Kenyon Daniel - Academia.edu (original) (raw)

Papers by Kenyon Daniel

Research paper thumbnail of Book Review: Essentials of Apoptosis: A Guide for Basic and Clinical Research

Cancer Control, Sep 1, 2003

Research paper thumbnail of Computational modeling and biological evaluation of methylated (-)-EGCG analogs

Cancer Research, Apr 15, 2006

Proc Amer Assoc Cancer Res, Volume 47, 2006 4897 The anti-cancer and cancer-preventive effects of... more Proc Amer Assoc Cancer Res, Volume 47, 2006 4897 The anti-cancer and cancer-preventive effects of green tea and its main constituent (-)-epigallocatechin-3-gallate [(-)-EGCG] are well documented by a variety of studies, including epidemiological, cell culture, animal, and clinical. While (-)-EGCG remains the most potent polyphenol in green tea, it is particularly unstable under neutral or alkaline conditions ( i.e . physiologic pH) and may be modified by methylation, glucuronidation and sulfonation. In order to understand the significance of methylation on cancer-preventative effects of tea polyphenols, we synthesized several (-)-EGCG and (-)-ECG analogs with various number of methyl groups (mono-, di-, and tri-) attached to the B- and/or D-rings. Additionally, we synthesized putative prodrugs that contain protective peracetate groups (removable by cellular cytosolic esterases) in place of the remaining hydroxyl groups. The structure-activity relationships (SARs) were studied by both in silico computational modeling of the methylated (-)-EGCG analogs to the proteasome active site and their in vitro inhibitory potencies against a purified 20S proteasome. While the number of methyl groups was increased, a gradual decrease was observed in the probability of methylated (-)-EGCG analogs to bind in silico to the active site of the proteasome. Consistently, as the number of methyl groups increased on the (-)-EGCG molecule, the in vitro proteasome-inhibitory potencies were also decreased. When human leukemic Jurkat T cells were tested, the pro-drug of the mono-methylated (-)-EGCG analog caused greater proteasome inhibition and apoptosis than the pro-drug of the tri-methylated (-)-EGCG analog. Our data suggest that methylation of (-)-EGCG lessens its proteasome-inhibitory ability that might lead to decreased cancer preventative effects.

Research paper thumbnail of Proteasome inhibitor patents (2010 – present)

Expert Opinion on Therapeutic Patents, Jan 23, 2014

Over the past 3 years, numerous patents and patent applications have been submitted and published... more Over the past 3 years, numerous patents and patent applications have been submitted and published involving compounds designed to inhibit the proteasome. Proteasome inhibition has been of great interest in cancer research since disruption of proteolysis leads to a significant buildup of cytotoxic proteins and activation of apoptotic pathways, particularly in rapidly proliferating cells. The current standards in proteasome inhibition are the only FDA-approved inhibitors, bortezomib and carfilzomib. Although these drugs are quite effective in treating multiple myeloma and other blood tumors, there are shortcomings, including toxicities and resistance. Most of the current patents attempt to improve on existing compounds, by increasing bioavailability and selectivity, while attempting to reduce toxicity. A general categorization of similar compounds was employed to evaluate and compare drug design strategies. This review focuses on novel compounds and subsequent analogs developed for proteasome inhibition, used in preventing and treating human cancers. A comprehensive description and categorization of patents related to each type of compound and its derivatives, as well as their uses and efficacies as anticancer agents is included. A review of combination therapy patents has also been included. Although there are many diverse chemical scaffolds being published, there are few patented proteasome inhibitors whose method of inhibition is genuinely novel. Most patents utilize a destructive chemical warhead to attack the catalytic threonine residue of the proteasome active sites. Few patents try to depart from this, emphasizing the need for developing new mechanisms of action and specific targeting.

Research paper thumbnail of Exploiting the Ubiquitin-Proteasome Pathway for Anticancer Drug Discovery: Unanswered Questions and Future Directions

Letters in Drug Design & Discovery, Feb 1, 2005

Research paper thumbnail of Identifying Biomolecular Targets of the Anticancer Vitamin-E-δ-Tocotrienol Using a Computational Approach: Virtual Target Screening

Clinical Oncology and Research, 2020

In recent years, evidence has mounted that a particular form of vitamin E (its δ-tocotrienol vari... more In recent years, evidence has mounted that a particular form of vitamin E (its δ-tocotrienol variant) may have cellular functions beyond that of an antioxidant, a role commonly ascribed to the tocotrienol class of compounds. In particular, numerous studies of δ-tocotrienol’s effect on cancer cells have identified it as a potent anticancer and antitumor agent. However, this important revelation of potential therapeutic use poses a series of new challenges, with arguably the most important being the elucidation of the precise mechanism of action responsible for the anticancer activity of δ-tocotrienol. As an initial step to address this question, we have used a computational tool, Virtual Target Screening (a molecular docking-based tool that identifies potential binding partners for small molecules), to identify potential biomolecular targets of δ-tocotrienol. Then, to gain a consensus as to the type of biomolecular entity that could be a target for δ-tocotrienol, we utilized PharmMap...

