Brenda Crews - Academia.edu (original) (raw)
Papers by Brenda Crews
Clinical Cancer Research, 2015
Journal of biomedical optics, 2015
Cyclooxygenase-2 (COX-2) is a promising target for the imaging of cancer in a range of diagnostic... more Cyclooxygenase-2 (COX-2) is a promising target for the imaging of cancer in a range of diagnostic and therapeutic settings. We report a near-infrared COX-2-targeted probe, fluorocoxib C (FC), for visualization of solid tumors by optical imaging. FC exhibits selective and potent COX-2 inhibition in both purified protein and human cancercell lines. In vivo optical imaging shows selective accumulation of FC in COX-2-overexpressing human tumor xenografts [1483 head and neck squamous cell carcinoma (HNSCC)] implanted in nude mice, while minimal uptake is detectable in COX-2-negative tumor xenografts (HCT116)or 1483 HNSCC xenografts preblocked with the COX-2-selective inhibitor celecoxib. Time course imaging studies conducted from 3 h to 7-day post-FC injection revealed a marked reduction in nonspecific fluorescent signals with retention of fluorescence in 1483 HNSCC tumors. Thus, use of FC in a delayed imaging protocol offers an approach to improve imaging signal-to-noise that should imp...
Bioconjugate Chemistry, Mar 15, 2013
Cancer Epidemiology Biomarkers Prevention, Dec 1, 2007
Clinical Cancer Research, 2015
Oncotarget, Jan 4, 2015
Cyclooxygenase-1 (COX-1) is implicated in ovarian cancer. However, patterns of COX expression and... more Cyclooxygenase-1 (COX-1) is implicated in ovarian cancer. However, patterns of COX expression and function have been unclear and controversial. In this report, patterns of COX-1 and COX-2 gene expression were obtained from RNA-seq data through The Cancer Genome Atlas. Our analysis revealed markedly higher COX-1 mRNA expression than COX-2 in high-grade serous ovarian cancers (HGSOC) and higher COX-1 expression in HGSOC tumors than 10 other tumor types. High expression of COX-1 in HGSOC tumors was confirmed in an independent tissue microarray. In contrast, lower or similar expression of COX-1 compared to COX-2 was observed in endometrioid, mucinous and clear cell tumors. Stable COX-1 knockdown in HGSOC-representative OVCAR-3 ovarian cancer cells reduced gene expression in multiple pro-tumorigenic pathways. Functional cell viability, clonogenicity, and migration/invasion assays were consistent with transcriptomic changes. These effects were reversed by stable over-expression of COX-1 i...
Angewandte Chemie (International ed. in English), Jan 12, 2015
Apoptolidin A has been described among the top 0.1 % most-cell-selective cytotoxic agents to be e... more Apoptolidin A has been described among the top 0.1 % most-cell-selective cytotoxic agents to be evaluated in the NCI 60 cell line panel. The molecular structure of apoptolidin A consists of a 20-membered macrolide with mono- and disaccharide moieties. In contrast to apoptolidin A, the aglycone (apoptolidinone) shows no cytotoxicity (>10 μM) when evaluated against several tumor cell lines. Apoptolidin H, the C27 deglycosylated analogue of apoptolidin A, displayed sub-micromolar activity against H292 lung carcinoma cells. Selective esterification of apoptolidins A and H with 5-azidopentanoic acid afforded azido-functionalized derivatives of potency equal to that of the parent macrolide. They also underwent strain-promoted alkyne-azido cycloaddition reactions to provide access to fluorescent and biotin-functionalized probes. Microscopy studies demonstrate apoptolidins A and H localize in the mitochondria of H292 human lung carcinoma cells.
