Patient-Derived Explants as a Precision Medicine Patient-Proximal Testing Platform Informing Cancer Management

Precision medicine approaches that inform clinical management of individuals with cancer are progressively advancing. Patient-derived explants (PDEs) provide a patient-proximal ex vivo platform that can be used to assess sensitivity to standard of care (SOC) therapies and novel agents. PDEs have several advantages as a patient-proximal model compared to current preclinical models, as they maintain the phenotype and microenvironment of the individual tumor. However, the longevity of PDEs is not compatible with the timeframe required to incorporate candidate therapeutic options identified by whole exome sequencing (WES) of the patient’s tumor. This review investigates how PDE longevity varies across tumor streams and how this is influenced by tissue preparation. Improving longevity of PDEs will enable individualized therapeutics testing, and thus contribute to improving outcomes for people with cancer.

Culture of Bladder Cancer Organoids as Precision Medicine Tools

Current in vitro therapeutic testing platforms lack relevance to tumor pathophysiology, typically employing cancer cell lines established as two-dimensional (2D) cultures on tissue culture plastic. There is a critical need for more representative models of tumor complexity that can accurately predict therapeutic response and sensitivity. The development of three-dimensional (3D) ex vivo culture of patient-derived organoids (PDOs), derived from fresh tumor tissues, aims to address these shortcomings. Organoid cultures can be used as tumor surrogates in parallel to routine clinical management to inform therapeutic decisions by identifying potential effective interventions and indicating therapies that may be futile. Here, this procedure aims to describe strategies and a detailed step-by-step protocol to establish bladder cancer PDOs from fresh, viable clinical tissue. Our well-established, optimized protocols are practical to set up 3D cultures for experiments using limited and diverse starting material directly from patients or patient-derived xenograft (PDX) tumor material. This procedure can also be employed by most laboratories equipped with standard tissue culture equipment. The organoids generated using this protocol can be used as ex vivo surrogates to understand both the molecular mechanisms underpinning urological cancer pathology and to evaluate treatments to inform clinical management.

The mitochondrial genome of the black-tailed dusky antechinus (Antechinus arktos)

In this study, we report the mitochondrial genome of the black-tailed antechinus (Antechinus arktos), a recently-discovered, endangered carnivorous marsupial inhabiting a caldera that straddles the border of Australia’s mid-east coast. The circular A. arktos genome is 17,334 bp in length and has an AT content of 63.3%. Its gene content and arrangement are consistent with reported marsupial mitogenome assemblies.

The mitochondrial genome of the black-tailed dasyure (Murexia melanurus)

In this study, we report the mitochondrial genome of the black-tailed dasyure (Murexia melanurus) of New Guinea. The circular genome is 17,736 bp in length and has an AT content of 60.5%. Its gene content – 13 protein-coding genes (PCGs), 2 ribosomal (rRNA) genes, 21 transfer RNA (tRNA) genes, a tRNA pseudogene (tRNA^Lys), and a non-coding control region (CR) – and gene arrangement are consistent with previous marsupial mitogenome assemblies.

The long non-coding RNA GHSROS facilitates breast cancer cell migration and orthotopic xenograft tumour growth

Recent evidence suggests that numerous long non-coding RNAs (lncRNAs) are dysregulated in cancer, and have critical roles in tumour development and progression. The present study investigated the ghrelin receptor antisense lncRNA growth hormone secretagogue receptor opposite strand (GHSROS) in breast cancer. Reverse transcription-quantitative polymerase chain reaction revealed that GHSROS expression was significantly upregulated in breast tumour tissues compared with normal breast tissue. Induced overexpression of GHSROS in the MDA-MB-231 breast cancer cell line significantly increased cell migration in vitro, without affecting cell proliferation, a finding similar to our previous study on lung cancer cell lines. Microarray analysis revealed a significant repression of a small cluster of major histocompatibility class II genes and enrichment of immune response pathways; this phenomenon may allow tumour cells to better evade the immune system. Ectopic overexpression of GHSROS in the MDA-MB-231 cell line significantly increased orthotopic xenograft growth in mice, suggesting that in vitro culture does not fully capture the function of this lncRNA. This study demonstrated that GHSROS may serve a relevant role in breast cancer. Further studies are warranted to explore the function and therapeutic potential of this lncRNA in breast cancer progression.

Limited short-term effects on human prostate cancer xenograft growth and epidermal growth factor receptor gene expression by the ghrelin receptor antagonist [D-Lys3]-GHRP-6

PURPOSE

The ghrelin axis regulates many physiological functions (including appetite, metabolism, and energy balance) and plays a role in disease processes. As ghrelin stimulates prostate cancer proliferation, the ghrelin receptor antagonist [D-Lys³]-GHRP-6 is a potential treatment for castrate-resistant prostate cancer and for preventing the metabolic consequences of androgen-targeted therapies. We therefore explored the effect of [D-Lys³]-GHRP-6 on PC3 prostate cancer xenograft growth.

