Growth hormone receptor overexpression predicts response of rectal cancers to pre-operative radiotherapy

Growth Hormone Action as a Target in Cancer: Significance, Mechanisms, and Possible Therapies

Growth hormone (GH) is a pituitary-derived endocrine hormone required for normal postnatal growth and development. Hypo- or hypersecretion of endocrine GH results in 2 pathologic conditions, namely GH deficiency (GHD) and acromegaly. Additionally, GH is also produced in nonpituitary and tumoral tissues, where it acts rather as a cellular growth factor with an autocrine/paracrine mode of action. An increasingly persuasive and large body of evidence over the last 70 years concurs that GH action is implicit in escalating several cancer-associated events, locally and systemically. This pleiotropy of GH's effects is puzzling, but the association with cancer risk automatically raises a concern for patients with acromegaly and for individuals treated with GH. By careful assessment of the available knowledge on the fundamental concepts of cancer, suggestions from epidemiological and clinical studies, and the evidence from specific reports, in this review we aimed to help clarify the distinction of endocrine vs autocrine/paracrine GH in promoting cancer and to reconcile the discrepancies between experimental and clinical data. Along this discourse, we critically weigh the targetability of GH action in cancer-first by detailing the molecular mechanisms which posit GH as a critical node in tumor circuitry; and second, by enumerating the currently available therapeutic options targeting GH action. On the basis of our discussion, we infer that a targeted intervention on GH action in the appropriate patient population can benefit a sizable subset of current cancer prognoses.

Covert actions of growth hormone: fibrosis, cardiovascular diseases and cancer

Since its discovery nearly a century ago, over 100,000 studies of growth hormone (GH) have investigated its structure, how it interacts with the GH receptor and its multiple actions. These include effects on growth, substrate metabolism, body composition, bone mineral density, the cardiovascular system and brain function, among many others. Recombinant human GH is approved for use to promote growth in children with GH deficiency (GHD), along with several additional clinical indications. Studies of humans and animals with altered levels of GH, from complete or partial GHD to GH excess, have revealed several covert or hidden actions of GH, such as effects on fibrosis, cardiovascular function and cancer. In this Review, we do not concentrate on the classic and controversial indications for GH therapy, nor do we cover all covert actions of GH. Instead, we stress the importance of the relationship between GH and fibrosis, and how fibrosis (or lack thereof) might be an emerging factor in both cardiovascular and cancer pathologies. We highlight clinical data from patients with acromegaly or GHD, alongside data from cellular and animal studies, to reveal novel phenotypes and molecular pathways responsible for these actions of GH in fibrosis, cardiovascular function and cancer.

Identification of growth hormone receptor as a relevant target for precision medicine in low-EGFR expressing glioblastoma

Objective

New therapeutic approaches are needed to improve the prognosis of glioblastoma (GBM) patients.

Methods

With the objective of identifying alternative oncogenic mechanisms to abnormally activated epidermal growth factor receptor (EGFR) signalling, one of the most common oncogenic mechanisms in GBM, we performed a comparative analysis of gene expression profiles in a series of 54 human GBM samples. We then conducted gain of function as well as genetic and pharmocological inhibition assays in GBM patient‐derived cell lines to functionnally validate our finding.

Results

We identified that growth hormone receptor (GHR) signalling defines a distinct molecular subset of GBMs devoid of EGFR overexpression. GHR overexpression was detected in one third of patients and was associated with low levels of suppressor of cytokine signalling 2 (SOCS2) expression due to SOCS2 promoter hypermethylation. In GBM patient‐derived cell lines, GHR signalling modulates the expression of proteins involved in cellular movement, promotes cell migration, invasion and proliferation in vitro and promotes tumourigenesis, tumour growth, and tumour invasion in vivo. GHR genetic and pharmacological inhibition reduced cell proliferation and migration in vitro.

Conclusion

This study pioneers a new field of investigation to improve the prognosis of GBM patients.

