NAMPT and NAPRT, Key Enzymes in NAD Salvage Synthesis Pathway, Are of Negative Prognostic Value in Colorectal Cancer

Abstract

Nicotinamide adenine dinucleotide (NAD) is a profoundly important cofactor in redox reactions. Nicotinamide phosphoribosyltransferase (NAMPT) and nicotinate phosphoribosyltransferase (NAPRT) are key enzymes for NAD salvage biosynthesis pathway, which reciprocally synthesize NAD to supply the main source of NAD biosythesis. However, the prognostic value of NAMPT and NAPRT in colorectal cancer (CRC) remains largely unknown. Our present study detected NAMPT and NAPRT protein expression in cancer and adjacent tissues from 261 CRC using immunohistochemical staining. We found that high expression of NAMPT or NAPRT was associated with vascular invasion, invasion depth and advanced TNM stage in CRC. High expression of NAMPT or NAPRT predicts short overall survival and disease-free survival time in CRC patients, which were further confirmed by public datasets. Furthermore, positive correlation between expression of NAMPT and NAPRT was revealed in CRC tissues and cell lines. NAPRT^high/NAMPT^high patients tended to have the shortest survival time. Using the TCGA RNA-sequencing data, we showed that gene amplification, mutation, and methylation of NAPRT are more common than NAMPT. On the other hand, NAMPT gene might be targeted by more miRNAs. Finally, genes that are correlated with NAPRT or NAMPT are enriched in different pathways. In conclusion, we found that high expression of NAMPT or NAPRT predicts poor prognosis of CRC patients, but the regulatory mechanism might be distinct from each other.

Keywords: NAD; NAMPT; NAPRT; colorectal cancer; prognosis.

Figure 1

High NAPRT expression is correlated with advanced TNM stage and poor prognosis of CRC patients. (A) The typical images showing the expression of NAPRT in CRC tissue and adjacent tissues. (B) Heat map showing the IHC scores of NAPRT in CRC tissues and corresponding normal intestinal epithelium. (C) IHC scores of NAPRT in CRC tissues with different TNM stages. (D) UALCAN analysis showing the mRNA expression of NAPRT in rectal cancer and normal intestinal epithelium. (E) UALCAN analysis showing the mRNA expression of NAPRT in different stages of rectal cancer. (F) The Kaplan–Meier survival analysis showing DFS of CRC patients with high or low NAPRT expression level. (G) The Kaplan–Meier survival analysis showing OS of CRC patients with high or low NAPRT expression level. (H) The Kaplan–Meier survival analysis showing that OS of CRC patients with high or low NAPRT mRNA expression from GSE24551. (I) The Kaplan–Meier survival analysis showing that OS of CRC patients with high or low NAPRT mRNA expression from GSE30378.COAD, colon adenocarcinoma; READ, rectal adenocarcinoma; *P < 0.05; **P < 0.01; ***P < 0.001.

Figure 2

High NAMPT expression is correlated with advanced TNM stage and poor prognosis of CRC patients. (A) The typical images showing the expression of NAMPT in CRC tissue and adjacent tissues. (B) Heat map showing the IHC scores of NAMPT in CRC tissues and corresponding normal intestinal epithelium. (C) IHC scores of NAMPT in CRC tissues with different TNM stages. (D) UALCAN analysis showing the mRNA expression of NAMPT in colon cancer and normal intestinal epithelium. (E) UALCAN analysis showing the mRNA expression of NAPRT in different stages of colon cancer. (F) UALCAN analysis showing the mRNA expression of NAMPT in rectal cancer and normal intestinal epithelium. (G) UALCAN analysis showing the mRNA expression of NAPRT in different stages of rectal cancer. (H) The Kaplan–Meier survival analysis showing DFS of CRC patients with high or low NAPRT expression level. (I) The Kaplan–Meier survival analysis showing OS of CRC patients with high or low NAPRT expression level. COAD, colon adenocarcinoma; READ, rectal adenocarcinoma; *P < 0.05; **P < 0.01; ***P < 0.001.

Figure 3

Positive association between the expression of NAMPT and NAPRT in CRC tissues. (A) Representative images show high expression of both NAPRT and NAMPT (case 1), as well as low expression of NAPRT and NAMPT (case 2). (B) Western bot showing the expression of NAPRT and NAMPT in normal intestinal epithelia NCM460 and CRC cell line HT29, HCT116, SW480, and LoVo cells. (C) Gray values detected from western blot results. (D,E) The Kaplan–Meier survival analysis showing that CRC patients with high expression of NAPRT and NAMPT tend to have a shorter DFS (D) or OS (E) time.

Figure 4

Bioinformatic analysis of the potential regulatory mechanism of NAMPT/NAPRT expression. (A) Mutation and amplification analysis of NAPRT gene in CRC via cBioportal. (B) Mutation and amplification analysis of NAMPT gene in CRC via cBioportal. (C) Promoter methylation of NAPRT in colon cancer using UALCAN. (D) Promoter methylation of NAPRT gene in different stages of colon cancer. (E) Promoter methylation of NAPRT in rectal cancer using UALCAN. (F) Promoter methylation of NAPRT gene in different stages of rectal cancer. (G) Promoter methylation of NAMPT gene in rectal cancer. (H) Promoter methylation of NAPRT in different stages of rectal cancer using UALCAN. (I) Predicted miRNAs that might bind with 3′-UTR of NAPRT/NAMPT gene by TargetScan. COAD, colon adenocarcinoma; READ, rectal adenocarcinoma; *P < 0.05; **P < 0.01; ***P < 0.001.

Figure 5

KEGG pathway analysis of genes associated with NAMPT/NAPRT expression in CRC. (A) The 178 genes that significantly correlated with NAPRT expression in both colon cancer and rectal cancer. (B) KEGG analysis of the correlated genes with NAPRT. (C) The 305 genes that significantly correlated with NAMPT expression in both colon cancer and rectal cancer. (D) KEGG analysis of the correlated genes with NAMPT.