METHODS

NOD/SCID mice with PC3 prostate cancer xenografts were administered 20 nmoles/mouse [D-Lys³]-GHRP-6 daily by intraperitoneal injection for 14 days and tumour volume and weight were measured. RNA sequencing of tumours was conducted to investigate expression changes following [D-Lys³]-GHRP-6 treatment. A second experiment, extending treatment time to 18 days and including a higher dose of [D-Lys³]-GHRP-6 (200 nmoles/mouse/day), was undertaken to ensure repeatability.

RESULTS

We demonstrate here that daily intraperitoneal injection of 20 nmoles/mouse [D-Lys³]-GHRP-6 reduces PC3 prostate cancer xenograft tumour volume and weight in NOD/SCID mice at two weeks post treatment initiation. RNA-sequencing revealed reduced expression of epidermal growth factor receptor (EGFR) in these tumours. Further experiments demonstrated that the effects of [D-Lys³]-GHRP-6 are transitory and lost after 18 days of treatment.

CONCLUSIONS

We show that [D-Lys³]-GHRP-6 has transitory effects on prostate xenograft tumours in mice, which rapidly develop an apparent resistance to the antagonist. Although further studies on [D-Lys³]-GHRP-6 are warranted, we suggest that daily treatment with the antagonist is not a suitable treatment for advanced prostate cancer.

No effect of unacylated ghrelin administration on subcutaneous PC3 xenograft growth or metabolic parameters in a Rag1-/- mouse model of metabolic dysfunction

Ghrelin is a peptide hormone which, when acylated, regulates appetite, energy balance and a range of other biological processes. Ghrelin predominately circulates in its unacylated form (unacylated ghrelin; UAG). UAG has a number of functions independent of acylated ghrelin, including modulation of metabolic parameters and cancer progression. UAG has also been postulated to antagonise some of the metabolic effects of acyl-ghrelin, including its effects on glucose and insulin regulation. In this study, Rag1-/- mice with high-fat diet-induced obesity and hyperinsulinaemia were subcutaneously implanted with PC3 prostate cancer xenografts to investigate the effect of UAG treatment on metabolic parameters and xenograft growth. Daily intraperitoneal injection of 100 μg/kg UAG had no effect on xenograft tumour growth in mice fed normal rodent chow or 23% high-fat diet. UAG significantly improved glucose tolerance in host Rag1-/- mice on a high-fat diet, but did not significantly improve other metabolic parameters. We propose that UAG is not likely to be an effective treatment for prostate cancer, with or without associated metabolic syndrome.

Abstract 2452: Dysregulated expression of the human long noncoding RNA GHSROS may influence prostate cancer progression and resistance to docetaxel

Long noncoding RNAs (lncRNAs) play key regulatory roles in cancer progression and are novel therapeutic targets. We recently discovered the lncRNA gene, GHSROS (GHSR opposite strand), on the antisense DNA strand of the ghrelin receptor gene (GHSR). Here, we studied the expression and function of GHSROS in prostate cancer. Interrogation of microarray and RNA-seq data sets revealed that (similar to other lncRNA oncogenes) GHSROS is actively transcribed, although expressed at very low levels in cancer cell lines and tissues. By quantitative RT-PCR we demonstrate that GHSROS is highly expressed in a subset of high-grade prostate cancers (~11.4%). Moreover, the lncRNA is upregulated in high Gleason-score prostate tumors in two clinical data sets. Forced GHSROS overexpression significantly increased in vitro cell proliferation and migration of PC3, DU145, and LNCaP prostate cancer cell lines (P ≤ 0.05, Student's t-test). Increased cell proliferation observed in GHSROS-overexpressing prostate cancer cell lines was recapitulated in PC3, DU145, and LNCaP prostate cancer xenografts in NOD/SCID mice. Cell survival was significantly increased in GHSROS-overexpressing LNCaP cells treated with the cytotoxic drug docetaxel (P ≤ 0.05, Student's t-test). Docetaxel treatment also increased GHSROS expression in native LNCaP and PC3 cells in a dose-dependent manner (P ≤ 0.05, Student's t-test). These data suggest that GHSROS mediates tumor survival and resistance to docetaxel. To identify fundamental drivers of the observed tumorigenic phenotype of GHSROS-overexpressing cell lines, high-throughput RNA-seq data from in vitro cultured PC3 cells and LNCaP xenografts were examined. A quarter of the genes differentially expressed by GHSROS-overexpressing PC3 cells were also differentially expressed by GHSROS-overexpressing LNCaP xenografts. These 101 genes include several transcription factors with established roles in prostate cancer (including the androgen receptor) and genes associated with metastasis and poor prognosis. Finally, we developed two distinct antisense oligonucleotides (ASOs) targeting GHSROS, achieving >60% knockdown, and their function was assessed in vitro. ASO inhibition of GHSROS expression reciprocally regulated cell growth and migration and the expression of a range of genes. These ASOs are currently being assessed in preclinical animal models. Our findings suggest that the long noncoding RNA GHSROS reprograms prostate cancer cells toward a more aggressive phenotype and that the lncRNA represents a promising therapeutic target.