Dual Characters of GH-IGF1 Signaling Pathways in Radiotherapy and Post-radiotherapy Repair of Cancers

Radiotherapy remains one of the most important cancer treatment modalities. In the course of radiotherapy for tumor treatment, the incidental irradiation of adjacent tissues could not be completely avoided. DNA damage is one of the main factors of cell death caused by ionizing radiation, including single-strand (SSBs) and double-strand breaks (DSBs). The growth hormone-Insulin-like growth factor 1 (GH-IGF1) axis plays numerous roles in various systems by promoting cell proliferation and inhibiting apoptosis, supporting its effects in inducing the development of multiple cancers. Meanwhile, the GH-IGF1 signaling involved in DNA damage response (DDR) and DNA damage repair determines the radio-resistance of cancer cells subjected to radiotherapy and repair of adjacent tissues damaged by radiotherapy. In the present review, we firstly summarized the studies on GH-IGF1 signaling in the development of cancers. Then we discussed the adverse effect of GH-IGF1 signaling in radiotherapy to cancer cells and the favorable impact of GH-IGF1 signaling on radiation damage repair to adjacent tissues after irradiation. This review further summarized recent advances on research into the molecular mechanism of GH-IGF1 signaling pathway in these effects, expecting to specify the dual characters of GH-IGF1 signaling pathways in radiotherapy and post-radiotherapy repair of cancers, subsequently providing theoretical basis of their roles in increasing radiation sensitivity during cancer radiotherapy and repairing damage after radiotherapy.

Unraveling the Resistance of IGF-Pathway Inhibition in Ewing Sarcoma

Simple Summary

The insulin-like growth factor-1 receptor (IGF1R) is a receptor commonly overexpressed and overactivated in a variety of cancers, including Ewing sarcoma, and promotes cell growth and survival. After promising results with targeting and inhibiting the receptor in vitro, multiple different IGF1R targeting compounds have been clinically tried but showed limited efficacy. Here we discuss several possible resistance mechanisms which could explain why IGF1R targeting fails in the clinic and discuss possible ways to overcome these resistances.

Abstract

Insulin-like growth factor-1 receptor (IGF1R) inhibitors are effective in preclinical studies, but so far, no convincing benefit in clinical studies has been observed, except in some rare cases of sustained response in Ewing sarcoma patients. The mechanism of resistance is unknown, but several hypotheses are proposed. In this review, multiple possible mechanisms of resistance to IGF-targeted therapies are discussed, including activated insulin signaling, pituitary-driven feedback loops through growth hormone (GH) secretion and autocrine loops. Additionally, the outcomes of clinical trials of IGF1-targeted therapies are discussed, as well as strategies to overcome the possible resistance mechanisms. In conclusion, lowering the plasma insulin levels or blocking its activity could provide an additional target in cancer therapy in combination with IGF1 inhibition. Furthermore, because Ewing sarcoma cells predominantly express the insulin receptor A (IRA) and healthy tissue insulin receptor B (IRB), it may be possible to synthesize a specific IRA inhibitor.

Human growth hormone level decreased in women aged <60 years but increased in men aged >50 years

To investigate the relationship amongst human growth hormone (HGH), sex, and age groups.A cross-sectional study was conducted on a health check-up population from Wannan area of China from 2014 to 2016. The study involved 6843 individuals aged 23 to 85 years. Logistic regression analysis and smooth curve were applied to determine the relationship amongst age, sex, and HGH.The average level of HGH in the population was 0.37 ± 0.59 ng/mL. There were significant differences in sex, age, body mass index (BMI), triglycerides (TG), total cholesterol (TC), systolic blood pressure (SBP), diastolic blood pressure (DBP), and glucose (GLU) amongst different quartiles of HGH (P < .001). A U-shape relationship was established between HGH and age. After sex stratification, the results showed that the thresholds of age were 60 years in women, and 50 years in men, after adjusting for body mass index, triglycerides, total cholesterol, blood pressure, and blood glucose. Logistic regression showed that HGH level decreased in women aged <60 years (OR = 1.472, P < .001) and increased in men aged >50 years (OR = 0.711, P < .001). So the distributive characteristics of HGH concentration vary with sex and age group.

