A metabolically competent human cell line expressing five cDNAs encoding procarcinogen-activating enzymes:...

Area of Science:

• Biochemistry
• Toxicology
• Cell Biology

Background:

• Drug metabolism is crucial for understanding chemical toxicity.
• Cytochrome P-450 enzymes play a key role in activating procarcinogens.
• Developing robust cell models is essential for toxicological screening.

Purpose of the Study:

• To develop a novel human cell line for studying procarcinogen activation.
• To evaluate the sensitivity of this cell line to various procarcinogens.
• To establish a screening system for mutagenicity analysis.

Main Methods:

• Development of MCL-5, a human B-lymphoblastoid cell line.
• Stable expression of five human drug-metabolizing enzyme cDNAs (CYP1A2, CYP2A6, mEH, CYP2E1, CYP3A4) and endogenous CYP1A1.
• Assessment of mutagenicity using hypoxanthine guanine phosphoribosyltransferase (hprt) and thymidine kinase (tk) assays with seven model procarcinogens.

Main Results:

• MCL-5 cells stably expressed all introduced drug-metabolizing enzymes.
• Exposure to procarcinogens like benzo[a]pyrene, NDMA, and AFB1 significantly increased mutant frequencies.
• MCL-5 cells demonstrated significantly higher sensitivity to procarcinogen-induced mutagenicity compared to the parent cell line, with sensitivity increases up to 40,000-fold for NDMA.

Conclusions:

• The MCL-5 cell line effectively activates and detects a range of procarcinogens.
• MCL-5 cells exhibit enhanced sensitivity, outperforming the parent cell line in mutagenicity assays.
• This cell line holds significant potential as a screening system for human procarcinogen/promutagen activation studies.