The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Joshua D Rabinowitz - One of the best experts on this subject based on the ideXlab platform.
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ZIP-5/bZIP transcription factor regulation of Folate Metabolism is critical for aging axon regeneration
2019Co-Authors: Vanisha Lakhina, Joshua D Rabinowitz, Melanie R. Mcreynolds, Daniel T. Grimes, Rebecca D. Burdine, Coleen T. MurphyAbstract:Aging is associated with reduced capacity for tissue repair, perhaps the most critical of which is a decline in the ability of aged neurons to recover after injury. Identifying factors that improve the regenerative ability of aging neurons is a prerequisite for therapy design and remains an enormous challenge, yet many of the genes that play a role in regeneration of youthful axons do not regulate axon regeneration in older animals, highlighting the need to identify aging-specific regeneration mechanisms. Previously, we found that increased DAF-16/FOXO activity enhances the regenerative ability of mechanosensory axons in aged animals. Here we show that DAF-16/FOXO mediates its pro-regenerative effects by upregulating Folate Metabolism genes via the ZIP-5 bZIP transcription factor. Remarkably, dietary folic acid supplementation improves the regeneration of aging C. elegans axons. Enzymes regulating Folate Metabolism are also up-regulated in regenerating zebrafish fins, and we show that dietary folic acid supplementation post-amputation enhances fin regrowth in aging zebrafish. Our results demonstrate that boosting Folate Metabolism is a conserved and non-invasive approach to increase the regenerative capacity of aging neurons and tissues. Given that lower Folate status has been linked with reduced cognition in the elderly, maintaining optimal Folate Metabolism may be a general strategy to achieve healthy brain aging.
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a two enzyme adaptive unit within bacterial Folate Metabolism
Cell Reports, 2019Co-Authors: Andrew F Schober, Joshua D Rabinowitz, Li Zi-chen, Andrew D Mathis, Christine Ingle, Junyoung O Park, Ivan Junier, Olivier Rivoire, Kimberly A ReynoldsAbstract:Enzyme function and evolution are influenced by the larger context of a metabolic pathway. Deleterious mutations or perturbations in one enzyme can often be compensated by mutations to others. We used comparative genomics and experiments to examine evolutionary interactions with the essential metabolic enzyme dihydroFolate reductase (DHFR). Analyses of synteny and co-occurrence across bacterial species indicate that DHFR is coupled to thymidylate synthase (TYMS) but relatively independent from the rest of Folate Metabolism. Using quantitative growth rate measurements and forward evolution in Escherichia coli, we demonstrate that the two enzymes adapt as a relatively independent unit in response to antibiotic stress. Metabolomic profiling revealed that TYMS activity must not exceed DHFR activity to prevent the depletion of reduced Folates and the accumulation of the intermediate dihydroFolate. Comparative genomics analyses identified >200 gene pairs with similar statistical signatures of modular co-evolution, suggesting that cellular pathways may be decomposable into small adaptive units.
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NADPH production by the oxidative pentose-phosphate pathway supports Folate Metabolism
Nature metabolism, 2019Co-Authors: Li Zi-chen, Henry D Zheng, Michael Morley, Zoltan Arany, Atsushi Hoshino, Zhaoyue Zhang, Joshua D RabinowitzAbstract:NADPH donates high energy electrons for antioxidant defense and reductive biosynthesis. Cytosolic NADP is recycled to NADPH by the oxidative pentose phosphate pathway (oxPPP), malic enzyme 1 (ME1) and isocitrate dehydrogenase 1 (IDH1). Here we show that any one of these routes can support cell growth, but the oxPPP is uniquely required to maintain a normal NADPH/NADP ratio, mammalian dihydroFolate reductase (DHFR) activity and Folate Metabolism. These findings are based on CRISPR deletions of glucose-6-phosphate dehydrogenase (G6PD, the committed oxPPP enzyme), ME1, IDH1, and combinations thereof in HCT116 colon cancer cells. Loss of G6PD results in high NADP, which induces compensatory increases in ME1 and IDH1 flux. But the high NADP inhibits dihydroFolate reductase (DHFR), resulting in impaired Folate-mediated biosynthesis, which is reversed by recombinant expression of E. coli DHFR. Across different cancer cell lines, G6PD deletion produced consistent changes in Folate-related metabolites, suggesting a general requirement for the oxPPP to support Folate Metabolism.
