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Research Interest: Transgenic cell modeling is used to determine the role of specific enzymes in cellular sensitivity to cytotoxic and genotoxic agents, including both cancer chemotherapeutic drugs and carcinogens.
Current Research:
Exposure of cells to reactive electrophilic agents can damage cellular protein and lipid structures, and can cause genetic changes leading to abnormal growth control and cancer. We are interested in the enzymatic mechanisms for activation vs. detoxification of carcinogenic mutagens. Transgenic cell lines provide an opportunity to measure protective effects of cloned genes that influence sensitivity to cytotoxic or genotoxic agents directly, quantitatively, and unambiguously, in comparison with matched controls.
One project is focused on the glutathione S-transferase (GST) isoenzyme family, that detoxifies electrophiles by conjugation with the thiol tripeptide glutathione (GSH). The specificity and efficacy of protection by GSTs against DNA damage and mutagenesis has not been examined in detail. The goal of this project is to utilize transgenic model cell lines to determine whether and under what conditions or limitations expression of GST isozymes can protect against chemical DNA damage and mutagenesis by detoxication of selected environmental carcinogens. Specific issues include : 1) how much activity is required for protection against different classes of agents; 2) whether detoxification is dominant over activation for specific agents; 3) mechanism of differential protection against cytotoxicity, DNA adduct formation, and mutagenesis; and 4) modulation by GSTs of chemical stress-induced signaling pathways.
A second major project concerns the mechanisms whereby lipid aldehydes produced during oxidative stress can damage cellular proteins and induce apoptosis. The structure-activity features for induction of apoptosis by 4-hydroxynonenal have been characterized. The project iwill now focus on signaling events associated with triggering of apoptosis. The role of aldehyde dehydrogenases in cellular defense against this damage is also a key aspect that is being studied with transgenic cell lines that express specific ALDH isozymes. A longer term goal is to develop transgenic animals that express ALDH3, which may result in resistance to diseases that involve lipid oxidation, e.g. atherosclerosis, fibrosis, autoimmunity, and cancer.
A third new project arose from our observation that cells expressing transfected cyclooxygenase (COX; prostaglandin synthase) isozymes are more sensitive to anticancer drugs. This effect can be amplified under certain experimental conditions. The goal of this research is to determine if this can be manipulated to therapeutic advantage, to reduce normal tissue toxicity or enhance killing of tumor cells. The focus is on discovering the signaling and downstream events whereby COX expression enhances cellular sensitivity to cytotoxic or genotoxic agents.
Recent Publications:
Kushman ME, Kabler SL, Ahmad S, Doehmer J, Morrow CS, Townsend AJ. Protective efficacy of hGSTM1-1 against B[a]P and (+)- or (-)-B[a]P-7,8-dihydrodiol cytotoxicity, mutagenicity, and macromolecular adducts in V79 cells co-expressing hCYP1A1. Toxicol Sci. 2007 May 24.
Kushman ME, Kabler SL, Ahmad S, Doehmer J, Morrow CS, Townsend AJ. Cytotoxicity and mutagenicity of dibenzo[a,l]pyrene and (+/-)-dibenzo[a,l]pyrene-11,12-dihydrodiol in V79MZ cells co-expressing either hCYP1A1 or hCYP1B1 together with human glutathione-S-transferase A1. Mutat Res. 2007 Apr 19.
Kushman ME, Kabler SL, Fleming MH, Ravoori S, Gupta RC, Doehmer J, Morrow CS, Townsend AJ. Expression of human glutathione S-transferase P1 confers resistance to benzo[a]pyrene or benzo[a]pyrene-7,8-dihydrodiol mutagenesis, macromolecular alkylation, and formation of stable N2-Gua-BPDE adducts in stably transfected V79MZ cells co-expressing hCYP1A1. Carcinogenesis. 2006 Aug 2.
Xu M, Moore JE, Leone-Kabler S, McCoy TP, Swank A, Nelson GB, Ross JA, Townsend AJ, Miller MS. Expression of glutathione S-transferases in fetal lung and liver tissue from parental strains and F1 crosses between C57BL/6 and BALB/c F1 mice following in utero exposure to 3-methylcholanthrene. Biochem Pharmacol. 2006 Jun 28;72(1):115-23.
Morrow CS, Peklak-Scott C, Bishwokarma B, Kute TE, Smitherman PK, Townsend AJ. Multi-drug resistance protein 1 (MRP1, ABCC1) mediates resistance to mitoxantrone via glutathione-dependent drug efflux. Mol Pharmacol. 2006 Apr;69(4):1499-505.
Publications:
For a listing of additional publications, refer to PubMed, a service provided by the National Library of Medicine
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