ABSTRACT
Increased de novo lipogenesis (DNL) in white adipose tissue is associated with insulin sensitivity. Under both Normal-Chow-Diet and High-Fat-Diet, mice expressing a kinase inactive Cyclin-dependent kinase 6 (Cdk6) allele (K43M) display an increase in DNL in visceral white adipose tissues (VAT) as compared to wild type mice (WT), accompanied by markedly increased lipogenic transcriptional factor Carbohydrate-responsive element-binding proteins (CHREBP) and lipogenic enzymes in VAT but not in the liver. Treatment of WT mice under HFD with a CDK6 inhibitor recapitulates the phenotypes observed in K43M mice. Mechanistically, CDK6 phosphorylates AMP-activated protein kinase, leading to phosphorylation and inactivation of acetyl-CoA carboxylase, a key enzyme in DNL. CDK6 also phosphorylates CHREBP thus preventing its entry into the nucleus. Ablation of runt related transcription factor 1 in K43M mature adipocytes reverses most of the phenotypes observed in K43M mice. These results demonstrate a role of CDK6 in DNL and a strategy to alleviate metabolic syndromes.
Subject(s)
Cyclin-Dependent Kinase 6 , Lipogenesis , Animals , Mice , Adipose Tissue, White/metabolism , Cyclin-Dependent Kinase 6/metabolism , Lipogenesis/genetics , Liver/metabolism , Transcription Factors/metabolismABSTRACT
INTRODUCTION: Human T-cell acute lymphoblastic leukemia/T-cell lymphoblastic lymphoma (T-ALL/LBL) is a type of cancer that originates from the bone marrow and spreads quickly to other organs. Long-term survival rate with current available chemotherapy is less than 20%. Despite the potentially huge market, a truly effective and safe therapy for T-ALL/LBL is elusive. Thus, it is imperative to identify new therapeutic ways to target essential pathways in T-ALL that regulate the proliferation and survival of these cancer cells. AREAS COVERED: The role of the Cyclin-dependent kinase 6 (CDK6) pathway in human T-ALL is of significant interest with major clinical/translational relevance. This review covers the recent advances in elucidating the essential roles of CDK6 and its closely regulated networks in proliferation, survival, and metabolism of T-ALL cells, with new insight into its mechanisms of action which hopefully could trigger the identification of new therapeutic avenues. EXPERT OPINION: Animal models showed that inhibition of CDK6 and its related networks blocked initiation, growth, and survival of T-ALL in vivo. Numerous clinical trials of CDK4/6 inhibitors are ongoing in T-ALL. Specific CDK6 inhibitors alone or novel combination regimens may hopefully delay the progression, or even reverse the symptoms of T-ALL, leading to disease eradication and cure.
Subject(s)
Cyclin-Dependent Kinase 6 , Precursor T-Cell Lymphoblastic Leukemia-Lymphoma , Animals , Humans , Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/drug therapy , Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/metabolism , Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/pathology , T-Lymphocytes/metabolismABSTRACT
Background: Overweight or obesity poses a significant risk of many obesity-related metabolic diseases. Among all the potential new therapies, stem cell-based treatments hold great promise for treating many obesity-related metabolic diseases. However, the mechanisms regulating adipocyte stem cells/progenitors (precursors) are unknown. The aim of this study is to investigate if CDK6 is required for mesenchymal stem cell proliferation and adipocyte differentiation. Methods: Cyclin-dependent kinase 6 (Cdk6) mouse models together with stem cells derived from stromal vascular fraction (SVF) or mouse embryonic fibroblasts (MEFs) of Cdk6 mutant mice were used to determine if CDK6 is required for mesenchymal stem cell proliferation and adipocyte differentiation. Results: We found that mice with a kinase inactive CDK6 mutants (K43M) had fewer precursor residents in the SVF of adult white adipose tissue (WAT). Stem cells from the SVF or MEFs of K43M mice had defects in proliferation and differentiation into the functional fat cells. In contrast, mice with a constitutively active kinase CDK6 mutant (R31C) had the opposite traits. Ablation of RUNX1 in both mature and precursor K43M cells, reversed the phenotypes. Conclusion: These results represent a novel role of CDK6 in regulating precursor numbers, proliferation, and differentiation, suggesting a potential pharmacological intervention for using CDK6 inhibitors in the treatment of obesity-related metabolic diseases.
