Semester

Fall

Date of Graduation

2006

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Physiology, Pharmacology & Neuroscience

Committee Chair

Joginder Nath.

Abstract

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.

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