Identifying the emerging role of adipokine as a diagnostic and prognostic biomarker of renal cell carcinoma

Positive Expression of Retinol-Binding Protein 4 Is Related to the Malignant Clinical Features Leading to Poor Prognosis of Glioblastoma

Backgrounds

Retinol-binding protein 4 (RBP4) is a monomeric-binding protein belonging to the lipocalin protein family, which has been reported to be dysregulated in several malignancies such as breast cancer and lung cancer. However, the expression and function of RBP4 in glioblastoma (GBM) are completely unknown.

Materials and Methods

TCGA datasets were used for analyzing the mRNA level of RBP4 in GBM and its clinical relevance. A retrospective GBM cohort (n = 73) was enrolled from our hospital to test the protein expression profile of RBP4 in GBM tissues as well as its correlation with patients' prognoses. Two human GBM cell lines, LN229 and U251, were collected to conduct overexpression and knockdown experiments targeting RBP4. The tumor-related effects of RBP4 in GBM were finally evaluated by proliferation and invasion assays.

Results

Both the higher mRNA level and protein level of RBP4 in GBM tissues were significantly correlated with poorer patients' overall survival. Multivariate analysis identified RBP4 as a novel independent prognostic predictor in GBM patients. Overexpression of RBP4 resulted in enhanced GBM proliferation capacity, which was consistent with clinical findings on the positive correlation between RBP4 level and tumor size. Meanwhile, overexpressing RBP4 promoted GBM cell migration and invasion, while silencing RBP4 led to the opposite results.

Conclusions

RBP4 overexpression in tumor tissues is correlated with poorer prognosis of GBM patients, which functions by promoting GBM proliferation and invasion, thus, may serve as an invaluable predictive biomarker and therapeutic target.

Potential Value of Visfatin, Omentin-1, Nesfatin-1 and Apelin in Renal Cell Carcinoma (RCC): A Systematic Review and Meta-Analysis

Renal cell carcinoma (RCC) is the most lethal genitourinary malignancy. Obesity is a risk factor for RCC development. The role of adipokines in the relationship between obesity and RCC requires confirmatory evidence in the form of a systematic review and meta-analysis, specifically for visfatin, omentin-1, nesfatin-1 and apelin. A search of databases up to July 2022 (PubMed, Web of Science and Scopus) for studies reporting the association of these selected adipokines with RCC was conducted. A total of 13 studies fulfilled the selection criteria. Only visfatin (p < 0.05) and nesfatin-1 (p < 0.05) had a significant association with RCC. Meanwhile, apelin and omentin-1 showed no association with RCC. The meta-analysis results of nesfatin-1 showed no association with early-stage (OR = 0.09, 95% CI = −0.12−0.29, p = 0.41), late-stage (OR = 0.36, 95% CI = 0.07−1.89, p = 0.23) and low-grade (OR = 1.75, 95% CI = 0.37−8.27, p = 0.48) RCC. However, nesfatin-1 showed an association with a high grade of the disease (OR = 0.29, 95% CI = 0.13−0.61, p = 0.001) and poorer overall survival (OS) (HR = 3.86, 95% CI = 2.18−6.85; p < 0.01). Apelin showed no association with the risk of RCC development (mean difference = 21.15, 95% CI = −23.69−65.99, p = 0.36) and OS (HR = 1.04, 95% Cl = 0.45−2.41; p = 0.92). Although the number of studies evaluated was limited, analysis from this systematic review and meta-analysis indicate that visfatin and nesfatin-1 were elevated. In summary, these adipokines may play a role in the development and progression of RCC and hence may have potential diagnostic and prognostic capabilities for RCC.

Increased Expression of Retinol-Binding Protein 4 in Ovarian Endometrioma and Its Possible Role in the Pathogenesis of Endometriosis

Although endometriosis is a benign disease characterized by the presence of endometrial tissues outside the uterus, ectopic endometrial cells can exhibit malignant biological behaviors. Retinol-binding protein4 (RBP4) is a novel adipocyte-derived cytokine, which has important roles in regulating insulin sensitivity and energy metabolism. RBP4 is a potent modulator of gene transcription, and acts by directly controlling cell growth, invasiveness, proliferation and differentiation. Here, we evaluated the possible role of RBP4 in the pathogenesis of endometriosis. We compared the levels of RBP4 in the tissues and peritoneal fluid (PF) of women with and without endometriosis and evaluated the in vitro effects of RBP4 on the viability, invasiveness, and proliferation of endometrial stromal cells (ESCs). RBP4 levels were significantly higher in the PF of the women in the endometriosis group than in the controls. RBP4 immunoreactivity was significantly higher in the ovarian endometriomas of women with advanced stage endometriosis than those of controls. In vitro treatment with human recombinant-RBP4 significantly increased the viability, bromodeoxyuridine expression, and invasiveness of ESCs. Transfection with RBP4 siRNA significantly reduced ESC viability and invasiveness. These findings suggest that RBP4 partakes in the pathogenesis of endometriosis by increasing the viability, proliferation and invasion of endometrial cells.