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nadph production by the oxidative pentose phosphate pathway supports Folate Metabolism
Nature metabolism, 2019Co-Authors: Li Zi-chen, Henry D Zheng, Michael Morley, Zoltan Arany, Atsushi Hoshino, Zhaoyue Zhang, Joshua D RabinowitzAbstract:NADPH donates high-energy electrons for antioxidant defence and reductive biosynthesis. Cytosolic NADP is recycled to NADPH by the oxidative pentose-phosphate pathway (oxPPP), malic enzyme 1 (ME1) and isocitrate dehydrogenase 1 (IDH1). Here we show that any one of these routes can support cell growth, but the oxPPP is uniquely required to maintain a normal NADPH/NADP ratio, mammalian dihydroFolate reductase (DHFR) activity and Folate Metabolism. These findings are based on CRISPR deletions of glucose-6-phosphate dehydrogenase (G6PD, the committed oxPPP enzyme), ME1, IDH1 and combinations thereof in HCT116 colon cancer cells. Loss of G6PD results in high NADP, which induces compensatory increases in ME1 and IDH1 flux. But the high NADP inhibits DHFR, resulting in impaired Folate-mediated biosynthesis, which is reversed by recombinant expression of Escherichia coli DHFR. Across different cancer cell lines, G6PD deletion produced consistent changes in Folate-related metabolites, suggesting a general requirement for the oxPPP to support Folate Metabolism. The oxidative pentose-phosphate pathway (oxPPP) is a major NADPH producer. Here the authors show that malic enzyme or isocitrate dehydrogenase can support the growth of cells lacking the oxPPP, but the oxPPP is necessary to maintain a normal NADPH/NADP ratio, DHFR activity and Folate Metabolism.
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a two enzyme adaptive unit in bacterial Folate Metabolism
bioRxiv, 2018Co-Authors: Andrew F Schober, Joshua D Rabinowitz, Li Zi-chen, Christine Ingle, Junyoung O Park, Ivan Junier, Olivier Rivoire, Kimberly A ReynoldsAbstract:The activity of a gene may be influenced or modified by other genes in the genome. Here, we show that co-evolution can be used to identify quasi-independent gene groups inside of larger cellular systems. Using Folate Metabolism as a case study, we show that co-evolution indicates a sparse architecture of interactions, with three small groups of genes co-evolving in the midst of others that evolve independently. For one such module - dihydroFolate reductase (DHFR) and thymidylate synthase (TYMS) - we use epistasis measurements and forward evolution to demonstrate both internal functional coupling and independence from the remainder of the genome. Mechanistically, the coupling is driven by a constraint on their relative activities, which must be balanced to prevent accumulation of a metabolic intermediate. Applying co-evolution analyses genome-wide reveals a number of other gene pairs with statistical signatures similar to DHFR/TYMS, suggesting that small adaptive units are a general feature of cellular systems.
Sarah S. Bacus - One of the best experts on this subject based on the ideXlab platform.
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kras mutation status is associated with enhanced dependency on Folate Metabolism pathways in non small cell lung cancer cells
Molecular Cancer Therapeutics, 2014Co-Authors: Diarmuid M. Moran, Patricia B Trusk, David Sidransky, Sarah S. BacusAbstract:KRAS gene mutation is linked to poor prognosis and resistance to therapeutics in non–small cell lung cancer (NSCLC). In this study, we have explored the possibility of exploiting inherent differences in KRAS-mutant cell Metabolism for treatment. This study identified a greater dependency on Folate Metabolism pathways in KRAS mutant compared with KRAS wild-type NSCLC cell lines. Microarray gene expression and biologic pathway analysis identified higher expression of Folate Metabolism– and purine synthesis–related pathways in KRAS -mutant NSCLC cells compared with wild-type counterparts. Moreover, pathway analysis and knockdown studies suggest a role for MYC transcriptional activity in the expression of these pathways in KRAS -mutant NSCLC cells. Furthermore, KRAS knockdown and overexpression studies demonstrated the ability of KRAS to regulate expression of genes that comprise Folate Metabolism pathways. Proliferation studies demonstrated higher responsiveness to methotrexate, pemetrexed, and other antiFolates in KRAS -mutant NSCLC cells. Surprisingly, KRAS gene expression is downregulated in KRAS wild-type and KRAS -mutant cells by antiFolates, which may also contribute to higher efficacy of antiFolates in KRAS -mutant NSCLC cells. In vivo analysis of multiple tumorgraft models in nude mice identified a KRAS -mutant tumor among the pemetrexed-responsive tumors and also demonstrated an association between expression of the Folate pathway gene, methylenetetrahydroFolate dehydrogenase 2 ( MTHFD2 ), and antiFolate activity. Collectively, we identify altered regulation of Folate Metabolism in KRAS-mutant NSCLC cells that may account for higher antiFolate activity in this subtype of NSCLC. Mol Cancer Ther; 13(6); 1611–24. ©2014 AACR .