The effects of growth hormone on therapy resistance in cancer

Pituitary derived and peripherally produced growth hormone (GH) is a crucial mediator of longitudinal growth, organ development, metabolic regulation with tissue specific, sex specific, and age-dependent effects. GH and its cognate receptor (GHR) are expressed in several forms of cancer and have been validated as an anti-cancer target through a large body of in vitro, in vivo and epidemiological analyses. However, the underlying molecular mechanisms of GH action in cancer prognosis and therapeutic response had been sparse until recently. This review assimilates the critical details of GH-GHR mediated therapy resistance across different cancer types, distilling the therapeutic implications based on our current understanding of these effects.

Growth hormone protects colorectal cancer cells from radiation by improving the ability of DNA damage repair

The present study aimed to examine the effects of recombinant human growth hormone (rhGH) on the sensitivity of a colorectal cancer cell line to radiotherapy, and to investigate its association with DNA damage and repair. Flow cytometry and immunofluorescence were employed to detect growth hormone receptor (GHR) expression in nine human colorectal cancer cell lines. A colony forming assay was performed to measure the colorectal cancer cell proliferation post‑radiotherapy, as an indicator of radiotherapy sensitivity. The comet assay results were interpreted as an indicator of radiotherapy‑induced DNA damage, and growth arrest and DNA damage 45 (GADD45) and apurinic/apyrimidinic endonuclease (APEN) protein expression were quantified with western blot analysis from the same cell lines. The results demonstrated that the colony‑forming efficiency (CFE) was significantly increased in HCT‑8 cells subject to radiotherapy and rhGH pretreatment compared with the cells treated with radiotherapy alone, in a dose‑dependent manner (0‑100 mg/l). This effect was enhanced under high doses of radiation (8 Gy; 52.1±2.9 vs. 21.0±2.7; P<0.001) and was ameliorated with GHR neutralizing antibody exposure. By contrast, rhGH pre‑incubation did not change the colony formation rate in GHR(‑) LOVO cells. rhGH intervention reduced the early HCT‑8 cell DNA damage (21.53±2.88 vs. 36.56±3.93; P=0.003) as well as the following plateau phase, compared with cells treated with radiotherapy alone (5.5±0.42 vs. 9.07±0.84; P=0.012). rhGH upregulated GADD45 and APEN protein expression, which is associated with cellular stress responses and DNA damage repair (P=0.007). The results suggest that rhGH is able to protect colorectal cancer cells from radiation through the interaction with GHR, which is associated with the promotion of DNA damage repair activity.

siRNA-targeted inhibition of growth hormone receptor in human colon cancer SW480 cells

AIM: To determine the effects of RNAi-mediated inhibition of the growth hormone receptor (GHR) gene on tumors and colon cancer cells in vivo.

METHODS: Construction of a eukaryotic vector for human GHR expression, the pcDNA™6.2-GW/EmGFP-small interfering RNAs (siRNAs)-GHR plasmid, was used to inhibit GHR expression. Thirty-six BALB/c nude mice were randomly divided into groups and treated with normal saline (NS), recombinant plasmid (G₂), growth hormone (GH), 5-fluorouracil (FU), G₂+FU or G₂+FU+GH. Each nude mouse was subcutaneously inoculated with 1×10⁷ human colon cancer SW480 cells; the nude mice were weighed before inoculation and on the 2^nd, 5^th, 8^th, 11^th, 14^th and 17^th day after inoculation. All nude mice were sacrificed after 17 d. Each subcutaneous tumor was removed and studied. Tumor volume was measured on the 5^th, 8^th, 11^th, 14^th and 17^th day after inoculation. The expression of GHR protein in the tumor tissue was detected by Western blotting analysis, and the differences in GHR mRNA expression in the tumor tissue were detected by real-time quantitative reverse transcription-polymerase chain reaction.

