Objectives To comprehensively investigate the role of the N6‐methyladenosine (m6A) erasers ALKBH5 and FTO in clear cell renal cell carcinoma (ccRCC), other RCC subtypes, and oncocytoma with respect to prognostic value and biomarker potential. Patients and Methods The collection of tissue samples was performed within the framework of the Biobank at the Centre for Integrated Oncology Cologne‐Bonn. The gene expressions of alkylation repair homologue 5 (ALKBH5) and fat mass and obesity‐associated protein (FTO) were determined using quantitative real‐time polymerase chain reaction. ALKBH5 and FTO expressions were further investigated in ccRCC, papillary RCC, chromophobe RCC, sarcomatoid RCC, oncocytoma, and benign renal tissue using tissue microarrays. Results ALKBH5 mRNA, as well as ALKBH5 and FTO protein expressions, was significantly downregulated in ccRCC compared to normal tissue and most of the other studied tumour entities. Decreased mRNA levels of ALKBH5 and FTO correlated with a shortened overall and cancer‐specific survival following nephrectomy. Conclusions Taken together, our present data indicate that the m6A‐demethylases ALKBH5 and FTO are dysregulated in ccRCC and could be used as prognostic biomarkers.

N6‐Methyladenosine (m6A) is the most common modification of messenger RNA (mRNA) in mammals. It critically influences RNA metabolism and plays an essential role in virtually all types of bioprocesses including gene expression, tissue development, self‐renewal and differentiation of stem cells, stress response and circadian clock control. It plays a crucial role in carcinogenesis and could be used as a prognostic and a diagnostic tool and as a target for new anticancer therapies. m6A modification is dynamically and reversibly regulated by three types of proteins. Methyltransferases, so‐called “writers” add a methyl group to the adenosine, which can be removed by demethylases, also called “erasers.” m6A‐specific RNA‐binding proteins, from here on referred to as “readers,” preferentially bind to the m6A site and mediate biological functions, such as translation, splicing or decay of RNA. In this study, we examined the expression of the six m6A readers HNRNPA2B1, HNRNPC, YTHDC1 and YTHDF1‐3 in clear cell renal carcinoma (ccRCC). We show that on mRNA level the expression of all six m6A readers is significantly downregulated compared to normal renal tissue and on protein level five out of six readers are dysregulated. Lower levels of some m6A readers are correlated with advanced stage and grade as well as associated with a shorter overall, progression‐free and cancer‐specific survival. In summary, we could show that m6A readers are dysregulated in ccRCC and might therefore act as a tumor marker, could give further information on the individual prognosis and be a target of innovative cancer therapy.

Objectives To investigate the regulation of the N‐6‐methyladenosine (m6A) methyltransferases METTL3, METTL14, WTAP, KIAA1429, and METTL4, referred to as “m6A writers,” in clear cell renal cell carcinoma (ccRCC), and other RCC subtypes in respect of the potential prognostic value. Patients and methods Tissue samples were collected within the framework of the Biobank at the Center for Integrated Oncology Bonn. The expression of the methyltransferases was systematically determined in clear cell renal carcinoma (ccRCC) on the RNA (real‐time PCR) and protein level (immunohistochemistry). Additionally, protein expression of the m6A writers was further investigated in papillary RCC, chromophobe RCC, sarcomatoid RCC, oncocytoma, and normal renal tissue (immunohistochemistry). Results The expression of all m6A‐methyltransferases was significantly downregulated in ccRCC compared to benign renal tissue. Low m6A‐methyltransferase levels were correlated with higher histological grade, advanced pT‐stage, pN‐stage, and metastatic disease. Reduced m6A‐methyltransferase expression was associated with shorter overall survival. Conclusion In conclusion, m6A‐methyltransferases are dysregulated in ccRCC and might act as tumor suppressor genes, which could be of particular importance for future diagnostic and therapeutic options.