Deciphering Glutamine Metabolism Patterns for Malignancy and Tumor Microenvironment in Clear Cell Renal Cell Carcinoma

Abstract Clear cell renal cell carcinoma (ccRCC) represents a prevalent primary malignancy of the urinary system. Glutamine metabolism is pivotal in metabolic reprogramming, contributing to the significant heterogeneity observed in ccRCC. Consequently, developing prognostic markers associated with glutamine metabolism could enhance personalized treatment strategies for ccRCC patients. This study obtained RNA sequencing and clinical data from 763 ccRCC cases sourced from multiple databases. Consensus clustering of 74 GMRGs (glutamine metabolism related genes) profiles stratified the samples into three clusters, each exhibiting distinct prognostic, genomic, tumor microenvironment (TME), and fundamental biological characteristics. Subsequently, six genes (SMTNL2, MIOX, TMEM27, SLC16A12, HRH2, and SAA1) were identified to develop a predictive signature related to glutamine metabolism, termed GMRScore, employing least absolute shrinkage and selection operator (LASSO) and Cox regression analyses. The novel signature was demonstrated exceptional robustness and predictive capability regarding patients' overall survival. The constructed nomogram incorporating the GMRScore and clinical features showed strong predictive performance. Additionally, patients stratified by GMRScore exhibited distinct immunological features and response to immunotherapy. Furthermore, we validated the reliability of the GMRScore in two external clinical cohort receiving immune checkpoint blockade (n=302). ALDH18A1, one of the GRMGs, exhibited elevated protein expression levels in tumor tissues, as indicated by proteomic profiling of 232 ccRCC samples obtained from Fudan University Shanghai Cancer Center. Conducting western blotting, CCK-8, transwell, and flow cytometry assays, we revealed that the knockdown of ALDH18A1 in ccRCC significantly promoted apoptosis and inhibited proliferation, invasion, and migration in two human ccRCC cell lines (786-O and 769-P). In conclusion, we developed a GMRScore for ccRCC closely associated with the immune landscape and response to ICB, potentially made for personalized treatment decisions for ccRCC patients. Additionally, this study is the first to suggest a role for ALDH18A1 in promoting progression in ccRCC.