RESULTS: Compared to the control group, the weights of the inoculated nude mice on the 17^th day after inoculation were: G₂: 21.60 ± 0.71 g, GH: 21.64 ± 0.45 g, FU: 18.94 ± 0.47 g, FU+G₂: 19.40 ± 0.60 g, G₂+FU+GH: 21.04 ± 0.78 g vs NS: 20.68 ± 0.66 g, P < 0.05; the tumor volumes after the subcutaneous inoculation were: G₂: 9.71 ± 3.82 mm³, FU: 11.54 ± 2.42 mm³, FU+G₂: 11.42 ± 1.11 mm³, G₂+FU+GH: 10.47 ± 1.02 mm³vs NS: 116.81 ± 10.61 mm³, P < 0.05. Compared to the GH group, the tumor volumes were significantly decreased in the experimental groups. The GHR protein expression (G₂: 0.39 ± 0.02, FU: 0.40 ± 0.02, FU+G₂: 0.38 ± 0.01, G₂+FU+GH: 0.39 ± 0.01 vs NS: 0.94 ± 0.02, P < 0.05) and the GHR mRNA expression (G₂: 14.12 ± 0.10, FU: 15.15 ± 0.44, FU+G₂: 16.46 ± 0.27, G₂+FU+GH: 15.37 ± 0.57 vs NS: 12.63 ± 0.14, P < 0.05) were significantly decreased and increased, respectively, in the experimental groups.

CONCLUSION: Inhibition of GHR in human colon cancer SW480 cells resulted in anti-tumor effects in nude mice.

Autocrine human GH promotes radioresistance in mammary and endometrial carcinoma cells

Although recent advances in breast cancer treatment regimes have improved patient prognosis, resistance to breast cancer therapies, such as radiotherapy, is still a major clinical challenge. In the current study, we have investigated the role of autocrine human GH (hGH) in resistance to ionising radiation (IR)-based therapy. Cell viability and total cell number assays demonstrated that autocrine hGH promoted cell regrowth in the mammary carcinoma cell lines, MDA-MB-435S and T47D, and the endometrial carcinoma cell line, RL95-2, following treatment with IR. In addition, autocrine hGH enhanced MDA-MB-435S and T47D cell clonogenic survival following radiation exposure. The enhanced clonogenic survival afforded by autocrine hGH was mediated by JAK2 and Src kinases. Investigation into the DNA repair capacity demonstrated that autocrine hGH reduced IR-induced DNA damage in MDA-MB-435S and T47D cells. Functional antagonism of hGH increased RL95-2 sensitivity to IR in cell viability and total cell number assays, reduced clonogenic survival and enhanced the induction of DNA damage. Thus, autocrine hGH reduced sensitivity to treatment with IR in mammary and endometrial carcinoma cell lines in vitro, while functional antagonism of hGH sensitised endometrial carcinoma cells to IR. Functional antagonism of hGH, used in conjunction with radiotherapy, may therefore enhance treatment efficacy and improve the prognosis of patients with breast and endometrial cancer.

Role of the growth hormone-IGF-1 axis in cancer

A substantial body of evidence supports a role for the growth hormone (GH)-IGF-1 axis in cancer incidence and progression. This includes epidemiological evidence relating elevated plasma IGF-1 to cancer incidence as well as a lack of cancers in GH/IGF-1 deficiency. Rodent models lacking GH or its receptor are strikingly resistant to the induction of a wide range of cancers, and treatment with the GH antagonist pegvisomant slows tumor progression. While GH receptor expression is elevated in many cancers, autocrine GH is present in several types, and overexpression of autocrine GH can induce cell transformation. While the mechanism of autocrine action is not clear, it does involve both STAT5 and STAT3 activation, and probably nuclear translocation of the GH receptor. Development of a more potent GH receptor antagonist or secretion inhibitor is warranted for cancer therapy.

Growth hormone, the insulin-like growth factor axis, insulin and cancer risk

Growth hormone (GH), insulin-like growth factor (IGF)-I and insulin have potent growth-promoting and anabolic actions. Their potential involvement in tumor promotion and progression has been of concern for several decades. The evidence that GH, IGF-I and insulin can promote and contribute to cancer progression comes from various sources, including transgenic and knockout mouse models and animal and human cell lines derived from cancers. Assessments of the GH-IGF axis in healthy individuals followed up to assess cancer incidence provide direct evidence of this risk; raised IGF-I levels in blood are associated with a slightly increased risk of some cancers. Studies of human diseases characterized by excess growth factor secretion or treated with growth factors have produced reassuring data, with no notable increases in de novo cancers in children treated with GH. Although follow-up for the vast majority of these children does not yet extend beyond young adulthood, a slight increase in cancers in those with long-standing excess GH secretion (as seen in patients with acromegaly) and no overall increase in cancer with insulin treatment, have been observed. Nevertheless, long-term surveillance for cancer incidence in all populations exposed to increased levels of GH is vitally important.