The Journal of Biological Chemistry, Mar 15, 1991
Lambs, maintained on a selenium-deficient diet supplemented with 94 atom % NaZz7SeO3, have been u... more Lambs, maintained on a selenium-deficient diet supplemented with 94 atom % NaZz7SeO3, have been used as a source of 77Se-enriched erythrocyte glutathione peroxidase. After 5 months on this diet, the percentage of selenium in the enzyme derived from the supplement had reached 88%. From each monthly bleeding of two sheep, -20 mg of 77Se-enriched glutathione peroxidase could be isolated in pure form. Although attempts to observe 77Se NMR signals from the native enzyme labeled with 6,6'-[77Se]diselenobis-(3-nitrobenzoic acid) failed, due to the low solubility of the enzyme, two 77Se resonances were observed after unfolding the enzyme with 8 M urea and reaction with iodoacetamide. These resonances, at 195 and 377 ppm, were from the selenoether alkylamide derivative and from protein cross-linked selenide sulfide species, respectively. Relaxation time measurements on the selenoether at 4.7 and 9.4 teslas enabled an estimate of the chemical shift anisotropy to be made. A value of 5262 ppm was determined. Reduction of the denatured selenide sulfide species with dithiothreitol gave an observable 77Se resonance from the Se-moiety at pH 8 and from SeH at pH 4.2. The chemical form of the selenocysteine residue in the resting state enzyme most consistent with formation of the acetamide derivative and the selenide sulfide is Seor SeH. From the magnitudes of the estimated chemical shift anisotropies, it is predicted that direct observation of selenium in the native enzyme will be feasible if the enzyme concentration can be increased to 0.25 mM tetrameric glutathione peroxidase.
Annals of the New York Academy of Sciences, Oct 1, 1994
ChemMedChem, 2014
Cyclooxygenase-2 (COX-2) is an enzyme involved in tumorigenesis, and inhibitors of the enzyme are... more Cyclooxygenase-2 (COX-2) is an enzyme involved in tumorigenesis, and inhibitors of the enzyme are increasingly used as adjuvant modulators in anticancer therapies due to their synergistic effects with traditional chemotherapeutics. COX-2 is also reported to cause resistance towards antitumor agents, such as cisplatin. Here, the first covalently linked conjugates of cisplatin and COX inhibitors are reported. These conjugates exhibit concerted transport of both drugs into tumor cells and simultaneous action upon intracellular cleavage. These platinum(IV) complexes show highly increased cytotoxicity compared with cisplatin and are even able to overcome cisplatin-related resistance of tumor cells. While the results reported show that COX-2 inhibition is not directly responsible for the potent activities of these conjugates, they do represent useful tool compounds for the elucidation of the influence of COX inhibitors on the efficacy of antitumor agents.
The Journal of biological chemistry, Jan 15, 1993
To determine the effects of differences in glycosylation on the structure and functional properti... more To determine the effects of differences in glycosylation on the structure and functional properties of recombinant human antithrombin (rHAT), we have characterized the properties of the recombinant protein overexpressed by baby hamster kidney cells. Three forms of rHAT, I-III, were isolated which differed in affinity for heparin. Form I had the lowest affinity and contained a high proportion of highly branched complex carbohydrate. Form II had higher affinity and contained both complex and high mannose-type chains. Form III had the highest affinity and was similar to form II in the type of carbohydrate present, but had a lower level of glycosylation, consistent with the absence of carbohydrate at one of the four glycosylation sites. 1H NMR spectra of plasma HAT and rHAT forms I-III suggested very similar protein structures for all forms. Heparin pentasaccharide produced almost identical NMR perturbation difference spectra. The only functional difference found was in the rates of ina...