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KRAS Mutation Status Is Associated with Enhanced Dependency on Folate Metabolism Pathways in Non–Small Cell Lung Cancer Cells
Molecular cancer therapeutics, 2014Co-Authors: Diarmuid M. Moran, Patricia B Trusk, Karen J Pry, K. Paz, David Sidransky, Sarah S. BacusAbstract:KRAS gene mutation is linked to poor prognosis and resistance to therapeutics in non-small cell lung cancer (NSCLC). In this study, we have explored the possibility of exploiting inherent differences in KRAS-mutant cell Metabolism for treatment. This study identified a greater dependency on Folate Metabolism pathways in KRAS mutant compared with KRAS wild-type NSCLC cell lines. Microarray gene expression and biologic pathway analysis identified higher expression of Folate Metabolism- and purine synthesis-related pathways in KRAS-mutant NSCLC cells compared with wild-type counterparts. Moreover, pathway analysis and knockdown studies suggest a role for MYC transcriptional activity in the expression of these pathways in KRAS-mutant NSCLC cells. Furthermore, KRAS knockdown and overexpression studies demonstrated the ability of KRAS to regulate expression of genes that comprise Folate Metabolism pathways. Proliferation studies demonstrated higher responsiveness to methotrexate, pemetrexed, and other antiFolates in KRAS-mutant NSCLC cells. Surprisingly, KRAS gene expression is downregulated in KRAS wild-type and KRAS-mutant cells by antiFolates, which may also contribute to higher efficacy of antiFolates in KRAS-mutant NSCLC cells. In vivo analysis of multiple tumorgraft models in nude mice identified a KRAS-mutant tumor among the pemetrexed-responsive tumors and also demonstrated an association between expression of the Folate pathway gene, methylenetetrahydroFolate dehydrogenase 2 (MTHFD2), and antiFolate activity. Collectively, we identify altered regulation of Folate Metabolism in KRAS-mutant NSCLC cells that may account for higher antiFolate activity in this subtype of NSCLC.
Li Zi-chen - One of the best experts on this subject based on the ideXlab platform.
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a two enzyme adaptive unit within bacterial Folate Metabolism
Cell Reports, 2019Co-Authors: Andrew F Schober, Joshua D Rabinowitz, Li Zi-chen, Andrew D Mathis, Christine Ingle, Junyoung O Park, Ivan Junier, Olivier Rivoire, Kimberly A ReynoldsAbstract:Enzyme function and evolution are influenced by the larger context of a metabolic pathway. Deleterious mutations or perturbations in one enzyme can often be compensated by mutations to others. We used comparative genomics and experiments to examine evolutionary interactions with the essential metabolic enzyme dihydroFolate reductase (DHFR). Analyses of synteny and co-occurrence across bacterial species indicate that DHFR is coupled to thymidylate synthase (TYMS) but relatively independent from the rest of Folate Metabolism. Using quantitative growth rate measurements and forward evolution in Escherichia coli, we demonstrate that the two enzymes adapt as a relatively independent unit in response to antibiotic stress. Metabolomic profiling revealed that TYMS activity must not exceed DHFR activity to prevent the depletion of reduced Folates and the accumulation of the intermediate dihydroFolate. Comparative genomics analyses identified >200 gene pairs with similar statistical signatures of modular co-evolution, suggesting that cellular pathways may be decomposable into small adaptive units.
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NADPH production by the oxidative pentose-phosphate pathway supports Folate Metabolism
Nature metabolism, 2019Co-Authors: Li Zi-chen, Henry D Zheng, Michael Morley, Zoltan Arany, Atsushi Hoshino, Zhaoyue Zhang, Joshua D RabinowitzAbstract:NADPH donates high energy electrons for antioxidant defense and reductive biosynthesis. Cytosolic NADP is recycled to NADPH by the oxidative pentose phosphate pathway (oxPPP), malic enzyme 1 (ME1) and isocitrate dehydrogenase 1 (IDH1). Here we show that any one of these routes can support cell growth, but the oxPPP is uniquely required to maintain a normal NADPH/NADP ratio, mammalian dihydroFolate reductase (DHFR) activity and Folate Metabolism. These findings are based on CRISPR deletions of glucose-6-phosphate dehydrogenase (G6PD, the committed oxPPP enzyme), ME1, IDH1, and combinations thereof in HCT116 colon cancer cells. Loss of G6PD results in high NADP, which induces compensatory increases in ME1 and IDH1 flux. But the high NADP inhibits dihydroFolate reductase (DHFR), resulting in impaired Folate-mediated biosynthesis, which is reversed by recombinant expression of E. coli DHFR. Across different cancer cell lines, G6PD deletion produced consistent changes in Folate-related metabolites, suggesting a general requirement for the oxPPP to support Folate Metabolism.
