Abstract B42: Overexpression of ENRAGE is an obesity-related alteration in clear cell renal cell carcinoma
Authors: Eckel-Passow Jeanette E. , Serie Daniel J. , Bot Brian M. , Joseph Richard W. , Hart Steven N. , Cheville John C. , Parker Alexander S. 
Published: May 2019

Background: The incidence of renal cell carcinoma (RCC) in the United States (U.S.) continues to rise and this trend cannot be fully attributed to incidental detection via increased use of abdominal imaging. Related to this, obesity rates have been rising steadily in the U.S. for several decades and obesity is one of the most widely accepted risk factors for the development of RCC. Interestingly, to date there are limited data regarding the molecular mechanisms that link obesity with an increased risk of RCC. Moreover, the few studies that have investigated the molecular underpinnings that link obesity and RCC have all used a candidate gene approach focusing exclusively on evaluation of germline genetic alterations (i.e., host genetics) and not somatic alterations in the tumor itself. Motivated by this, we used a multi-stage design to identify and validate genes that are associated with obesity-related clear cell RCC (ccRCC).

Methods: We conducted a gene-expression microarray study of ccRCC and compared gene expression between 19 obese and 46 non-obese patients in both ccRCC tumors and patient-matched normal kidney tissues. Analyses were first stratified by smoking status, the other widely acceptable risk factor for RCC, and subsequently performed on the pooled cohort. To identify genes that are specific to obesity-related ccRCC, we identified Affymetrix probesets that had a tissue type-by-obesity status interaction p-value &lt;0.01 amongst non-smokers (stage 1), an interaction p-value &lt;0.05 in patients with a history of smoking (stage 2) and an interaction p-value&lt;0.01 in the pooled analysis (stage 3). Lastly, targeted validation was performed via RT-PCR on an independent cohort of 19 obese and 54 non-obese patients in both ccRCC tumors and patient-matched normal kidney tissues (stage 4). In addition to evaluating differential expression, an enrichment analysis was performed using DAVID and the results were compared to the Genetic Association Database.

Results: From our microarray analyses, we identified two genes and one non-coding RNA as having candidate associations with obesity-related ccRCC: EFCAB6, ENRAGE and NCRNA00263, respectively. Using RT-PCR, we validated that while expression of ENRAGE is similar in normal kidney tissue across obese and non-obese subjects, ENRAGE is significantly over expressed in ccRCC tissues from obese patients compared to non-obese subjects. Others have shown that ENRAGE is a useful biomarker of inflammation and has a positive association with visceral fat adiposity, which provides further credence to our observations. As an alternative analysis approach, using the Genetic Association Database to identify medically-relevant somatic features, we also observed a putative relationship between GAL, IL6R, NMB and SORBS1 with obesity. Although the results of this alternative analysis approach are exploratory and thus need to be validated, there are some interesting relationships to note. Particularly, several variants in IL6R have been previously linked to obesity, diabetes and fat mass. Also, GAL is thought to play a role in drug resistance to chemotherapy in cell lines, warranting continued investigation to see if obese individuals with high or low expression show differential drug response.

Conclusions: We provide evidence that overexpression of ENRAGE in ccRCC tumor tissue is an obesity-associated alteration. Up regulation of ENRAGE could lead to local, autocrine stimulation of the RAGE receptor and thus support cancer progression. Additionally, we show evidence of a putative relationship between GAL, IL6R, NMB and SORBS1 with obesity; however, these results need to be validated.

Citation Format: Jeanette E. Eckel-Passow, Daniel J. Serie, Brian M. Bot, Richard W. Joseph, Steven N. Hart, John C. Cheville, Alexander S. Parker. Overexpression of ENRAGE is an obesity-related alteration in clear cell renal cell carcinoma. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr B42.