ABSTRACT
Activation of adipose tissue thermogenesis is a promising strategy in the treatment of obesity and obesity-related metabolic disorders. Kaempferol (KPF) is a predominant dietary flavonoid with multiple pharmacological properties, such as anti-inflammatory and antioxidant activities. In this study, we sought to characterize the role of KPF in adipocyte thermogenesis. We demonstrated that KPF-treated mice were protected from diet-induced obesity, glucose tolerance, and insulin resistance, accompanied by markedly increased energy expenditure, ex vivo oxygen consumption of white fat, and increased expression of proteins related to adaptive thermogenesis. KPF-promoted beige cell formation is a cell-autonomous effect, since the overexpression of cyclin-dependent kinase 6 (CDK6) in preadipocytes partially reversed browning phenotypes observed in KPF-treated cells. Overall, these data implicate that KPF is involved in promoting beige cell formation by suppressing CDK6 protein expression. This study provides evidence that KPF is a promising natural product for obesity treatment by boosting energy expenditure.
Subject(s)
Core Binding Factor Alpha 2 Subunit , Cyclin-Dependent Kinase 6 , Animals , Mice , Cyclin-Dependent Kinase 6/metabolism , Cyclin-Dependent Kinase 6/pharmacology , Cyclin-Dependent Kinase 6/therapeutic use , Core Binding Factor Alpha 2 Subunit/metabolism , Core Binding Factor Alpha 2 Subunit/pharmacology , Core Binding Factor Alpha 2 Subunit/therapeutic use , Adipose Tissue, Brown/metabolism , Kaempferols/pharmacology , Adipocytes , Obesity/drug therapy , Obesity/genetics , Obesity/metabolism , Adipose Tissue, White/metabolism , Diet, High-Fat/adverse effects , Signal Transduction , Thermogenesis , Mice, Inbred C57BL , Energy MetabolismABSTRACT
Adipocyte browning increases energy expenditure by thermogenesis, which has been considered a potential strategy against obesity and its related metabolic diseases. Phytochemicals derived from natural products with the ability to improve adipocyte thermogenesis have aroused extensive attention. Acteoside (Act), a phenylethanoid glycoside, exists in various medicinal or edible plants and has been shown to regulate metabolic disorders. Here, the browning effect of Act was evaluated by stimulating beige cell differentiation from the stromal vascular fraction (SVF) in the inguinal white adipose tissue (iWAT) and 3T3-L1 preadipocytes, and by converting the iWAT-SVF derived mature white adipocytes. Act improves adipocyte browning by differentiation of the stem/progenitors into beige cells and by direct conversion of mature white adipocytes into beige cells. Mechanistically, Act inhibited CDK6 and mTOR, and consequently relieved phosphorylation of the transcription factor EB (TFEB) and increased its nuclear retention, leading to induction of PGC-1α, a driver of mitochondrial biogenesis, and UCP1-dependent browning. These data thus unveil a CDK6-mTORC1-TFEB pathway that regulates Act-induced adipocyte browning.
