Paclitaxel inhibits N-acetyltransferase activity and gene expression in human stomach tumor cells (SC-M1)

Area of Science:

• Biochemistry
• Pharmacology
• Cancer Research

Background:

• N-acetyltransferase (NAT) enzymes acetylate 2-aminofluorene (AF) to N-acetyl-2-aminofluorene (AAF).
• AAF is metabolized by cytochrome P450 (CYP) and other enzymes into ultimate carcinogens that form DNA adducts, potentially leading to cancer.
• Paclitaxel (taxol) is a chemotherapy drug, but its effect on NAT activity and DNA adduct formation is not fully understood.

Purpose of the Study:

• To investigate the inhibitory effects of paclitaxel on NAT activity, NAT gene expression, and DNA-AF adduct formation in the human stomach tumor cell line (SC-M1).

Main Methods:

• NAT activity was measured using high-performance liquid chromatography (HPLC) assaying acetylated and non-acetylated substrates (AF or PABA).
• Experiments were conducted using both SC-M1 cell cytosols and intact SC-M1 cells.
• NAT gene expression (NAT1 mRNA) and DNA-AF adduct formation were assessed in intact cells.

Main Results:

• Paclitaxel treatment led to a dose-dependent decrease in NAT activity and DNA-AF adduct formation in SC-M1 cells compared to controls.
• Paclitaxel reduced the apparent K(m) and V(max) values for NAT activity in both cytosol and intact SC-M1 cells.
• Paclitaxel did not significantly affect NAT1 mRNA expression in SC-M1 cells.

Conclusions:

• Paclitaxel inhibits NAT enzyme activity and reduces DNA-AF adduct formation in human stomach tumor cells.
• The inhibition of NAT activity by paclitaxel is likely a key mechanism by which it may reduce carcinogen-induced DNA damage.
• Further research is warranted to explore paclitaxel's role in cancer prevention and treatment strategies targeting carcinogen metabolism.