Effect of tea polyphenols on the growth of human papillomavirus 16 subgenes-immortalized human cervical epithelial cells

Objective To explore the effect of tea polyphenols on the growth of human papillomavirus 16 (HPV16) subgenes-immortalized human cervical epithelial cells (H8 cells) . Methods Cultured H8 cells were divided into 5 groups to be treated with 0 (control group) , 6.25, 12.5, 25 and 50 mg/L tea polyphenols respectively for 24, 36, and 48 hours, and then cell counting kit-8 (CCK8) assay was performed to detect cell proliferation. After 24 hours of incubation, flow cytometry was conducted to detect cell apoptosis and cell cycle, and fluorescence microscopy to observe the morphology of apoptotic cells. Results After incubation with tea polyphenols at different concentrations for 24, 36 and 48 hours, the proliferation of H8 cells was inhibited, and 12.5 mg/L tea polyphenols could inhibit the relative growth rate of H8 cells in a time-dependent manner. Flow cytometry showed that there was a significant difference in cell apoptosis rate among the 6.25-, 12.5-, 25-, 50-mg/L tea polyphenols groups and the control group (52.62% ± 0.62%, 52.22% ± 0.72%, 42.52% ± 0.90%, 45.96% ± 2.11%, 29.96% ± 0.70% respectively, F = 272.0, P < 0.05) . Moreover, all the tea polyphenol groups showed significantly increased cell apoptosis rate compared with the control group (all P < 0.05) . Fluorescence microscopy showed karyopyknosis, nuclear fragmentation and other typical apoptotic morphological changes in H8 cells in tea polyphenols groups. There were significant differences in the percentage of cells in G1, G2 phase and cell proliferation index among the 5 groups (all P < 0.05) . Compared with the control group, the 6.25-, 12.5-, 25-mg/L tea polyphenols groups showed significantly increased percentage of cells in G1 phase (55.96% ± 0.72%, 54.12% ± 3.20%, 65.30% ± 1.51% respectively, all P < 0.05) , but significantly decreased percentage of cells in G2 phase (3.17 ± 1.82%, 4.94 ± 1.46%, 4.65 ± 4.26% respectively, all P < 0.05) and lower cell proliferation index (0.44 ± 0.01, 0.46 ± 0.02, 0.36 ± 0.01 respectively, all P < 0.05) . Conclusion Tea polyphenols can inhibit the proliferation of H8 cells, induce cell apoptosis, and block cell cycle progression. Key words: Catechin; Cell line, transformed; Cell proliferation; Apoptosis; Cell cycle; Precancerous conditions; Tea polyphenols; Immortalized human cervical epithelial cells