Subject(s)
Adipose Tissue, White , Metabolic Diseases , Humans , Mechanistic Target of Rapamycin Complex 1/metabolism , Adipose Tissue, White/metabolism , Obesity/drug therapy , Obesity/metabolism , Adipocytes, White/metabolism , Metabolic Diseases/metabolism , Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/metabolism , Cyclin-Dependent Kinase 6/metabolism , Cyclin-Dependent Kinase 6/pharmacologyABSTRACT
ETHNOPHARMACOLOGICAL RELEVANCE: Hypericum perforatum L. (genus Hypericum, family Hypericaceae) is a flowering plant native to Europe, North Africa and Asia, which can be used in the treatment of psychiatric disorder, cardiothoracic depression and diabetes. Crataegus pinnatifida Bunge (genus Crataegus pinnatifida Bunge, family Rosaceae) was another traditional Chinese medicine for treating hyperlipidemia. Hyperoside (Hype), a major flavonoid glycoside component of Hypericum perforatum L. and Crataegus pinnatifida Bunge, possesses multiple physiological activities, such as anti-inflammatory and antioxidant effects. However, the role of Hype on obesity and related metabolic diseases still needs to be further investigated. AIM OF THE STUDY: We explored the effect of Hype on high-fat diet (HFD)-induced obesity and its metabolic regulation on white fat tissues. MATERIALS AND METHODS: In vivo four-week-old male C57BL/6J mice were randomly assigned to vehicle (0.5% methycellulose) and Hype (80 mg/kg/day by gavage) group under a normal chow diet (NCD) or HFD for 8 weeks. In vitro, 3T3-L1 preadipocyte cell line and primary stromal vascular fraction (SVF) cells from inguinal white adipose tissue (iWAT) of mice were used to investigate the molecular mechanisms of Hype regulation on adipocyte energy metabolism. RESULTS: Hype treatment in vivo promotes UCP1-dependent white to beige fat transition, increases glucose and lipid metabolism, and resists HFD-induced obesity. Meanwhile, Hype induces lipophagy, a specific autophagy that facilitates the breakdown of lipid droplets, and blocking autophagy partially reduces UCP1 expression. Mechanistically, Hype inhibited CDK6, leading to the increased nuclear translocation of TFEB, while overexpression of CDK6 partially reversed the enhancement of UCP1 by Hype. CONCLUSIONS: Hype protects mice from HFD-induced obesity by increasing energy expenditure of white fat tissue via CDK6-TFEB pathway.
Subject(s)
Diet, High-Fat , Obesity , Animals , Mice , Adipose Tissue, White , Autophagy , Mice, Inbred C57BL , Obesity/drug therapy , ThermogenesisABSTRACT
The neocortex, the center for higher brain function, first emerged in mammals and has become massively expanded and folded in humans, constituting almost half the volume of the human brain. Primary microcephaly, a developmental disorder in which the brain is smaller than normal at birth, results mainly from there being fewer neurons in the neocortex because of defects in neural progenitor cells (NPCs). Outer radial glia (oRGs), NPCs that are abundant in gyrencephalic species but rare in lissencephalic species, are thought to play key roles in the expansion and folding of the neocortex. However, how oRGs expand, whether they are necessary for neocortical folding, and whether defects in oRGs cause microcephaly remain important questions in the study of brain development, evolution, and disease. Here, we show that oRG expansion in mice, ferrets, and human cerebral organoids requires cyclin-dependent kinase 6 (CDK6), the mutation of which causes primary microcephaly via an unknown mechanism. In a mouse model in which increased Hedgehog signaling expands oRGs and intermediate progenitor cells and induces neocortical folding, CDK6 loss selectively decreased oRGs and abolished neocortical folding. Remarkably, this function of CDK6 in oRG expansion did not require its kinase activity, was not shared by the highly similar CDK4 and CDK2, and was disrupted by the mutation causing microcephaly. Therefore, our results indicate that CDK6 is conserved to promote oRG expansion, that oRGs are necessary for neocortical folding, and that defects in oRG expansion may cause primary microcephaly.
