Kyle Brimacombe | National Institutes of Health (original) (raw)
Papers by Kyle Brimacombe
Methods, 2015
Hutchinson-Gilford Progeria Syndrome (HGPS) is an early onset lethal premature aging disorder cau... more Hutchinson-Gilford Progeria Syndrome (HGPS) is an early onset lethal premature aging disorder caused by constitutive production of progerin, a mutant form of the nuclear architectural protein lamin A. The presence of progerin causes extensive morphological, epigenetic and DNA damage related nuclear defects that ultimately disrupt tissue and organismal functioning. Hypothesis-driven approaches focused on HGPS affected pathways have been used in attempts to identify druggable targets with anti-progeroid effects. Here, we report an unbiased discovery approach to HGPS by implementation of a high-throughput, high-content imaging based screening method that enables systematic identification of small molecules that prevent the formation of multiple progerin-induced aging defects. Screening a library of 2816 FDA approved compounds, we identified retinoids as a novel class of compounds that reverses aging defects in HGPS patient skin fibroblasts through lowering the expression of progerin and other A-type lamins. These findings establish a complementary approach to anti-progeroid drug discovery.
Developmental dynamics : an official publication of the American Association of Anatomists, 2007
The CUG-BP and ETR-3-like factor (CELF) protein family has been implicated in the regulation of p... more The CUG-BP and ETR-3-like factor (CELF) protein family has been implicated in the regulation of pre-mRNA alternative splicing, mRNA stability, and translation. Here we discuss the evolution and radiation of the CELF protein subfamilies, and report the cloning of the chicken CELF family members. In this study, we examined the embryonic expression patterns of the CELF family in the chick by in situ hybridization. We found that the tissue specificity reported for CELF proteins in the adult is established early during embryogenesis. Members of one subfamily, CUG-BP1 and ETR-3, are broadly expressed in the early embryo, while members of the second subfamily, CELF4-6, are restricted primarily to the nervous system. Expression patterns of individual CELF genes in several tissues, including the heart, liver, eye, and neural tube, exhibit distinct, yet overlapping, expression patterns. This suggests that different members of the CELF family play distinct functional roles during embryogenesis.
Journal of Molecular and Cellular Cardiology, 2009
During the transition from juvenile to adult life, the heart undergoes programmed remodeling at t... more During the transition from juvenile to adult life, the heart undergoes programmed remodeling at the levels of transcription and alternative splicing. Members of the CUG-BP and ETR-3-like factor (CELF) family have been implicated in driving developmental transitions in alternative splicing of cardiac transcripts during maturation of the heart. Here, we investigated the timing of the requirement for CELF activity in the postnatal heart using a previously described transgenic mouse model (MHC-CELFDelta). In MHC-CELFDelta mice, nuclear CELF activity has been disrupted specifically in the heart by cardiac-specific expression of a dominant negative CELF protein. Longitudinal analyses of two lines of MHC-CELFDelta mice with differing levels of dominant negative protein expression demonstrate that CELF splicing activity is required for healthy cardiac function during juvenile, but not adult, life. Cardiac function, chamber dilation, and heart size all recover with age in the mild line of MHC-CELFDelta mice without a loss of dominant negative protein expression or change in expression of endogenous CELF proteins or known CELF antagonists. This is the first example of a mouse model with genetically induced cardiomyopathy that spontaneously recovers without intervention. Our results suggest that CELF proteins are key players in the integrated gene expression program involved in postnatal cardiac remodeling and maturation.
Journal of Medicinal Chemistry, 2013
The discovery and characterization of a novel chemical series of phosphorothioyl-containing imida... more The discovery and characterization of a novel chemical series of phosphorothioyl-containing imidazopyridines as potent neuropeptide S receptor antagonists is presented. The synthesis of analogues and their structure-activity relationship with respect to the Gq, Gs, and ERK pathways is detailed. The pharmacokinetics and in vivo efficacy of a potent analogue in a food intake rodent model are also included, underscoring its potential therapeutic value for the treatment of sleep, anxiety, and addiction disorders.