Research paper thumbnail of Evaluation of digestion methods for analysis of trace metals in mammalian tissues and NIST 1577c

Analytical biochemistry, Jan 23, 2017

Digestion techniques for ICP analysis have been poorly studied for biological samples. This repor... more Digestion techniques for ICP analysis have been poorly studied for biological samples. This report describes an optimized method for analysis of trace metals that can be used across a variety of sample types. Digestion methods were tested and optimized with the analysis of trace metals in cancerous as compared to normal tissue as the end goal. Anthropological, forensic, oncological and environmental research groups can employ this method reasonably cheaply and safely whilst still being able to compare between laboratories. We examined combined HNO3 and H2O2 digestion at 170 °C for human, porcine and bovine samples whether they are frozen, fresh or lyophilized powder. Little discrepancy is found between microwave digestion and PFA Teflon pressure vessels. The elements of interest (Cu, Zn, Fe and Ni) yielded consistently higher and more accurate values on standard reference material than samples heated to 75 °C or samples that utilized HNO3 alone. Use of H2SO4 does not improve homogen...

Research paper thumbnail of Copper-binding compounds as proteasome inhibitors and apoptosis inducers in human cancer

Frontiers in Bioscience, 2007

Research paper thumbnail of Structure-activity relationships OF N-methylthiolated beta-lactam antibiotics with c3 substitutions and their selective induction of apoptosis in human cancer cells

Frontiers in Bioscience, 2005

Research paper thumbnail of Exploiting the Ubiquitin-Proteasome Pathway for Anticancer Drug Discovery: Unanswered Questions and Future Directions

Letters in Drug Design & Discovery, 2005

Research paper thumbnail of Interruption of tumor cell cycle progression through proteasome inhibition: implications for cancer therapy

Progress in cell cycle research, 2003

The ubiquitin/proteasome-dependent protein degradation pathway plays an essential role in both up... more The ubiquitin/proteasome-dependent protein degradation pathway plays an essential role in both up-regulation of cell proliferation and down-regulation of cell death in human cancer cells. The idea that proteasome function is required for tumor cell survival has prompted the design, synthesis and evaluation of various pharmacological proteasome inhibitors. Both in vitro and in vivo experimental and clinical results have demonstrated the potential use of proteasome inhibitors as novel anticancer drugs.

Research paper thumbnail of Beta-lactams and their potential use as novel anticancer chemotherapeutics drugs

Frontiers in Bioscience, 2004

Introduction 3. Current antibiotic modalities in cancer treatment 4. Traditional roles of beta-la... more Introduction 3. Current antibiotic modalities in cancer treatment 4. Traditional roles of beta-lactams 5. Beta-lactams as prodrugs for anticancer chemotherapies 5.1. Background 5.2. Nitrogen mustards 5.3. Methoxytrexate 5.4. 5-Fluorouracil 5.5. Vinca alkaloids 5.6. Doxorubicin 5.7. Mitomycin C 5.8. Paclitaxel 5.9. Radioimmunoconjugates 6. Potential use of beta-lactams as anticancer drugs 6.1. N-thiolated beta-lactams 6.1.1. Structure-activity relationships 6.1.2. Apoptosis induction 6.1.3. DNA-damage and signal transduction pathways 6.1.4. Preferential tumor cell killing 6.2. 4-alkylidene-beta-lactams 6.3. Polyaromatic beta-lactams 7. Conclusion and perspectives 8. Acknowledgments 9. References

Research paper thumbnail of Proteasome inhibitor patents (2010 – present)

Expert Opinion on Therapeutic Patents, 2014

Over the past 3 years, numerous patents and patent applications have been submitted and published... more Over the past 3 years, numerous patents and patent applications have been submitted and published involving compounds designed to inhibit the proteasome. Proteasome inhibition has been of great interest in cancer research since disruption of proteolysis leads to a significant buildup of cytotoxic proteins and activation of apoptotic pathways, particularly in rapidly proliferating cells. The current standards in proteasome inhibition are the only FDA-approved inhibitors, bortezomib and carfilzomib. Although these drugs are quite effective in treating multiple myeloma and other blood tumors, there are shortcomings, including toxicities and resistance. Most of the current patents attempt to improve on existing compounds, by increasing bioavailability and selectivity, while attempting to reduce toxicity. A general categorization of similar compounds was employed to evaluate and compare drug design strategies. This review focuses on novel compounds and subsequent analogs developed for proteasome inhibition, used in preventing and treating human cancers. A comprehensive description and categorization of patents related to each type of compound and its derivatives, as well as their uses and efficacies as anticancer agents is included. A review of combination therapy patents has also been included. Although there are many diverse chemical scaffolds being published, there are few patented proteasome inhibitors whose method of inhibition is genuinely novel. Most patents utilize a destructive chemical warhead to attack the catalytic threonine residue of the proteasome active sites. Few patents try to depart from this, emphasizing the need for developing new mechanisms of action and specific targeting.