Citation Format: Patrick B. Thomas, Penny L. Jeffery, Gahete D. Manuel, Eliza J. Whiteside, Michelle Maugham, Carina Walpole, Jennifer H. Gunter, Elizabeth D. Williams, Colleen C. Nelson, Adrian C. Herington, Raul M. Luque, Rakesh N. Veedu, Lisa K. Chopin, Inge Seim. Dysregulated expression of the human long noncoding RNA GHSROS may influence prostate cancer progression and resistance to docetaxel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2452.

Abstract 3442: The long non-coding RNA GHSROS mediates expression of genes associated with tumor growth, metastasis and adverse disease outcome

Long non-coding RNAs (lncRNAs) play key regulatory roles in cancer progression and are emerging therapeutic targets. The objective of this study was to investigate the expression and function of the lncRNA GHSROS in prostate cancer. Quantitative RT-PCR revealed that GHSROS is highly expressed in a subset of prostate cancers (Gleason score 8-10; z-score >1; Mann-Whitney-Wilcoxon test P=0.0021). Forced overexpression of the lncRNA stimulated cell migration in vitro in the PC3 (1.82 ± 0.35, P=0.006; Student’s t-test), DU145 (1.94 ± 0.34, P=0.017), and LNCaP (1.27 ± 0.02, P=0.0002) prostate cancer cell lines. Cell proliferation was increased in GHSROS overexpressing PC3 (3.36 ± 1.91, P=0.029), DU145 (1.749 ± 0.59, P=0.026), and LNCaP (1.39 ± 0.26, P=0.040) prostate cancer cell lines. These results were recapitulated in NOD/SCID mice, with increased tumor growth and Ki67 immunohistochemical staining in PC3 (P=0.0040) and DU145 (P = 0.036) xenografts overexpressing the lncRNA.High-throughput transcriptome sequencing (RNA-seq) identified 400 differentially expressed genes in GHSROS overexpressing PC3 cells, with enrichment of genes associated with motility, migration and regulation of cell growth. Further interrogation of the 400 gene set using Oncomine concept mapping, and interrogation of publicly-available clinical prostate cancer data sets, revealed a 34-gene signature associated with poorer disease outcome and metastatic progression. Preliminary analysis of The Cancer Genome Atlas (TCGA) data, suggest that the signature has potential as a prognostic indicator for disease free- or overall survival in numerous cancers. Finally, locked antisense oligonucleotide (LNA-ASO) inhibition of endogenous GHSROS reciprocally regulated cell growth (Student’s t-test; RNV124: -1.14 ± 0.06, P=0.049 and RNV104L: -1.18 ± 0.05, P=0.030, migration (RNV124: -1.96 ± 0.11, P=0.004) and gene expression changes, supporting the observations from forced GHSROS overexpression experiments.In summary, we provide evidence that GHSROS is a prostate cancer associated lncRNA that promotes a gene expression signature which enhances the propensity for metastasis and adverse disease outcomes. We also demonstrate that GHSROS can be targeted using antisense oligonucleotides. Further studies on this lncRNA may provide new prognostic and therapeutic opportunities.

Citation Format: Patrick B. Thomas, Penny L. Jeffery, Eliza Whiteside, Carina Walpole, Michelle Maugham, Lidija Jovanovic, Jennifer H. Gunter, Colleen C. Nelson, Adrian C. Herington, Rakesh Veedu, Lisa K. Chopin, Inge Seim. The long non-coding RNA GHSROS mediates expression of genes associated with tumor growth, metastasis and adverse disease outcome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3442. doi:10.1158/1538-7445.AM2017-3442

Abstract 4819: Insights from engraftable immunodeficient mouse models of hyperinsulinaemia

Hyperinsulinemia, obesity and dyslipidemia are independent and collective risk factors for many cancers, however, there is a lack of suitable mouse models available to study this association.

We examined the long-term effects of a “Western style” 23% high fat diet (HFD, 46% of total calculated energy from lipids) in two immunodeficient mouse strains (NOD/SCID and Rag1 -/-) suitable for engraftment with human-derived cell lines and tissue xenografts. HFD-fed mice of both strains exhibited diet-induced impairments in glucose tolerance at 16 and 23 weeks post initiation of HFD feeding. Only Rag1 -/- mice developed higher fasting insulin levels (2.16 ± 1.01ng/ml versus 0.71 ± 0.12ng/ml, P = 0.01) and increased insulin resistance (6.70 ± 1.68 HOMA-IR, versus 2.91 ± 0.42, P = 0.01) when fed a HFD. Similarly, hepatic steatosis was more extensive, and intramyocellular lipid storage was increased in HFD-fed Rag1 -/- mice. Conversely, NOD/SCID mice exhibited relatively low levels of steatosis and no intramyocellular lipid was observed. These data suggest that Rag1 -/- mice are a more suitable pre-clinical model for examining the interactions between hyperinsulinemia, obesity and hyperlipidemia and cancer than the more commonly used NOD/SCID mouse model.

