I or IGFBPs in adult female chickens. We conclude that the relative levels of IGF-I, IGF-II, and the IGFBPs change with age. In addition, circulating concentrations of estrogen may play a role in the regulation of IGF-I and IGFBPs.

Circulating insulin-like growth factor system changes in women with acute estrogen deficiency induced by GnRH agonist

This prospective longitudinal study was undertaken to examine the short-term effects (6 months) of estrogen withdrawal on the circulating IGF system. A series of 40 patients suffering from endometriosis was studied before and after a 6-month treatment period with gonadotrophin releasing hormone (GnRH) agonist and calcium, with or without nasal salmon calcitonin. The plasma concentrations of insulin-like growth factor I (IGF-I) and insulin-like growth factor II (IGF-II) were measured by radioimmunoassay and radioreceptor assay respectively. Plasma IGF binding proteins (IGFBPs) were quantified and characterized by ligand blot and immunoblot. In all patients, a secondary hypoestrogenism was observed, including a 4% decrease in lumbar bone mineral density (L-BMD). The plasma IGF-I and IGF-II concentrations increased after treatment (24%, p < 0.0005 and 40%, p < 0.004 respectively), with no significant difference between the treatment groups. There was a positive correlation between plasma IGF-I (but not IGF-II) changes and changes in urinary deoxypyridinoline (r = 0.32, p < 0.05), urinary C telopeptide of type 1 collagen (r = 0.33, p < 0.04) and total plasma alkaline phosphatases (r = 0.33, p < 0.04). No correlation was found between IGF-I and L-BMD changes, while there was a positive correlation between the changes in plasma IGF-II and L-BMD (r = 0.32, p < 0.05). Ligand blot analysis revealed a significant increase in IGF-II binding to a 29-31 kilodalton region where positive staining with specific antibodies to IGFBP-3 or IGFBP-1 was observed. In conclusion, IGF-I and IGF-II plasma concentrations are both increased following a short period of treatment with a GnRH agonist. The changes in individual IGF peptides are differently correlated with changes in markers of bone remodelling and L-BMD.

Free and total insulin-like growth factors and insulin-like growth factor binding proteins during 14 days of growth hormone administration in healthy adults

The objective was to investigate the effect of growth hormone (GH) administration on circulating levels of free insulin-like growth factors (IGFs) in healthy adults. Eight healthy male subjects were given placebo and two doses of GH (3 and 6 IU/m2 per day) for 14 days in a double-blind crossover study. Fasting blood samples were obtained every second day. Free IGF-I and IGF-II were determined by ultrafiltration of serum. Total IGF-I and IGF-II were measured after acid-ethanol extraction. In addition, GH, insulin, IGF binding protein 1 (IGFBP-1) and IGFBP-3 were measured. Serum-free and total IGF-I increased in a dose-dependent manner during the 14 days of GH administration. After 14 days, serum-free IGF-I values were 610 +/- 100 ng/l (mean +/- SEM) (placebo), 2760 +/- 190 ng/l (3 IU/ m2) and 3720 +/- 240 ng/l (6 IU/m2) (p = 0.0001 for 3 and 6 IU/m2 vs placebo; p = 0.004 for 3 IU/m2 vs 6 IU/m2). Total IGF-I values were 190 +/- 10 micrograms/l (placebo), 525 +/- 10 (3 IU/m2), and 655 +/- 40 micrograms/l (6 IU/m2) (p < 0.0001 for 3 and 6 IU/m2 vs placebo; p = 0.04 for 3 IU/m2). There were no differences in the levels of free or total IGF-II during the three study periods. Insulin-like growth factor binding protein 1 was decreased during GH administration (p = 0.04 for placebo vs 3 IU/m2; p = 0.006 for placebo vs 6 IU/m2). In conclusion, fasting serum free IGF-I increased dose dependently during GH administration and free IGF-I increased relatively more than total IGF-I. This may partly be due to the decrease in IGFBP-1.