Research paper thumbnail of Computational Design, Organic Synthesis, and Biological Evaluation of Polyphenol Proteasome Inhibitors: Significance in Drug Discovery and Cancer Prevention

Drug Design Reviews - Online, 2005

... compbio. ucsf.edu/), and FRED (http://www.eyesopen.com/docs/ html/fred/). Results ... Mutat. ... more ... compbio. ucsf.edu/), and FRED (http://www.eyesopen.com/docs/ html/fred/). Results ... Mutat. Res., 1993; 2: 221-32. [25] Xu, M.; Bailey, AC; Hernaez, JF; Taoka, CR; Schut, HA; Dashwood, RH Carcinogenesis, 1996; 7: 1429-34. [26 ...

Research paper thumbnail of Anti-Angiogenic and Anti-Tumor Properties of Proteasome Inhibitors

Current Cancer Drug Targets, 2005

Tumor growth and metastasis depend on the formation of blood vessels, angiogenesis, to supply the... more Tumor growth and metastasis depend on the formation of blood vessels, angiogenesis, to supply the developing mass with nutrients, oxygen, and waste removal. The proteasome, a massive multisubunit catabolic body, exerts a regulatory influence on angiogenesis. Inhibition of the proteasome activity has been found to inhibit angiogenesis and induce apoptosis in human cancer cells with limited toxicity to normal cells. Therefore, the dual action of angiogenesis inhibition and cell death induction makes proteasome inhibition an attractive modality for chemotherapy. A variety of proteasome inhibitors have been studied including: antibiotics such as lactacystin, the green tea polyphenols, and the boronic acid Velcade (MLN-341). Most recently, certain classes of copper compounds have been found to act as potent proteasome inhibitors. The potential of particular organic compounds, such as 8-hydroxyquinoline, to spontaneously bind with tumor cellular copper and form proteasome inhibitors provides a new modality of anti-proteasome and anti-angiogenesis chemotherapy. This review examines angiogenesis, the proteasome, representative proteasome inhibitors, and the emerging role of copper. The formation of new blood vessels, or angiogenesis, is an important and necessary function in both embryonic development and wound repair. Therefore, the ability to regenerate or form new vessels for blood flow is essential. The control of angiogenic pathways is tightly regulated in normal differentiated adult cells, which generally do not stimulate blood vessel growth unless injury occurs. However, cancerous tissues stimulate angiogenesis that in turn leads to increased tumor formation and possible metastases. Many of the factors involved in angiogenesis are regulated by the proteasome, which recently has become a focus in anti-cancer therapies due to its involvement in cell cycle and apoptosis control. Here we discuss angiogenesis and its relation to the proteasome. Additionally, current modalities of anti-angiogenic treatment, mainly proteasome inhibitory strategies, are reviewed. Furthermore, proteasome inhibitors, both natural and synthetic, and their anti-angiogenic effects as well as future approaches to anti-angiogenic chemotherapies are also discussed.

Research paper thumbnail of Dietary flavonoids as proteasome inhibitors and apoptosis inducers in human leukemia cells

Biochemical Pharmacology, 2005

It has been shown that proteasome activity is required for cancer cell survival and consumption o... more It has been shown that proteasome activity is required for cancer cell survival and consumption of fruits and vegetables is associated with decreased cancer risk. Previously, we reported that grape extract could inhibit proteasome activity and induce apoptosis in tumor cells. In this study, we examined the flavonoids apigenin, quercetin, kaempferol and myricetin for their proteasome-inhibitory and apoptosis-inducing abilities in human tumor cells. We report that apigenin and quercetin are much more potent than kaempferol and myricetin at: (i) inhibiting chymotrypsin-like activity of purified 20S proteasome and of 26S proteasome in intact leukemia Jurkat T cells; (ii) accumulating putative ubiquitinated forms of two proteasome target proteins, Bax and Inhibitor of nuclear factor kb-a in Jurkat T cells and (iii) inducing activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase in Jurkat T cells. The proteasome-inhibitory abilities of these compounds correlated with their apoptosis-inducing potencies. Results from computational modeling of the potential interactions of these flavonoids to the chymotrypsin site (b5 subunit) of the proteasome were consistent with the obtained proteasomeinhibitory activities. We found that the C 4 carbon may be a site of nucleophilic attack by the OH group of N-terminal threonine of proteasomal b5 subunit and that the C 3 hydroxyl may alter the ability of these flavonoids to inhibit the proteasome. Finally, apigenin neither effectively inhibited the proteasome activity nor induced apoptosis in non-transformed human natural killer cells. Our results suggested that the proteasome may be a target of these dietary flavonoids in human tumor cells and that inhibition of the proteasome by flavonoids may be one of the mechanisms responsible for their cancer-preventive effects.