Developmental Dynamics, 2007
The CUG-BP and ETR-3-like factor (CELF) protein family has been implicated in the regulation of p... more The CUG-BP and ETR-3-like factor (CELF) protein family has been implicated in the regulation of pre-mRNA alternative splicing, mRNA stability, and translation. Here we discuss the evolution and radiation of the CELF protein subfamilies, and report the cloning of the chicken CELF family members. In this study, we examined the embryonic expression patterns of the CELF family in the chick by in situ hybridization. We found that the tissue specificity reported for CELF proteins in the adult is established early during embryogenesis. Members of one subfamily, CUG-BP1 and ETR-3, are broadly expressed in the early embryo, while members of the second subfamily, CELF4-6, are restricted primarily to the nervous system. Expression patterns of individual CELF genes in several tissues, including the heart, liver, eye, and neural tube, exhibit distinct, yet overlapping, expression patterns. This suggests that different members of the CELF family play distinct functional roles during embryogenesis. Developmental Dynamics 236: 2216 -2224, 2007.
Developmental Dynamics, 2009
The development of the valves and septa of the heart depends on the formation and remodeling of e... more The development of the valves and septa of the heart depends on the formation and remodeling of endocardial cushions. Here, we report that the alternative splicing regulator muscleblind-like 1 (MBNL1) exhibits a regionally restricted pattern of expression in canal region endocardium and ventricular myocardium during endocardial cushion development in chicken. Knockdown of MBNL1 in atrioventricular explants leads to a transforming growth factor β-dependent increase in epithelial-mesenchymal transition (EMT) of endocardial cells. This reveals a novel role for MBNL1 during embryonic development, and represents the first evidence that an alternative splicing regulator is a key player in endocardial cushion development.
The protist Trypansoma brucei is the causative agent of Human African Trypanosomiasis (HAT), a di... more The protist Trypansoma brucei is the causative agent of Human African Trypanosomiasis (HAT), a disease that is endemic to sub-Saharan Africa and is responsible for approximately 50,000 deaths each year worldwide. Current therapies employed to treat HAT generally suffer from poor selectivity profiles, and consequently, lead to high rates of deleterious side effects. Furthermore, growing resistance to these drugs has highlighted a need for the identification of novel therapies. The glycolytic enzyme phosphofructokinase (PFK) has been recognized as a potential therapeutic target in the fight against the bloodstream form of T. brucei due to the reliance of this parasite on the metabolism of glucose as its sole mechanism for the generation of adenosine triphosphates (ATP). The importance of this enzyme has been confirmed by genetic validation, and thus, its inhibition may represent a novel strategy for the treatment of HAT. Currently, no inhibitors of Tb PFK have been described that poss...
The ability of all cells to regulate levels of reactive oxygen species (ROS) is vital for control... more The ability of all cells to regulate levels of reactive oxygen species (ROS) is vital for controlling many aspects of proliferation and survival and we have discovered that pyruvate kinase M2 (PKM2) is important for cancer cell biology. PKM2 is directly oxidized on Cys(358) to inhibit its catalytic activity, which allows for diversion of glucose-6-phosphate into the pentose phosphate pathway. This, in turn, allows the synthesis of NADPH, which is critical for generating reduced glutathione, necessary for ROS detoxification. In a cellular context, our PKM2 activator, ML285 protects the enzyme from oxidation by ROS and results in sensitization to oxidative stress and increased apoptosis.
Journal of Medicinal Chemistry, 2015
Aldehyde dehydrogenases (ALDHs) metabolize reactive aldehydes and possess important physiological... more Aldehyde dehydrogenases (ALDHs) metabolize reactive aldehydes and possess important physiological and toxicological functions in areas such as CNS, metabolic disorders, and cancers. Increased ALDH (e.g., ALDH1A1) gene expression and catalytic activity are vital biomarkers in a number of malignancies and cancer stem cells, highlighting the need for the identification and development of small molecule ALDH inhibitors. A new series of theophylline-based analogs as potent ALDH1A1 inhibitors is described. The optimization of hits identified from a quantitative high throughput screening (qHTS) campaign led to analogs with improved potency and early ADME properties. This chemotype exhibits highly selective inhibition against ALDH1A1 over ALDH3A1, ALDH1B1, and ALDH2 isozymes as well as other dehydrogenases such as HPGD and HSD17β4. Moreover, the pharmacokinetic evaluation of selected analog 64 (NCT-501) is also highlighted.
