NAD+associated genes as potential biomarkers for predicting the prognosis of gastric cancer

Nicotinamide adenine dinucleotide(NAD+)plays an essential role in cellular metabolism,mitochondrial homeostasis,inflammation,and senescence.However,the role of NAD+-regulated genes,including coding and long non-coding genes in cancer development is poorly understood.We constructed a prediction model based on the expression level of NAD+metabolism-related genes(NMRGs).Furthermore,we validated the expression of NMRGs in gastric cancer(GC)tissues and cell lines;additionally,β-nicotinamide mononucleotide(NMN),a precursor of NAD+,was used to treat the GC cell lines to analyze its effects on the expression level of NMRGs lncRNAs and cellular proliferation,cell cycle,apoptosis,and senescence-associated secretory phenotype(SASP).A total of 13 NMRGs-related lncRNAs were selected to construct prognostic risk signatures,and patients with high-risk scores had a poor prognosis.Some immune checkpoint genes were upregulated in the high-risk group.In addition,cell cycle,epigenetics,and senescence were significantly downregulated in the high-risk group.Notably,we found that the levels of immune cell infiltration,including CD8 T cells,CD4 naïve T cells,CD4 memory-activated T cells,B memory cells,and naïve B cells,were significantly associated with risk scores.Furthermore,the treatment of NMN showed increased proliferation of AGS and MKN45 cells.In addition,the expression of SASP factors(IL6,IL8,IL10,TGF-β,and TNF-α)was significantly decreased after NMN treatment.We conclude that the lncRNAs associated with NAD+metabolism can potentially be used as biomarkers for predicting clinical outcomes of GC patients.