1985 — 1986 |
Skibo, Edward B |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Design and Mechanistic Study of Reductive Alkylators @ Arizona State University-Tempe Campus
This proposal describes a mechanistic study of the process of reductive alkylation by which many synthetic and naturally occurring quinones are proposed to exert cytotoxicity. Also described is the design of new reductive alkylating quinones having the active sites of purine-utilizing enzymes as their target. Reductive alkylation is carried out by certain quinone systems containing an appropriately positioned leaving group when in their hydroquinone forms. Alkylation could occur either by formation of a hydroquinone stablized carbonium ion or a reactive quinone methide. Both mechanisms have been proposed for the antitumor antibiotic Mitomycin C which when activated by an intracellular quinone reductase preferably alkylates the DNA of hypoxic tumor cells. Cytotoxicity of Mitomycin C and other quinone antibiotics may also pertain to the generation of reactive oxygen species by cycling between the hydroquinone and quinone forms via a semiquinone intermediate. In this proposal the possible formation of a quinone methiode from the semiquinone form by elimination of the leaving group as a radical is considered. This mechanism is consistent with observations cited in the literature and could unify the two postulated mechanisms for cytotoxicity mentioned above. Kinetic methodologies for establishing the presence of a quinone methide or carbonium ion in various hydroquinone systems under non-biological conditions are presented. From this study a knowledge of the structural requirements for reductive alkylation will be gained with which new antitumor agents may designed. The imidazo [4,5-g] quinazoline-4,9-dione system may be described as an extended purine able to be functionalized to act as a reductive alkylator. Based on precedents, entry of this system into the active sites of xanthine oxidase or guanase is proposed. The potential utility of these compounds in cancer chemotherapy is that alkylation of these enzymes will occur only under reducing conditions. Since certain purine antitumor agents are degraded by these enzymes, such agents will be potentiated in hypoxic tumors only. Similarly, reductive alkylators of key enzymes in purine de novo synthesis may be designed. This aspect of the project will involve synthetic, kinetic, and enzyme binding studies.
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1 |
1987 — 1991 |
Skibo, Edward B |
K04Activity Code Description: Undocumented code - click on the grant title for more information. R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
The Design of Antitumor Reductive Alkylators @ Arizona State University-Tempe Campus
The proposal describes the rational design of antitumor agents by exploiting biochemical differences between normal and tumor cells. Certain tumor cells possess high levels of the purine de novo synthetic enzymes IMP dehydrogenase and adenylosuccinate synthetase, as well as low reduction potential environment. The strategy is to design inhibitors directed towards these enzymes which act only (or preferably) in this low potential environment. A parallel effort will be to design crosslinkers of DNA that do likewise. The design to be employed for both cellular targets is based on a class of naturally occurring quinones known as reductive alkylators (e.g. mitomycin C, the saframycins, and the anthracyclines). These compounds become alkylators when reduced to the hydroquinone form, presumably as a result of quinone methide formation upon elimination of a leaving group. Reductive alkylators based on the imidazo (4,5-g) quinazoline ring system have been shown to mimick purine substrates in enzymatic reactions as well as form an alkylating quinone methide species upon reduction. Thus, a reductive alkylator for xanthine oxidase was designed which acts as a substrate in the oxidized form but inactivates the enzyme upon reduction. The proposed research involves designing nucleotide reductive alkylators of the title enzymes based on the imidazo(4,5-g) quinazoline ring system. Another proposed area of study is the design of mechanistic probes of the title enzymes employing this ring system. This aspect of the project will involve synthesis, enzyme kinetic studies and antitumor screening. Quinone methides based on the benzimidazole and quinazoline ring systems have also been documented and found to be excellent nucleophile traps. It appears that the presence of nitrogen atoms in the quinone methide favor nucleophilic addition over electrophilic addition. Effective alkylators of DNA may be realized by replacing the indole nucleus of the mitosene form of mitomycin C with benzimidazole and quinazoline. The proposed research involves the synthesis of the mitosene-like systems, DNA crosslinking studies, and antitumor screening. A DNA fragment of defined sequence will be employed to investigate the site of crosslinking.
