Ghrelin does not influence cancer progression in a lung adenocarcinoma cell line

GHS-R1a deficiency mitigates lipopolysaccharide-induced lung injury in mice via the downregulation of macrophage activity

Acute respiratory distress syndrome (ARDS) is a critical illness syndrome characterized by dysregulated pulmonary inflammation. Currently, effective pharmacological treatments for ARDS are unavailable. Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor type 1a (GHS-R1a), has a pivotal role in regulating energy metabolism and immunomodulation. The role of endogenous ghrelin in ARDS remains unresolved. Herein, we investigated the role of endogenous ghrelin signaling by using GHS-R1a-null (ghsr^-/-) mice and lipopolysaccharide (LPS)-induced ARDS model. Ghsr^-/- mice survived longer than controls after LPS-induced lung injury. Ghsr^-/- mice showed lower levels of pro-inflammatory cytokines and higher oxygenation levels after lung injury. The peritoneal macrophages isolated from ghsr^-/- mice exhibited lower levels of cytokines production and oxygen consumption rate after LPS stimulation. Our results indicated that endogenous ghrelin plays a pivotal role in initiation and continuation in acute inflammatory response in LPS-induced ARDS model by modulating macrophage activity, and highlighted endogenous GHS-R1a signaling in macrophage as a potential therapeutic target in this relentless disease.

Ghrelin and its role in gastrointestinal tract tumors (Review)

Ghrelin, an orexigenic hormone, is a peptide that binds to the growth hormone secretagogue receptor; it is secreted mainly by enteroendocrine cells in the oxyntic glands of the stomach. Ghrelin serves a role in both local and systemic physiological processes, and is implicated in various pathologies, including neoplasia, with tissue expression in several types of malignancies in both in vitro and in vivo studies. However, the precise implications of the ghrelin axis in metastasis, invasion and cancer progression regulation has yet to be established. In the case of gastrointestinal (GI) tract malignancies, ghrelin has shown potential to become a prognostic factor or even a therapeutic target, although data in the literature are inconsistent and unsystematic, with reports untailored to a specific histological subtype of cancer or a particular localization. The evaluation of immunohistochemical expression shows a limited outlook owing to the low number of cases analyzed, and in vivo analyses have conflicting data regarding differences in ghrelin serum levels in patients with cancer. The aim of this review was to examine the relationship between ghrelin and GI tract malignancies to demonstrate the inconsistencies in current results and to highlight its clinical significance in the outcome of these patients.

Attribution of Ghrelin to Cancer; Attempts to Unravel an Apparent Controversy

Ghrelin is an endogenous peptide hormone mainly produced in the stomach. It has been known to regulate energy homeostasis, stimulate secretion of growth hormone, and mediate many other physiologic effects. Various effects attributed to ghrelin contribute to many aspects of cancer development and progression. Accordingly, a large body of evidence has emerged about the association of ghrelin with several types of cancer in scales of cell-line, animal, and human studies. However, existing data are controversial. This controversy occurs in two main domains: one is the controversial results in local effects of ghrelin on different types of human cancer cell-lines; the second is the apparent disagreement in the results of in-vitro and clinical studies that investigated ghrelin association to one type of cancer. These inconsistencies have hampered the indications to consider ghrelin as a potential tumor biomarker or therapeutic agent in cancer patients. Previous studies have reviewed different parts of current literature about the ghrelin-cancer relationship. Although they have highlighted these controversial results in various ways, no specific recommendations have been given to address it. In this study, we comprehensively reviewed in-vitro, in-vivo, and clinical studies and attempted to use the following approaches to unravel the inconsistencies detected: (a) to distinguish local and systemic effects of ghrelin in interpreting its summary clinical role in each cancer; (b) scrutinizing factors that regulate local effects of ghrelin and could justify different effects of ghrelin on different cancer cell-lines. These approaches could have notable implications for future in-vitro and clinical studies.