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Targeted deletion of Nrf2 reduces urethane-induced lung tumor development in mice.

Bauer AK, Cho HY, Miller-Degraff L, Walker C, Helms K, Fostel J, Yamamoto M, Kleeberger SR - PLoS ONE (2011)

Bottom Line: However, permanent Nrf2 activation in human lung carcinomas promotes pulmonary malignancy and chemoresistance.Nrf2 modulated expression of genes involved cell-cell signaling, glutathione metabolism and oxidative stress response, and immune responses during early stage neoplasia.Our results were consistent with the concept that Nrf2 over-activation is an adaptive response of cancer conferring resistance to anti-cancer drugs and promoting malignancy.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States of America. alison.bauer@ucdenver.edu

ABSTRACT
Nrf2 is a key transcription factor that regulates cellular redox and defense responses. However, permanent Nrf2 activation in human lung carcinomas promotes pulmonary malignancy and chemoresistance. We tested the hypothesis that Nrf2 has cell survival properties and lack of Nrf2 suppresses chemically-induced pulmonary neoplasia by treating Nrf2(+/+) and Nrf2(-/-) mice with urethane. Airway inflammation and injury were assessed by bronchoalveolar lavage analyses and histopathology, and lung tumors were analyzed by gross and histologic analysis. We used transcriptomics to assess Nrf2-dependent changes in pulmonary gene transcripts at multiple stages of neoplasia. Lung hyperpermeability, cell death and apoptosis, and inflammatory cell infiltration were significantly higher in Nrf2(-/-) mice compared to Nrf2(+/+) mice 9 and 11 wk after urethane. Significantly fewer lung adenomas were found in Nrf2(-/-) mice than in Nrf2(+/+) mice at 12 and 22 wk. Nrf2 modulated expression of genes involved cell-cell signaling, glutathione metabolism and oxidative stress response, and immune responses during early stage neoplasia. In lung tumors, Nrf2-altered genes had roles in transcriptional regulation of cell cycle and proliferation, carcinogenesis, organismal injury and abnormalities, xenobiotic metabolism, and cell-cell signaling genes. Collectively, Nrf2 deficiency decreased susceptibility to urethane-induced lung tumorigenesis in mice. Cell survival properties of Nrf2 were supported, at least in part, by reduced early death of initiated cells and heightened advantage for tumor cell expansion in Nrf2(+/+) mice relative to Nrf2(-/-) mice. Our results were consistent with the concept that Nrf2 over-activation is an adaptive response of cancer conferring resistance to anti-cancer drugs and promoting malignancy.

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Proposed role for Nrf2 in urethane-induced lung tumorigenesis.Urethane treatment causes pulmonary inflammation and injury during the pre-neoplastic stage, which results in overproduction of reactive oxygen species (ROS) and cellular death by necrosis and apoptosis. Compared to Nrf2+/+ mice, Nrf2-/- mice have lowered cell survival factors including cellular redox and drug metabolism enzymes (e.g., glutathione synthetase, UDP glucuronosyl transferase 1 family) and cell maintenance systems including numerous metabolic enzymes and transport proteins (e.g., solute carrier family). These mice therefore have heightened cellular destruction factors (e.g., ROS, airway secretion, inflammation), which overwhelms cellular cytoprotection tools and causes mass death of injured cells including tumor initiated cells during the pre-neoplastic stage. Nrf2-/- mice also exhibit dysregulated expressions of many genes involved in cell cycle and death (e.g., CDC28 protein kinases, cyclin D1, cyclin dependent kinase inhibitor 2C, B-cell leukemia/lymphoma 6, unc-119 homolog) relative to wild type mice during tumorigenesis. Overall, increased susceptibility to acute injury due to lack of survival signals leading to net cell loss is beneficial to Nrf2-/- mice for their tumor suppression.
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pone-0026590-g007: Proposed role for Nrf2 in urethane-induced lung tumorigenesis.Urethane treatment causes pulmonary inflammation and injury during the pre-neoplastic stage, which results in overproduction of reactive oxygen species (ROS) and cellular death by necrosis and apoptosis. Compared to Nrf2+/+ mice, Nrf2-/- mice have lowered cell survival factors including cellular redox and drug metabolism enzymes (e.g., glutathione synthetase, UDP glucuronosyl transferase 1 family) and cell maintenance systems including numerous metabolic enzymes and transport proteins (e.g., solute carrier family). These mice therefore have heightened cellular destruction factors (e.g., ROS, airway secretion, inflammation), which overwhelms cellular cytoprotection tools and causes mass death of injured cells including tumor initiated cells during the pre-neoplastic stage. Nrf2-/- mice also exhibit dysregulated expressions of many genes involved in cell cycle and death (e.g., CDC28 protein kinases, cyclin D1, cyclin dependent kinase inhibitor 2C, B-cell leukemia/lymphoma 6, unc-119 homolog) relative to wild type mice during tumorigenesis. Overall, increased susceptibility to acute injury due to lack of survival signals leading to net cell loss is beneficial to Nrf2-/- mice for their tumor suppression.