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nadph production by the oxidative pentose phosphate pathway supports Folate Metabolism
Nature metabolism, 2019Co-Authors: Li Zi-chen, Henry D Zheng, Michael Morley, Zoltan Arany, Atsushi Hoshino, Zhaoyue Zhang, Joshua D RabinowitzAbstract:NADPH donates high-energy electrons for antioxidant defence and reductive biosynthesis. Cytosolic NADP is recycled to NADPH by the oxidative pentose-phosphate pathway (oxPPP), malic enzyme 1 (ME1) and isocitrate dehydrogenase 1 (IDH1). Here we show that any one of these routes can support cell growth, but the oxPPP is uniquely required to maintain a normal NADPH/NADP ratio, mammalian dihydroFolate reductase (DHFR) activity and Folate Metabolism. These findings are based on CRISPR deletions of glucose-6-phosphate dehydrogenase (G6PD, the committed oxPPP enzyme), ME1, IDH1 and combinations thereof in HCT116 colon cancer cells. Loss of G6PD results in high NADP, which induces compensatory increases in ME1 and IDH1 flux. But the high NADP inhibits DHFR, resulting in impaired Folate-mediated biosynthesis, which is reversed by recombinant expression of Escherichia coli DHFR. Across different cancer cell lines, G6PD deletion produced consistent changes in Folate-related metabolites, suggesting a general requirement for the oxPPP to support Folate Metabolism. The oxidative pentose-phosphate pathway (oxPPP) is a major NADPH producer. Here the authors show that malic enzyme or isocitrate dehydrogenase can support the growth of cells lacking the oxPPP, but the oxPPP is necessary to maintain a normal NADPH/NADP ratio, DHFR activity and Folate Metabolism.
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a two enzyme adaptive unit in bacterial Folate Metabolism
bioRxiv, 2018Co-Authors: Andrew F Schober, Joshua D Rabinowitz, Li Zi-chen, Christine Ingle, Junyoung O Park, Ivan Junier, Olivier Rivoire, Kimberly A ReynoldsAbstract:The activity of a gene may be influenced or modified by other genes in the genome. Here, we show that co-evolution can be used to identify quasi-independent gene groups inside of larger cellular systems. Using Folate Metabolism as a case study, we show that co-evolution indicates a sparse architecture of interactions, with three small groups of genes co-evolving in the midst of others that evolve independently. For one such module - dihydroFolate reductase (DHFR) and thymidylate synthase (TYMS) - we use epistasis measurements and forward evolution to demonstrate both internal functional coupling and independence from the remainder of the genome. Mechanistically, the coupling is driven by a constraint on their relative activities, which must be balanced to prevent accumulation of a metabolic intermediate. Applying co-evolution analyses genome-wide reveals a number of other gene pairs with statistical signatures similar to DHFR/TYMS, suggesting that small adaptive units are a general feature of cellular systems.
Erica D. Watson - One of the best experts on this subject based on the ideXlab platform.
