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George AJ, Purdue BW, Gould CM, Thomas DW, Handoko Y, Qian H, Quaife-Ryan GA, Morgan KA, Simpson KJ, Thomas WG, Hannan RD. A functional siRNA screen identifies genes modulating angiotensin II-mediated EGFR transactivation. J Cell Sci 2013; 126:5377-90. [PMID: 24046455 DOI: 10.1242/jcs.128280] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The angiotensin type 1 receptor (AT1R) transactivates the epidermal growth factor receptor (EGFR) to mediate cellular growth, however, the molecular mechanisms involved have not yet been resolved. To address this, we performed a functional siRNA screen of the human kinome in human mammary epithelial cells that demonstrate a robust AT1R-EGFR transactivation. We identified a suite of genes encoding proteins that both positively and negatively regulate AT1R-EGFR transactivation. Many candidates are components of EGFR signalling networks, whereas others, including TRIO, BMX and CHKA, have not been previously linked to EGFR transactivation. Individual knockdown of TRIO, BMX or CHKA attenuated tyrosine phosphorylation of the EGFR by angiotensin II stimulation, but this did not occur following direct stimulation of the EGFR with EGF, indicating that these proteins function between the activated AT1R and the EGFR. Further investigation of TRIO and CHKA revealed that their activity is likely to be required for AT1R-EGFR transactivation. CHKA also mediated EGFR transactivation in response to another G protein-coupled receptor (GPCR) ligand, thrombin, indicating a pervasive role for CHKA in GPCR-EGFR crosstalk. Our study reveals the power of unbiased, functional genomic screens to identify new signalling mediators important for tissue remodelling in cardiovascular disease and cancer.
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Affiliation(s)
- Amee J George
- School of Biomedical Sciences, The University of Queensland, St. Lucia, Queensland, 4072, Australia
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de la Cueva A, Ramírez de Molina A, Álvarez-Ayerza N, Ramos MA, Cebrián A, del Pulgar TG, Lacal JC. Combined 5-FU and ChoKα inhibitors as a new alternative therapy of colorectal cancer: evidence in human tumor-derived cell lines and mouse xenografts. PLoS One 2013; 8:e64961. [PMID: 23762272 PMCID: PMC3677921 DOI: 10.1371/journal.pone.0064961] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 04/22/2013] [Indexed: 12/31/2022] Open
Abstract
Background Colorectal cancer (CRC) is the third major cause of cancer related deaths in the world. 5-fluorouracil (5-FU) is widely used for the treatment of colorectal cancer but as a single-agent renders low response rates. Choline kinase alpha (ChoKα), an enzyme that plays a role in cell proliferation and transformation, has been reported overexpressed in many different tumors, including colorectal tumors. ChoKα inhibitors have recently entered clinical trials as a novel antitumor strategy. Methodology/Principal Findings ChoKα specific inhibitors, MN58b and TCD-717, have demonstrated a potent antitumoral activity both in vitro and in vivo against several tumor-derived cell line xenografts including CRC-derived cell lines. The effect of ChoKα inhibitors in combination with 5-FU as a new alternative for the treatment of colon tumors has been investigated both in vitro in CRC-tumour derived cell lines, and in vivo in mouse xenografts models. The effects on thymidilate synthase (TS) and thymidine kinase (TK1) levels, two enzymes known to play an essential role in the mechanism of action of 5-FU, were analyzed by western blotting and quantitative PCR analysis. The combination of 5-FU with ChoKα inhibitors resulted in a synergistic effect in vitro in three different human colon cancer cell lines, and in vivo against human colon xenografts in nude mice. ChoKα inhibitors modulate the expression levels of TS and TK1 through inhibition of E2F production, providing a rational for its mechanism of action. Conclusion/Significance Our data suggest that both drugs in combination display a synergistic antitumoral effect due to ChoKα inhibitors-driven modulation of the metabolization of 5-FU. The clinical relevance of these findings is strongly supported since TCD-717 has recently entered Phase I clinical trials against solid tumors.