Mentions: (A) Biological function and disorder categories of the Nrf2-dependent genes (i.e. differentially expressed between Nrf2+/+ and Nrf2-/- mice) significantly changed in pre-/early neoplastic stage at 12 wk (top) and in tumors at 22 wk (bottom) were analysis by Ingenuity Pathway Analysis (IPA). Top-ranked [-log(p)] categories are depicted and compared between the two tumorigenesis stages. (B) A total of 118 gene transcripts varied significantly (p<0.05) between Nrf2+/+ and Nrf2-/- mice 12 wk after urethane treatment were grouped into 4 expression profiles (set 0–3). Expression level of each transcript was normalized to corresponding Nrf2+/+ saline controls and indicated as relative log ratio [log2 (normalized average intensity)]. Genes are listed in Dataset 1 and in Table 1. Sal = saline-treated lung, UT = urethane-treated lung. (C) Lung tumor genes (n = 376) significantly (p<0.05) different between Nrf2+/+ and Nrf2-/- mice at 22 wk after urethane treatment are clustered into 4 expression profile groups (set 0–3). Expression level of each gene was normalized to that of Nrf2+/+ saline controls and indicated as relative log ratio [log2 (normalized average intensity)]. Genes are listed in Dataset 2 and in Table 2. Sal = saline-treated lung, UN = uninvolved tissue, Tum = tumor tissue. (D) Among the Nrf2-dependently changed genes in pre-/early neoplastic stage at 12 wk (n = 118) and in tumors at 22 wk (n = 376), Venn diagram analysis identified gene transcripts that were changed at either time point (12 and 22 wk) and/or were genes in common between the two time points (i.e. 12 genes).


Targeted deletion of Nrf2 reduces urethane-induced lung tumor development in mice.

Bauer AK, Cho HY, Miller-Degraff L, Walker C, Helms K, Fostel J, Yamamoto M, Kleeberger SR - PLoS ONE (2011)

Proposed role for Nrf2 in urethane-induced lung tumorigenesis.Urethane treatment causes pulmonary inflammation and injury during the pre-neoplastic stage, which results in overproduction of reactive oxygen species (ROS) and cellular death by necrosis and apoptosis. Compared to Nrf2+/+ mice, Nrf2-/- mice have lowered cell survival factors including cellular redox and drug metabolism enzymes (e.g., glutathione synthetase, UDP glucuronosyl transferase 1 family) and cell maintenance systems including numerous metabolic enzymes and transport proteins (e.g., solute carrier family). These mice therefore have heightened cellular destruction factors (e.g., ROS, airway secretion, inflammation), which overwhelms cellular cytoprotection tools and causes mass death of injured cells including tumor initiated cells during the pre-neoplastic stage. Nrf2-/- mice also exhibit dysregulated expressions of many genes involved in cell cycle and death (e.g., CDC28 protein kinases, cyclin D1, cyclin dependent kinase inhibitor 2C, B-cell leukemia/lymphoma 6, unc-119 homolog) relative to wild type mice during tumorigenesis. Overall, increased susceptibility to acute injury due to lack of survival signals leading to net cell loss is beneficial to Nrf2-/- mice for their tumor suppression.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3198791&req=5