Subject(s)
Cyclin-Dependent Kinase 6 , Ependymoglial Cells , Microcephaly , Neocortex , Animals , Cyclin-Dependent Kinase 6/genetics , Cyclin-Dependent Kinase 6/metabolism , Ependymoglial Cells/cytology , Ependymoglial Cells/enzymology , Ferrets , Hedgehog Proteins/metabolism , Humans , Mice , Microcephaly/genetics , Neocortex/abnormalities , Neocortex/enzymology , Neural Stem Cells/cytology , Neural Stem Cells/enzymology , Organoids/embryologyABSTRACT
BACKGROUND: To investigate the value of endobronchial ultrasound (EBUS) and virtual bronchoscopic navigation (VBN) combined with rapid on-site evaluation (ROSE) in diagnosing peripheral pulmonary lesions (PPLs). METHODS: Between January 1st 2019 to September 1st 2021, EBUS and VBN examination were performed in expected consecutive patients with PPLs who were admitted to Zhangzhou Affiliated Hospital of Fujian Medical University (Fujian, China). Finally, based on the calculation of expected diagnostic yield of R-EBUS biopsy and drop out, 198 eligible patients were randomly divided into ROSE group (100 cases) and non-ROSE group (98 cases). The diagnostic yield of brushing and biopsy, the complications, the procedure time, the diagnosis time and expense during diagnosis were analyzed. RESULTS: In the ROSE group, the positive rate of EBUS brushing and biopsy were 68%, 84%, respectively. The average procedure time and diagnosis time were 18.6 ± 6.8 min, 3.84 ± 4.28 days, respectively, and the average expense was 643.44 ± 706.56 US.$ (4093.15 ± 4494.67 yuan ¥). In the controls, the positive rate of brushing and biopsy were 44%, 74%, respectively. The average procedure time and diagnosis time were 15.4 ± 5.7 min, 6.46 ± 3.66 days, respectively. And the average expense during diagnosis was 1009.27 ± 713.89 US.$ (6420.28 ± 4541.33 yuan ¥). There was significant difference in the positive rate of EBUS brushing and biopsy, diagnosis time and expense during diagnosis between both groups. And no significant difference was observed in the complications and the procedure time. Additionally, the impact of ROSE on diagnostic yield in right upper lobe and the size of lesion ≤ 2 cm in diameter was significant. CONCLUSION: In combination with ROSE, EBUS could significantly improve the positive rate of diagnosing PPLs, shorten diagnosis time and reduce expense during diagnosis. ROSE will be of great importance in the diagnosis of PPLs and medical resource.
Subject(s)
Lung Neoplasms , Rapid On-site Evaluation , Bronchoscopy/methods , Endosonography/methods , Humans , Lung/diagnostic imaging , Lung/pathology , Lung Neoplasms/diagnostic imaging , Lung Neoplasms/pathologyABSTRACT
Cervical carcinoma is a leading malignant tumor among women worldwide, characterized by the dysregulation of cell cycle. Cyclin-dependent kinase 6 (CDK6) plays important roles in the cell cycle progression, cell differentiation, and tumorigenesis. However, the role of CDK6 in cervical cancer remains controversial. Here, we found that loss of CDK6 in cervical adenocarcinoma HeLa cell line inhibited cell proliferation but induced apoptosis as well as autophagy, accompanied by attenuated expression of mammalian target of rapamycin complex 1 (mTORC1) and hexokinase 2 (HK2), reduced glycolysis, and production of protein, nucleotide, and lipid. Similarly, we showed that CDK6 knockout inhibited the survival of CDK6-high CaSki but not CDK6-low SiHa cervical cancer cells by regulation of glycolysis and autophagy process. Collectively, our studies indicate that CDK6 is a critical regulator of human cervical cancer cells, especially with high CDK6 level, through its ability to regulate cellular apoptosis and metabolism. Thus, inhibition of CDK6 kinase activity could be a powerful therapeutic avenue used to treat cervical cancers.