Insulin-like growth factor-II is an autocrine survival factor for differentiating myoblasts

Recent studies indicate that insulin-like growth factor-II (IGF-II) acts as an autocrine differentiation factor for skeletal myoblasts in culture. IGF-II mRNA and protein are induced as early events in muscle differentiation, and the rate and extent of IGF-II secretion correlate with both biochemical and morphological differentiation. Here we show that IGF-II also functions as an essential survival factor during the transition from proliferating to differentiating myoblasts. Stably transfected C2 muscle cell lines were established in which a mouse IGF-II cDNA was expressed in the antisense orientation relative to the constitutively active Moloney sarcoma virus promoter. IGF-II antisense cells proliferated normally in growth medium containing 20% serum but underwent rapid death when placed in low serum differentiation medium. Death was accompanied by characteristic markers of apoptosis with more than 90% of cells showing DNA fragmentation within 12-16 h. Myoblast death was prevented by IGF-I, des [1-3] IGF-I, IGF-II, and insulin with a dose potency consistent with activation of the IGF-I receptor; death also could be blocked by the protein synthesis inhibitor, cycloheximide. Exogenous IGFs additionally stimulated passage through a single cell cycle and subsequently induced terminal differentiation. Cell survival and cell cycle progression also were enhanced by fibroblast growth factor-2 and platelet-derived growth factor-bb, but these peptides did not promote differentiation. Our results define a novel system for studying apoptotic cell death and its prevention by growth factors, underscore the importance of IGF action in minimizing inappropriate cell death, and indicate that shared signal transduction pathways may mediate myoblast survival in vitro.

Long-term effects of insulin-like growth factor (IGF)-I treatment on serum IGFs and IGF binding proteins in adolescent patients with growth hormone receptor deficiency

OBJECTIVE

The aim of this investigation was to study the effect of relatively high dose IGF-I therapy given for several months, on serum levels of IGF-I, IGF-II and IGFBP-3, and on IGF-I pharmacokinetics in patients with growth hormone insensitivity due to GH receptor dysfunction.

DESIGN AND PATIENTS

Two adolescent subjects from Ecuador were treated with recombinant IGF-I at a dosage of 120 micrograms/kg s.c. twice daily, in combination with a GnRH analogue for 8 months.

MEASUREMENTS

Serum was sampled at baseline and at 3-8 months, for determination of IGF-I, IGF-II and IGFBP-3 by radioimmunoassay, and for evaluation of IGFBPs and IGFBP-3 protease activity by Western ligand blot and protease assay, respectively.

RESULTS

Peak serum IGF-I levels ranged from 272 to 492 micrograms/l. Mean serum IGF-II levels were decreased concurrently with the increase in IGF-I. Serum IGFBP-3 levels failed to rise with prolonged IGF-I treatment. There was no apparent change in the half-life of IGF-I during the treatment period.

CONCLUSIONS

IGF-I administration does not increase serum levels of IGFBP-3 or significantly alter IGF-I pharmacokinetics.

9-Cis retinoic acid inhibits growth of breast cancer cells and down-regulates estrogen receptor RNA and protein

