Paclitaxel (Taxol) Inhibits the Arylamine N‐Acetyltransferase Activity and Gene Expression (mRNA NAT1) and 2‐Aminofluorene‐DNA Adduct Formation in Human Bladder Carcinoma Cells (T24 and TSGH 8301)

Abstract

Acetylator polymorphism in man results from differential expression of human liver N-acetyltransferase. NAcetyltransferase enzyme activity has been demonstrated to be involved in some types of chemical carcinogenesis. Paclitaxel (taxol) had been shown to affect N-acetyltransferase activity of human lung cancer cells. In this study, paclitaxel was chosen to investigate the effects of arylamine N-acetyltransferase activity (N-acetylation of substrate), gene expresssion and 2-aminofluorene-DNA adduct formation in human bladder carcinoma cell lines (T24 and TSGH 8301). The Nacetyltrasnsferase activity (N-acetylation of substrates) was determined by high performance liquid chromatography assaying for the amounts of acetylated 2-aminofluorene and p-aminobenzoic acid and nonacetylated 2-aminofluorene and p-aminobenzoic acid. Intact human bladder carcinoma T24 and TSGH 8301 cells were used for examining N-acetyltransferase activity, gene expression and 2-aminofluorene-DNA adduct formation. The results demonstrated that the N-acetyltransferase activity, gene expression (NAT1 mRNA) and 2-aminofluorene-DNA adduct formation in intact human bladder carcinoma cells were inhibited and decreased by paclitaxel in a dose-dependent manner. The effects of paclitaxel on the apparent values of Km and Vmax of N-acetyltransferase enzyme from intact human bladder carcinoma cells were also determined in these cell lines. A marked influence of paclitaxel was observed on the decreasing apparent values of K m and V max from intact human bladder carcinoma cells (T24 and TSGH 8301). Thus, paclitaxel is an uncompetitive inhibitor to the NAT enzyme.

Electrochemical Genotoxicity Screening for Arylamines Bioactivated by N-Acetyltransferase

“…In the second pathway, 2-AF is converted to 2-AAF ( 2 ) by cytosolic NAT. Many papers have indicated that N-acetylation of 2-AF plays a role in metabolic activation to carcinogens. − , Species 2 undergoes hydroxylation by cyt P450 1A2 forming N−OH−2-AAF ( 3 ), which undergoes either intramolecular acetyl transfer or sulfonation to give reactive metabolites. The sulfonation of 3 is the only known branch point in this mechanism that produces N-acetylated DNA adducts, 2-AAF−guanine, due to the enhanced leaving ability of the sulfoxy moiety.…”

“…Previous arylamine genotoxicity studies addressing 2-AF metabolism have employed animal models, ,, in vitro cell lines, − or microsomal 57 or bacterial assays (i.e., Ames test) 58 that contain a range of phase I and phase II enzymes. Researchers employed selective inhibitors to demonstrate the importance of NAT in the bioactivation of 2-AF.…”

“…2-AF−DNA adduct formation in mice was used as an indicator of arylamine-induced DNA damage . NAT inhibitor studies in rat glial tumor cells, mouse leukemia cells, and human bladder carcinoma cells showed good correlation with 2-AF−DNA adduct formation. NAT-generated electrophiles leading to 2-AF−nucleobase adducts is thought to be a predominant pathway for mutagenic and carcinogenic effects associated with exposure to arylamines .…”

Potential chemoprotective effects of the coffee components kahweol and cafestol palmitates via modification of hepatic N‐acetyltransferase and glutathione S‐transferase activities

“…Such studies involved, for example, cell lines, blood cells [Ho et al, 2001], bacteria [Chung et al, 1997;Lo and Chung, 1999], liver cytosols of untreated rats [Chen et al, 2000], and human tumor cell lines originating from both liver [Wu and Chung, 1998;Wu et al, 2001] and colon [Chen et al, 1998;Chang et al, 2001]. In vitro decreases in NAT mRNAs were observed in extrahepatic and extracolonic tumor cell systems treated with aloe-emodin, berberin, curcurmin, and paclitaxel [Wang et al, 2002;Chen et al, 2003;Chung et al, 2003;Yang et al, 2003].…”

Icaritin acts synergistically with epirubicin to suppress bladder cancer growth through inhibition of autophagy

“…Although a routine intravesical perfusion with EPI after surgery may reduce the recurrence rate, the acquired resistance to EPI is common in cancer patients (29). Therefore, increased attention has been paid to uncover the mechanism of drug resistance, and seeking novel agents among natural herbal ingredients (29).…”