Nature, Jan 20, 2015
Multiple sclerosis involves an aberrant autoimmune response and progressive failure of remyelinat... more Multiple sclerosis involves an aberrant autoimmune response and progressive failure of remyelination in the central nervous system. Prevention of neural degeneration and subsequent disability requires remyelination through the generation of new oligodendrocytes, but current treatments exclusively target the immune system. Oligodendrocyte progenitor cells are stem cells in the central nervous system and the principal source of myelinating oligodendrocytes. These cells are abundant in demyelinated regions of patients with multiple sclerosis, yet fail to differentiate, thereby representing a cellular target for pharmacological intervention. To discover therapeutic compounds for enhancing myelination from endogenous oligodendrocyte progenitor cells, we screened a library of bioactive small molecules on mouse pluripotent epiblast stem-cell-derived oligodendrocyte progenitor cells. Here we show seven drugs function at nanomolar doses selectively to enhance the generation of mature oligode...
ABSTRACT Cancer cells have altered metabolic processes compared to normal differentiated cells an... more ABSTRACT Cancer cells have altered metabolic processes compared to normal differentiated cells and the expression of the M2 isozyme of pyruvate kinase (PKM2) plays an important role in this aberrant metabolism. The M1 isoform is a highly active enzyme typically expressed in muscle and brain tissue, the alternatively spliced M2 variant is considerably less active and expressed in many tumors studied to date. This report describes the use of the PKM2 activator, ML265, and details some of the biophysical, ex vivo and in vivo activity of this compound. ML265 induces the more active tetrameric state of PKM2 and the X-ray co-crystal structure shows that the activator binds at the dimer-dimer interface between two subunits of PKM2. This compound was tested in a H1299 mouse xenograft model and showed significant reduction in tumor size, weight, and occurrence with no apparent toxicity over the 7-week experiment.
Molecular Endocrinology, 2014
Glucocorticoid steroids affect almost every tissue-type and thus are widely used to treat a varie... more Glucocorticoid steroids affect almost every tissue-type and thus are widely used to treat a variety of human pathologies. However, the severity of numerous side-effects limits the frequency and duration of glucocorticoid treatments. Of the numerous approaches to control off-target responses to glucocorticoids, small molecules and pharmaceuticals offer several advantages. Here we describe a new, extended high throughput screen in intact cells to identify small molecule modulators of dexamethasone-induced glucocorticoid receptor (GR) transcriptional activity. The novelty of this assay is that it monitors changes in both GR maximal activity (A max ) and EC 50 , or the position of the dexamethasone dose-response curve. Upon screening 1280 chemicals, ten with the greatest change in the absolute value of A max or EC 50 were selected for further examination. Qualitatively identical behaviors for 60 -90% of the chemicals were observed in a completely different system, suggesting that other systems will be similarly affected by these chemicals. Additional analysis of the ten chemicals in a recently described competition assay determined their kinetically-defined mechanism and site of action. Some chemicals had similar mechanisms of action despite divergent effects on the level of GR-induced product. These combined assays offer a straightforward method of identifying numerous new pharmaceuticals that can alter GR transactivation in ways that could be clinically useful.
Journal of Biological Chemistry, 2014
Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of cancer. MDR is o... more Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of cancer. MDR is often the result of overexpression of ATP-binding cassette transporters following chemotherapy. A common ATP-binding cassette transporter that is overexpressed in MDR cancer cells is P-glycoprotein, which actively effluxes drugs against a concentration gradient, producing an MDR phenotype. Collateral sensitivity (CS), a phenomenon of drug hypersensitivity, is defined as the ability of certain compounds to selectively target MDR cells, but not the drug-sensitive parent cells from which they were derived. The drug tiopronin has been previously shown to elicit CS. However, unlike other CS agents, the mechanism of action was not dependent on the expression of P-glycoprotein in MDR cells. We have determined that the CS activity of tiopronin is mediated by the generation of reactive oxygen species (ROS) and that CS can be reversed by a variety of ROS-scavenging compounds. Specifically, selective toxicity of tiopronin toward MDR cells is achieved by inhibition of glutathione peroxidase (GPx), and the mode of inhibition of GPx1 by tiopronin is shown in this report. Why MDR cells are particularly sensitive to ROS is discussed, as is the difficulty in exploiting this hypersensitivity to tiopronin in the clinic.
