Abstract
Arylamine N-acetyltransferase-1 (NAT1) is an enzyme that catalyzes the biotransformation of arylamine and hydrazine substrates. It also has a role in the catabolism of the folate metabolite p-aminobenzoyl glutamate. Recent bioinformatics studies have correlated NAT1 expression with various cancer subtypes. However, a direct role for NAT1 in cell biology has not been established. In this study, we have knocked down NAT1 in the colon adenocarcinoma cell-line HT-29 and found a marked change in cell morphology that was accompanied by an increase in cell-cell contact growth inhibition and a loss of cell viability at confluence. NAT1 knock-down also led to attenuation in anchorage independent growth in soft agar. Loss of NAT1 led to the up-regulation of E-cadherin mRNA and protein levels. This change in E-cadherin was not attributed to RNAi off-target effects and was also observed in the prostate cancer cell-line 22Rv1. In vivo, NAT1 knock-down cells grew with a longer doubling time compared to cells stably transfected with a scrambled RNAi or to parental HT-29 cells. This study has shown that NAT1 affects cell growth and morphology. In addition, it suggests that NAT1 may be a novel drug target for cancer therapeutics.
Highlights
Human arylamine N-acetyltransferase-1 (NAT1; EC 2.3.1.5) is a well characterized enzyme that catalyzes the transfer of an acetyl group from acetyl coenzyme A to the amino group of arylamine and/or hydrazine compounds [1]
HT-29 cells were stably transfected with a shRNA expression vector targeting NAT1 mRNA
NAT1 activity was decreased by greater than 85% compared to the non-transfected parental HT-29 cells or control cells transfected with a scrambled shRNA sequence (Figure 1A)
Summary
Human arylamine N-acetyltransferase-1 (NAT1; EC 2.3.1.5) is a well characterized enzyme that catalyzes the transfer of an acetyl group from acetyl coenzyme A to the amino group of arylamine and/or hydrazine compounds [1]. NAT1 is genetically polymorphic and different alleles express proteins with altered catalytic activity [2]. NAT1 gene expression involves 2 promoters that generate at least 9 different transcripts, all with an identical protein coding sequence. In human breast cancer samples, NAT1 mRNA levels have been shown to cluster with a group of genes that included the estrogen receptor, being highest in luminal-type carcinomas and lowest in basal-like carcinomas [7,8,9]. The selective expression of NAT1 in tumor subtypes is not confined to breast cancer. In a gene profiling study, Lapointe and coworkers identified 3 separate prostate cancer subtypes, each with markedly different levels of NAT1 expression [10]. NAT1 mRNA levels appear to be upregulated in p53 wild-type tumors compared to p53 loss-offunction tumors [11]
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