Research paper thumbnail of Synthetic peracetate tea polyphenols as potent proteasome inhibitors and apoptosis inducers in human cancer cells

Frontiers in Bioscience, 2005

Research paper thumbnail of Computational Chemistry Tools

Burger's Medicinal Chemistry and Drug Discovery, 2021

Farmers' participation in water resource management in Indonesia has been accommodated through La... more Farmers' participation in water resource management in Indonesia has been accommodated through Law No. 7/2004 and Government Regulation No. 20/2006 regarding irrigation. In government regulations, farmers' participation in irrigation water management has been described in detail, with one of the components of irrigation network management being operations and maintenance. Most irrigation system problems are related to irrigation networks. Farmers' participation in the Water Users Association (WUA), a farmer institution responsible for managing and developing irrigation networks at the tertiary level, determines how irrigation network management activities are carried out. The purpose of this study was to determine the effect of the socioeconomic characteristics of farmers and of group participation of a WUA in carrying out irrigation management activities in operations and maintenance activities. The result is connected to the physical condition of the irrigation network. The research took place in the village of Sumber Rejo in the Punggur Utara irrigation area, which is in Lampung Province, Indonesia, and is where WUA Harapan Maju is active. Samples were determined based on a random sampling method, which found that the sample size required for the study was 80 farmers. The results show that of socioeconomic factors, the most influential is the number of farmers' dependents, followed by the land area owned by each farmer. It was also found that group participation of WUA Harapan Maju

Research paper thumbnail of Ligand-mediated protein degradation reveals functional conservation among sequence variants of the CUL4-type E3 ligase substrate receptor cereblon

The Journal of biological chemistry, Jan 15, 2018

Upon binding to thalidomide and other immunomodulatory drugs, the E3 ligase substrate receptor ce... more Upon binding to thalidomide and other immunomodulatory drugs, the E3 ligase substrate receptor cereblon (CRBN) promotes proteasomal destruction by engaging the DDB1-CUL4A-Roc1-RBX1 E3-ubiquitin ligase in human cells but not in mouse cells suggesting that sequence variations in CRBN may cause its inactivation. Therapeutically, CRBN engagers have the potential for broad applications in cancer and immune therapy by specifically reducing protein expression through targeted ubiquitin-mediated degradation. To examine the effects of defined sequence changes on CRBNs activity, we performed a comprehensive study using complementary theoretical, biophysical, and biological assays aimed at understanding CRBNs non-primate sequence variations. With a series of recombinant thalidomide-binding domain (TBD) proteins, we show that CRBN sequence variants retain their drug binding properties to both classical immunomodulatory drugs and to dBET1, a chemical compound and targeting ligand designed to deg...

Research paper thumbnail of Cupriphilic compounds to aid in proteasome inhibition

Bioorganic & Medicinal Chemistry Letters, 2016

It has been found that tumor cells and tissues, compared to normal cells, have higher levels of c... more It has been found that tumor cells and tissues, compared to normal cells, have higher levels of copper and possibly other metal ions. This presents a potential vulnerability of tumor cells that can serve as a physiological difference between cancer cells and normal cells and allows design of compounds that selectively target tumor cells while sparing normal cells. Recently we have identified compounds that have potential to inhibit the proteasome in tumor cells and induce cell death by mobilizing endogenous tumor copper resulting in in cellulo activation of the compound. These compounds hence act as pro-drugs, becoming active drugs in tumor cells with high copper content but remaining essentially inactive in normal cells, thereby greatly reducing adverse effects in patients. Such use would be of significant benefit in early detection and treatment of cancers, in particular, aggressive cancers such as pancreatic cancer which is usually not detected until it has reached an advanced stage. Six compounds were identified following virtual screening of the NCI Diversity Set with our proteasome computer model followed by confirmation with a biochemical assay that showed significant inhibition of the proteasome by the compounds in the presence of copper ions. In a dose response assay, NSC 37408 (6,7-dihydroxy-1-benzofuran-3-one), our best compound, exhibited an IC50 of 3μM in the presence of 100nM copper.

Research paper thumbnail of Association of mitochondrial calpain activation with increased expression and autolysis of calpain small subunit in an early stage of apoptosis

International Journal of Molecular Medicine, 2003

Various stimuli including anticancer drugs are capable of initiating the apoptotic death program ... more Various stimuli including anticancer drugs are capable of initiating the apoptotic death program in human tumor cells via activation of caspases. Mitochondria play an essential role for cell apoptotic commitment. Previous studies have shown a potential role of calpain activation in apoptosis, however, the involved molecular mechanisms remain to be defined. In the current study, we have examined the expression and activation of mitochondrial calpain in Jurkat T leukemia cells, MCF-7 breast carcinoma and LNCaP prostate cancer cells during apoptosis induced by an anticancer drug (VP-16, tamoxifen) or the specific p38 kinase inhibitor PD-169316. Our results suggest that increased expression and autolysis of the mitochondrial calpain small subunit are tightly associated with calpain activation in an early stage of apoptosis. In contrast, there were no correlations observed between the early calpain activation and changes in levels of mitochondrial calpain large subunit and the endogenous calpain inhibitor calpastatin. Furthermore, pretreatment with the specific pharmacological calpain inhibitor calpeptin blocked the druginduced calpain small subunit autolysis and calpain activation in mitochondria and inhibited apoptosis-associated caspase-3 activation, demonstrating that mitochondrial calpain activation through small subunit cleavage is an essential step for inducing tumor cell apoptosis by various anticancer drugs.

