Role of the Long Non‐Coding RNA Growth Arrest‐Specific 5 in Glucocorticoid Response in Children with Inflammatory Bowel Disease

Abstract

Glucocorticoids (GCs) are widely employed in inflammatory, autoimmune and neoplastic diseases, and, despite the introduction of novel therapies, remain the first-line treatment for inducing remission in inflammatory bowel disease (IBD). Given the high incidence of suboptimal response, associated with a significant number of side-effects, that are particularly severe in paediatric patients, the identification of subjects that are most likely to respond poorly to GCs is extremely important. Recent evidence suggests that the long non-coding RNA (lncRNA) GAS5 could be a potential marker of GC resistance. To address this issue, we evaluated the association between the lncRNA GAS5 and the efficacy of steroids, in terms of inhibition of proliferation, in two cell lines derived from colon and ovarian cancers, to confirm the sensitivity and specificity of these lncRNAs. These cells showed a different sensitivity to GCs and revealed differential expression of GAS5 after treatment. GAS5 was up-regulated in GC-resistant cells and accumulated more in the cytoplasm compared to the nucleus in response to the drug. The functions of GAS5 were assessed by silencing, and we found that GAS5 knock-down reduced the proliferation during GC treatment. Furthermore, for the first time, we measured GAS5 levels in 19 paediatric IBD patients at diagnosis and after the first cycle of GCs, and we demonstrated an up-regulation of the lncRNA in patients with unfavourable steroid response. Our preliminary results indicate that GAS5 could be considered a novel pharmacogenomic marker useful for the personalization of GC therapy.Due to their anti-inflammatory and immunosuppressive properties, glucocorticoids (GCs) are widely used in the treatment of many inflammatory and autoimmune diseases [1,2]. In particular, they play a critical role in the treatment of inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), where they are used to induce remission in patients with moderate to severe disease [3]. However, a considerable interindividual variability in GC response has been documented [4,5]: close to 20% of patients are resistant to these agents, while 40% of patients become dependent from GCs for maintaining clinical remission. Presently, there are no means to predict patients' response to GCs in advance [6,7].GCs diffuse across the cell membrane and exert their biological effects primarily by binding to the cytoplasmic GC receptor (GR) [8,9], which translocates into the nucleus and interacts, through its DNA-binding domain (DBD) [10,11], with steroid-responsive genes promoter regions known as GC responsive elements (GREs) [12][13][14].Recent reports have shown that the growth arrest-specific 5 (GAS5) gene encodes for a long non-coding RNA (lncRNA) which can act as a riborepressor of the GR [15]. In particular, GAS5 exon 12-derived sequence has been shown to structurally mimic the GREs, preventing the binding of the activated GR complex to its target DNA sequences [16].In previous studies conducted i...

The emerging role of lncRNAs in inflammatory bowel disease

“…In a recent study using both cell lines and IBD patient samples, an increased level of lncRNA GAS5 was identified after treatment with glucocorticoids (GCs). A significant increase in the level of GAS5 was shown to be the rate-limiting factor in the remission of at least 20% of IBD patients showing resistance to GC treatment 72 . GCs are one of the first line medications in the treatment of both main types of IBD.…”

“…It has been shown that GAS5 is differentially expressed in cell lines before and after methylprednisolone treatment and is positively correlated with drug resistance. A 4-week treatment of 19 pediatric IBD patients who were categorized as steroid-resistant (SR), steroid-sensitive (SS), or steroid-dependent (SD) showed that SR and SD patients had higher levels of GAS5 expression than the SS group 72 . As a result of these findings, the authors suggest that GAS5 expression can be considered a candidate marker of GC resistance.…”

Which long noncoding RNAs and circular RNAs contribute to inflammatory bowel disease?

“…In poor responders to GCs, the levels of lncRNA growth arrest-specific 5 (GAS5) were higher than those in good responders; therefore, GAS5 may be associated with GCs resistance 123,124 . A later study demonstrated that the expression of GAS5 differed between GCssensitive and GCs-resistant cells, and GAS5 is positively correlated with GCs resistance in children with IBD 125 . Additionally, endogenous GAS5 affects GCs effectiveness, likely because it accumulates in the cytoplasm and plays a role at the post-transcriptional level 125 .…”

Twenty-First Century Glucocorticoid Receptor Molecular Biology

“…This GAS5-dependent GC inhibitory pathway appears to also be active in some immune cells [113,114]. Although there are no crystal structures of GR bound to RNA, such structures have been modeled [110].…”