Figure 4.

Gg inhibits CYP1 enzyme activities and suppresses B[a]P-induced CYP1A gene expression in non-invasive MCF-7 breast cancer cells. (A) Human recombinant CYP1B1-catalysed 7-ethoxyresorufin activity (0.37μM), CYPs 1A1 catalysed 7-ethoxy-3-cyanocoumarin deethylase activity (0.5μM), were determined in the presence of varying concentrations of Gg (0-20μM, as described in Materials and Methods for IC₅₀ determinations. Control enzyme activity (mean ± SEM) for CYPs 1B1 and 1A1 were 0.34 ± 0.08, 0.86 ± 0.01 μM/min/pmol of CYP respectively. (B) Human recombinant CYP activity (as indicated by relative fluorescence) for isoforms CYP1A1, CYP1B1, CYP2C19, CYP2D6 and CYP3A4 following treatment with Gg reported as IC₅₀ values in accordance with Materials and Methods. Results are represented as the mean of at least three independent experiments ±SEM. (C) MCF-7 cells were exposed to B[a]P alone or in combination with Gg at indicated concentrations for 24 h. Cells were harvested, RNA extracted and quantitative real-time PCR analysis performed in accordance with Materials and methods to evaluate CYP1A1 and CYP1A2 mRNA expression. Data represent the mean ± SEM of three independent experiments. Statistical significance as indicated by ** P< 0.01 or ***P < 0.001 versus treatment with B[a]P only.