Subject(s)
Cyclin-Dependent Kinase 6 , Uterine Cervical Neoplasms , Apoptosis , Autophagy , Cell Line, Tumor , Cell Proliferation , Female , Glycolysis , HeLa Cells , Hexokinase/genetics , Hexokinase/metabolism , Humans , Male , Mechanistic Target of Rapamycin Complex 1/metabolism , Uterine Cervical Neoplasms/pathologyABSTRACT
BACKGROUND: Obstructive sleep apnea (OSA) has been demonstrated to be associated with an increase of oxidative stress. However, whether circulating malondialdehyde (MDA), a widely used biomarker of oxidative stress, could be reduced by the treatment of OSA by continuous positive airway pressure (CPAP) is debated. The present meta-analysis was performed to determine the effect of CPAP treatment on circulating MDA among patients with OSA. METHODS: A systematic search of PubMed, Embase, and Web of Science was performed for literature covering the period between 1967 and August 2019. Standardized mean difference (SMD) was calculated to estimate the treatment effects of pre- and post-CPAP therapy. RESULTS: A total of 10 studies with 220 patients were included in this meta-analysis. A significant decrease in circulating MDA was observed after CPAP treatment (SMD = 1.164, 95% CI = 0.443 to 1.885, z = 3.16, p = 0.002) in OSA patients. Subgroup analyses revealed that CPAP therapy was associated with a significant decrease of circulating MDA in elder (SMD = 1.629, 95% CI = 0.265 to 2.994, z = 2.34, p = 0.019), more obese patients (SMD = 0.954, 95% CI = 0.435 to 1.473, z = 3.61, p = 0.000), more severe OSA patients (SMD = 0.879, 95% CI = 0.421 to 1.336, z = 3.76, p = 0.000), patients with therapeutic duration ≥ 3 months (SMD = 1.867, 95% CI = 0.563 to 3.172, z = 2.80, p = 0.005), and patients with good compliance (SMD = 1.004, 95% CI = 0.703 to 1.305, z = 6.54, p = 0.000). CONCLUSIONS: This meta-analysis suggested that CPAP therapy exerted significant lowering effects on circulating MDA, especially in elder, more obese, and more severe OSA patients and patients with good compliance as well as longer duration of CPAP application.
Subject(s)
Continuous Positive Airway Pressure , Malondialdehyde/blood , Sleep Apnea, Obstructive/blood , Sleep Apnea, Obstructive/therapy , Adult , Biomarkers/blood , Female , Humans , Male , Middle Aged , Treatment OutcomeABSTRACT
Neural stem cells give rise to granule dentate neurons throughout life in the hippocampus. Upon activation, these stem cells generate fast proliferating progenitors that complete several rounds of divisions before differentiating into neurons. Although the mechanisms regulating the activation of stem cells have been intensively studied, little attention has been given so far to the intrinsic machinery allowing the expansion of the progenitor pool. The cell cycle protein Cdk6 positively regulates the proliferation of hippocampal progenitors, but the mechanism involved remains elusive. Whereas Cdk6 functions primarily as a cell cycle kinase, it can also act as transcriptional regulator in cancer cells and hematopoietic stem cells. Using mouse genetics, we show here that the function of Cdk6 in hippocampal neurogenesis relies specifically on its kinase activity. The present study also reveals a specific regulatory mechanism for Cdk6 in hippocampal progenitors. In contrast to the classical model of the cell cycle, we observe that the Cip/Kip family member p27, rather than the Ink4 family, negatively regulates Cdk6 in the adult hippocampus. Altogether, our data uncover a unique, cell type-specific regulatory mechanism controlling the expansion of hippocampal progenitors, where Cdk6 kinase activity is modulated by p27.
Subject(s)
Cell Proliferation , Cyclin-Dependent Kinase 6/metabolism , Cyclin-Dependent Kinase Inhibitor p27/metabolism , Animals , Cyclin-Dependent Kinase 2/metabolism , Cyclin-Dependent Kinase 6/genetics , Cyclin-Dependent Kinase Inhibitor p18/deficiency , Cyclin-Dependent Kinase Inhibitor p18/genetics , Cyclin-Dependent Kinase Inhibitor p27/genetics , Dentate Gyrus/metabolism , Dentate Gyrus/pathology , Hippocampus/cytology , Hippocampus/metabolism , Hippocampus/pathology , Mice , Mice, Inbred C57BL , Mice, Knockout , Mutagenesis, Site-Directed , Neural Stem Cells/cytology , Neural Stem Cells/metabolism , NeurogenesisABSTRACT
Whereas white adipose tissue depots contribute to the development of metabolic diseases, brown and beige adipose tissue has beneficial metabolic effects. Here we show that CDK6 regulates beige adipocyte formation. We demonstrate that mice lacking the CDK6 protein or its kinase domain (K43M) exhibit significant increases beige cell formation, enhanced energy expenditure, better glucose tolerance, and improved insulin sensitivity, and are more resistant to high-fat diet-induced obesity. Re-expression of CDK6 in Cdk6 -/- mature or precursor cells, or ablation of RUNX1 in K43M mature or precursor cells, reverses these phenotypes. Furthermore, RUNX1 positively regulates the expression of Ucp-1 and Pgc1α by binding to proximal promoter regions. Our findings indicate that CDK6 kinase activity negatively regulates the conversion of fat-storing cells into fat-burning cells by suppressing RUNX1, and suggest that CDK6 may be a therapeutic target for the treatment of obesity and related metabolic diseases.
