Date of Graduation
School of Medicine
Physiology, Pharmacology & Neuroscience
This study investigated metabolic activation by benzopyrenes (BP and B[e]P) in human mammary cells and modulation by chlorophyllin (CHL, a chemopreventive agent). Among 6 NHMEC strains monitored using microarrays, 54 genes were up-regulated and 11 down-regulated by signal log ratio (SLR) ≥ 1.5 on treatment with BP alone. Pre CHL + post BP+CHL treatment up-regulated the expression of 129 genes and down-regulated those of 35 genes by SLR ≥ 1.5. Studies on CYP1 gene induction and BP-DNA adduct formation among 20 NHMECs revealed wide inter-individual variations both in the induction (3-96-fold for CYP1A1 and 4-43-fold for CYP1B1, respectively) and modulation (2-54-fold and 1-39-fold for CYP1A1 and CYP1B1, respectively) of CYP1 gene expression and reduction of BP-DNA adduct formation (0% to 86%) on treatment with BP+/-CHL. B[e]P was a very poor inducer of CYP1 gene expression and also exhibited no detectable adduct formation among the 2 NHMEC strains used, when compared to BP. There was a reduction of BP induced CY1A1 (0-40% among the 2 cell strains) and CYP1B1 expression (5-50% among the 2 cell strains) across all CHL treatments except for pre CHL+ post BP treatment and pre CHL + post BP+CHL treatment in one of the cell strains. CHL enhanced B[e]P induced CYP1 gene expression on treatment of cells with B[e]P + CHL and pre CHL + post B[e]P + CHL. When MCF-7 cells were compared to NHMECs, though basal CYP1B1 expression was nearly 348 times that of CYP1A1, MCF-7 cells exhibited highly inducible CYP1A1 expression (114 fold) compared to CYP1B1 expression (5 fold). None of the different CHL treatments modulated CYP1 gene expression or BP-DNA adduct formation in MCF-7 cells as opposed to NHMECs. When MCF-7 cells were compared to M00012, a NHMEC, across a range of CHL concentrations, only 3muM, 4muM and 16muM CHL mitigated CYP1 expression to different extents. BP-DNA adduct levels were unaltered in MCF-7 cells but reduced in concentration dependent manner in M00012. These studies show the wide inter-individual variability in response to carcinogens and chemopreventive agents which are to be accounted for while designing intervention strategies.
John, Kaarthik, "Modulation of gene expression and DNA adduct formation by chlorophyllin in human mammary cells exposed to benzopyrenes" (2006). Graduate Theses, Dissertations, and Problem Reports. 2439.