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Affiliation(s)
- Ana de la Cueva
- Traslational Oncology Unit, Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain
| | - Ana Ramírez de Molina
- Traslational Oncology Unit, Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain
| | - Néstor Álvarez-Ayerza
- Traslational Oncology Unit, Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain
| | - Ma Angeles Ramos
- Traslational Oncology Unit, Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain
| | - Arancha Cebrián
- Traslational Oncology Unit, Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain
| | | | - Juan Carlos Lacal
- Traslational Oncology Unit, Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain
- Instituto de Investigación Sanitaria IdiPAZ, Madrid, Spain
- * E-mail:
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Dominguez CL, Floyd DH, Xiao A, Mullins GR, Kefas BA, Xin W, Yacur MN, Abounader R, Lee JK, Wilson GM, Harris TE, Purow BW. Diacylglycerol kinase α is a critical signaling node and novel therapeutic target in glioblastoma and other cancers. Cancer Discov 2013; 3:782-97. [PMID: 23558954 DOI: 10.1158/2159-8290.cd-12-0215] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Although diacylglycerol kinase α (DGKα) has been linked to several signaling pathways related to cancer cell biology, it has been neglected as a target for cancer therapy. The attenuation of DGKα activity via DGKα-targeting siRNA and small-molecule inhibitors R59022 and R59949 induced caspase-mediated apoptosis in glioblastoma cells and in other cancers, but lacked toxicity in noncancerous cells. We determined that mTOR and hypoxia-inducible factor-1α (HIF-1α) are key targets of DGKα inhibition, in addition to its regulation of other oncogenes. DGKα regulates mTOR transcription via a unique pathway involving cyclic AMP. Finally, we showed the efficacy of DGKα inhibition with short hairpin RNA or a small-molecule agent in glioblastoma and melanoma xenograft treatment models, with growth delay and decreased vascularity. This study establishes DGKα as a central signaling hub and a promising therapeutic target in the treatment of cancer.
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Affiliation(s)
- Charli L Dominguez
- Division of Neuro-Oncology, Department of Neurology, College of Nursing and Health Professions, University of Southern Indiana, Evansville, Indiana, USA
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Metabolic biomarkers for response to PI3K inhibition in basal-like breast cancer. Breast Cancer Res 2013; 15:R16. [PMID: 23448424 PMCID: PMC3672699 DOI: 10.1186/bcr3391] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 02/28/2013] [Indexed: 12/18/2022] Open
Abstract
Introduction The phosphatidylinositol 3-kinase (PI3K) pathway is frequently activated in cancer cells through numerous mutations and epigenetic changes. The recent development of inhibitors targeting different components of the PI3K pathway may represent a valuable treatment alternative. However, predicting efficacy of these drugs is challenging, and methods for therapy monitoring are needed. Basal-like breast cancer (BLBC) is an aggressive breast cancer subtype, frequently associated with PI3K pathway activation. The objectives of this study were to quantify the PI3K pathway activity in tissue sections from xenografts representing basal-like and luminal-like breast cancer before and immediately after treatment with PI3K inhibitors, and to identify metabolic biomarkers for treatment response. Methods Tumor-bearing animals (n = 8 per treatment group) received MK-2206 (120 mg/kg/day) or BEZ235 (50 mg/kg/day) for 3 days. Activity in the PI3K/Akt/mammalian target of rapamycin pathway in xenografts and human biopsies was evaluated using a novel method for semiquantitative assessment of Aktser473 phosphorylation. Metabolic changes were assessed by ex vivo high-resolution magic angle spinning magnetic resonance spectroscopy. Results Using a novel dual near-infrared immunofluorescent imaging method, basal-like xenografts had a 4.5-fold higher baseline level of pAktser473 than luminal-like xenografts. Following treatment, basal-like xenografts demonstrated reduced levels of pAktser473 and decreased proliferation. This correlated with metabolic changes, as both MK-2206 and BEZ235 reduced lactate concentration and increased phosphocholine concentration in the basal-like tumors. BEZ235 also caused increased glucose and glycerophosphocholine concentrations. No response to treatment or change in metabolic profile was seen in luminal-like xenografts. Analyzing tumor sections from five patients with BLBC demonstrated that two of these patients had an elevated pAktser473 level. Conclusion The activity of the PI3K pathway can be determined in tissue sections by quantitative imaging using an antibody towards pAktser473. Long-term treatment with MK-2206 or BEZ235 resulted in significant growth inhibition in basal-like, but not luminal-like, xenografts. This indicates that PI3K inhibitors may have selective efficacy in basal-like breast cancer with increased PI3K signaling, and identifies lactate, phosphocholine and glycerophosphocholine as potential metabolic biomarkers for early therapy monitoring. In human biopsies, variable pAktser473 levels were observed, suggesting heterogeneous PI3K signaling activity in BLBC.
