Apelin and apelin receptor expression in renal cell carcinoma.

BACKGROUND: The APLNR (apelin receptor) has been shown to be an essential gene for cancer immunotherapy, with deficiency in APLNR leading to immunotherapy failure. The aim of this study is to investigate the expression of APLN (apelin) and APLNR in patients with renal cell carcinoma (RCC), and its association with clinicopathological parameters and survival. METHODS: Three well-characterised patient cohorts with RCC were used: Study cohort 1 (clear-cell RCC; APLN/APLNR mRNA expression; n = 166); TCGA validation cohort (clear-cell RCC; APLN/APLNR mRNA expression; n = 481); Study cohort 2 (all RCC subtypes; APLNR protein expression/immunohistochemistry; n = 300). Associations between mRNA/protein expression and clinicopathological variables/patients' survival were tested statistically. RESULTS: While APLN showed only very weak association with tumour histological grade (TCGA cohort), APLNR/mRNA protein expression correlate significantly with ccRCC aggressiveness. APLNR is expressed in tumour vasculature and tumour cells at different levels, and these expression levels associate with tumour aggressiveness in opposing directions. APLNR expression was negatively correlated with PD-L1 expression by tumour cells in a subset of patients with ccRCC. APLNR expression in either compartment is an independent prognostic factor for survival of patients with ccRCC. CONCLUSION: The APLNR/APLN-system appears to play an important role in ccRCC, warranting further clinical investigation.

Apelin modulates murine gastric vagal afferent mechanosensitivity.

Gastric vagal afferents play an important role in the peripheral control of food intake. Apelin, a central appetite regulating hormone, is also abundantly released from the stomach. Whether apelin modulates gastric vagal afferent signalling is unknown. We aimed to determine whether apelin modulates gastric vagal afferent signalling under different states of nutrition. Female C57BL/6 mice were fed either a standard laboratory diet (SLD) or a high fat diet (HFD) for 12 weeks. An in vitro gastric vagal afferent preparation was used to determine the effect of apelin on gastric vagal afferent mechanosensitivity in SLD mice, fed ad libitum or fasted overnight, and HFD mice. To determine the signalling pathway of apelin via gastric vagal afferents, we determined the expression of apelin receptor (APJ receptor) in the gastric mucosa, the whole nodose ganglion and in gastric vagal afferent neurons innervating the stomach using retrograde tracing and real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The location of apelin and APJ receptor within the gastric mucosa was determined by immunohistochemistry. Expression of apelin and APJ receptor mRNA in gastric mucosa was determined using qRT-PCR. Apelin inhibited the response of gastric mucosal vagal afferents to mucosal stroking in fasted SLD mice, but not in mice fed ad libitum a SLD or HFD. Apelin inhibited the response of gastric tension sensitive afferents to circular stretch in SLD mice fed ad libitum or fasted, an effect not observed in HFD mice. APJ receptor mRNA was detected in the gastric mucosa and whole nodose ganglion, but not specifically in gastric vagal afferents neurons. In the gastric mucosa, APJ receptor immunoreactive cells were co-localised or closely associated with apelin containing cells and co-localised with serotonin, gastrin, histamine and gastric intrinsic factor containing cells. In conclusion, apelin modulates gastric vagal afferent signalling in a nutritional status dependent manner. Further, apelin modulates gastric vagal afferents through an indirect pathway, possibly through the release of hormones/peptides from the gastric mucosa.

APJ Is Associated with Treatment Response in Gastric Cancer Patients Receiving Concurrent Chemoradiotherapy and Endostar Therapy.

BACKGROUND: Endostar combined with concurrent chemoradiotherapy (CRT) has been used in patients with gastric cancers (GCs). However, there are no reliable markers to predict the treatment response and prognosis of these patients. Apelin and its receptor (APJ) are involved in angiogenesis in tumor tissues. We aimed to study whether Apelin and Apelin receptor (APJ) tumor expression can predict the treatment response of combination therapy of endostar and CRT. MATERIALS AND METHODS: We enrolled patients with locally advanced GC receiving CRT only and CRT+endostar combination therapy. Apelin receptor (APJ) in tumor samples was determined by immunohistological staining and scored by measuring staining area and signal intensity. RESULTS: The high APJ expression has significantly higher rates of tumor invasion, local lymph node, and distant metastasis (all p < 0.001). In the CRT only group, the distribution of high and low APJ expression in patients with good and poor treatment response to CRT is not significantly different (p = 0.235). However, in the CRT+endostar group, the chance of having poor response to combined treatment is 3.645-fold higher in those having high APJ expression levels than those who have low APJ expression levels. Our prognostic analysis shows that in the CRT+endostar group, high APJ expression had significantly shorter overall survival (OS) period than those with low APJ expression (p < 0.001). Furthermore, multivariate survival analysis reveals that the APJ expression is an independent predictor for the OS period in GC patients treated with CRT+endostar. CONCLUSION: Tumor APJ can be used to predict the therapy response and prognosis in GC patients receiving CRT+endostar therapy.