Hasan Koc Research Assistant Professor of Biochemistry and Molecular Biology 103 Althouse Laboratory, University Park, PA 16802 Phone: (814) 865-1245 Fax: (814) 863-7024 E-mail: huk12@psu.edu B.S. in Chemistry, Ege University, Izmir, Turkey Ph.D. in Chemistry, New Mexico State University, Las Cruces, NM Postdoctoral in Toxicology and Bioanalytical Chemistry, University of North Carolina, Chapel Hill, NC Koc Lab Web Site

Mechanistic Studies of Carcinogenecity Induced by Electrophilic Agents

     Many electrophilic reagents are implicated in cancer initiation through modification of DNA bases.  Living systems are equipped with mechanisms to repair such modifications under normal circumstances, however, they can go unrepaired and cause mutations when there are too many modifications to handle or repair mechanisms are for some reason not functioning properly.   One such electrophile is 1,2,3,4-diepoxybutane (DEB), a metabolite of 1,3-butadine  (BD) formed upon activation by CYP450 along with the mono epoxide and epoxydiol metabolites.  DEB is of a special interest to us and others because it is the metabolite that is by many considered to be responsible for most of the BD-induced mutagenicity and genotoxicity.  The mutagenicity of DEB is widely attributed to its ability to form cross-links due to its bi-functional nature. It has indeed been shown to form DNA-DNA and DNA-protein cross-links in vitro.  One of the findings of our earlier molecular dosimetry studies with rats and mice exposed to BD by inhalation was that DEB was circulating in the blood of exposed rats and mice at a steady-state concentration.  However, there is no in vivo evidence that DEB detected in blood actually reaches DNA and reacts with it since there was no DEB-specific adduct known at the time of the study.  Since then, we characterized formation of a cyclic adduct of DEB with globin using a proteomics approach.  This cyclic adduct /modification that can only formed by the bi-functional DEB.  We are utilizing this diagnostic modification to determine spread of DEB in the cell and whether or not it reaches and modifies the genetic material. 

     In order to build a stronger case for DEB being responsible for most of the BD-originated mutagenicity, more in vivo evidence for reaction of DEB with DNA needs to be gathered.  Our approaches to accomplish this task are to do it in a direct manner by detection of the cyclic modification in DNA or by detection of the same modification in proteins nearby, i.e. histones, which would demonstrate that DEB is at least making it that far, the second most powerful evidence.

       Recently, we also became interested in studying in a global fashion the changes induced by electrophilic agents (DEB would serve as a model electrophile in this case) in protein expression profiles and post translational modifications (PTM), especially phosphorylation.   In our recent experiments we found that DEB induced apoptosis in a similar manner to other well-known apoptosis inducing agents such as STS at concentrations as low as 10 µM (in Jurkat cells) besides its established role in mutagenesis.  We are utilizing both traditional and cutting-edge mass spectrometry based proteomics technologies to monitor changes in the proteomes of DEB-treated cell lines and try to understand what determines the outcome of action of electrophilic agents on biomolecules.

Representative Publications:

• Moura AA, Koc H, Chapman DA, Killian GJ. 2006. Identification of proteins in the accessory sex gland fluid and their association with fertility indexes of dairy bull: a proteomics approach. Journal of Andrology . 27(2): 2001-11.
• Rusyn I, Asakura S, Li Y, Kosyk O, Koc H, Nakamura J, Upton PB, Swenberg JA. 2005. Effects of ethylene oxide and ethylene inhalation on DNA adducts, apurinic/apyrimidinic sites and expression of base excision DNA repair genes in rat brain, spleen, and liver. DNA Repair (Amst). 4(10):1099-110

• Abbas A, Koc H, Liu F, Tien M. 2005. Fungal degradation of wood: initial proteomic analysis of extracellular proteins of Phanerochaete chrysosporium grown on oak substrate. Curr Genet 47(1): 49-56

• Ham AJ, Engelward BP, Koc H, Sangaiah R, Meira LB, Samson LD, Swenberg JA. 2004. New immunoaffinity-LC-MS/MS methodology reveals that Aag null mice are deficient in their ability to clear 1,N6-etheno-deoxyadenosine DNA lesions from lung and liver in vivo. DNA Repair (Amst). 3(3):257-65
• Swenberg JA, Ham AJ, Koc H, Morinello E, Ranasinghe A, Upton PB, Nakamura J, Schoonhoven R, McDorman K. 2003. Methods for measuring DNA adducts and Abasic sites, Current Protocols in Toxicology:
• Jayaraj K, Georgieva NI, Gold A, Sangaiah R, Koc H, Klapper DG, Ball LM, Reddy AP, Swenberg JA. 2003. Synthesis and characterization of peptides containing a cyclic Val adduct of diepoxybutane, a possible biomarker of human exposure to butadiene. Chemical Research in Toxicology 16(5): 637-643
• Georgieva NI, Jayaraj K, Koc H, Begemann P, Gold A, Swenberg JA. 2003. Cyclic N-terminal hemoglobin adduct as a butadiene diepoxide biomarker. Toxicological Sciences 72(1): 248-248
• Swenberg JA, Gorgeiva N, Ham A, Koc H, Morinello E, Ranasinghe A, Upton P, Walker V. 2002. Linking pharmacokinetics and biomarker data to mechanism of action in risk assessment. Human and Ecological Risk Assessment 8(6): 1315-1338
• Koc H, Mar MH, Ranasinghe A, Swenberg JA, Zeisel SH. 2002. Quantitation of choline and its metabolites in tissues and foods by liquid chromatography/electrospray ionization-isotope dilution mass spectrometry. Analytical Chemistry 74(18): 4734-4740
• Koc H, Swenberg JA. 2002. Applications of mass spectrometry for quantitation of DNA adducts. Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences 778(1-2): 323-343
• Swenberg JA, Koc H, Upton PB, Georguieva N, Ranasinghe A, Walker VE, Henderson R. 2001. Using DNA and hemoglobin adducts to improve the risk assessment of butadiene. Chemico-Biological Interactions 135: 387-403

• Koc EC, Ranasinghe A, Burkhart W, Blackburn K, Koc H, Moseley A, Spremulli LL. 2001. A new face on apoptosis: death-associated protein 3 and PDCD9 are mitochondrial ribosomal proteins. Febs Letters 492(1-2): 166-+

• Swenberg JA, Ham A, Koc H, Morinello E, Ranasinghe A, Tretyakova N, Upton PB, Wu KY. 2000. DNA adducts: effects of low exposure to ethylene oxide, vinyl chloride and butadiene. Mutation Research-Genetic Toxicology and Environmental Mutagenesis 464(1): 77-86
• Ham AJ, Ranasinghe A, Koc H, Swenberg JA. 2000. 4-Hydroxy-2-nonenal and ethyl linoleate form N(2),3-ethenoguanine under peroxidizing conditions. Chemical Research in Toxicology 13(12): 1243-1250
• Koc H, Tretyakova NY, Walker VE, Henderson RF, Swenberg JA. 1999. Molecular dosimetry of N-7 guanine adduct formation in mice and rats exposed to 1,3-butadiene. Chemical Research in Toxicology 12(7): 566-574

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