We next investigated the growth of human prostate cancer cell lines (PC3 and LNCaP) subcutaneously injected into hyperinsulinemic Rag1 -/- mice. Compared to normal chow-fed mice, tumor growth velocity was greater in HFD-fed mice with PC3 and LNCaP xenografts, and mice reached humane endpoints (cancer-associated cachexia and tumor burden) significantly earlier (P = 0.0078 and P = 0.031). Strikingly, HFD-fed mice bearing PC3 xenografts presented with significantly greater normalized wet tumor weight (485.16 ± 143.80% vs. 1562.69 ± 338.20%, P = 0.032), tumor volume (485.16 ± 143.80% vs.1562.69 ± 338.20%, P = 0.032) and number of Ki67 positive (proliferating) tumor cells (36.08 ± 2.53% vs. 66.14 ± 8.514, P = 0.032), compared to mice fed a normal chow diet.

In summary, this is the first study of the metabolic effects of a long-term “Western style” HFD in two immunodeficient mouse strains suitable for xenograft studies. We demonstrate that the Rag1 -/- mouse is an appropriate and novel model for studying the interactions between hyperinsulinaemia and cancer.

Citation Format: Michelle L. Maugham, Patrick B. Thomas, Gabrielle J. Crisp, Lisa K. Philp, Esha T. Shah, Adrian C. Herington, Chen Chen, Laura S. Gregory, Colleen C. Nelson, Inge Seim, Penny L. Jeffery, Lisa K. Chopin. Insights from engraftable immunodeficient mouse models of hyperinsulinaemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4819. doi:10.1158/1538-7445.AM2017-4819

Whole-Genome Sequence of the Metastatic PC3 and LNCaP Human Prostate Cancer Cell Lines

The bone metastasis-derived PC3 and the lymph node metastasis-derived LNCaP prostate cancer cell lines are widely studied, having been described in thousands of publications over the last four decades. Here, we report short-read whole-genome sequencing (WGS) and de novo assembly of PC3 (ATCC CRL-1435) and LNCaP (clone FGC; ATCC CRL-1740) at ∼70 × coverage. A known homozygous mutation in TP53 and homozygous loss of PTEN were robustly identified in the PC3 cell line, whereas the LNCaP cell line exhibited a larger number of putative inactivating somatic point and indel mutations (and in particular a loss of stop codon events). This study also provides preliminary evidence that loss of one or both copies of the tumor suppressor Capicua (CIC) contributes to primary tumor relapse and metastatic progression, potentially offering a treatment target for castration-resistant prostate cancer (CRPC). Our work provides a resource for genetic, genomic, and biological studies employing two commonly-used prostate cancer cell lines.

Insights from engraftable immunodeficient mouse models of hyperinsulinaemia

Hyperinsulinaemia, obesity and dyslipidaemia are independent and collective risk factors for many cancers. Here, the long-term effects of a 23% Western high-fat diet (HFD) in two immunodeficient mouse strains (NOD/SCID and Rag1 -/-) suitable for engraftment with human-derived tissue xenografts, and the effect of diet-induced hyperinsulinaemia on human prostate cancer cell line xenograft growth, were investigated. Rag1 -/-and NOD/SCID HFD-fed mice demonstrated diet-induced impairments in glucose tolerance at 16 and 23 weeks post weaning. Rag1 -/- mice developed significantly higher fasting insulin levels (2.16 ± 1.01 ng/ml, P = 0.01) and increased insulin resistance (6.70 ± 1.68 HOMA-IR, P = 0.01) compared to low-fat chow-fed mice (0.71 ± 0.12 ng/ml and 2.91 ± 0.42 HOMA-IR). This was not observed in the NOD/SCID strain. Hepatic steatosis was more extensive in Rag1 -/- HFD-fed mice compared to NOD/SCID mice. Intramyocellular lipid storage was increased in Rag1 -/- HFD-fed mice, but not in NOD/SCID mice. In Rag1 -/- HFD-fed mice, LNCaP xenograft tumours grew more rapidly compared to low-fat chow-fed mice. This is the first characterisation of the metabolic effects of long-term Western HFD in two mouse strains suitable for xenograft studies. We conclude that Rag1 -/- mice are an appropriate and novel xenograft model for studying the relationship between cancer and hyperinsulinaemia.

MUC13 overexpression in renal cell carcinoma plays a central role in tumor progression and drug resistance

Metastatic renal cell carcinoma is a largely incurable disease, and existing treatments targeting angiogenesis and tyrosine kinase receptors are only partially effective. Here we reveal that MUC13, a cell surface mucin glycoprotein, is aberrantly expressed by most renal cell carcinomas, with increasing expression positively correlating with tumor grade. Importantly, we demonstrated that high MUC13 expression was a statistically significant independent predictor of poor survival in two independent cohorts, particularly in stage 1 cancers. In cultured renal cell carcinoma cells MUC13 promoted proliferation and induced the cell cycle regulator, cyclin D1, and inhibited apoptosis by inducing the anti-apoptotic proteins, BCL-xL and survivin. Silencing of MUC13 expression inhibited migration and invasion, and sensitized renal cancer cells to killing by the multi-kinase inhibitors used clinically, sorafenib and sunitinib, and reversed acquired resistance to these drugs. Furthermore, we demonstrated that MUC13 promotion of renal cancer cell growth and survival is mediated by activation of nuclear factor κB, a transcription factor known to regulate the expression of genes that play key roles in the development and progression of cancer. These results show that MUC13 has potential as a prognostic marker for aggressive early stage renal cell cancer and is a plausible target to sensitize these tumors to therapy.