Transcriptional regulation of the human growth hormone receptor (hGHR) gene V2 promoter by transcriptional activators and repressor

The V2 transcript is the major ubiquitously expressed human GH receptor (hGHR) mRNA in all tissues examined to date. In a previous investigation, we defined the V2 promoter as TATA-less and exhibiting many characteristics of a housekeeping gene promoter. We also demonstrated that its basal activity is determined by several different cis-regulatory regions within both the promoter and the V2 exon. In the present study, we used luciferase-reporter, site-directed mutagenesis, gel shift, chromatin immunoprecipitation, and quantitative RT-PCR assays to investigate the ability of certain transcription factors to regulate hGHR V2 transcription through these regions in mammalian cells, including human adipocytes. Ets1 was found to transactivate the V2 proximal promoter through specific Ets sites. Two CCAAT/enhancer-binding protein (C/EBP) family members [C/EBP-homologous protein (CHOP) and C/EBPbeta] enhanced V2 transcription via different pathways: indirectly, by association with a V2 exon region (CHOP), and directly, using a V2 proximal promoter noncanonical binding site (C/EBPbeta). The Notch signaling mediator, Hes1, potently suppressed V2 promoter activity through interaction with two Hes sites within the V2 exon. We propose that these transcriptional factors regulate hGHR V2 expression by acting as downstream nuclear effectors, linking specific signaling cascades (e.g. MAPK and Notch) triggered by different growth factor-, development-, and nutrition- as well as stress-related stimuli. Our data also suggest that these factors are likely to be important in the differentiation-induced increase in V2 mRNA expression in adipocytes, with Ets1 and CHOP functioning at the preadipocyte stage to prepare the cells for differentiation and increasing C/EBPs and decreasing Hes1 levels contributing during adipocyte maturation.

The contribution of growth hormone to mammary neoplasia

While the effects of growth hormone (GH) on longitudinal growth are well established, the observation that GH contributes to neoplastic progression is more recent. Accumulating literature implicates GH-mediated signal transduction in the development and progression of a wide range malignancies including breast cancer. Recently autocrine human GH been demonstrated to be an orthotopically expressed oncogene for the human mammary gland. This review will highlight recent evidence linking GH and mammary carcinoma and discuss GH-antagonism as a potential therapeutic approach for treatment of breast cancer.

The somatomedin hypothesis 2007: 50 years later

CONTEXT

The somatomedin/IGF hypothesis was based on the observation that GH was inactive when added to an in vitro incubation system but required a GH-dependent substance in the circulation to mediate its activity. Newer experimental evidence has led to several modifications of the hypothesis, but none of the proposed modifications accounts for all of the integrated actions of GH and IGF-I. In this paper, we propose an augmentative/counteractive modification of the existing hypothesis that takes into account all the actions of the GH-IGF system.

EVIDENCE ACQUISITION

The modification is based on experimental evidence published since the hypothesis was originally developed.

EVIDENCE SYNTHESIS

The modification is based on an integration of the results of published experimental evidence regarding the actions of GH and the IGF complex.

CONCLUSION

We propose a new augmentative/counteractive modification of the hypothesis that the actions of the GH-IGF system provide a distinct evolutionary advantage to the organism by augmenting the anabolic actions of GH while countering its potentially deleterious effects of hyperglycemia and depletion of lipid stores.