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abnormal Folate Metabolism causes age sex and parent of origin specific haematological defects in mice
The Journal of Physiology, 2018Co-Authors: Nisha Padmanabhan, Katerina Menelaou, Jiali Gao, Alexander Anderson, Georgina E.t. Blake, Nuala B Daw, Erica D. WatsonAbstract:Key points Folate (folic acid) deficiency and mutations in Folate-related genes in humans result in megaloblastic anaemia. Folate Metabolism, which requires the enzyme methionine synthase reductase (MTRR), is necessary for DNA synthesis and the transmission of one-carbon methyl groups for cellular methylation. In this study, we show that the hypomorphic Mtrrgt/gt mutation in mice results in late-onset and sex-specific blood defects, including macrocytic anaemia, extramedullary haematopoiesis and lymphopenia. Notably, when either parent carries an Mtrrgt allele, blood phenotypes result in their genetically wildtype adult daughters, the effects of which are parent specific. Our data establish a new model for studying the mechanism of Folate Metabolism in macrocytic anaemia aetiology and suggest that assessing parental Folate status might be important when diagnosing adult patients with unexplained anaemia. Abstract The importance of the vitamin Folate (also known as folic acid) in erythrocyte formation, maturation and/or longevity is apparent since Folate deficiency in humans causes megaloblastic anaemia. Megaloblastic anaemia is a type of macrocytic anaemia whereby erythrocytes are enlarged and fewer in number. Folate Metabolism is required for thymidine synthesis and one-carbon Metabolism, though its specific role in erythropoiesis is not well understood. Methionine synthase reductase (MTRR) is a key enzyme necessary for the progression of Folate Metabolism since knocking down the Mtrr gene in mice results in hyperhomocysteinaemia and global DNA hypomethylation. We demonstrate here that abnormal Folate Metabolism in mice caused by Mtrrgt/gt homozygosity leads to haematopoietic phenotypes that are sex and age dependent. Specifically, Mtrrgt/gt female mice displayed macrocytic anaemia, which might be due to defective erythroid differentiation at the exclusion of haemolysis. This was associated with increased renal Epo mRNA expression, hypercellular bone marrow, and splenic extramedullary haematopoiesis. In contrast, the male response differed since Mtrrgt/gt male mice were not anaemic but did display erythrocytic macrocytosis and lymphopenia. Regardless of sex, these phenotypes were late onset. Remarkably, we also show that when either parent carries an Mtrrgt allele, a haematological defect results in their adult wildtype daughters. However, the specific phenotype was dependent upon the sex of the parent. For instance, wildtype daughters of Mtrr+/gt females displayed normocytic anaemia. In contrast, wildtype daughters of Mtrr+/gt males exhibited erythrocytic microcytosis not associated with anaemia. Therefore, abnormal Folate Metabolism affects adult haematopoiesis in an age-, sex- and parent-specific manner.
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Abnormal Folate Metabolism causes age‐, sex‐ and parent‐of‐origin‐specific haematological defects in mice
The Journal of physiology, 2018Co-Authors: Nisha Padmanabhan, Katerina Menelaou, Jiali Gao, Alexander Anderson, Georgina E.t. Blake, B. Nuala Daw, Erica D. WatsonAbstract:Key points Folate (folic acid) deficiency and mutations in Folate-related genes in humans result in megaloblastic anaemia. Folate Metabolism, which requires the enzyme methionine synthase reductase (MTRR), is necessary for DNA synthesis and the transmission of one-carbon methyl groups for cellular methylation. In this study, we show that the hypomorphic Mtrrgt/gt mutation in mice results in late-onset and sex-specific blood defects, including macrocytic anaemia, extramedullary haematopoiesis and lymphopenia. Notably, when either parent carries an Mtrrgt allele, blood phenotypes result in their genetically wildtype adult daughters, the effects of which are parent specific. Our data establish a new model for studying the mechanism of Folate Metabolism in macrocytic anaemia aetiology and suggest that assessing parental Folate status might be important when diagnosing adult patients with unexplained anaemia. Abstract The importance of the vitamin Folate (also known as folic acid) in erythrocyte formation, maturation and/or longevity is apparent since Folate deficiency in humans causes megaloblastic anaemia. Megaloblastic anaemia is a type of macrocytic anaemia whereby erythrocytes are enlarged and fewer in number. Folate Metabolism is required for thymidine synthesis and one-carbon Metabolism, though its specific role in erythropoiesis is not well understood. Methionine synthase reductase (MTRR) is a key enzyme necessary for the progression of Folate Metabolism since knocking down the Mtrr gene in mice results in hyperhomocysteinaemia and global DNA hypomethylation. We demonstrate here that abnormal Folate Metabolism in mice caused by Mtrrgt/gt homozygosity leads to haematopoietic phenotypes that are sex and age dependent. Specifically, Mtrrgt/gt female mice displayed macrocytic anaemia, which might be due to defective erythroid differentiation at the exclusion of haemolysis. This was associated with increased renal Epo mRNA expression, hypercellular bone marrow, and splenic extramedullary haematopoiesis. In contrast, the male response differed since Mtrrgt/gt male mice were not anaemic but did display erythrocytic macrocytosis and lymphopenia. Regardless of sex, these phenotypes were late onset. Remarkably, we also show that when either parent carries an Mtrrgt allele, a haematological defect results in their adult wildtype daughters. However, the specific phenotype was dependent upon the sex of the parent. For instance, wildtype daughters of Mtrr+/gt females displayed normocytic anaemia. In contrast, wildtype daughters of Mtrr+/gt males exhibited erythrocytic microcytosis not associated with anaemia. Therefore, abnormal Folate Metabolism affects adult haematopoiesis in an age-, sex- and parent-specific manner.