Bioorganic & medicinal chemistry letters, 2015
Classic Galactosemia is a rare inborn error of metabolism that is caused by deficiency of galacto... more Classic Galactosemia is a rare inborn error of metabolism that is caused by deficiency of galactose-1-phosphate uridyltransferase (GALT), an enzyme within the Leloir pathway that is responsible for the conversion of galactose-1-phosphate (gal-1-p) and UDP-glucose to glucose-1-phosphate and UDP-galactose. This deficiency results in elevated intracellular concentrations of its substrate, gal-1-p, and this increased concentration is believed to be the major pathogenic mechanism in Classic Galactosemia. Galactokinase (GALK) is an upstream enzyme of GALT in the Leloir pathway and is responsible for conversion of galactose and ATP to gal-1-p and ADP. Therefore, it was hypothesized that the identification of a small-molecule inhibitor of human GALK would act to prevent the accumulation of gal-1-p and offer a novel entry therapy for this disorder. Herein we describe a quantitative high-throughput screening campaign that identified a single chemotype that was optimized and validated as a GAL...
Proceedings of the National Academy of Sciences, 2011
The radiotracer [ 11 C]N-desmethyl-loperamide (dLop) images the in vivo function of P-glycoprotei... more The radiotracer [ 11 C]N-desmethyl-loperamide (dLop) images the in vivo function of P-glycoprotein (P-gp), a transporter that blocks the entry of drugs that are substrates into brain. When P-gp is inhibited, [ 11 C]dLop, a potent opiate agonist, enters and becomes trapped in the brain. This trapping is beneficial from an imaging perspective, because it amplifies the PET signal, essentially by accumulating radioactivity over time. As we previously demonstrated that this trapping was not caused by binding to opiate receptors, we examined whether [ 11 C]dLop, a weak base, is ionically trapped in acidic lysosomes. To test this hypothesis, we measured [ 3 H]dLop accumulation in human cells by using lysosomotropics. Because the in vivo trapping of dLop was seen after P-gp inhibition, we also measured [ 3 H]dLop uptake in P-gp-expressing cells treated with the P-gp inhibitor tariquidar. All lysosomotropics decreased [ 3 H]dLop accumulation by at least 50%. In P-gp-expressing cells, tariquidar (and another P-gp inhibitor) surprisingly decreased [ 3 H]dLop uptake. Consequently, we measured [ 11 C]dLop uptake before and after tariquidar preadministration in lysosome-rich organs of P-gp KO mice and humans. After tariquidar pretreatment in both species, radioactivity uptake in these organs decreased by 35% to 40%. Our results indicate that dLop is trapped in lysosomes and that tariquidar competes with dLop for lysosomal accumulation in vitro and in vivo. Although tariquidar and dLop compete for lysosomal trapping in the periphery, such competition does not occur in brain because tariquidar has negligible entry into brain. In summary, tariquidar and [ 11 C]dLop can be used in combination to selectively measure the function of P-gp at the blood-brain barrier.
Journal of Translational Medicine, 2008
Background: Effective transvascular delivery of nanoparticle-based chemotherapeutics across the b... more Background: Effective transvascular delivery of nanoparticle-based chemotherapeutics across the blood-brain tumor barrier of malignant gliomas remains a challenge. This is due to our limited understanding of nanoparticle properties in relation to the physiologic size of pores within the blood-brain tumor barrier. Polyamidoamine dendrimers are particularly small multigenerational nanoparticles with uniform sizes within each generation. Dendrimer sizes increase by only 1 to 2 nm with each successive generation. Using functionalized polyamidoamine dendrimer generations 1 through 8, we investigated how nanoparticle size influences particle accumulation within malignant glioma cells.
