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 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

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.