Research paper thumbnail of Book Review: Essentials of Apoptosis: A Guide for Basic and Clinical Research

Cancer Control, Sep 1, 2003

Research paper thumbnail of Computational modeling and biological evaluation of methylated (-)-EGCG analogs

Cancer Research, Apr 15, 2006

Proc Amer Assoc Cancer Res, Volume 47, 2006 4897 The anti-cancer and cancer-preventive effects of... more Proc Amer Assoc Cancer Res, Volume 47, 2006 4897 The anti-cancer and cancer-preventive effects of green tea and its main constituent (-)-epigallocatechin-3-gallate [(-)-EGCG] are well documented by a variety of studies, including epidemiological, cell culture, animal, and clinical. While (-)-EGCG remains the most potent polyphenol in green tea, it is particularly unstable under neutral or alkaline conditions ( i.e . physiologic pH) and may be modified by methylation, glucuronidation and sulfonation. In order to understand the significance of methylation on cancer-preventative effects of tea polyphenols, we synthesized several (-)-EGCG and (-)-ECG analogs with various number of methyl groups (mono-, di-, and tri-) attached to the B- and/or D-rings. Additionally, we synthesized putative prodrugs that contain protective peracetate groups (removable by cellular cytosolic esterases) in place of the remaining hydroxyl groups. The structure-activity relationships (SARs) were studied by both in silico computational modeling of the methylated (-)-EGCG analogs to the proteasome active site and their in vitro inhibitory potencies against a purified 20S proteasome. While the number of methyl groups was increased, a gradual decrease was observed in the probability of methylated (-)-EGCG analogs to bind in silico to the active site of the proteasome. Consistently, as the number of methyl groups increased on the (-)-EGCG molecule, the in vitro proteasome-inhibitory potencies were also decreased. When human leukemic Jurkat T cells were tested, the pro-drug of the mono-methylated (-)-EGCG analog caused greater proteasome inhibition and apoptosis than the pro-drug of the tri-methylated (-)-EGCG analog. Our data suggest that methylation of (-)-EGCG lessens its proteasome-inhibitory ability that might lead to decreased cancer preventative effects.

Research paper thumbnail of Proteasome inhibitor patents (2010 – present)

Expert Opinion on Therapeutic Patents, Jan 23, 2014

Over the past 3 years, numerous patents and patent applications have been submitted and published... more Over the past 3 years, numerous patents and patent applications have been submitted and published involving compounds designed to inhibit the proteasome. Proteasome inhibition has been of great interest in cancer research since disruption of proteolysis leads to a significant buildup of cytotoxic proteins and activation of apoptotic pathways, particularly in rapidly proliferating cells. The current standards in proteasome inhibition are the only FDA-approved inhibitors, bortezomib and carfilzomib. Although these drugs are quite effective in treating multiple myeloma and other blood tumors, there are shortcomings, including toxicities and resistance. Most of the current patents attempt to improve on existing compounds, by increasing bioavailability and selectivity, while attempting to reduce toxicity. A general categorization of similar compounds was employed to evaluate and compare drug design strategies. This review focuses on novel compounds and subsequent analogs developed for proteasome inhibition, used in preventing and treating human cancers. A comprehensive description and categorization of patents related to each type of compound and its derivatives, as well as their uses and efficacies as anticancer agents is included. A review of combination therapy patents has also been included. Although there are many diverse chemical scaffolds being published, there are few patented proteasome inhibitors whose method of inhibition is genuinely novel. Most patents utilize a destructive chemical warhead to attack the catalytic threonine residue of the proteasome active sites. Few patents try to depart from this, emphasizing the need for developing new mechanisms of action and specific targeting.

Research paper thumbnail of Exploiting the Ubiquitin-Proteasome Pathway for Anticancer Drug Discovery: Unanswered Questions and Future Directions

Letters in Drug Design & Discovery, Feb 1, 2005

Research paper thumbnail of Identifying Biomolecular Targets of the Anticancer Vitamin-E-δ-Tocotrienol Using a Computational Approach: Virtual Target Screening

Clinical Oncology and Research, 2020

In recent years, evidence has mounted that a particular form of vitamin E (its δ-tocotrienol vari... more In recent years, evidence has mounted that a particular form of vitamin E (its δ-tocotrienol variant) may have cellular functions beyond that of an antioxidant, a role commonly ascribed to the tocotrienol class of compounds. In particular, numerous studies of δ-tocotrienol’s effect on cancer cells have identified it as a potent anticancer and antitumor agent. However, this important revelation of potential therapeutic use poses a series of new challenges, with arguably the most important being the elucidation of the precise mechanism of action responsible for the anticancer activity of δ-tocotrienol. As an initial step to address this question, we have used a computational tool, Virtual Target Screening (a molecular docking-based tool that identifies potential binding partners for small molecules), to identify potential biomolecular targets of δ-tocotrienol. Then, to gain a consensus as to the type of biomolecular entity that could be a target for δ-tocotrienol, we utilized PharmMap...