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Sahún-Roncero M, Rubio-Ruiz B, Saladino G, Conejo-García A, Espinosa A, Velázquez-Campoy A, Gervasio FL, Entrena A, Hurtado-Guerrero R. The mechanism of allosteric coupling in choline kinase α1 revealed by the action of a rationally designed inhibitor. Angew Chem Int Ed Engl 2013; 52:4582-6. [PMID: 23441033 DOI: 10.1002/anie.201209660] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 01/16/2013] [Indexed: 01/21/2023]
Abstract
Applying a CHOK hold: Combined experimental and computational studies of the binding mode of a rationally designed inhibitor of the dimeric choline kinase α1 (CHOKα1) explain the molecular mechanism of negative cooperativity (see scheme) and how the monomers are connected. The results give insight into how the symmetry of the dimer can be partially conserved despite a lack of conservation in the static crystal structures.
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Affiliation(s)
- María Sahún-Roncero
- Institute of Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza, BIFI-IQFR (CSIC) Joint Unit, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D; Fundacion ARAID, Edificio Pignatelli 36, Spain
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Sahún-Roncero M, Rubio-Ruiz B, Saladino G, Conejo-García A, Espinosa A, Velázquez-Campoy A, Gervasio FL, Entrena A, Hurtado-Guerrero R. The Mechanism of Allosteric Coupling in Choline Kinase α1 Revealed by the Action of a Rationally Designed Inhibitor. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201209660] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Hudson CS, Knegtel RM, Brown K, Charlton PA, Pollard JR. Kinetic and mechanistic characterisation of Choline Kinase-α. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:1107-16. [PMID: 23416529 DOI: 10.1016/j.bbapap.2013.02.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 02/01/2013] [Accepted: 02/05/2013] [Indexed: 10/27/2022]
Abstract
Choline Kinase is a key component of the Kennedy pathway that converts choline into a number of structural and signalling lipids that are essential for cell growth and survival. One member of the family, Choline Kinase-α (ChoKα) is frequently up-regulated in human cancers, and expression of ChoKα is sufficient to transform cells. Consequently ChoKα has been studied as a potential target for therapeutic agents in cancer research. Despite great interest in the enzyme, mechanistic studies have not been reported. In this study, a combination of initial velocity and product inhibition studies, together with the kinetic and structural characterisation of a novel ChoKα inhibitor is used to support a mechanism of action for human ChoKα. Substrate and inhibition kinetics are consistent with an iso double displacement mechanism, in which the γ-phosphate from ATP is transferred to choline in two distinct steps via a phospho-enzyme intermediate. Co-crystal structures, and existing site-specific mutation studies, support an important role for Asp306, in stabilising the phospho-enzyme intermediate. The kinetics also indicate a distinct kinetic (isomerisation) step associated with product release, which may be attributed to a conformational change in the protein to disrupt an interaction between Asp306 and the phosphocholine product, facilitating product release. This study describes a mechanism for ChoKα that is unusual amongst kinases, and highlights the availability of different enzyme states that can be exploited for drug discovery.