Subject(s)
Adipose Tissue, Brown/physiology , Adipose Tissue, White/physiology , Core Binding Factor Alpha 2 Subunit/antagonists & inhibitors , Cyclin-Dependent Kinase 6/metabolism , Gene Expression Regulation , Adipocytes/cytology , Animals , Body Composition , Cell Differentiation , Core Binding Factor Alpha 2 Subunit/genetics , Core Binding Factor Alpha 2 Subunit/metabolism , Crosses, Genetic , Cyclin-Dependent Kinase 6/genetics , Diet, High-Fat , Female , Gene Expression Profiling , Glucose Tolerance Test , Male , Metabolic Diseases/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Obesity/genetics , Obesity/metabolism , Oxygen Consumption , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/metabolism , Phenotype , Uncoupling Protein 1/metabolismABSTRACT
Angiogenin (ANG) is a secreted ribonuclease (RNase) with cell-type- and context-specific roles in growth, survival, and regeneration. Although these functions require receptor-mediated endocytosis and appropriate subcellular localization, the identity of the cell surface receptor remains undefined. Here, we show that plexin-B2 (PLXNB2) is the functional receptor for ANG in endothelial, cancer, neuronal, and normal hematopoietic and leukemic stem and progenitor cells. Mechanistically, PLXNB2 mediates intracellular RNA processing that contribute to cell growth, survival, and regenerative capabilities of ANG. Antibodies generated against the ANG-binding site on PLXNB2 restricts ANG activity in vitro and in vivo, resulting in inhibition of established xenograft tumors, ANG-induced neurogenesis and neuroprotection, levels of pro-self-renewal transcripts in hematopoietic and patient-derived leukemic stem and progenitor cells, and reduced progression of leukemia in vivo. PLXNB2 is therefore required for the physiological and pathological functions of ANG and has significant therapeutic potential in solid and hematopoietic cancers and neurodegenerative diseases.
Subject(s)
Nerve Tissue Proteins/metabolism , Ribonuclease, Pancreatic/metabolism , Animals , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Cell Proliferation , Female , Glioblastoma/metabolism , Glioblastoma/pathology , Hematopoietic Stem Cells/metabolism , Heterografts , Humans , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology , Male , Mice , Mice, Inbred C57BL , Neoplasm Transplantation , Nerve Tissue Proteins/antagonists & inhibitors , Neurogenesis , Ribonuclease, Pancreatic/chemistryABSTRACT
Regulation of stem and progenitor cell populations is critical in the development, maintenance, and regeneration of tissues. Here, we define a novel mechanism by which a niche-secreted RNase, angiogenin (ANG), distinctively alters the functional characteristics of primitive hematopoietic stem/progenitor cells (HSPCs) compared with lineage-committed myeloid-restricted progenitor (MyePro) cells. Specifically, ANG reduces the proliferative capacity of HSPC while simultaneously increasing proliferation of MyePro cells. Mechanistically, ANG induces cell-type-specific RNA-processing events: tRNA-derived stress-induced small RNA (tiRNA) generation in HSPCs and rRNA induction in MyePro cells, leading to respective reduction and increase in protein synthesis. Recombinant ANG protein improves survival of irradiated animals and enhances hematopoietic regeneration of mouse and human HSPCs in transplantation. Thus, ANG plays a non-cell-autonomous role in regulation of hematopoiesis by simultaneously preserving HSPC stemness and promoting MyePro proliferation. These cell-type-specific functions of ANG suggest considerable therapeutic potential.