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1 |
1988 |
Skibo, Edward B |
K04Activity Code Description: Undocumented code - click on the grant title for more information. |
Design of Antitumor Reductive Alkyators @ Arizona State University-Tempe Campus
This proposal describes the rational design of antitumor agents by exploiting biochemical differences between normal and tumor cells. Certain tumor cells possess high levels of the purine de novo synthetic enzymes IMP dehydrogenase and adenylosuccinate synthetase, as well as a low reduction potential environment. The strategy is to design inhibitors directed towards these enzymes which act only (or preferably) in this low potential environment. A parallel effort will be to design crosslinkers of DNA that do likewise. The design to be employed for both cellular targets is based on a class of naturally occurring quinones known as reductive alkylators (e.g. mitomycin C, the saframycins, and the anthracyclines). These compounds become alkylators when reduced to the hydroquinone form, presumably as a result of quinone methide formation upon elimination of a leaving group. Reductive alkylators based on the imidazo(4,5-g)quinazoline ring system have been shown to mimick murine substrates in enzymatic reactions as well as form an alkylating quinone methide species upon reduction. Thus, a reductive alkylator for xanthine oxidase was designed which acts as a substrate in the oxidized form but inactivates the enzyme upon reduction. The proposed research involves designing nucleotide reductive alkylators of the title en based on the imidazo(4,5 g)quinazoline ring system. Another proposed area of study is the design of mechanistic probes of the title enzymes employing this ring system. This aspect of the project will involve synthesis, enzyme kinetic studies and antitumor screening. Quinone methides based on the benzimidazole and quinazoline ring systems have also been documented and found to be excellent nucleophile traps. It appears that the presence of nitrogen atoms in the quinone methide favor nucleophilic addition over electrophilic addition. Effective alkylators of DNA may be realized by replacing the indole nucleus of the mitosene form of mitomycin C with benzimidazole, quinazoline and other heterocyclic rings. The proposed research involves the synthesis of the mitosene-like systems, DNA crosslinking studies, and antitumor screening. A DNA fragment of defined sequence will be employed to investigate the site of crosslinking.
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1 |
1989 |
Skibo, Edward B |
K04Activity Code Description: Undocumented code - click on the grant title for more information. |
The Design of Antitumor Reductive Alkyators @ Arizona State University-Tempe Campus
This proposal describes the rational design of antitumor agents by exploiting biochemical differences between normal and tumor cells. Certain tumor cells possess high levels of the purine de novo synthetic enzymes IMP dehydrogenase and adenylosuccinate synthetase, as well as a low reduction potential environment. The strategy is to design inhibitors directed towards these enzymes which act only (or preferably) in this low potential environment. A parallel effort will be to design crosslinkers of DNA that do likewise. The design to be employed for both cellular targets is based on a class of naturally occurring quinones known as reductive alkylators (e.g. mitomycin C, the saframycins, and the anthracyclines). These compounds become alkylators when reduced to the hydroquinone form, presumably as a result of quinone methide formation upon elimination of a leaving group. Reductive alkylators based on the imidazo(4,5-g)quinazoline ring system have been shown to mimick murine substrates in enzymatic reactions as well as form an alkylating quinone methide species upon reduction. Thus, a reductive alkylator for xanthine oxidase was designed which acts as a substrate in the oxidized form but inactivates the enzyme upon reduction. The proposed research involves designing nucleotide reductive alkylators of the title en based on the imidazo(4,5 g)quinazoline ring system. Another proposed area of study is the design of mechanistic probes of the title enzymes employing this ring system. This aspect of the project will involve synthesis, enzyme kinetic studies and antitumor screening. Quinone methides based on the benzimidazole and quinazoline ring systems have also been documented and found to be excellent nucleophile traps. It appears that the presence of nitrogen atoms in the quinone methide favor nucleophilic addition over electrophilic addition. Effective alkylators of DNA may be realized by replacing the indole nucleus of the mitosene form of mitomycin C with benzimidazole, quinazoline and other heterocyclic rings. The proposed research involves the synthesis of the mitosene-like systems, DNA crosslinking studies, and antitumor screening. A DNA fragment of defined sequence will be employed to investigate the site of crosslinking.