Multi-species sequence comparison reveals conservation of ghrelin gene-derived splice variants encoding a truncated ghrelin peptide

The peptide hormone ghrelin is a potent orexigen produced predominantly in the stomach. It has a number of other biological actions, including roles in appetite stimulation, energy balance, the stimulation of growth hormone release and the regulation of cell proliferation. Recently, several ghrelin gene splice variants have been described. Here, we attempted to identify conserved alternative splicing of the ghrelin gene by cross-species sequence comparisons. We identified a novel human exon 2-deleted variant and provide preliminary evidence that this splice variant and in1-ghrelin encode a C-terminally truncated form of the ghrelin peptide, termed minighrelin. These variants are expressed in humans and mice, demonstrating conservation of alternative splicing spanning 90 million years. Minighrelin appears to have similar actions to full-length ghrelin, as treatment with exogenous minighrelin peptide stimulates appetite and feeding in mice. Forced expression of the exon 2-deleted preproghrelin variant mirrors the effect of the canonical preproghrelin, stimulating cell proliferation and migration in the PC3 prostate cancer cell line. This is the first study to characterise an exon 2-deleted preproghrelin variant and to demonstrate sequence conservation of ghrelin gene-derived splice variants that encode a truncated ghrelin peptide. This adds further impetus for studies into the alternative splicing of the ghrelin gene and the function of novel ghrelin peptides in vertebrates.

Effect of Deletion of Ghrelin-O-Acyltransferase on the Pulsatile Release of Growth Hormone in Mice

Ghrelin, a gut hormone originating from the post-translational cleavage of preproghrelin, is the endogenous ligand of growth hormone secretagogue receptor 1a (GHS-R1a). Within the growth hormone (GH) axis, the biological activity of ghrelin requires octanoylation by ghrelin-O-acyltransferase (GOAT), conferring selective binding to the GHS-R1a receptor via acylated ghrelin. Complete loss of preproghrelin-derived signalling (through deletion of the Ghrl gene) contributes to a decline in peak GH release; however, the selective contribution of endogenous acyl-ghrelin to pulsatile GH release remains to be established. We assessed the pulsatile release of GH in ad lib. fed male germline goat(-/-) mice, extending measures to include mRNA for key hypothalamic regulators of GH release, and peripheral factors that are modulated relative to GH release. The amount of GH released was reduced in young goat(-/-) mice compared to age-matched wild-type mice, whereas pulse frequency and irregularity increased. Altered GH release did not coincide with alterations in hypothalamic Ghrh, Srif, Npy or Ghsr mRNA expression, or pituitary GH content, suggesting that loss of Goat does not compromise canonical mechanisms that contribute to pituitary GH production and release. Although loss of Goat resulted in an irregular pattern of GH release (characterised by an increase in the number of GH pulses observed during extended secretory events), this did not contribute to a change in the expression of sexually dimorphic GH-dependent liver genes. Of interest, circulating levels of insulin-like growth factor (IGF)-1 were elevated in goat(-/-) mice. This rise in circulating levels of IGF-1 was correlated with an increase in GH pulse frequency, suggesting that sustained or increased IGF-1 release in goat(-/-) mice may occur in response to altered GH release patterning. Our observations demonstrate that germline loss of Goat alters GH release and patterning. Although the biological relevance of altered GH secretory patterning remains unclear, we propose that this may contribute to sustained IGF-1 release and growth in goat(-/-) mice.

Rapid method for growth hormone receptor exon 3 delete (GHRd3) SNP genotyping from archival human placental samples

Analysis of archival samples from cohorts of pregnant women may be key to discovering prognosticators of stillbirth and pregnancy/perinatal complications. Growth hormone (GH) and its receptor (GHR) are pivotal in feto-placental development and pregnancy maintenance. We report a rapid, optimized method for genotyping the GHR full-length versus exon 3-deleted isoform (GHRd3). TaqMan single nucleotide polymorphism (SNP) genotyping proved superior to standard multiplex polymerase chain reaction (PCR) in allele detection and GHR genotyping from archived samples, including those with poor genomic deoxyribonucleic acid quality/quantity such as formalin fixed, paraffin embedded, blood, and serum. Furthermore, this assay is suitable for high through put 96 or 384-well plate quantitative PCR machines with automated genotype calling software. The TaqMan genotyping assay can increase the data obtained from precious archival human samples.