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Falcon SC, Hudson CS, Huang Y, Mortimore M, Golec JM, Charlton PA, Weber P, Sundaram H. A non-catalytic role of choline kinase alpha is important in promoting cancer cell survival. Oncogenesis 2013; 2:e38. [PMID: 25522435 PMCID: PMC3641355 DOI: 10.1038/oncsis.2013.2] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 01/11/2013] [Accepted: 01/17/2013] [Indexed: 01/09/2023] Open
Abstract
Choline kinase alpha (ChoKα) is regarded as an attractive cancer target. The enzyme catalyses the formation of phosphocholine(PCho), an important precursor in the generation of phospholipids essential for cell growth. ChoKα has oncogenic properties and is critical for the survival of cancer cells. Overexpression of the ChoKα protein can transform noncancer cells into cells with a cancerous phenotype, and depletion of the ChoKα protein can result in cancer cell death. However, the mechanisms underlying the tumourigenic properties of ChoKα are not fully understood. ChoKα was recently demonstrated to associate with other oncogenic proteins, raising the possibility that a non-catalytic protein scaffolding function drives the tumourigenic properties of ChoKα rather than a catalytic function. In order to differentiate these two roles, we compared the impact on cancer cell survival using two tools specific for ChoKα: (1) small interfering RNA (siRNA) to knockdown the ChoKα protein levels; and (2) compound V-11-0711, a novel potent and selective ChoKα inhibitor (ChoKα IC50 20 nM), to impede the catalytic activity. Both treatments targeted the endogenous ChoKα protein in HeLa cells, as demonstrated by a substantial reduction in the PCho levels. siRNA knockdown of the ChoKα protein in HeLa cells resulted in significant cell death through apoptosis. In contrast, compound V-11-0711 caused a reversible growth arrest. This suggests that inhibition of ChoKα catalytic activity alone is not sufficient to kill cancer cells, and leads us to conclude that there is a role for the ChoKα protein in promoting cancer cell survival that is independent of its catalytic activity.
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Affiliation(s)
- S C Falcon
- Vertex Pharmaceuticals (Europe) Limited, Abingdon, Oxfordshire, UK
| | - C S Hudson
- Vertex Pharmaceuticals (Europe) Limited, Abingdon, Oxfordshire, UK
| | - Y Huang
- Vertex Pharmaceuticals Inc, Cambridge, MA, USA
| | - M Mortimore
- Vertex Pharmaceuticals (Europe) Limited, Abingdon, Oxfordshire, UK
| | - J M Golec
- Vertex Pharmaceuticals (Europe) Limited, Abingdon, Oxfordshire, UK
| | - P A Charlton
- Vertex Pharmaceuticals (Europe) Limited, Abingdon, Oxfordshire, UK
| | - P Weber
- Vertex Pharmaceuticals (Europe) Limited, Abingdon, Oxfordshire, UK
| | - H Sundaram
- Vertex Pharmaceuticals (Europe) Limited, Abingdon, Oxfordshire, UK
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Barlin JN, Jelinic P, Olvera N, Bogomolniy F, Bisogna M, Dao F, Barakat RR, Chi DS, Levine DA. Validated gene targets associated with curatively treated advanced serous ovarian carcinoma. Gynecol Oncol 2012; 128:512-7. [PMID: 23168173 DOI: 10.1016/j.ygyno.2012.11.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 11/09/2012] [Accepted: 11/10/2012] [Indexed: 10/27/2022]
Abstract
OBJECTIVES High-grade serous ovarian cancer (HGSOC) mostly presents at an advanced stage and has a low overall survival rate. However, a subgroup of patients are seemingly cured after standard initial therapy. We hypothesize that the molecular profiles of these patients vary from long-term survivors who recur. METHODS Patients with advanced HGSOC who underwent primary cytoreductive surgery and platinum-based chemotherapy were identified from The Cancer Genome Atlas (TCGA) and institutional (MSKCC) samples. A curative-intent group was defined by recurrence-free survival of >5years. A long-term recurrent group was composed of patients who recurred but survived >5years. RNA was hybridized to Affymetrix U133A transcription microarrays. The NanoString nCounter gene expression system was used for validation in an independent patient population. RESULTS In 30 curative and 84 recurrent patients, class comparison identified twice as many differentially expressed probes between the groups than expected by chance alone. TCGA and MSKCC data sets had 19 overlapping genes. Pathway analyses identified over-represented networks that included nuclear factor kappa B (NFkB) transcription and extracellular signal-regulated kinase (ERK) signaling. External validation was performed in an independent population of 28 curative and 38 recurrent patients. Three genes (CYP4B1, CEPT1, CHMP4A) in common between our original data sets remained differentially expressed in the external validation data. CONCLUSIONS There are distinct transcriptional elements in HGSOC from patients likely to be cured by standard primary therapy. Three genes have withstood rigorous validation and are plausible targets for further study, which may provide insight into molecular features associated with long-term survival and chemotherapy resistance mechanisms.
