A modified 4NQO-induced oral carcinogenesis model defines a chemopreventive intervention window and reveals progression-modulatory effects of black tea polyphenols

Abstract

The 4-nitroquinoline-1-oxide (4NQO) model closely recapitulates oral squamous cell carcinoma (OSCC) progression but is limited by cumulative toxicity in conventional protocols. This study aimed to develop a modified 4NQO regimen with defined carcinogen-free intervals and evaluate the chemopreventive potential of black tea-derived polyphenols. C57BL/6 mice were subjected to conventional and modified 4NQO regimens (50 and 100 ppm). Tumour incidence, multiplicity, and volume were assessed alongside histopathology. Systemic toxicity was monitored using body weight, fluid intake, and serum biochemistry. Chemoprevention was evaluated using thearubigins and decaffeinated extracts (1.5% and 10%) administered during pre- and concurrent intervention phases. Molecular analyses included western blotting and qualitative immunohistochemistry. The modified regimen improved body weight maintenance without compromising tumour incidence or progression. No significant differences in tumour burden were observed between the 50 and 100 ppm groups. Histopathological analysis confirmed the presence of lesions across the disease spectrum in all carcinogen-treated groups. In chemoprevention studies, tumour incidence remained unchanged; however, the 10% decaffeinated extract significantly reduced tumour volume, while thearubigins showed a non-significant trend. Molecular analyses revealed no statistically significant differences, though directional changes were observed. The modified protocol enables defined intervention windows, addressing limitations of continuous carcinogen exposure, and the reduction in tumour volume without changes in incidence suggests an effect on tumour progression rather than initiation. Collectively, the modified 4NQO model provides a robust platform for stage-specific chemoprevention evaluation, with black tea polyphenols, particularly decaffeinated extracts, demonstrating modest progression-modulating effects that warrant further investigation.