Comparative analysis reveals loss of the appetite-regulating peptide hormone ghrelin in falcons

Ghrelin and leptin are key peripherally secreted appetite-regulating hormones in vertebrates. Here we consider the ghrelin gene (GHRL) of birds (class Aves), where it has been reported that ghrelin inhibits rather than augments feeding. Thirty-one bird species were compared, revealing that most species harbour a functional copy of GHRL and the coding region for its derived peptides ghrelin and obestatin. We provide evidence for loss of GHRL in saker and peregrine falcons, and this is likely to result from the insertion of an ERVK retrotransposon in intron 0. We hypothesise that the loss of anorexigenic ghrelin is a predatory adaptation that results in increased food-seeking behaviour and feeding in falcons.

Ghrelin O-acyltransferase (GOAT) is expressed in prostate cancer tissues and cell lines and expression is differentially regulated in vitro by ghrelin

BACKGROUND

Ghrelin is a 28 amino acid peptide hormone that is expressed in the stomach and a range of peripheral tissues, where it frequently acts as an autocrine/paracrine growth factor. Ghrelin is modified by a unique acylation required for it to activate its cognate receptor, the growth hormone secretagogue receptor (GHSR), which mediates many of the actions of ghrelin. Recently, the enzyme responsible for adding the fatty acid residue (octanoyl/acyl group) to the third amino acid of ghrelin, GOAT (ghrelin O-acyltransferase), was identified.

METHODS

We used cell culture, quantitative real-time reverse transcription (RT)-PCR and immunohistochemistry to demonstrate the expression of GOAT in prostate cancer cell lines and tissues from patients. Real-time RT-PCR was used to demonstrate the expression of prohormone convertase (PC)1/3, PC2 and furin in prostate cancer cell lines. Prostate-derived cell lines were treated with ghrelin and desacyl ghrelin and the effect on GOAT expression was measured using quantitative RT-PCR.

RESULTS

We have demonstrated that GOAT mRNA and protein are expressed in the normal prostate and human prostate cancer tissue samples. The RWPE-1 and RWPE-2 normal prostate-derived cell lines and the LNCaP, DU145, and PC3 prostate cancer cell lines express GOAT and at least one other enzyme that is necessary to produce mature, acylated ghrelin from proghrelin (PC1/3, PC2 or furin). Finally, ghrelin, but not desacyl ghrelin (unacylated ghrelin), can directly regulate the expression of GOAT in the RWPE-1 normal prostate derived cell line and the PC3 prostate cancer cell line. Ghrelin treatment (100nM) for 6 hours significantly decreased GOAT mRNA expression two-fold (P < 0.05) in the PC3 prostate cancer cell line, however, ghrelin did not regulate GOAT expression in the DU145 and LNCaP prostate cancer cell lines.

CONCLUSIONS

This study demonstrates that GOAT is expressed in prostate cancer specimens and cell lines. Ghrelin regulates GOAT expression, however, this is likely to be cell-type specific. The expression of GOAT in prostate cancer supports the hypothesis that the ghrelin axis has autocrine/paracrine roles. We propose that the RWPE-1 prostate cell line and the PC3 prostate cancer cell line may be useful for investigating GOAT regulation and function.

Silencing of ghrelin receptor expression inhibits endometrial cancer cell growth in vitro and in vivo

Ghrelin is a 28-amino acid peptide hormone produced predominantly in the stomach but also in a range of normal cell types and tumors, where it has endocrine, paracrine, and autocrine roles. Previously, we have demonstrated that ghrelin has proliferative and antiapoptotic effects in endometrial cancer cell lines, suggesting a potential role in promoting tumor growth. In the present study, we investigated the effect of ghrelin receptor, GHSR, and gene silencing in vitro and in vivo and characterized ghrelin and GHSR1a protein expression in human endometrial tumors. GHSR gene silencing was achieved in the Ishikawa and KLE endometrial cancer cell lines, using a lentiviral short-hairpin RNA targeting GHSR. The effects of GHSR1a knockdown were further analyzed in vivo using the Ishikawa cell line in a NOD/SCID xenograft model. Cell proliferation was reduced in cultured GHSR1a knockdown Ishikawa and KLE cells compared with scrambled controls in the absence of exogenously applied ghrelin and in response to exogenous ghrelin (1,000 nM). The tumor volumes were reduced significantly in GHSR1a knockdown Ishikawa mouse xenograft tumors compared with scrambled control tumours. Using immunohistochemistry, we demonstrated that ghrelin and GHSR1a are expressed in benign and cancerous glands in human endometrial tissue specimens, although there was no correlation between the intensity of staining and cancer grade. These data indicate that downregulation of GHSR expression significantly inhibits endometrial cancer cell line and mouse xenograft tumour growth. This is the first preclinical evidence that downregulation of GHSR may be therapeutic in endometrial cancer.

IL-10 promotes production of intestinal mucus by suppressing protein misfolding and endoplasmic reticulum stress in goblet cells

BACKGROUND & AIMS

Protein misfolding and endoplasmic reticulum (ER) stress have been observed in intestinal secretory cells from patients with inflammatory bowel diseases and induce intestinal inflammation in mice. However, it is not clear how immune factors affect ER stress and therefore disease symptoms.