pone-0026590-g007: Proposed role for Nrf2 in urethane-induced lung tumorigenesis.Urethane treatment causes pulmonary inflammation and injury during the pre-neoplastic stage, which results in overproduction of reactive oxygen species (ROS) and cellular death by necrosis and apoptosis. Compared to Nrf2+/+ mice, Nrf2-/- mice have lowered cell survival factors including cellular redox and drug metabolism enzymes (e.g., glutathione synthetase, UDP glucuronosyl transferase 1 family) and cell maintenance systems including numerous metabolic enzymes and transport proteins (e.g., solute carrier family). These mice therefore have heightened cellular destruction factors (e.g., ROS, airway secretion, inflammation), which overwhelms cellular cytoprotection tools and causes mass death of injured cells including tumor initiated cells during the pre-neoplastic stage. Nrf2-/- mice also exhibit dysregulated expressions of many genes involved in cell cycle and death (e.g., CDC28 protein kinases, cyclin D1, cyclin dependent kinase inhibitor 2C, B-cell leukemia/lymphoma 6, unc-119 homolog) relative to wild type mice during tumorigenesis. Overall, increased susceptibility to acute injury due to lack of survival signals leading to net cell loss is beneficial to Nrf2-/- mice for their tumor suppression.
Mentions: (A) Biological function and disorder categories of the Nrf2-dependent genes (i.e. differentially expressed between Nrf2+/+ and Nrf2-/- mice) significantly changed in pre-/early neoplastic stage at 12 wk (top) and in tumors at 22 wk (bottom) were analysis by Ingenuity Pathway Analysis (IPA). Top-ranked [-log(p)] categories are depicted and compared between the two tumorigenesis stages. (B) A total of 118 gene transcripts varied significantly (p<0.05) between Nrf2+/+ and Nrf2-/- mice 12 wk after urethane treatment were grouped into 4 expression profiles (set 0–3). Expression level of each transcript was normalized to corresponding Nrf2+/+ saline controls and indicated as relative log ratio [log2 (normalized average intensity)]. Genes are listed in Dataset 1 and in Table 1. Sal = saline-treated lung, UT = urethane-treated lung. (C) Lung tumor genes (n = 376) significantly (p<0.05) different between Nrf2+/+ and Nrf2-/- mice at 22 wk after urethane treatment are clustered into 4 expression profile groups (set 0–3). Expression level of each gene was normalized to that of Nrf2+/+ saline controls and indicated as relative log ratio [log2 (normalized average intensity)]. Genes are listed in Dataset 2 and in Table 2. Sal = saline-treated lung, UN = uninvolved tissue, Tum = tumor tissue. (D) Among the Nrf2-dependently changed genes in pre-/early neoplastic stage at 12 wk (n = 118) and in tumors at 22 wk (n = 376), Venn diagram analysis identified gene transcripts that were changed at either time point (12 and 22 wk) and/or were genes in common between the two time points (i.e. 12 genes).

Bottom Line: However, permanent Nrf2 activation in human lung carcinomas promotes pulmonary malignancy and chemoresistance.Nrf2 modulated expression of genes involved cell-cell signaling, glutathione metabolism and oxidative stress response, and immune responses during early stage neoplasia.Our results were consistent with the concept that Nrf2 over-activation is an adaptive response of cancer conferring resistance to anti-cancer drugs and promoting malignancy.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States of America. alison.bauer@ucdenver.edu

ABSTRACT
Nrf2 is a key transcription factor that regulates cellular redox and defense responses. However, permanent Nrf2 activation in human lung carcinomas promotes pulmonary malignancy and chemoresistance. We tested the hypothesis that Nrf2 has cell survival properties and lack of Nrf2 suppresses chemically-induced pulmonary neoplasia by treating Nrf2(+/+) and Nrf2(-/-) mice with urethane. Airway inflammation and injury were assessed by bronchoalveolar lavage analyses and histopathology, and lung tumors were analyzed by gross and histologic analysis. We used transcriptomics to assess Nrf2-dependent changes in pulmonary gene transcripts at multiple stages of neoplasia. Lung hyperpermeability, cell death and apoptosis, and inflammatory cell infiltration were significantly higher in Nrf2(-/-) mice compared to Nrf2(+/+) mice 9 and 11 wk after urethane. Significantly fewer lung adenomas were found in Nrf2(-/-) mice than in Nrf2(+/+) mice at 12 and 22 wk. Nrf2 modulated expression of genes involved cell-cell signaling, glutathione metabolism and oxidative stress response, and immune responses during early stage neoplasia. In lung tumors, Nrf2-altered genes had roles in transcriptional regulation of cell cycle and proliferation, carcinogenesis, organismal injury and abnormalities, xenobiotic metabolism, and cell-cell signaling genes. Collectively, Nrf2 deficiency decreased susceptibility to urethane-induced lung tumorigenesis in mice. Cell survival properties of Nrf2 were supported, at least in part, by reduced early death of initiated cells and heightened advantage for tumor cell expansion in Nrf2(+/+) mice relative to Nrf2(-/-) mice. Our results were consistent with the concept that Nrf2 over-activation is an adaptive response of cancer conferring resistance to anti-cancer drugs and promoting malignancy.

Show MeSH
Related in: MedlinePlus