Research paper thumbnail of Evaluation of digestion methods for analysis of trace metals in mammalian tissues and NIST 1577c

Analytical biochemistry, Jan 23, 2017

Digestion techniques for ICP analysis have been poorly studied for biological samples. This repor... more Digestion techniques for ICP analysis have been poorly studied for biological samples. This report describes an optimized method for analysis of trace metals that can be used across a variety of sample types. Digestion methods were tested and optimized with the analysis of trace metals in cancerous as compared to normal tissue as the end goal. Anthropological, forensic, oncological and environmental research groups can employ this method reasonably cheaply and safely whilst still being able to compare between laboratories. We examined combined HNO3 and H2O2 digestion at 170 °C for human, porcine and bovine samples whether they are frozen, fresh or lyophilized powder. Little discrepancy is found between microwave digestion and PFA Teflon pressure vessels. The elements of interest (Cu, Zn, Fe and Ni) yielded consistently higher and more accurate values on standard reference material than samples heated to 75 °C or samples that utilized HNO3 alone. Use of H2SO4 does not improve homogen...

Research paper thumbnail of Copper-binding compounds as proteasome inhibitors and apoptosis inducers in human cancer

Frontiers in Bioscience, 2007

Research paper thumbnail of Structure-activity relationships OF N-methylthiolated beta-lactam antibiotics with c3 substitutions and their selective induction of apoptosis in human cancer cells

Frontiers in Bioscience, 2005

Research paper thumbnail of Exploiting the Ubiquitin-Proteasome Pathway for Anticancer Drug Discovery: Unanswered Questions and Future Directions

Letters in Drug Design & Discovery, 2005

Research paper thumbnail of Interruption of tumor cell cycle progression through proteasome inhibition: implications for cancer therapy

Progress in cell cycle research, 2003

The ubiquitin/proteasome-dependent protein degradation pathway plays an essential role in both up... more The ubiquitin/proteasome-dependent protein degradation pathway plays an essential role in both up-regulation of cell proliferation and down-regulation of cell death in human cancer cells. The idea that proteasome function is required for tumor cell survival has prompted the design, synthesis and evaluation of various pharmacological proteasome inhibitors. Both in vitro and in vivo experimental and clinical results have demonstrated the potential use of proteasome inhibitors as novel anticancer drugs.

Research paper thumbnail of Beta-lactams and their potential use as novel anticancer chemotherapeutics drugs

Frontiers in Bioscience, 2004

Introduction 3. Current antibiotic modalities in cancer treatment 4. Traditional roles of beta-la... more Introduction 3. Current antibiotic modalities in cancer treatment 4. Traditional roles of beta-lactams 5. Beta-lactams as prodrugs for anticancer chemotherapies 5.1. Background 5.2. Nitrogen mustards 5.3. Methoxytrexate 5.4. 5-Fluorouracil 5.5. Vinca alkaloids 5.6. Doxorubicin 5.7. Mitomycin C 5.8. Paclitaxel 5.9. Radioimmunoconjugates 6. Potential use of beta-lactams as anticancer drugs 6.1. N-thiolated beta-lactams 6.1.1. Structure-activity relationships 6.1.2. Apoptosis induction 6.1.3. DNA-damage and signal transduction pathways 6.1.4. Preferential tumor cell killing 6.2. 4-alkylidene-beta-lactams 6.3. Polyaromatic beta-lactams 7. Conclusion and perspectives 8. Acknowledgments 9. References

Research paper thumbnail of Proteasome inhibitor patents (2010 – present)

Expert Opinion on Therapeutic Patents, 2014

Over the past 3 years, numerous patents and patent applications have been submitted and published... more Over the past 3 years, numerous patents and patent applications have been submitted and published involving compounds designed to inhibit the proteasome. Proteasome inhibition has been of great interest in cancer research since disruption of proteolysis leads to a significant buildup of cytotoxic proteins and activation of apoptotic pathways, particularly in rapidly proliferating cells. The current standards in proteasome inhibition are the only FDA-approved inhibitors, bortezomib and carfilzomib. Although these drugs are quite effective in treating multiple myeloma and other blood tumors, there are shortcomings, including toxicities and resistance. Most of the current patents attempt to improve on existing compounds, by increasing bioavailability and selectivity, while attempting to reduce toxicity. A general categorization of similar compounds was employed to evaluate and compare drug design strategies. This review focuses on novel compounds and subsequent analogs developed for proteasome inhibition, used in preventing and treating human cancers. A comprehensive description and categorization of patents related to each type of compound and its derivatives, as well as their uses and efficacies as anticancer agents is included. A review of combination therapy patents has also been included. Although there are many diverse chemical scaffolds being published, there are few patented proteasome inhibitors whose method of inhibition is genuinely novel. Most patents utilize a destructive chemical warhead to attack the catalytic threonine residue of the proteasome active sites. Few patents try to depart from this, emphasizing the need for developing new mechanisms of action and specific targeting.