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Affiliation(s)
- Joyce N Barlin
- Gynecology Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
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Arsenault DJ, Yoo BH, Rosen KV, Ridgway ND. ras-Induced up-regulation of CTP:phosphocholine cytidylyltransferase α contributes to malignant transformation of intestinal epithelial cells. J Biol Chem 2012; 288:633-43. [PMID: 23155050 DOI: 10.1074/jbc.m112.347682] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Cancer cells have enhanced lipogenic capacity characterized by increased synthesis of fatty acids and complex lipids, including phosphatidylcholine (PC). As the rate-limiting enzyme in the CDP-choline pathway for PC synthesis, CTP:phosphocholine cytidylyltransferase α (CCTα) is implicated in the provision of membranes and bioactive lipids necessary of cell proliferation. In this study, we assessed the role of CCTα in malignant intestinal epithelial cells transformed with activated H-ras (IEC-ras). Three IEC-ras clones had significant up-regulation CCTα expression, but PC synthesis and in vitro activity of CCTα were similar to control IEC. RNA interference of CCTα in adherent IEC-ras did not affect PC synthesis, confirming that the enzyme was relatively inactive. However, CCTα silencing in ras-transformed IEC reduced anchorage-independent growth, a criterion for malignant transformation, as well as tumorigenicity in mice. Relative to their adherent counterparts, detached IEC-ras had increased PC synthesis that was attenuated by inducible CCTα silencing. Detachment of IEC-ras was accompanied by increased CCTα phosphorylation and cytosolic enzyme activity. We conclude that the expanded pool of CCTα in IEC-ras is activated by detachment. This provides the increased PC biosynthetic capacity that contributes to malignant transformation of intestinal epithelial cells when detached from the extracellular matrix.
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Affiliation(s)
- Daniel J Arsenault
- Atlantic Research Centre, Department of Pediatrics and Biochemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
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Agassandian M, Mallampalli RK. Surfactant phospholipid metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1831:612-25. [PMID: 23026158 DOI: 10.1016/j.bbalip.2012.09.010] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 09/07/2012] [Accepted: 09/16/2012] [Indexed: 12/16/2022]
Abstract
Pulmonary surfactant is essential for life and is composed of a complex lipoprotein-like mixture that lines the inner surface of the lung to prevent alveolar collapse at the end of expiration. The molecular composition of surfactant depends on highly integrated and regulated processes involving its biosynthesis, remodeling, degradation, and intracellular trafficking. Despite its multicomponent composition, the study of surfactant phospholipid metabolism has focused on two predominant components, disaturated phosphatidylcholine that confers surface-tension lowering activities, and phosphatidylglycerol, recently implicated in innate immune defense. Future studies providing a better understanding of the molecular control and physiological relevance of minor surfactant lipid components are needed. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.
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Affiliation(s)
- Marianna Agassandian
- Department of Medicine, Acute Lung Injury Center of Excellence, the University of Pittsburgh, Pittsburgh, PA 15213, USA
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Choline-releasing glycerophosphodiesterase EDI3 drives tumor cell migration and metastasis. Proc Natl Acad Sci U S A 2012; 109:8155-60. [PMID: 22570503 DOI: 10.1073/pnas.1117654109] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Metastasis from primary tumors remains a major problem for tumor therapy. In the search for markers of metastasis and more effective therapies, the tumor metabolome is relevant because of its importance to the malignant phenotype and metastatic capacity of tumor cells. Altered choline metabolism is a hallmark of cancer. More specifically, a decreased glycerophosphocholine (GPC) to phosphocholine (PC) ratio was reported in breast, ovarian, and prostate cancers. Improved strategies to exploit this altered choline metabolism are therefore required. However, the critical enzyme cleaving GPC to produce choline, the initial step in the pathway controlling the GPC/PC ratio, remained unknown. In the present work, we have identified the enzyme, here named EDI3 (endometrial differential 3). Purified recombinant EDI3 protein cleaves GPC to form glycerol-3-phosphate and choline. Silencing EDI3 in MCF-7 cells decreased this enzymatic activity, increased the intracellular GPC/PC ratio, and decreased downstream lipid metabolites. Downregulating EDI3 activity inhibited cell migration via disruption of the PKCα signaling pathway, with stable overexpression of EDI3 showing the opposite effect. EDI3 was originally identified in our screening study comparing mRNA levels in metastasizing and nonmetastasizing endometrial carcinomas. Both Kaplan-Meier and multivariate analyses revealed a negative association between high EDI3 expression and relapse-free survival time in both endometrial (P < 0.001) and ovarian (P = 0.029) cancers. Overall, we have identified EDI3, a key enzyme controlling GPC and choline metabolism. Because inhibition of EDI3 activity corrects the GPC/PC ratio and decreases the migration capacity of tumor cells, it represents a possible target for therapeutic intervention.