Obesity-Dependent Adipokine Chemerin Suppresses Fatty Acid Oxidation to Confer Ferroptosis Resistance

Clear cell renal cell carcinoma (ccRCC) is characterized by accumulation of neutral lipids and adipogenic transdifferentiation. We assessed adipokine expression in ccRCC and found that tumor tissues and patient plasma exhibit obesity-dependent elevations of the adipokine chemerin. Attenuation of chemerin by several approaches led to significant reduction in lipid deposition and impairment of tumor cell growth in vitro and in vivo. A multi-omics approach revealed that chemerin suppresses fatty acid oxidation, preventing ferroptosis, and maintains fatty acid levels that activate hypoxia-inducible factor 2α expression. The lipid coenzyme Q and mitochondrial complex IV, whose biogeneses are lipid-dependent, were found to be decreased after chemerin inhibition, contributing to lipid reactive oxygen species production. Monoclonal antibody targeting chemerin led to reduced lipid storage and diminished tumor growth, demonstrating translational potential of chemerin inhibition. Collectively, the results suggest that obesity and tumor cells contribute to ccRCC through the expression of chemerin, which is indispensable in ccRCC biology. SIGNIFICANCE: Identification of a hypoxia-inducible factor-dependent adipokine that prevents fatty acid oxidation and causes escape from ferroptosis highlights a critical metabolic dependency unique in the clear cell subtype of kidney cancer. Targeting lipid metabolism via inhibition of a soluble factor is a promising pharmacologic approach to expand therapeutic strategies for patients with ccRCC.See related commentary by Reznik et al., p. 1879.This article is highlighted in the In This Issue feature, p. 1861.

Lower circulating adiponectin is associated with higher risk of renal cell carcinoma: A meta-analysis

BACKGROUND

Changes in circulating adiponectin have been related to the risks of various cancers. However, the association between circulating adiponectin and the risk of renal cell carcinoma has not been fully determined. A meta-analysis was performed to evaluate the relationship between circulating adiponectin and renal cell carcinoma risk.

METHODS

Observational studies that evaluated the association between circulating adiponectin and renal cell carcinoma risk were identified via a systematic search of PubMed and Embase databases. The difference between circulating adiponectin in renal cell carcinoma cases and healthy controls, and the multivariable adjusted association between circulating adiponectin and renal cell carcinoma risk were evaluated. A random effects model was used if significant heterogeneity existed; otherwise a fixed effects model was applied.

RESULTS

Eight case-control studies with 2624 renal cell carcinoma cases and 2904 healthy controls were included. Pooled results showed that circulating adiponectin was significantly lower in renal cell carcinoma cases than in healthy controls (mean difference = -1.08 ug/mL; 95% confidence interval (CI) -1.62, -0.54; P < 0.001). Higher circulating adiponectin was independently associated with a significantly lowered risk of renal cell carcinoma (adjusted odds ratio for 1 SD increment of adiponectin = 0.78; 95% CI: 0.63, 0.96; P = 0.02). Subgroup analyses according to characteristics including study design, ethnics of participants, blood samples, numbers of participants, mean ages of participants, and study quality showed consistent results.

CONCLUSIONS

Lower circulating adiponectin is associated with increased risk of renal cell carcinoma. The potential pathophysiological mechanisms underlying the role of circulating adiponectin in the pathogenesis of renal cell carcinoma deserve further investigation.

Role of leptin as a biomarker for early detection of renal cell carcinoma? No evidence from a systematic review and meta-analysis

Renal cell carcinoma (RCC) is the commonest from of renal neoplasm. Although surgery is a successful curative treatment for localized RCC, most patients are diagnosed with advanced or metastatic RCC, which has poor prognosis. RCC is classified by stage and grade using tissue samples. Whilst these provide good prognostic information, they are not very useful for early detection. Proteins that are dysregulated in patient's serum can be a valuable alternative and less invasive biomarker for early detection of the disease. For this reason, a hypothesis was formed that leptin is a possible biomarker for early detection and prognostication of RCC. The literature has disparate results on the usefulness of leptin as a biomarker for the early detection of RCC. Hence, a systematic review and a meta-analysis was carried out to investigate whether serum leptin could be a reliable diagnostic and prognostic factor in RCC patients. Literature on the available cohort and case-control studies on serum leptin in RCC was searched in electronic databases and included to evaluate this adipokine in the progression of RCC. The relevant studies were evaluated for the diagnostic and prognostic value of leptin in RCC patients. Overall, only 6 original research studies matched selection criteria and were included for meta-analysis. This study was hypothesised that; leptin might be a useful biomarker for early detection and prognostication of RCC. However, the data were presented in this study did not support our hypothesis. Serum leptin levels in RCC patients do not strongly associate with the development or progression of RCC, thus cannot act as a biomarker for early detection in RCC in patients. Extending our hypothesis further to include levels of obesity and RCC development may be worthwhile, but studies are currently limited.