Research paper thumbnail of Computational Design, Organic Synthesis, and Biological Evaluation of Polyphenol Proteasome Inhibitors: Significance in Drug Discovery and Cancer Prevention

Drug Design Reviews - Online, 2005

... compbio. ucsf.edu/), and FRED (http://www.eyesopen.com/docs/ html/fred/). Results ... Mutat. ... more ... compbio. ucsf.edu/), and FRED (http://www.eyesopen.com/docs/ html/fred/). Results ... Mutat. Res., 1993; 2: 221-32. [25] Xu, M.; Bailey, AC; Hernaez, JF; Taoka, CR; Schut, HA; Dashwood, RH Carcinogenesis, 1996; 7: 1429-34. [26 ...

Research paper thumbnail of Anti-Angiogenic and Anti-Tumor Properties of Proteasome Inhibitors

Current Cancer Drug Targets, 2005

Tumor growth and metastasis depend on the formation of blood vessels, angiogenesis, to supply the... more Tumor growth and metastasis depend on the formation of blood vessels, angiogenesis, to supply the developing mass with nutrients, oxygen, and waste removal. The proteasome, a massive multisubunit catabolic body, exerts a regulatory influence on angiogenesis. Inhibition of the proteasome activity has been found to inhibit angiogenesis and induce apoptosis in human cancer cells with limited toxicity to normal cells. Therefore, the dual action of angiogenesis inhibition and cell death induction makes proteasome inhibition an attractive modality for chemotherapy. A variety of proteasome inhibitors have been studied including: antibiotics such as lactacystin, the green tea polyphenols, and the boronic acid Velcade (MLN-341). Most recently, certain classes of copper compounds have been found to act as potent proteasome inhibitors. The potential of particular organic compounds, such as 8-hydroxyquinoline, to spontaneously bind with tumor cellular copper and form proteasome inhibitors provides a new modality of anti-proteasome and anti-angiogenesis chemotherapy. This review examines angiogenesis, the proteasome, representative proteasome inhibitors, and the emerging role of copper. The formation of new blood vessels, or angiogenesis, is an important and necessary function in both embryonic development and wound repair. Therefore, the ability to regenerate or form new vessels for blood flow is essential. The control of angiogenic pathways is tightly regulated in normal differentiated adult cells, which generally do not stimulate blood vessel growth unless injury occurs. However, cancerous tissues stimulate angiogenesis that in turn leads to increased tumor formation and possible metastases. Many of the factors involved in angiogenesis are regulated by the proteasome, which recently has become a focus in anti-cancer therapies due to its involvement in cell cycle and apoptosis control. Here we discuss angiogenesis and its relation to the proteasome. Additionally, current modalities of anti-angiogenic treatment, mainly proteasome inhibitory strategies, are reviewed. Furthermore, proteasome inhibitors, both natural and synthetic, and their anti-angiogenic effects as well as future approaches to anti-angiogenic chemotherapies are also discussed.

Research paper thumbnail of Dietary flavonoids as proteasome inhibitors and apoptosis inducers in human leukemia cells

Biochemical Pharmacology, 2005

It has been shown that proteasome activity is required for cancer cell survival and consumption o... more It has been shown that proteasome activity is required for cancer cell survival and consumption of fruits and vegetables is associated with decreased cancer risk. Previously, we reported that grape extract could inhibit proteasome activity and induce apoptosis in tumor cells. In this study, we examined the flavonoids apigenin, quercetin, kaempferol and myricetin for their proteasome-inhibitory and apoptosis-inducing abilities in human tumor cells. We report that apigenin and quercetin are much more potent than kaempferol and myricetin at: (i) inhibiting chymotrypsin-like activity of purified 20S proteasome and of 26S proteasome in intact leukemia Jurkat T cells; (ii) accumulating putative ubiquitinated forms of two proteasome target proteins, Bax and Inhibitor of nuclear factor kb-a in Jurkat T cells and (iii) inducing activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase in Jurkat T cells. The proteasome-inhibitory abilities of these compounds correlated with their apoptosis-inducing potencies. Results from computational modeling of the potential interactions of these flavonoids to the chymotrypsin site (b5 subunit) of the proteasome were consistent with the obtained proteasomeinhibitory activities. We found that the C 4 carbon may be a site of nucleophilic attack by the OH group of N-terminal threonine of proteasomal b5 subunit and that the C 3 hydroxyl may alter the ability of these flavonoids to inhibit the proteasome. Finally, apigenin neither effectively inhibited the proteasome activity nor induced apoptosis in non-transformed human natural killer cells. Our results suggested that the proteasome may be a target of these dietary flavonoids in human tumor cells and that inhibition of the proteasome by flavonoids may be one of the mechanisms responsible for their cancer-preventive effects.