METHODS

We analyzed the effects of interleukin (IL)-10 on ER stress in intestinal tissues in wild-type C57BL/6, Winnie, IL-10(-/-), and Winnie × IL-10(+/-) mice. In Winnie mice, misfolding of the intestinal mucin Muc2 initiates ER stress and inflammation. We also analyzed the effects of different inhibitors of IL-10 signaling and the N-glycosylation inhibitor tunicamycin in cultured human LS174T goblet cells.

RESULTS

Administration of neutralizing antibodies against IL-10 or its receptor (IL-10R1) to Winnie mice rapidly exacerbated ER stress and intestinal inflammation compared with mice given vehicle (controls). Antibodies against IL-10 also increased accumulation of misfolded Muc2 in the ER of goblet cells of Winnie mice and increased T-cell production of inflammatory cytokines. Winnie × IL-10(+/-) mice and IL-10(-/-) mice with a single Winnie allele each developed more severe inflammation than Winnie mice or IL-10(-/-) mice. Administration of tunicamycin to wild-type mice caused intestinal ER stress, which increased when IL-10R1 was blocked. In LS174T cells, induction of ER stress with tunicamycin and misfolding of MUC2 were reduced by administration of IL-10; this reduction required STAT1 and STAT3. In LS174T cells incubated with tunicamycin, IL-10 up-regulated genes involved in MUC2 folding and in ER-associated degradation and maintained correct folding of MUC2, its transport from the ER, and its O-glycosylation and secretion.

CONCLUSIONS

IL-10 prevents protein misfolding and ER stress by maintaining mucin production in goblet cells and helps the intestine preserve the mucus barrier.

The MUC13 cell-surface mucin protects against intestinal inflammation by inhibiting epithelial cell apoptosis

BACKGROUND AND AIMS

The MUC13 transmembrane mucin is highly and constitutively expressed in the small and large intestine. Although MUC13 polymorphisms have been associated with human inflammatory bowel diseases and susceptibility to Escherichia coli infection in pigs, the biological functions of MUC13 are unknown. This study aimed to explore whether MUC13 modulates intestinal inflammation.

METHODS

Muc13(-/-) mice were generated, phenotyped and challenged with the colitis-inducing agent, dextran sodium sulphate (DSS). Colitis was assessed by clinical symptoms and intestinal histopathology. Intestinal epithelial cell apoptosis and proliferation, macrophage infiltration and cytokine production were also quantified. Apoptosis of human LS513 intestinal epithelial cells in response to apoptotic agents, including DSS, was also measured, following knockdown of MUC13 with siRNA.

RESULTS

Muc13(-/-) mice were viable, fertile and developed normally, with no spontaneous intestinal pathology except mild focal neutrophilic inflammation in the small and large intestines of old mice. In response to DSS challenge, Muc13(-/-) mice developed more severe acute colitis, as reflected by increased weight loss, rectal bleeding, diarrhoea and histological colitis scores compared with wild-type mice. Increased numbers of F4/80(+) macrophages in inflamed mucosa of Muc13(-/-) mice were accompanied by increased expression of intestinal IL-1β and TNFα mRNA. Muc13(-/-) mice had significantly increased intestinal epithelial cell apoptosis within 3 days of DSS exposure. LS513 cells were more susceptible to DSS, actinomycin-D, ultraviolet irradiation and TRAIL-induced apoptosis when MUC13 was knocked down by siRNA.

CONCLUSIONS

These novel findings indicate a protective role for Muc13 in the colonic epithelium by inhibiting toxin-induced apoptosis and have important implications for intestinal infections, inflammatory diseases and the development of intestinal cancer.

Endocrine impact of Helicobacter pylori: Focus on ghrelin and ghrelin o-acyltransferase

Ghrelin is predominantly produced by the gastric enteroendocrine cell compartment and is octanoylated by the recently discovered ghrelin o-acyltransferase (GOAT) before secretion into the bloodstream. This octanoylation is essential for many of the biological properties of ghrelin including appetite stimulation and anti-inflammatory properties as only the acylated form of ghrelin binds to the ghrelin receptor, the growth hormone secretagogue receptor (GHS-R). Given the gastric location of ghrelin production, it is perhaps not surprising that insult to the gastric mucosa affects circulating ghrelin levels in humans. Helicobacter pylori (H. pylori) infects more than fifty percent of the world’s population and once established within the gastric mucosa, can persist for life. Infection is associated with chronic gastritis, gastric atrophy and ulceration, reduced appetite and a lower body mass index (BMI). The large majority of studies investigating levels of circulating ghrelin and ghrelin expression in the stomach in patients with H. pylori infection indicate that the bacterium has a negative impact on ghrelin production and/or secretion. Eradication of infection restores ghrelin, improves appetite and increases BMI in some studies, however, a causative relationship between H. pylori-associated serum ghrelin decline and food intake and obesity has not been established. Most studies measure total ghrelin in the circulation although the measurement of the ratio of acyl/total ghrelin gives a clearer indication that the ghrelin acylation process is altered during infection and atrophy. GOAT is essential for the production of biologically-active, acyl ghrelin and the impact of H. pylori on GOAT expression and activity will be highly informative in the future.