ACS medicinal chemistry letters, Jan 13, 2014
We report the design and synthesis of fluorine-containing cyclooxygenase-1 (COX-1)-selective inhi... more We report the design and synthesis of fluorine-containing cyclooxygenase-1 (COX-1)-selective inhibitors to serve as prototypes for the development of a COX-1-targeted imaging agent. Deletion of the SO2CH3 group of rofecoxib switches the compound from a COX-2- to a COX-1-selective inhibitor, providing a 3,4-diarylfuran-2(5H)-one scaffold for structure-activity relationship studies of COX-1 inhibition. A wide range of fluorine-containing 3,4-diarylfuran-2(5H)-ones were designed, synthesized, and tested for their ability to selectively inhibit COX-1 in purified protein and human cancer cell assays. Compounds containing a fluoro-substituent on the C-3 phenyl ring and a methoxy-substituent on the C-4 phenyl ring of the 3,4-diarylfuran-2(5H)-one scaffold were the best COX-1-selective agents of those evaluated, exhibiting IC50s in the submicromolar range. These compounds provide the foundation for development of an agent to facilitate radiologic imaging of ovarian cancer expressing elevate...
Journal of Biological Chemistry, 2002
Cyclooxygenase-2 (COX-2) action on the endocannabinoids, 2-arachidonylglycerol (2-AG) and anandam... more Cyclooxygenase-2 (COX-2) action on the endocannabinoids, 2-arachidonylglycerol (2-AG) and anandamide (AEA), generates prostaglandin glycerol esters (PG-G) and ethanolamides (PG-EA), respectively. The diversity of PG-Gs and PG-EAs that can be formed enzymatically following COX-2 oxygenation of endocannabinoids was examined in cellular and subcellular systems. In cellular systems, glycerol esters and ethanolamides of PGE 2 , PGD 2 , and PGF 2␣ were major products of the endocannabinoid-derived COX-2 products, PGH 2 -G and PGH 2 -EA. The sequential action of purified COX-2 and thromboxane synthase on AEA and 2-AG provided thromboxane A 2 ethanolamide and glycerol ester, respectively. Similarly, bovine prostacyclin synthase catalyzed the isomerization of the intermediate endoperoxides, PGH 2 -G and PGH 2 -EA, to the corresponding prostacyclin derivatives. Quantification of the efficiency of prostaglandin and thromboxane synthase-directed endoperoxide isomerization demonstrated that PGE, PGD, and PGI synthases catalyze the isomerization of PGH 2 -G at rates approaching those observed with PGH 2 . In contrast, thromboxane synthase was far more efficient at catalyzing PGH 2 isomerization than at catalyzing the isomerization of PGH 2 -G. These results define the in vitro diversity of endocannabinoid-derived prostanoids and will permit focused investigations into their production and potential biological actions in vivo.
Journal of Biological Chemistry, 1999
The chemical mandates for arachidonic acid conversion to prostaglandin G 2 within the cyclooxygen... more The chemical mandates for arachidonic acid conversion to prostaglandin G 2 within the cyclooxygenase (COX) active site predict that the substrate will orient in a kinked or L-shaped conformation. Molecular modeling of arachidonic acid in sheep COX-1 confirms that this L-shaped conformation is possible, with the carboxylate moiety binding to Arg-120 and the -end positioned above Ser-530 in a region termed the top channel. Mutations of Gly-533 to valine or leucine in the top channel of mCOX-2 abolished the conversion of arachidonic acid to prostaglandin G 2 , presumably because of a steric clash between the -end of the substrate and the introduced side chains. A smaller G533A mutant retained partial COX activity. The loss of COX activity with these mutants was not the result of reduced peroxidase activity, because the activity of all mutants was equivalent to the wild-type enzyme and the addition of exogenous peroxide did not restore full COX activity to any of the mutants. However, the Gly-533 mutants were able to oxidize the carbon 18 fatty acid substrates linolenic acid and stearidonic acid, which contain an allylic carbon at the -5 position. In contrast, linoleic acid, which is like arachidonic acid in that its most -proximal allylic carbon is at the -8 position, was not oxidized by the Gly-533 mutants. Finally, the ability of Gly-533 mutants to efficiently process -5 allylic substrates suggests that the top channel does not serve as a product exit route indicating that oxygenated substrate diffuses from the cyclooxygenase active site in a membrane proximal direction.