Subject(s)
Hematopoietic Stem Cells/metabolism , Ribonuclease, Pancreatic/metabolism , Animals , Cell Proliferation , Hematopoiesis , Hematopoietic Stem Cells/cytology , Humans , Mice , Mice, Inbred C57BL , Myeloid Cells/metabolism , RNA, Transfer/metabolism , RNA, Untranslated/metabolismSubject(s)
Cell Differentiation , Melanocytes/metabolism , Mutation , Proto-Oncogene Proteins B-raf/genetics , Schwann Cells/metabolism , Animals , Cell Lineage , Crosses, Genetic , Humans , Ki-67 Antigen/metabolism , Melanins/metabolism , Melanocytes/cytology , Mice , Mice, Inbred C57BL , Mice, Transgenic , Neural Crest/metabolism , Phenotype , PigmentationABSTRACT
UNLABELLED: The androgen receptor (AR) is a critical effector of prostate cancer development and progression. Androgen-dependent prostate cancer is reliant on the function of AR for growth and progression. Most castration-resistant prostate cancer (CRPC) remains dependent on AR signaling for survival and growth. Ribosomal RNA (rRNA) is essential for both androgen-dependent and castration-resistant growth of prostate cancer cells. During androgen-dependent growth of prostate cells, androgen-AR signaling leads to the accumulation of rRNA. However, the mechanism by which AR regulates rRNA transcription is unknown. Here, investigation revealed that angiogenin (ANG), a member of the secreted ribonuclease superfamily, is upregulated in prostate cancer and mediates androgen-stimulated rRNA transcription in prostate cancer cells. Upon androgen stimulation, ANG undergoes nuclear translocation in androgen-dependent prostate cancer cells, where it binds to the rDNA promoter and stimulates rRNA transcription. ANG antagonists inhibit androgen-induced rRNA transcription and cell proliferation in androgen-dependent prostate cancer cells. Interestingly, ANG also mediates androgen-independent rRNA transcription through a mechanism that involves its constitutive nuclear translocation in androgen-insensitive prostate cancer cells, resulting in a constant rRNA overproduction and thereby stimulating cell proliferation. Critically, ANG overexpression in androgen-dependent prostate cancer cells enables castration-resistant growth of otherwise androgen-dependent cells. Thus, ANG-stimulated rRNA transcription is not only an essential component for androgen-dependent growth of prostate cancer but also contributes to the transition of prostate cancer from androgen-dependent to castration-resistant growth status. IMPLICATIONS: The ability of angiogenin to regulate rRNA transcription and prostate cancer growth makes it a viable target for therapy.
Subject(s)
Angiogenesis Inducing Agents/metabolism , Prostatic Neoplasms, Castration-Resistant/metabolism , Prostatic Neoplasms/metabolism , RNA, Ribosomal/genetics , Ribonuclease, Pancreatic/metabolism , Androgens/metabolism , Animals , Cell Line, Tumor , Cell Proliferation/drug effects , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Heterografts , Humans , Male , Mice , Mice, SCID , Neoplasm Transplantation , Promoter Regions, Genetic , Prostatic Neoplasms/genetics , Prostatic Neoplasms/pathology , Prostatic Neoplasms, Castration-Resistant/genetics , Prostatic Neoplasms, Castration-Resistant/pathology , Protein Binding , Receptors, Androgen/genetics , Receptors, Androgen/metabolism , Ribonuclease, Pancreatic/antagonists & inhibitors , Transcription, GeneticABSTRACT
Both genetic mutations and UV irradiation (UVR) can predispose individuals to melanoma. Although BRAF(V600E) is the most prevalent oncogene in melanoma, the BRAF(V600E) mutant is not sufficient to induce tumors in vivo. Mutation at the CDKN2A locus is another melanoma-predisposing event that can disrupt the function of both p16(INK4a) and ARF. Numerous studies have focused on the role of p16(INK4a) in melanoma, but the involvement of ARF, a well-known p53 activator, is still controversial. Using a transgenic BRAF(V600E) mouse model previously generated in our laboratory, we report that loss of ARF is able to enhance spontaneous melanoma formation and cause profound sensitivity to neonatal UVB exposure. Mechanistically, BRAF(V600E) and ARF deletion synergize to inhibit nucleotide excision repair by epigenetically repressing XPC and inhibiting the E2F4/DP1 complex. We suggest that the deletion of ARF promotes melanomagenesis not by abrogating p53 activation but by acting in concert with BRAF(V600E) to increase the load of DNA damage caused by UVR.