All-trans retinoic acid (tRA) inhibits growth of estrogen receptor-positive (ER+) breast cancer cells in vitro, and a variety of retinoids inhibit development of breast cancer in animal models. 9-cis retinoic acid (9-cis RA) is a naturally occurring high affinity ligand for the retinoid X receptors, as well as the retinoic acid receptors (RARs). Whether 9-cis RA has a different spectrum of biological activity from tRA, which only binds RARs with high affinity, is largely unknown. We studied the effects of 9-cis RA on growth and gene expression in ER+ and ER- human breast cancer cells. 9-cis RA inhibited the growth in monolayer culture of several ER+, but not ER-, cell lines in a dose-dependent manner. Growth inhibition and morphological changes by 9-cis RA were similar to those of tRA, suggesting that the ability to bind both RAR and retinoid X receptors did not significantly augment growth inhibition or confer sensitivity to tRA-resistant lines. MCF-7 cells exposed to 9-cis RA showed a dose-dependent accumulation in G1. Northern analyses showed that RAR-alpha and RAR-beta were not significantly regulated, while RAR-gamma was up-regulated and retinoid X receptor alpha was down-regulated by 9-cis RA. Since interactions between tRA and ER-dependent transcription have recently been reported, we investigated whether these retinoids regulate expression of ER itself or estrogen-responsive genes. Both 9-cis RA and tRA induce down-regulation of ER mRNA and protein in MCF-7 cells. 9-cis RA down-regulates expression of the estrogen-responsive genes PR and pS2 in MCF-7 cells as reported previously for tRA. In several ER-positive subclones, we found that the degree of ER expression and regulation, but not always estrogen-sensitivity, correlates with the growth-inhibitory effects of 9-cis RA. Further, in an ER-, retinoid-unresponsive breast cancer cell line, induced ER expression confers responsiveness to retinoid growth inhibition. These data, combined with reports of additive growth inhibition of tRA and tamoxifen in vitro, suggest that 9-cis RA might augment the ability of tamoxifen to inhibit growth of ER+ breast cancer cells in vivo.

Bone morphogenetic protein 2 increases insulin-like growth factor I and II transcripts and polypeptide levels in bone cell cultures

Insulin-like growth factors (IGF) I and II are among the most prevalent growth factors secreted by bone cells and are presumed to act as autocrine regulators of bone formation. Certain growth factors, synthesized by skeletal cells and known to stimulate the replication but not the differentiated function of cells of the osteoblastic lineage, have been shown to inhibit skeletal IGF-I and II synthesis. We postulated that growth factors with limited mitogenic activity and with differentiation-inducing properties, such as bone morphogenetic protein (BMP) 2, have the opposite effect and enhance IGF-I and II synthesis. We tested the effects of BMP-2 on IGF-I and II mRNA expression and polypeptide concentrations in cultures of osteoblast-enriched (OB) cells from 22 day fetal rat calvariae. Steady-state IGF-I and II mRNA levels were determined by northern blot analysis, and IGF-I and II concentrations were determined in acidified and fractionated culture medium by a specific radioimmunoassay. After 24-48 h of treatment, BMP-2 at 3.3 nM increased IGF-I and II transcripts by up to twofold and polypeptide levels by up to fourfold. BMP-2 was a more potent stimulator of IGF-II synthesis, and it was active at doses as low as 0.03 nM for IGF-II mRNA and 0.3 nM for IGF-II protein, whereas a dose of 3.3 nM was required to observe the effect on IGF-I synthesis. The effects of BMP-2 on IGF-I and II transcripts and polypeptide levels were dependent on protein synthesis and decreased in the presence of cycloheximide at 3.6 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

All-trans-retinoic acid inhibits the growth of human rhabdomyosarcoma cell lines

We have been evaluating the role of all-trans-retinoic acid (RA) in the differentiation and growth of human rhabdomyosarcoma (RMS) cell lines. Treatment of both embryonal (RD) and alveolar (RH30) human RMS cell lines with all-trans-RA resulted in a dose-dependent inhibition of cell growth with a maximal inhibition of 92 and 66%, respectively, at 5 x 10(-6) M. When 13-cis-RA was used under identical experimental conditions, maximal growth inhibition was 41 and 37%, respectively. This stereo-specific growth inhibition was not associated with morphological or biochemical evidence of myogenic differentiation. Furthermore, all-trans-RA demonstrated no evidence of competition with binding of insulin-like growth factor II (IGF-II), an autocrine growth factor in RMS, to its membrane receptor as evaluated by an [125I]IGF-I-receptor-binding assay. Attempts to rescue all-trans-RA growth-inhibited RMS cells with exogenous IGF-II resulted in no increase in growth compared to cells treated with all-trans-RA alone. We conclude that RA inhibits the growth of human RMS cell lines in a dose-dependent, stereo-specific manner, is not associated with differentiation, and does not appear to be directly related to IGF-II.