![Research paper thumbnail of [IMAGE][IMAGE]-Macroglobulin Bait Region Variants](https://attachments.academia-assets.com/46711223/thumbnails/1.jpg)
](Journal of Biological Chemistry, 1995
Clinical Cancer Research, 2015
Journal of biomedical optics, 2015
Cyclooxygenase-2 (COX-2) is a promising target for the imaging of cancer in a range of diagnostic... more Cyclooxygenase-2 (COX-2) is a promising target for the imaging of cancer in a range of diagnostic and therapeutic settings. We report a near-infrared COX-2-targeted probe, fluorocoxib C (FC), for visualization of solid tumors by optical imaging. FC exhibits selective and potent COX-2 inhibition in both purified protein and human cancercell lines. In vivo optical imaging shows selective accumulation of FC in COX-2-overexpressing human tumor xenografts [1483 head and neck squamous cell carcinoma (HNSCC)] implanted in nude mice, while minimal uptake is detectable in COX-2-negative tumor xenografts (HCT116)or 1483 HNSCC xenografts preblocked with the COX-2-selective inhibitor celecoxib. Time course imaging studies conducted from 3 h to 7-day post-FC injection revealed a marked reduction in nonspecific fluorescent signals with retention of fluorescence in 1483 HNSCC tumors. Thus, use of FC in a delayed imaging protocol offers an approach to improve imaging signal-to-noise that should imp...
Bioconjugate Chemistry, Mar 15, 2013
Cancer Epidemiology Biomarkers Prevention, Dec 1, 2007
Clinical Cancer Research, 2015
Oncotarget, Jan 4, 2015
Cyclooxygenase-1 (COX-1) is implicated in ovarian cancer. However, patterns of COX expression and... more Cyclooxygenase-1 (COX-1) is implicated in ovarian cancer. However, patterns of COX expression and function have been unclear and controversial. In this report, patterns of COX-1 and COX-2 gene expression were obtained from RNA-seq data through The Cancer Genome Atlas. Our analysis revealed markedly higher COX-1 mRNA expression than COX-2 in high-grade serous ovarian cancers (HGSOC) and higher COX-1 expression in HGSOC tumors than 10 other tumor types. High expression of COX-1 in HGSOC tumors was confirmed in an independent tissue microarray. In contrast, lower or similar expression of COX-1 compared to COX-2 was observed in endometrioid, mucinous and clear cell tumors. Stable COX-1 knockdown in HGSOC-representative OVCAR-3 ovarian cancer cells reduced gene expression in multiple pro-tumorigenic pathways. Functional cell viability, clonogenicity, and migration/invasion assays were consistent with transcriptomic changes. These effects were reversed by stable over-expression of COX-1 i...
Angewandte Chemie (International ed. in English), Jan 12, 2015
Apoptolidin A has been described among the top 0.1 % most-cell-selective cytotoxic agents to be e... more Apoptolidin A has been described among the top 0.1 % most-cell-selective cytotoxic agents to be evaluated in the NCI 60 cell line panel. The molecular structure of apoptolidin A consists of a 20-membered macrolide with mono- and disaccharide moieties. In contrast to apoptolidin A, the aglycone (apoptolidinone) shows no cytotoxicity (>10 μM) when evaluated against several tumor cell lines. Apoptolidin H, the C27 deglycosylated analogue of apoptolidin A, displayed sub-micromolar activity against H292 lung carcinoma cells. Selective esterification of apoptolidins A and H with 5-azidopentanoic acid afforded azido-functionalized derivatives of potency equal to that of the parent macrolide. They also underwent strain-promoted alkyne-azido cycloaddition reactions to provide access to fluorescent and biotin-functionalized probes. Microscopy studies demonstrate apoptolidins A and H localize in the mitochondria of H292 human lung carcinoma cells.