Research paper thumbnail of Synthetic peracetate tea polyphenols as potent proteasome inhibitors and apoptosis inducers in human cancer cells

Frontiers in Bioscience, 2005

Research paper thumbnail of Computational Chemistry Tools

Burger's Medicinal Chemistry and Drug Discovery, 2021

Farmers' participation in water resource management in Indonesia has been accommodated through La... more Farmers' participation in water resource management in Indonesia has been accommodated through Law No. 7/2004 and Government Regulation No. 20/2006 regarding irrigation. In government regulations, farmers' participation in irrigation water management has been described in detail, with one of the components of irrigation network management being operations and maintenance. Most irrigation system problems are related to irrigation networks. Farmers' participation in the Water Users Association (WUA), a farmer institution responsible for managing and developing irrigation networks at the tertiary level, determines how irrigation network management activities are carried out. The purpose of this study was to determine the effect of the socioeconomic characteristics of farmers and of group participation of a WUA in carrying out irrigation management activities in operations and maintenance activities. The result is connected to the physical condition of the irrigation network. The research took place in the village of Sumber Rejo in the Punggur Utara irrigation area, which is in Lampung Province, Indonesia, and is where WUA Harapan Maju is active. Samples were determined based on a random sampling method, which found that the sample size required for the study was 80 farmers. The results show that of socioeconomic factors, the most influential is the number of farmers' dependents, followed by the land area owned by each farmer. It was also found that group participation of WUA Harapan Maju

Research paper thumbnail of Ligand-mediated protein degradation reveals functional conservation among sequence variants of the CUL4-type E3 ligase substrate receptor cereblon

The Journal of biological chemistry, Jan 15, 2018

Upon binding to thalidomide and other immunomodulatory drugs, the E3 ligase substrate receptor ce... more Upon binding to thalidomide and other immunomodulatory drugs, the E3 ligase substrate receptor cereblon (CRBN) promotes proteasomal destruction by engaging the DDB1-CUL4A-Roc1-RBX1 E3-ubiquitin ligase in human cells but not in mouse cells suggesting that sequence variations in CRBN may cause its inactivation. Therapeutically, CRBN engagers have the potential for broad applications in cancer and immune therapy by specifically reducing protein expression through targeted ubiquitin-mediated degradation. To examine the effects of defined sequence changes on CRBNs activity, we performed a comprehensive study using complementary theoretical, biophysical, and biological assays aimed at understanding CRBNs non-primate sequence variations. With a series of recombinant thalidomide-binding domain (TBD) proteins, we show that CRBN sequence variants retain their drug binding properties to both classical immunomodulatory drugs and to dBET1, a chemical compound and targeting ligand designed to deg...

Research paper thumbnail of Cupriphilic compounds to aid in proteasome inhibition

Bioorganic & Medicinal Chemistry Letters, 2016

It has been found that tumor cells and tissues, compared to normal cells, have higher levels of c... more It has been found that tumor cells and tissues, compared to normal cells, have higher levels of copper and possibly other metal ions. This presents a potential vulnerability of tumor cells that can serve as a physiological difference between cancer cells and normal cells and allows design of compounds that selectively target tumor cells while sparing normal cells. Recently we have identified compounds that have potential to inhibit the proteasome in tumor cells and induce cell death by mobilizing endogenous tumor copper resulting in in cellulo activation of the compound. These compounds hence act as pro-drugs, becoming active drugs in tumor cells with high copper content but remaining essentially inactive in normal cells, thereby greatly reducing adverse effects in patients. Such use would be of significant benefit in early detection and treatment of cancers, in particular, aggressive cancers such as pancreatic cancer which is usually not detected until it has reached an advanced stage. Six compounds were identified following virtual screening of the NCI Diversity Set with our proteasome computer model followed by confirmation with a biochemical assay that showed significant inhibition of the proteasome by the compounds in the presence of copper ions. In a dose response assay, NSC 37408 (6,7-dihydroxy-1-benzofuran-3-one), our best compound, exhibited an IC50 of 3μM in the presence of 100nM copper.

Research paper thumbnail of Association of mitochondrial calpain activation with increased expression and autolysis of calpain small subunit in an early stage of apoptosis

International Journal of Molecular Medicine, 2003

Various stimuli including anticancer drugs are capable of initiating the apoptotic death program ... more Various stimuli including anticancer drugs are capable of initiating the apoptotic death program in human tumor cells via activation of caspases. Mitochondria play an essential role for cell apoptotic commitment. Previous studies have shown a potential role of calpain activation in apoptosis, however, the involved molecular mechanisms remain to be defined. In the current study, we have examined the expression and activation of mitochondrial calpain in Jurkat T leukemia cells, MCF-7 breast carcinoma and LNCaP prostate cancer cells during apoptosis induced by an anticancer drug (VP-16, tamoxifen) or the specific p38 kinase inhibitor PD-169316. Our results suggest that increased expression and autolysis of the mitochondrial calpain small subunit are tightly associated with calpain activation in an early stage of apoptosis. In contrast, there were no correlations observed between the early calpain activation and changes in levels of mitochondrial calpain large subunit and the endogenous calpain inhibitor calpastatin. Furthermore, pretreatment with the specific pharmacological calpain inhibitor calpeptin blocked the druginduced calpain small subunit autolysis and calpain activation in mitochondria and inhibited apoptosis-associated caspase-3 activation, demonstrating that mitochondrial calpain activation through small subunit cleavage is an essential step for inducing tumor cell apoptosis by various anticancer drugs.