Subject(s)
Cyclin-Dependent Kinase Inhibitor p16/genetics , DNA-Binding Proteins/genetics , Melanoma, Experimental/genetics , Melanoma/genetics , Neoplasms, Radiation-Induced/genetics , Proto-Oncogene Proteins B-raf/genetics , Animals , Cell Line, Tumor , Cells, Cultured , DNA Methylation , DNA Repair , DNA-Binding Proteins/antagonists & inhibitors , E2F4 Transcription Factor/genetics , Humans , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Promoter Regions, Genetic , Transcription Factor DP1/genetics , Tumor Suppressor Protein p53/genetics , Ultraviolet RaysABSTRACT
Altered RNA processing is an underlying mechanism of amyotrophic lateral sclerosis (ALS). Missense mutations in a number of genes involved in RNA function and metabolisms are associated with ALS. Among these genes is angiogenin (ANG), the fifth member of the vertebrate-specific, secreted ribonuclease superfamily. ANG is an angiogenic ribonuclease, and both its angiogenic and ribonucleolytic activities are important for motor neuron health. Ribonuclease 4 (RNASE4), the fourth member of this superfamily, shares the same promoters with ANG and is co-expressed with ANG. However, the biological role of RNASE4 is unknown. To determine whether RNASE4 is involved in ALS pathogenesis, we sequenced the coding region of RNASE4 in ALS and control subjects and characterized the angiogenic, neurogenic, and neuroprotective activities of RNASE4 protein. We identified an allelic association of SNP rs3748338 with ALS and demonstrated that RNASE4 protein is able to induce angiogenesis in in vitro, ex vivo, and in vivo assays. RNASE4 also induces neural differentiation of P19 mouse embryonal carcinoma cells and mouse embryonic stem cells. Moreover, RNASE4 not only stimulates the formation of neurofilaments from mouse embryonic cortical neurons, but also protects hypothermia-induced degeneration. Importantly, systemic treatment with RNASE4 protein slowed weight loss and enhanced neuromuscular function of SOD1 (G93A) mice.
Subject(s)
Neovascularization, Physiologic , Neurogenesis , Ribonucleases/metabolism , Animals , Base Sequence , Cell Line , DNA Primers , Humans , In Situ Hybridization , Mice , Polymerase Chain Reaction , Polymorphism, Genetic , Ribonucleases/geneticsABSTRACT
Overexpression of cyclin D1 is believed to endow mammary epithelial cells (MEC) with a proliferative advantage by virtue of its contribution to pRB inactivation. Accordingly, abrogation of the kinase-dependent function of cyclin D1 is sufficient to render mice resistant to breast cancer initiated by ErbB2. Here, we report that mouse cyclin D1(KE/KE) MECs (deficient in cyclin D1 activity) upregulate an autophagy-like process but fail to implement ErbB2-induced senescence in vivo. In addition, immortalized cyclin D1(KE/KE) MECs retain high rates of autophagy and reduced ErbB2-mediated transformation in vitro. However, highlighting its dual role during tumorigenesis, downregulation of autophagy led to an increase in senescence in cyclin D1(KE/KE) MECs. Autophagy upregulation was also confirmed in human mammary epithelial cells (HMEC) subjected to genetic and pharmacologic inhibition of cyclin D1 activity and, similar to our murine system, simultaneous inhibition of Cdk4/6 and autophagy in HMECs enhanced the senescence response. Collectively, our findings suggest a previously unrecognized function of cyclin D1 in suppressing autophagy in the mammary epithelium.