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1 |
1992 |
Skibo, Edward B |
K04Activity Code Description: Undocumented code - click on the grant title for more information. |
Design of Antitumor Reductive Alkylators @ Arizona State University-Tempe Campus
This proposal describes the rational design of antitumor agents by exploiting biochemical differences between normal and tumor cells. Certain tumor cells possess high levels of the purine de novo synthetic enzymes IMP dehydrogenase and adenylosuccinate synthetase, as well as a low reduction potential environment. The strategy is to design inhibitors directed towards these enzymes which act only (or preferably) in this low potential environment. A parallel effort will be to design crosslinkers of DNA that do likewise. The design to be employed for both cellular targets is based on a class of naturally occurring quinones known as reductive alkylators (e.g. mitomycin C, the saframycins, and the anthracyclines). These compounds become alkylators when reduced to the hydroquinone form, presumably as a result of quinone methide formation upon elimination of a leaving group. Reductive alkylators based on the imidazo(4,5-g)quinazoline ring system have been shown to mimick murine substrates in enzymatic reactions as well as form an alkylating quinone methide species upon reduction. Thus, a reductive alkylator for xanthine oxidase was designed which acts as a substrate in the oxidized form but inactivates the enzyme upon reduction. The proposed research involves designing nucleotide reductive alkylators of the title en based on the imidazo(4,5 g)quinazoline ring system. Another proposed area of study is the design of mechanistic probes of the title enzymes employing this ring system. This aspect of the project will involve synthesis, enzyme kinetic studies and antitumor screening. Quinone methides based on the benzimidazole and quinazoline ring systems have also been documented and found to be excellent nucleophile traps. It appears that the presence of nitrogen atoms in the quinone methide favor nucleophilic addition over electrophilic addition. Effective alkylators of DNA may be realized by replacing the indole nucleus of the mitosene form of mitomycin C with benzimidazole, quinazoline and other heterocyclic rings. The proposed research involves the synthesis of the mitosene-like systems, DNA crosslinking studies, and antitumor screening. A DNA fragment of defined sequence will be employed to investigate the site of crosslinking.
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1 |
1995 — 1998 |
Skibo, Edward |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Studies of Quinone Methides and Related Reactive Species @ Arizona State University
The focus of this research is to design artificial nucleases based on quinone methides which hydrolyse the DNA phosphate backbone under mild conditions. To determine the mechanistic details of action of quinone methides, natural products, such as mitomycin C and daunamycin, will be investigated by electrochemical studies, Nernst-Clark plots, pH rate profiles and product studies. Cyclopropyl quinone methides will be investigated by spectroscopic studies. Aziridinyl hydroquinones will be studied to obtain a structure activity relationship for fate and nucleophile selectivity of reduced aziridinyl quinones. With this award, the Synthetic Organic Program is supporting the research of Dr. Edward B. Skibo of the Department of Chemistry and Biochemistry at Arizona State University. Professor Skibo will focus his work on the study of the formation and fate of reactive species such as quinone methides.These studies will impact areas including natural product chemistry and the design of artificial DNA cleaving agents.