Non-operative treatment after neoadjuvant chemoradiotherapy for rectal cancer

The past decade has seen pronounced changes in the treatment of locally advanced rectal cancer. Historically, the standard of care involved surgery followed by adjuvant radiotherapy or chemoradiotherapy. More recently, the emergence of neo-adjuvant chemoradiotherapy has fundamentally changed the management of patients with locally advanced disease. In clinical trials, pathological complete responses of up to 25% have raised the question as to whether surgery can be avoided in a select cohort of patients. A trial of omission of surgery for selected patients with complete response after preoperative chemoradiotherapy has shown favourable long-term results. In this article, we outline emerging factors for achieving pathological complete response, non-operative strategies to date, methods for prediction of response to chemoradiotherapy, and future directions with the addition of MRI as a radiological guide to complete response.

Clinical pharmacodynamic effects of the growth hormone receptor antagonist pegvisomant: implications for cancer therapy

PURPOSE

The present study evaluated and compared the efficacy of pegvisomant and octreotide in blocking the growth hormone (GH) axis in humans based on pharmacodynamic biomarkers associated with the GH axis. The study also evaluated the safety of pegvisomant given at high s.c. doses for 14 days.

EXPERIMENTAL DESIGN

Eighty healthy subjects were enrolled in five cohorts: cohorts 1 to 3, s.c. pegvisomant at 40, 60, or 80 mg once dailyx14 days (n=18 per cohort); cohort 4, s.c. octreotide at 200 microg thrice dailyx14 days (n=18); and cohort 5, untreated control (n=8). Serial blood samples were collected to measure plasma concentrations of total insulin-like growth factor type I (IGF-I), free IGF-I, IGF-II, IGF-binding protein 3 (IGFBP-3), and GH in all subjects and serum pegvisomant concentrations in subjects of cohorts 1 to 3. All subjects receiving treatment were monitored for adverse events (AE).

RESULTS

After s.c. dosing of pegvisomant once daily for 14 days, the mean maximum suppression values of total IGF-I were 57%, 60%, and 62%, at 40, 60, and 80 mg dose levels, respectively. The maximum suppression was achieved approximately 7 days after the last dose and was sustained for approximately 21 days. Pegvisomant also led to a sustained reduction in free IGF-I, IGFBP-3, and IGF-II concentrations by up to 33%, 46%, and 35%, respectively, and an increase in GH levels. In comparison, octreotide resulted in a considerably weaker inhibition of total IGF-I and IGFBP-3 for a much shorter duration, and no inhibition of IGF-II. AEs in pegvisomant-treated subjects were generally either grade 1 or 2. The most frequent treatment-related AEs included injection site reactions, headache, and fatigue.

CONCLUSIONS

Pegvisomant at well-tolerated s.c. doses was considerably more efficacious than octreotide in suppressing the GH axis, resulting in substantial and sustained inhibition of circulating IGF-I, IGF-II, and IGFBP-3 concentrations. These results provide evidence in favor of further testing the hypothesis that pegvisomant, through blocking the GH receptor-mediated signal transduction pathways, could be effective in treating tumors that may be GH, IGF-I, and/or IGF-II dependent, such as breast and colorectal cancer.

Growth hormone treatment and cancer risk

Increasing numbers of children receive growth hormone (GH) to treat a range of growth disorders, including those rendered GH deficient (GHD) by tumors or their treatment. Young persons with persistent growth hormone deficiency (GHD) and adults with severe GHD are also eligible to receive GH treatment. As in vitro and in vivo studies and epidemiologic observations provide some evidence that the GH--insulin like growth factor-I (IGF-I) axis is associated with tumorigenesis, it is important to assess, in practice, the incidence of tumors related to GH treatment. Reassuringly, surveillance studies in large cohorts of children and in smaller cohorts of adults indicate that GH is not associated with an increased incidence of tumor occurrence or recurrence. Nevertheless, all children who have received GH, in particular cancer survivors and those receiving GH in adulthood, should be in surveillance programs to assess whether an increased rate od late-onset and rare tumours may occur.

The oncogenic potential of growth hormone

A growing body of recent literature indicates that in addition to an essential role in growth and development, growth hormone may also play a more sinister role in oncogenic transformation and neoplastic progression. Here we review the accumulating evidence implicating growth hormone in the development and progression of cancer and describe what is known of the mechanisms utilised by this hormone in neoplastic transformation.