Methods, 2015
Hutchinson-Gilford Progeria Syndrome (HGPS) is an early onset lethal premature aging disorder cau... more Hutchinson-Gilford Progeria Syndrome (HGPS) is an early onset lethal premature aging disorder caused by constitutive production of progerin, a mutant form of the nuclear architectural protein lamin A. The presence of progerin causes extensive morphological, epigenetic and DNA damage related nuclear defects that ultimately disrupt tissue and organismal functioning. Hypothesis-driven approaches focused on HGPS affected pathways have been used in attempts to identify druggable targets with anti-progeroid effects. Here, we report an unbiased discovery approach to HGPS by implementation of a high-throughput, high-content imaging based screening method that enables systematic identification of small molecules that prevent the formation of multiple progerin-induced aging defects. Screening a library of 2816 FDA approved compounds, we identified retinoids as a novel class of compounds that reverses aging defects in HGPS patient skin fibroblasts through lowering the expression of progerin and other A-type lamins. These findings establish a complementary approach to anti-progeroid drug discovery.
Developmental dynamics : an official publication of the American Association of Anatomists, 2007
The CUG-BP and ETR-3-like factor (CELF) protein family has been implicated in the regulation of p... more The CUG-BP and ETR-3-like factor (CELF) protein family has been implicated in the regulation of pre-mRNA alternative splicing, mRNA stability, and translation. Here we discuss the evolution and radiation of the CELF protein subfamilies, and report the cloning of the chicken CELF family members. In this study, we examined the embryonic expression patterns of the CELF family in the chick by in situ hybridization. We found that the tissue specificity reported for CELF proteins in the adult is established early during embryogenesis. Members of one subfamily, CUG-BP1 and ETR-3, are broadly expressed in the early embryo, while members of the second subfamily, CELF4-6, are restricted primarily to the nervous system. Expression patterns of individual CELF genes in several tissues, including the heart, liver, eye, and neural tube, exhibit distinct, yet overlapping, expression patterns. This suggests that different members of the CELF family play distinct functional roles during embryogenesis.
Journal of Molecular and Cellular Cardiology, 2009
During the transition from juvenile to adult life, the heart undergoes programmed remodeling at t... more During the transition from juvenile to adult life, the heart undergoes programmed remodeling at the levels of transcription and alternative splicing. Members of the CUG-BP and ETR-3-like factor (CELF) family have been implicated in driving developmental transitions in alternative splicing of cardiac transcripts during maturation of the heart. Here, we investigated the timing of the requirement for CELF activity in the postnatal heart using a previously described transgenic mouse model (MHC-CELFDelta). In MHC-CELFDelta mice, nuclear CELF activity has been disrupted specifically in the heart by cardiac-specific expression of a dominant negative CELF protein. Longitudinal analyses of two lines of MHC-CELFDelta mice with differing levels of dominant negative protein expression demonstrate that CELF splicing activity is required for healthy cardiac function during juvenile, but not adult, life. Cardiac function, chamber dilation, and heart size all recover with age in the mild line of MHC-CELFDelta mice without a loss of dominant negative protein expression or change in expression of endogenous CELF proteins or known CELF antagonists. This is the first example of a mouse model with genetically induced cardiomyopathy that spontaneously recovers without intervention. Our results suggest that CELF proteins are key players in the integrated gene expression program involved in postnatal cardiac remodeling and maturation.
Journal of Medicinal Chemistry, 2013
The discovery and characterization of a novel chemical series of phosphorothioyl-containing imida... more The discovery and characterization of a novel chemical series of phosphorothioyl-containing imidazopyridines as potent neuropeptide S receptor antagonists is presented. The synthesis of analogues and their structure-activity relationship with respect to the Gq, Gs, and ERK pathways is detailed. The pharmacokinetics and in vivo efficacy of a potent analogue in a food intake rodent model are also included, underscoring its potential therapeutic value for the treatment of sleep, anxiety, and addiction disorders.