The Journal of Biological Chemistry, Mar 15, 1991
Lambs, maintained on a selenium-deficient diet supplemented with 94 atom % NaZz7SeO3, have been u... more Lambs, maintained on a selenium-deficient diet supplemented with 94 atom % NaZz7SeO3, have been used as a source of 77Se-enriched erythrocyte glutathione peroxidase. After 5 months on this diet, the percentage of selenium in the enzyme derived from the supplement had reached 88%. From each monthly bleeding of two sheep, -20 mg of 77Se-enriched glutathione peroxidase could be isolated in pure form. Although attempts to observe 77Se NMR signals from the native enzyme labeled with 6,6'-[77Se]diselenobis-(3-nitrobenzoic acid) failed, due to the low solubility of the enzyme, two 77Se resonances were observed after unfolding the enzyme with 8 M urea and reaction with iodoacetamide. These resonances, at 195 and 377 ppm, were from the selenoether alkylamide derivative and from protein cross-linked selenide sulfide species, respectively. Relaxation time measurements on the selenoether at 4.7 and 9.4 teslas enabled an estimate of the chemical shift anisotropy to be made. A value of 5262 ppm was determined. Reduction of the denatured selenide sulfide species with dithiothreitol gave an observable 77Se resonance from the Se-moiety at pH 8 and from SeH at pH 4.2. The chemical form of the selenocysteine residue in the resting state enzyme most consistent with formation of the acetamide derivative and the selenide sulfide is Seor SeH. From the magnitudes of the estimated chemical shift anisotropies, it is predicted that direct observation of selenium in the native enzyme will be feasible if the enzyme concentration can be increased to 0.25 mM tetrameric glutathione peroxidase.
Annals of the New York Academy of Sciences, Oct 1, 1994
ChemMedChem, 2014
Cyclooxygenase-2 (COX-2) is an enzyme involved in tumorigenesis, and inhibitors of the enzyme are... more Cyclooxygenase-2 (COX-2) is an enzyme involved in tumorigenesis, and inhibitors of the enzyme are increasingly used as adjuvant modulators in anticancer therapies due to their synergistic effects with traditional chemotherapeutics. COX-2 is also reported to cause resistance towards antitumor agents, such as cisplatin. Here, the first covalently linked conjugates of cisplatin and COX inhibitors are reported. These conjugates exhibit concerted transport of both drugs into tumor cells and simultaneous action upon intracellular cleavage. These platinum(IV) complexes show highly increased cytotoxicity compared with cisplatin and are even able to overcome cisplatin-related resistance of tumor cells. While the results reported show that COX-2 inhibition is not directly responsible for the potent activities of these conjugates, they do represent useful tool compounds for the elucidation of the influence of COX inhibitors on the efficacy of antitumor agents.
The Journal of biological chemistry, Jan 15, 1993
To determine the effects of differences in glycosylation on the structure and functional properti... more To determine the effects of differences in glycosylation on the structure and functional properties of recombinant human antithrombin (rHAT), we have characterized the properties of the recombinant protein overexpressed by baby hamster kidney cells. Three forms of rHAT, I-III, were isolated which differed in affinity for heparin. Form I had the lowest affinity and contained a high proportion of highly branched complex carbohydrate. Form II had higher affinity and contained both complex and high mannose-type chains. Form III had the highest affinity and was similar to form II in the type of carbohydrate present, but had a lower level of glycosylation, consistent with the absence of carbohydrate at one of the four glycosylation sites. 1H NMR spectra of plasma HAT and rHAT forms I-III suggested very similar protein structures for all forms. Heparin pentasaccharide produced almost identical NMR perturbation difference spectra. The only functional difference found was in the rates of ina...