Circulating adiponectin as a biomarker in renal cell carcinoma: a systematic review and meta-analysis

Context: Metabolic imbalance in renal cell carcinoma (RCC) can lead to abnormal adiponectin levels. Objective: To evaluate circulating adiponectin as a detection or predictive marker for RCC. Methods: A comprehensive literature search and meta-analysis was performed on studies reporting circulating adiponectin levels and RCC. The meta-analysis was performed using RevMan. Results: Seven studies compared the circulating adiponection levels between RCC cases and controls. Adiponectin level was significantly lower in RCC cases compared to controls at pre-diagnosis and pre-operative time-points. RCC stage, grade and subtype did not affect adiponectin levels. Conclusion: Low circulating adiponectin could be a predictive or risk factor for RCC.

Prognostic biomarkers in renal cell carcinoma: is there a relationship with obesity?

Obesity is a recognized risk factor for renal cell carcinoma (RCC) the commonest form of kidney cancer. Both obesity and RCC are serious diseases with increasing incidence yearly. This review examined certain obesity associated measurements and adipokines as detection/prognostic indicators for RCC. The obesity related measurements such as body mass index (BMI), waist circumstance (WC), waist-hip ratio (WHR) in predicting RCC are valid when used in conjunction with other risk factors such as age and sex or with histological findings. The adipokine adiponectin holds promising outcomes as a predictive marker in assessing the risk of developing RCC. In addition, tissue leptin/leptin receptor may be a distinguishing marker for RCC subtypes. However, circulating leptin may not be a suitable detection or prognostic biomarker for RCC. The other less investigated adipokines; omentin, visfatin, apelin and resistin are also expressed in RCC but their prognostic capabilities are still inconclusive. BMI, WC and adipokines may be useful additions in a nomogram which includes TNM staging and pathological grading system to detect, confirm and follow-up RCC cases.

Association between leptin level and renal cell carcinoma susceptibility and progression: A meta-analysis

Objectives

It is well-documented that obesity participated in the development of renal cell carcinoma (RCC). Leptin is closely associated with obesity. This study is aimed to investigate the relationship between leptin level and RCC susceptibility and progression.

Methods

A meta-analysis was conducted to explore the association between leptin level and RCC susceptibility and progression. The studies were retrieved from electronic databases during January 1990-September 2017 with keywords. The qualified studies were screened with inclusion and exclusion criteria. A random effects model was applied to calculate the pooled standard mean differences and the corresponding confidence intervals.

Results

Ten studies were finally included in this meta-analysis. The serum leptin level in male RCC was significantly lower than that of in female RCC in overall populations, Asians, and Caucasians while no marked difference was noted between genders in the plasma samples. Plasma leptin level in Stage I-II RCC was significantly higher than that in the Stage III-IV. In addition, no significant difference was observed between following parameters, including RCC and non-RCC, clear and non-clear RCC, Grade I-II and Grade III-IV RCC, M0 and M1 RCC, N0 and N1 RCC, and size <4 cm and size >4 cm RCC. No evidence of publication bias was observed.

Conclusions

Our findings indicated that serum leptin level was lower in men with RCC than in women with RCC. Leptin level may not be related to the risk and progression of RCC. However, more studies should be performed in the future.

Adiponectin gene polymorphisms and obesity increase the susceptibility to arsenic-related renal cell carcinoma

Our recent study found that high urinary total arsenic levels were associated with renal cell carcinoma (RCC). Recent studies demonstrated that low circulating adiponectin was related to RCC. The aim of the present study was to explore the relationship between adiponectin gene (ADIPOQ) polymorphisms and RCC and investigate whether individuals with an ADIPOQ risk genotype, obesity, and high urinary total arsenic levels have a modified odds ratio (OR) of RCC. A total of 389 RCC patients and 389 age- and sex-matched controls were recruited between November 2006 and December 2012 in Taiwan. Image-guided biopsy or surgical resection of renal tumors was performed to pathologically verify RCC. Genomic DNA was used to examine the genotypes of the ADIPOQ rs182052, ADIPOQ rs2241766, ADIPOQ rs1501299, and ADIPOQ rs1063539 SNPs by PCR-RFLP. HPLC-HG-AAS was used to measure the concentrations of urinary arsenic species. Participants with the ADIPOQ rs182052 G/A+A/A genotype had a significantly higher OR of RCC compared with those with the ADIPOQ rs182052 G/G genotype. The OR (95% confidence interval [CI]) was 1.70 (1.23-2.36). The OR of RCC for the combined effect of high urinary total arsenic levels and obesity, which was dose-dependent, in individuals with the ADIPOQ rs182052 G/A+A/A genotype was 9.33 (3.85-22.62). The present study found significant combined effects of obesity and the ADIPOQ rs182052 G/A+A/A genotype on the arsenic-related risk of RCC in a population with low arsenic exposure. Arsenic exposure, obesity, and the ADIPOQ rs182052 polymorphism could be predictors of a higher OR of RCC.