Developmental Dynamics, 2007
The CUG-BP and ETR-3-like factor (CELF) protein family has been implicated in the regulation of p... more The CUG-BP and ETR-3-like factor (CELF) protein family has been implicated in the regulation of pre-mRNA alternative splicing, mRNA stability, and translation. Here we discuss the evolution and radiation of the CELF protein subfamilies, and report the cloning of the chicken CELF family members. In this study, we examined the embryonic expression patterns of the CELF family in the chick by in situ hybridization. We found that the tissue specificity reported for CELF proteins in the adult is established early during embryogenesis. Members of one subfamily, CUG-BP1 and ETR-3, are broadly expressed in the early embryo, while members of the second subfamily, CELF4-6, are restricted primarily to the nervous system. Expression patterns of individual CELF genes in several tissues, including the heart, liver, eye, and neural tube, exhibit distinct, yet overlapping, expression patterns. This suggests that different members of the CELF family play distinct functional roles during embryogenesis. Developmental Dynamics 236: 2216 -2224, 2007.
Developmental Dynamics, 2009
The development of the valves and septa of the heart depends on the formation and remodeling of e... more The development of the valves and septa of the heart depends on the formation and remodeling of endocardial cushions. Here, we report that the alternative splicing regulator muscleblind-like 1 (MBNL1) exhibits a regionally restricted pattern of expression in canal region endocardium and ventricular myocardium during endocardial cushion development in chicken. Knockdown of MBNL1 in atrioventricular explants leads to a transforming growth factor β-dependent increase in epithelial-mesenchymal transition (EMT) of endocardial cells. This reveals a novel role for MBNL1 during embryonic development, and represents the first evidence that an alternative splicing regulator is a key player in endocardial cushion development.
The protist Trypansoma brucei is the causative agent of Human African Trypanosomiasis (HAT), a di... more The protist Trypansoma brucei is the causative agent of Human African Trypanosomiasis (HAT), a disease that is endemic to sub-Saharan Africa and is responsible for approximately 50,000 deaths each year worldwide. Current therapies employed to treat HAT generally suffer from poor selectivity profiles, and consequently, lead to high rates of deleterious side effects. Furthermore, growing resistance to these drugs has highlighted a need for the identification of novel therapies. The glycolytic enzyme phosphofructokinase (PFK) has been recognized as a potential therapeutic target in the fight against the bloodstream form of T. brucei due to the reliance of this parasite on the metabolism of glucose as its sole mechanism for the generation of adenosine triphosphates (ATP). The importance of this enzyme has been confirmed by genetic validation, and thus, its inhibition may represent a novel strategy for the treatment of HAT. Currently, no inhibitors of Tb PFK have been described that poss...
The ability of all cells to regulate levels of reactive oxygen species (ROS) is vital for control... more The ability of all cells to regulate levels of reactive oxygen species (ROS) is vital for controlling many aspects of proliferation and survival and we have discovered that pyruvate kinase M2 (PKM2) is important for cancer cell biology. PKM2 is directly oxidized on Cys(358) to inhibit its catalytic activity, which allows for diversion of glucose-6-phosphate into the pentose phosphate pathway. This, in turn, allows the synthesis of NADPH, which is critical for generating reduced glutathione, necessary for ROS detoxification. In a cellular context, our PKM2 activator, ML285 protects the enzyme from oxidation by ROS and results in sensitization to oxidative stress and increased apoptosis.
Journal of Medicinal Chemistry, 2015
Aldehyde dehydrogenases (ALDHs) metabolize reactive aldehydes and possess important physiological... more Aldehyde dehydrogenases (ALDHs) metabolize reactive aldehydes and possess important physiological and toxicological functions in areas such as CNS, metabolic disorders, and cancers. Increased ALDH (e.g., ALDH1A1) gene expression and catalytic activity are vital biomarkers in a number of malignancies and cancer stem cells, highlighting the need for the identification and development of small molecule ALDH inhibitors. A new series of theophylline-based analogs as potent ALDH1A1 inhibitors is described. The optimization of hits identified from a quantitative high throughput screening (qHTS) campaign led to analogs with improved potency and early ADME properties. This chemotype exhibits highly selective inhibition against ALDH1A1 over ALDH3A1, ALDH1B1, and ALDH2 isozymes as well as other dehydrogenases such as HPGD and HSD17β4. Moreover, the pharmacokinetic evaluation of selected analog 64 (NCT-501) is also highlighted.