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0.915 |
1998 — 2000 |
Skibo, Edward B |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Synthesis and Evaluation of New Antitumor Agents @ Arizona State University-Tempe Campus
DESCRIPTION: (Principal Investigator's) The proposed research project involves the synthesis and evaluation of new antitumor agents capable of inhibiting topoisomerase II and cleaving DNA. Although many clinically used antitumor agents target topoisomerase II and cleave DNA, the compounds from this laboratory act by novel mechanisms, which translates to a unique spectrum of antitumor activity. Currently, there are 14 compounds from this laboratory undergoing in vivo evaluation at the National Cancer Institute. The current proposal presents new designs based on the compounds currently under study. Th topoisomerase II-DNA crosslinkers are designed to link the DNA to the enzyme thereby causing irreversible damage. The iminoquinone-based topoisomerase II inhibitors are based on the pyrrolo(1,2-a)benzimidazole-based antitumor agents discovered in this laboratory and the pyrroloiminoquinone natural products. These inhibitors are designed to intercalate DNA and then alkylate the tyrosin residue important in topoisomerase II activity. In vivo results indicate that inhibitors of this type possess activity, particularly against melanoma and ovarian cancers. Finally, DNA cleaving agents acting at the phosphate backbone reductively alkylate the phosphate backbone at specific base pairs followed by hydrolytic cleavage of the resulting phosphate triester. This new class of DNA cleaving agent is known to possess antitumor activity and may also be convenient reagents for DNA chemical cleavage. This proposal presents new and improved DNA cleaving agents of this class.
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1 |
2000 — 2003 |
Skibo, Edward |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
The Chemistry of Alkylating Agents, Enriched 13c Nmr and Kinetic Studies @ Arizona State University
With this renewal award the Organic and Macromolecular Chemistry Program continues its support for the work of Dr. Edward. B. Skibo of the Department of Chemistry at Arizona State University in Tempe, Arizona. The research builds on earlier work studying reactive intermediates such as quinone methides, cyclopropyl quinone methides, activated aziridines, and iminium ions. Methods were developed to synthesize mitosenes labeled with 13C at the 1- and 10- positions using single-carbon 13C starting materials. These labeled mitosenes and similarly labeled aziridines incorporated into other know aklylating agents will be used to study the chemo and regioselectivity of reductive alkylation of DNA. 13 C NMR will be used to determine the initial product distributions and as a probe to follow product isolation.
The majority of antitumor agents function by the chemical modification of DNA, for example by the addition of alkyl groups which interfere with replication of the rapidly growing cells. Very little is known about what factors control the sites of alkylation, in part because of the difficulties of isolating the identifying the many possible products formed. The use of 13C enriched alkylating agents, coupled with 13C Nuclear Magnetic Resonance spectroscopy, should make it possible to determine alkylation sites and product distributions in crude reaction mixtures - giving fundamental insights which might assist the development of more effective chemotherapy treatments. This research is highly interdisciplinary, cutting across physical organic chemistry, medicinal chemistry, and biochemistry.
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0.915 |
2004 — 2007 |
Hayes, Mark (co-PI) [⬀] Skibo, Edward Brune, Daniel Francisco, Wilson [⬀] Blankenship, Robert (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Mass Spectrometry Across the Chemistry and Biochemistry Curriculum @ Arizona State University
Chemistry (12) This project aims to introduce mass spectrometry (MS) into all levels of the undergraduate chemistry and biochemistry curriculum at Arizona State University. A major objective of the project is to use MS as a means for developing "molecular thinking" in students. Acquisition of Gas Chromatography/Mass Spectrometry (GC/MS) and Matrix-Assisted Laser Desorption Ionization - Time of Flight (MALDI-TOF) mass spectrometers are enabling students to perform experiments using mass spectrometry in course-related laboratory work and independent student research. A number of experiments, with increasing complexity, are being adapted from the current scientific literature for instructional purposes at various levels of the curriculum including general chemistry, organic chemistry, instrumental analysis and biochemistry. Assessment of the outcomes of the project is being accomplished through a variety of methods including ongoing evaluation of students, TAs and faculty, as well as exit interviews and tests designed to measure how well the methods help students learn key mass spectrometry and chemistry concepts.
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0.915 |