Expression and function of the ghrelin axis, including a novel preproghrelin isoform, in human breast cancer tissues and cell lines

While oestrogen, progesterone and growth factors, including growth hormone (GH), are clearly implicated in the pathogenesis of breast cancer, there is now evidence that the newly described ghrelin axis is also involved. The aims of this study were to investigate the expression of the ghrelin axis in breast cancer tissues and cell lines and to examine the effect of ghrelin on breast cancer cell proliferation in vitro. Ghrelin and its functional receptor, the growth hormone secretagogue receptor (GHSR) type 1a, were expressed in normal breast tissue and breast cancer specimens and cell lines. In contrast, the truncated GHSR type 1b isoform was exclusively expressed in breast carcinoma, suggesting that it has potential as a diagnostic marker. Ghrelin treatment significantly increases the proliferation of the MDA-MB-435 and MDA-MB-231 breast cancer cell lines in vitro. In addition, we have described the expression of a human preproghrelin isoform, exon 3-deleted preproghrelin, which encodes mature ghrelin plus a novel C-terminal peptide. Quantitative RT-PCR was used to demonstrate that this mRNA isoform is highly expressed in the MDA-MB-435 metastatic breast cancer cell line relative to the benign MCF-10A breast epithelial cell line. The unique C-terminal peptide of exon 3-deleted preproghrelin is expressed in the glandular epithelium of breast cancer tissues, with high-grade carcinoma exhibiting the strongest immunoreactivity. The data presented here suggest that components of the ghrelin axis may represent novel markers for breast cancer and potential therapeutic targets.

Expression of the ghrelin axis in the mouse: an exon 4-deleted mouse proghrelin variant encodes a novel C terminal peptide

Ghrelin, an n-octanoylated 28-amino-acid peptide capable of inducing GH secretion and food intake in humans and rats, is the endogenous ligand for the GH secretagogue receptor (GHS-R). Here we describe the expression and tissue distribution of the ghrelin/GHS-R axis in the mouse. We also report for the first time the identification of a novel mouse ghrelin mRNA variant in which there is a complete deletion of exon 4. Translation of this variant mRNA yields a protein containing ghrelin and an alternative C-terminal domain with a unique C-terminal peptide sequence. RT-PCR with primers specific for mouse ghrelin was used to demonstrate the mRNA expression of the full preproghrelin transcript and the exon 4-deleted variant in multiple mouse tissues. Real-time PCR was also employed to quantitate mRNA expression of ghrelin, the novel isoform and a previously reported ghrelin gene variant, ghrelin gene-derived transcript. We also demonstrated the tissue expression of the functional GHS-R in the mouse. Immunohistochemistry, employing antibodies raised against the mature human n-octanoylated ghrelin peptide and the putative C-terminal peptide encoded by the exon 4-deleted proghrelin variant, was used to demonstrate protein expression of ghrelin and the variant in multiple mouse tissues including stomach, kidney, and reproductive tissues. The coexpression of ghrelin and its receptor in a wide range of murine tissues suggests varied autocrine/paracrine roles for these peptides. Exon 4-deleted proghrelin, a novel mouse proghrelin isoform with a unique C-terminal peptide sequence, is also widely expressed in the mouse and thus may possess biological activity in these tissues.

The potential autocrine/paracrine roles of ghrelin and its receptor in hormone-dependent cancer

Ghrelin is a recently identified 28 amino acid peptide capable of stimulating pituitary growth hormone release in humans. The actions of ghrelin are mediated via the naturally occurring ghrelin receptor, also known as the growth hormone secretagogue receptor (GHS-R). Ghrelin and its receptors are now being recognized as components of the growth hormone axis and are therefore potentially involved in tissue growth and development. As is the case for other members of this axis, evidence is rapidly emerging to indicate that ghrelin/GHS-R may play an important autocrine/paracrine role in some cancers. This review highlights the evidence for the expression, regulation and potential functional role of ghrelin and its receptor in hormone-dependent cancers, such as prostate and breast cancer.

Expression and action of the growth hormone releasing peptide ghrelin and its receptor in prostate cancer cell lines

This study has examined the expression of two new facets of the growth hormone axis, the growth hormone secretagogue receptor (GHS-R) and its recently identified putative natural ligand ghrelin, in prostate cancer cells. GHS-R 1a and 1b isoforms and ghrelin mRNA expression were detected by RT-PCR in the ALVA-41, LNCaP, DU145 and PC3 prostate cancer cell lines. A normal prostate cDNA library expressed GHS-R1a, but not the 1b isoform or ghrelin. Immunohistochemical staining for the GHS-R 1a isoform and ghrelin was positive in the four cell lines studied. PC3 cells showed increased cell proliferation in vitro in response to ghrelin to levels 33% above untreated controls, implying a potential tumour-promoting role for ghrelin in this tissue. This study is the first to demonstrate the co-expression of the GHS-R and ghrelin in prostate cancer cells. It is also the first study to provide evidence that a previously unrecognised autocrine/paracrine pathway involving ghrelin, that is capable of stimulating growth, exists in prostate cancer.