Nature, Jan 20, 2015
Multiple sclerosis involves an aberrant autoimmune response and progressive failure of remyelinat... more Multiple sclerosis involves an aberrant autoimmune response and progressive failure of remyelination in the central nervous system. Prevention of neural degeneration and subsequent disability requires remyelination through the generation of new oligodendrocytes, but current treatments exclusively target the immune system. Oligodendrocyte progenitor cells are stem cells in the central nervous system and the principal source of myelinating oligodendrocytes. These cells are abundant in demyelinated regions of patients with multiple sclerosis, yet fail to differentiate, thereby representing a cellular target for pharmacological intervention. To discover therapeutic compounds for enhancing myelination from endogenous oligodendrocyte progenitor cells, we screened a library of bioactive small molecules on mouse pluripotent epiblast stem-cell-derived oligodendrocyte progenitor cells. Here we show seven drugs function at nanomolar doses selectively to enhance the generation of mature oligode...
ABSTRACT Cancer cells have altered metabolic processes compared to normal differentiated cells an... more ABSTRACT Cancer cells have altered metabolic processes compared to normal differentiated cells and the expression of the M2 isozyme of pyruvate kinase (PKM2) plays an important role in this aberrant metabolism. The M1 isoform is a highly active enzyme typically expressed in muscle and brain tissue, the alternatively spliced M2 variant is considerably less active and expressed in many tumors studied to date. This report describes the use of the PKM2 activator, ML265, and details some of the biophysical, ex vivo and in vivo activity of this compound. ML265 induces the more active tetrameric state of PKM2 and the X-ray co-crystal structure shows that the activator binds at the dimer-dimer interface between two subunits of PKM2. This compound was tested in a H1299 mouse xenograft model and showed significant reduction in tumor size, weight, and occurrence with no apparent toxicity over the 7-week experiment.
Molecular Endocrinology, 2014
Glucocorticoid steroids affect almost every tissue-type and thus are widely used to treat a varie... more Glucocorticoid steroids affect almost every tissue-type and thus are widely used to treat a variety of human pathologies. However, the severity of numerous side-effects limits the frequency and duration of glucocorticoid treatments. Of the numerous approaches to control off-target responses to glucocorticoids, small molecules and pharmaceuticals offer several advantages. Here we describe a new, extended high throughput screen in intact cells to identify small molecule modulators of dexamethasone-induced glucocorticoid receptor (GR) transcriptional activity. The novelty of this assay is that it monitors changes in both GR maximal activity (A max ) and EC 50 , or the position of the dexamethasone dose-response curve. Upon screening 1280 chemicals, ten with the greatest change in the absolute value of A max or EC 50 were selected for further examination. Qualitatively identical behaviors for 60 -90% of the chemicals were observed in a completely different system, suggesting that other systems will be similarly affected by these chemicals. Additional analysis of the ten chemicals in a recently described competition assay determined their kinetically-defined mechanism and site of action. Some chemicals had similar mechanisms of action despite divergent effects on the level of GR-induced product. These combined assays offer a straightforward method of identifying numerous new pharmaceuticals that can alter GR transactivation in ways that could be clinically useful.
Journal of Biological Chemistry, 2014
Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of cancer. MDR is o... more Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of cancer. MDR is often the result of overexpression of ATP-binding cassette transporters following chemotherapy. A common ATP-binding cassette transporter that is overexpressed in MDR cancer cells is P-glycoprotein, which actively effluxes drugs against a concentration gradient, producing an MDR phenotype. Collateral sensitivity (CS), a phenomenon of drug hypersensitivity, is defined as the ability of certain compounds to selectively target MDR cells, but not the drug-sensitive parent cells from which they were derived. The drug tiopronin has been previously shown to elicit CS. However, unlike other CS agents, the mechanism of action was not dependent on the expression of P-glycoprotein in MDR cells. We have determined that the CS activity of tiopronin is mediated by the generation of reactive oxygen species (ROS) and that CS can be reversed by a variety of ROS-scavenging compounds. Specifically, selective toxicity of tiopronin toward MDR cells is achieved by inhibition of glutathione peroxidase (GPx), and the mode of inhibition of GPx1 by tiopronin is shown in this report. Why MDR cells are particularly sensitive to ROS is discussed, as is the difficulty in exploiting this hypersensitivity to tiopronin in the clinic.