Diarmuid M. Moran - One of the best experts on this subject based on the ideXlab platform.
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kras mutation status is associated with enhanced dependency on Folate Metabolism pathways in non small cell lung cancer cells
Molecular Cancer Therapeutics, 2014Co-Authors: Diarmuid M. Moran, Patricia B Trusk, David Sidransky, Sarah S. BacusAbstract:KRAS gene mutation is linked to poor prognosis and resistance to therapeutics in non–small cell lung cancer (NSCLC). In this study, we have explored the possibility of exploiting inherent differences in KRAS-mutant cell Metabolism for treatment. This study identified a greater dependency on Folate Metabolism pathways in KRAS mutant compared with KRAS wild-type NSCLC cell lines. Microarray gene expression and biologic pathway analysis identified higher expression of Folate Metabolism– and purine synthesis–related pathways in KRAS -mutant NSCLC cells compared with wild-type counterparts. Moreover, pathway analysis and knockdown studies suggest a role for MYC transcriptional activity in the expression of these pathways in KRAS -mutant NSCLC cells. Furthermore, KRAS knockdown and overexpression studies demonstrated the ability of KRAS to regulate expression of genes that comprise Folate Metabolism pathways. Proliferation studies demonstrated higher responsiveness to methotrexate, pemetrexed, and other antiFolates in KRAS -mutant NSCLC cells. Surprisingly, KRAS gene expression is downregulated in KRAS wild-type and KRAS -mutant cells by antiFolates, which may also contribute to higher efficacy of antiFolates in KRAS -mutant NSCLC cells. In vivo analysis of multiple tumorgraft models in nude mice identified a KRAS -mutant tumor among the pemetrexed-responsive tumors and also demonstrated an association between expression of the Folate pathway gene, methylenetetrahydroFolate dehydrogenase 2 ( MTHFD2 ), and antiFolate activity. Collectively, we identify altered regulation of Folate Metabolism in KRAS-mutant NSCLC cells that may account for higher antiFolate activity in this subtype of NSCLC. Mol Cancer Ther; 13(6); 1611–24. ©2014 AACR .
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KRAS Mutation Status Is Associated with Enhanced Dependency on Folate Metabolism Pathways in Non–Small Cell Lung Cancer Cells
Molecular cancer therapeutics, 2014Co-Authors: Diarmuid M. Moran, Patricia B Trusk, Karen J Pry, K. Paz, David Sidransky, Sarah S. BacusAbstract:KRAS gene mutation is linked to poor prognosis and resistance to therapeutics in non-small cell lung cancer (NSCLC). In this study, we have explored the possibility of exploiting inherent differences in KRAS-mutant cell Metabolism for treatment. This study identified a greater dependency on Folate Metabolism pathways in KRAS mutant compared with KRAS wild-type NSCLC cell lines. Microarray gene expression and biologic pathway analysis identified higher expression of Folate Metabolism- and purine synthesis-related pathways in KRAS-mutant NSCLC cells compared with wild-type counterparts. Moreover, pathway analysis and knockdown studies suggest a role for MYC transcriptional activity in the expression of these pathways in KRAS-mutant NSCLC cells. Furthermore, KRAS knockdown and overexpression studies demonstrated the ability of KRAS to regulate expression of genes that comprise Folate Metabolism pathways. Proliferation studies demonstrated higher responsiveness to methotrexate, pemetrexed, and other antiFolates in KRAS-mutant NSCLC cells. Surprisingly, KRAS gene expression is downregulated in KRAS wild-type and KRAS-mutant cells by antiFolates, which may also contribute to higher efficacy of antiFolates in KRAS-mutant NSCLC cells. In vivo analysis of multiple tumorgraft models in nude mice identified a KRAS-mutant tumor among the pemetrexed-responsive tumors and also demonstrated an association between expression of the Folate pathway gene, methylenetetrahydroFolate dehydrogenase 2 (MTHFD2), and antiFolate activity. Collectively, we identify altered regulation of Folate Metabolism in KRAS-mutant NSCLC cells that may account for higher antiFolate activity in this subtype of NSCLC.