ACS medicinal chemistry letters, Jan 13, 2014
We report the design and synthesis of fluorine-containing cyclooxygenase-1 (COX-1)-selective inhi... more We report the design and synthesis of fluorine-containing cyclooxygenase-1 (COX-1)-selective inhibitors to serve as prototypes for the development of a COX-1-targeted imaging agent. Deletion of the SO2CH3 group of rofecoxib switches the compound from a COX-2- to a COX-1-selective inhibitor, providing a 3,4-diarylfuran-2(5H)-one scaffold for structure-activity relationship studies of COX-1 inhibition. A wide range of fluorine-containing 3,4-diarylfuran-2(5H)-ones were designed, synthesized, and tested for their ability to selectively inhibit COX-1 in purified protein and human cancer cell assays. Compounds containing a fluoro-substituent on the C-3 phenyl ring and a methoxy-substituent on the C-4 phenyl ring of the 3,4-diarylfuran-2(5H)-one scaffold were the best COX-1-selective agents of those evaluated, exhibiting IC50s in the submicromolar range. These compounds provide the foundation for development of an agent to facilitate radiologic imaging of ovarian cancer expressing elevate...
Journal of Biological Chemistry, 2002
Cyclooxygenase-2 (COX-2) action on the endocannabinoids, 2-arachidonylglycerol (2-AG) and anandam... more Cyclooxygenase-2 (COX-2) action on the endocannabinoids, 2-arachidonylglycerol (2-AG) and anandamide (AEA), generates prostaglandin glycerol esters (PG-G) and ethanolamides (PG-EA), respectively. The diversity of PG-Gs and PG-EAs that can be formed enzymatically following COX-2 oxygenation of endocannabinoids was examined in cellular and subcellular systems. In cellular systems, glycerol esters and ethanolamides of PGE 2 , PGD 2 , and PGF 2␣ were major products of the endocannabinoid-derived COX-2 products, PGH 2 -G and PGH 2 -EA. The sequential action of purified COX-2 and thromboxane synthase on AEA and 2-AG provided thromboxane A 2 ethanolamide and glycerol ester, respectively. Similarly, bovine prostacyclin synthase catalyzed the isomerization of the intermediate endoperoxides, PGH 2 -G and PGH 2 -EA, to the corresponding prostacyclin derivatives. Quantification of the efficiency of prostaglandin and thromboxane synthase-directed endoperoxide isomerization demonstrated that PGE, PGD, and PGI synthases catalyze the isomerization of PGH 2 -G at rates approaching those observed with PGH 2 . In contrast, thromboxane synthase was far more efficient at catalyzing PGH 2 isomerization than at catalyzing the isomerization of PGH 2 -G. These results define the in vitro diversity of endocannabinoid-derived prostanoids and will permit focused investigations into their production and potential biological actions in vivo.
Journal of Biological Chemistry, 1999
The chemical mandates for arachidonic acid conversion to prostaglandin G 2 within the cyclooxygen... more The chemical mandates for arachidonic acid conversion to prostaglandin G 2 within the cyclooxygenase (COX) active site predict that the substrate will orient in a kinked or L-shaped conformation. Molecular modeling of arachidonic acid in sheep COX-1 confirms that this L-shaped conformation is possible, with the carboxylate moiety binding to Arg-120 and the -end positioned above Ser-530 in a region termed the top channel. Mutations of Gly-533 to valine or leucine in the top channel of mCOX-2 abolished the conversion of arachidonic acid to prostaglandin G 2 , presumably because of a steric clash between the -end of the substrate and the introduced side chains. A smaller G533A mutant retained partial COX activity. The loss of COX activity with these mutants was not the result of reduced peroxidase activity, because the activity of all mutants was equivalent to the wild-type enzyme and the addition of exogenous peroxide did not restore full COX activity to any of the mutants. However, the Gly-533 mutants were able to oxidize the carbon 18 fatty acid substrates linolenic acid and stearidonic acid, which contain an allylic carbon at the -5 position. In contrast, linoleic acid, which is like arachidonic acid in that its most -proximal allylic carbon is at the -8 position, was not oxidized by the Gly-533 mutants. Finally, the ability of Gly-533 mutants to efficiently process -5 allylic substrates suggests that the top channel does not serve as a product exit route indicating that oxygenated substrate diffuses from the cyclooxygenase active site in a membrane proximal direction.
Journal of Biological Chemistry, 1995