Day 1 :
University of Arkansas for Medical Sciences, USA
Time : 09:00-09:30
Alexei G Basnakian received his PhD and DSc degrees from the Russian Academy of Medical Science, both in the field of DNA endonucleases. He had Post-doctoral trainings in molecular biology at the Harvard Medical School and in toxicology/cancer research at the National Center for Toxicological Research. He is Professor in the Department of Pharmacology and Toxicology, and Director of the DNA Damage and Toxicology Core Center at the University of Arkansas for Medical Sciences, and Research Career Scientist at the Veteran’s Hospital in Little Rock, Arkansas, USA. He is an author of more than 85 peer-reviewed papers and 12 reviews or book chapters. He is an Editorial Board Member of several biomedical journals, and a member of NIH and VA grant study sections. His research interests are in DNA endonucleases and DNA damage associated with toxicity, anti-cancer therapy, cell injury and cell death.
DNA is the longest polymer and the only cellular molecule that cannot be resynthesized if destroyed. The destruction of DNA beyond DNA repair capacity is provided by DNA endonucleases and causes the termination of DNA and mRNA syntheses. Since DNA destruction occurs immediately prior and after cell death, the endonucleases do not need to be induced to provide DNA fragmentation. Independently of cell death cause and mechanism, the endonuclease-mediated DNA fragmentation is the universal marker of irreversible cell death. Most active cellular DNA-fragmenting endonucleases are DNase I and Endonuclease G (EndoG). We studied whether overexpression of these two endonucleases would cause DNA fragmentation (TUNEL) and cell death (LDH release) without and in the presence of anticancer drugs (cyclophosphamide, cisplatin, docetaxel, etoposide, or camptothecin). Our experiments showed that expression levels of the two endonucleases strongly correlated with drug sensitivity of breast cancer and prostate cancer cells. Invasive cancer cell lines usually did not express DNase I, and the level of EndoG expression correlated with the degree of dedifferentiation. Overexpression of the endonucleases was not very cytotoxic by itself but made the cancer cell lines more sensitive to the drugs, while silencing of the endonucleases partially protected them from the drug toxicities. Orthotopic EndoG-deficient prostate cancer xenografts were not sensitive to docetaxel, but became sensitive after overexpression of EndoG. Normal kidney cells and mouse kidneys in vivo were highly sensitive to cisplatin toxicity, which was mediated by the same endonucleases. Newly developed chemical inhibitors of DNase I and EndoG protected cancer and kidney cells from anticancer drugs. These observations indicate the importance of the endonucleases in cancer drug toxicities, and suggest potential benefits of using them as helper drugs for anticancer therapy and as targets for protecting normal tissues against drug toxicities.
University of Debrecen, Hungary
Time : 09:30-10:00
István Fábián has received his PhD degree from University of Debrecen (the former Kossuth Lajos University) in 1982. Currently, he is the Head of the Department of Inorganic and Analytical Chemistry. His main interest lies in the kinetics and mechanisms of solution phase redox reactions. He has published more than 100 papers in high level scientific journals. Since 2010 he has been serving as Editor-in-Chief of Reaction Kinetics, Mechanisms and Catalysis (Springer - Akadémiai Kiadó).
N-chlorinated amines are of utmost importance in environmental technologies and physiological processes. They are formed from hypochlorous acid and the corresponding amines in fast reactions. In biological systems, N-chloramines are important intermediates in the degradation of invading pathogens and known regulators of cell metabolism. However, they also contribute to adverse effects in living cells and the derivatives formed from these chlorinated compounds may also have significant biological effects. While earlier studies on the chemistry of N-chloroamino acids recognized the significance of these compounds, the results on the decomposition of these species are controversial. Now we present a detailed study on the kinetics and mechanism of the decomposition of N-chloroglycine. Spectrophotometric as well as systematic 1H and 13C NMR experiments were performed to identify and follow the concentration changes of the reactant, intermediates and products. Our results clarify some of the discrepancies in previous data. It is confirmed that the decomposition kinetics is far more complex than it was proposed before, the kinetic traces feature two well defined first-order processes. The reaction proceeds via various reactive intermediates which may have profound effects in biological systems. Notably, one of these intermediates is N-oxalylglycine which inhibits α-ketoglutarate-dependent enzymes. Earlier, formaldehyde was postulated as the final product of the decomposition. In contrast, it is now confirmed that the main product is N-formylglycine which may also act as an enzyme inhibitor. Additional studies on the decomposition of N-chloro-α-alanine corroborate the results with N-chloroglycine although this reaction also exhibits distinct features.
University of Texas, USA
Time : 10:00-10:30
Lawrence C Sowers received his PhD in Physical Biochemistry from Duke University. Following Post-doctoral positions at Harvard and the University of Southern California, he began his independent career at the City of Hope National Medical Center. He then moved on to Loma Linda Medical School and then to the University of Texas Medical Branch where he is currently Professor and Chair of the Department of Pharmacology and Toxicology. He is currently a member of the Cancer Etiology study section and a Member of the Editorial Board of the Journal of Biological Chemistry.
The DNA of all organisms undergoes persistent DNA damage and repair. Additionally, DNA bases undergo enzymatically-mediated modifications involved in both stem cell differentiation and increased immune diversity. Many of these modified bases are removed from DNA by glycosylases of the base excision repair system. Therefore, the released free bases represent the end product of DNA metabolism in most organisms. While a substantial number of investigations have focused on the identification and measurement of modified bases in DNA, few have examined the free bases products released either spontaneously or enzymatically. We have developed a method for examining free bases in extracts of animal tissues which involves HPLC separation followed by GC/MC/MS analysis using stable isotope analogs. The challenges and advantages of this method, which has been applied to the normal rodent brain, will be discussed.