Bioorganic & medicinal chemistry letters, 2015
Classic Galactosemia is a rare inborn error of metabolism that is caused by deficiency of galacto... more Classic Galactosemia is a rare inborn error of metabolism that is caused by deficiency of galactose-1-phosphate uridyltransferase (GALT), an enzyme within the Leloir pathway that is responsible for the conversion of galactose-1-phosphate (gal-1-p) and UDP-glucose to glucose-1-phosphate and UDP-galactose. This deficiency results in elevated intracellular concentrations of its substrate, gal-1-p, and this increased concentration is believed to be the major pathogenic mechanism in Classic Galactosemia. Galactokinase (GALK) is an upstream enzyme of GALT in the Leloir pathway and is responsible for conversion of galactose and ATP to gal-1-p and ADP. Therefore, it was hypothesized that the identification of a small-molecule inhibitor of human GALK would act to prevent the accumulation of gal-1-p and offer a novel entry therapy for this disorder. Herein we describe a quantitative high-throughput screening campaign that identified a single chemotype that was optimized and validated as a GAL...
Proceedings of the National Academy of Sciences, 2011
The radiotracer [ 11 C]N-desmethyl-loperamide (dLop) images the in vivo function of P-glycoprotei... more The radiotracer [ 11 C]N-desmethyl-loperamide (dLop) images the in vivo function of P-glycoprotein (P-gp), a transporter that blocks the entry of drugs that are substrates into brain. When P-gp is inhibited, [ 11 C]dLop, a potent opiate agonist, enters and becomes trapped in the brain. This trapping is beneficial from an imaging perspective, because it amplifies the PET signal, essentially by accumulating radioactivity over time. As we previously demonstrated that this trapping was not caused by binding to opiate receptors, we examined whether [ 11 C]dLop, a weak base, is ionically trapped in acidic lysosomes. To test this hypothesis, we measured [ 3 H]dLop accumulation in human cells by using lysosomotropics. Because the in vivo trapping of dLop was seen after P-gp inhibition, we also measured [ 3 H]dLop uptake in P-gp-expressing cells treated with the P-gp inhibitor tariquidar. All lysosomotropics decreased [ 3 H]dLop accumulation by at least 50%. In P-gp-expressing cells, tariquidar (and another P-gp inhibitor) surprisingly decreased [ 3 H]dLop uptake. Consequently, we measured [ 11 C]dLop uptake before and after tariquidar preadministration in lysosome-rich organs of P-gp KO mice and humans. After tariquidar pretreatment in both species, radioactivity uptake in these organs decreased by 35% to 40%. Our results indicate that dLop is trapped in lysosomes and that tariquidar competes with dLop for lysosomal accumulation in vitro and in vivo. Although tariquidar and dLop compete for lysosomal trapping in the periphery, such competition does not occur in brain because tariquidar has negligible entry into brain. In summary, tariquidar and [ 11 C]dLop can be used in combination to selectively measure the function of P-gp at the blood-brain barrier.
Journal of Translational Medicine, 2008
Background: Effective transvascular delivery of nanoparticle-based chemotherapeutics across the b... more Background: Effective transvascular delivery of nanoparticle-based chemotherapeutics across the blood-brain tumor barrier of malignant gliomas remains a challenge. This is due to our limited understanding of nanoparticle properties in relation to the physiologic size of pores within the blood-brain tumor barrier. Polyamidoamine dendrimers are particularly small multigenerational nanoparticles with uniform sizes within each generation. Dendrimer sizes increase by only 1 to 2 nm with each successive generation. Using functionalized polyamidoamine dendrimer generations 1 through 8, we investigated how nanoparticle size influences particle accumulation within malignant glioma cells.