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Zhu M, Fischl AS, Trowbridge MA, Shannon HE. Reproducibility of total choline/water ratios in mouse U87MG xenograft tumors by 1H-MRS. J Magn Reson Imaging 2012; 36:459-67. [DOI: 10.1002/jmri.23664] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2011] [Accepted: 03/07/2012] [Indexed: 12/17/2022] Open
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Gruber J, See Too WC, Wong MT, Lavie A, McSorley T, Konrad M. Balance of human choline kinase isoforms is critical for cell cycle regulation. FEBS J 2012; 279:1915-28. [DOI: 10.1111/j.1742-4658.2012.08573.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Fan TWM, Lorkiewicz PK, Sellers K, Moseley HNB, Higashi RM, Lane AN. Stable isotope-resolved metabolomics and applications for drug development. Pharmacol Ther 2012; 133:366-91. [PMID: 22212615 PMCID: PMC3471671 DOI: 10.1016/j.pharmthera.2011.12.007] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 12/06/2011] [Indexed: 12/14/2022]
Abstract
Advances in analytical methodologies, principally nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS), during the last decade have made large-scale analysis of the human metabolome a reality. This is leading to the reawakening of the importance of metabolism in human diseases, particularly cancer. The metabolome is the functional readout of the genome, functional genome, and proteome; it is also an integral partner in molecular regulations for homeostasis. The interrogation of the metabolome, or metabolomics, is now being applied to numerous diseases, largely by metabolite profiling for biomarker discovery, but also in pharmacology and therapeutics. Recent advances in stable isotope tracer-based metabolomic approaches enable unambiguous tracking of individual atoms through compartmentalized metabolic networks directly in human subjects, which promises to decipher the complexity of the human metabolome at an unprecedented pace. This knowledge will revolutionize our understanding of complex human diseases, clinical diagnostics, as well as individualized therapeutics and drug response. In this review, we focus on the use of stable isotope tracers with metabolomics technologies for understanding metabolic network dynamics in both model systems and in clinical applications. Atom-resolved isotope tracing via the two major analytical platforms, NMR and MS, has the power to determine novel metabolic reprogramming in diseases, discover new drug targets, and facilitates ADME studies. We also illustrate new metabolic tracer-based imaging technologies, which enable direct visualization of metabolic processes in vivo. We further outline current practices and future requirements for biochemoinformatics development, which is an integral part of translating stable isotope-resolved metabolomics into clinical reality.
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Affiliation(s)
- Teresa W-M Fan
- Department of Chemistry, University of Louisville, KY 40292, USA.
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KUCHTA ANNAM, KELLY PHILIPM, STANTON CATHERINE, DEVERY ROSALEENA. Milk fat globule membrane - a source of polar lipids for colon health? A review. INT J DAIRY TECHNOL 2012. [DOI: 10.1111/j.1471-0307.2011.00759.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Natarajan N, Telang S, Miller D, Chesney J. Novel immunotherapeutic agents and small molecule antagonists of signalling kinases for the treatment of metastatic melanoma. Drugs 2011; 71:1233-50. [PMID: 21770473 DOI: 10.2165/11591380-000000000-00000] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Melanoma incidence is increasing annually and over 40,000 die of this disease each year worldwide. In this review, we discuss the rationale and recent trial results of several novel immunotherapeutic approaches and small molecule inhibitors of signalling kinases. Ipilimumab is a humanized anti-CTLA4 antibody that has been proven to increase the median overall survival of large cohorts of patients with unresectable melanoma in two phase III trials. OncoVEX(GM-CSF) is an oncolytic herpes simplex virus-1 recombined with granulocyte-macrophage colony-stimulating factor that has demonstrated durable objective responses in a phase II trial. Tumour-infiltrating lymphocytes given after lymphocyte depletion and followed by high-dose interleukin (IL)-2 yield durable complete responses in a significant percentage of melanoma patients. Lastly, denileukin diftitox, a fusion of IL-2 and diphtheria toxin, was recently observed to deplete regulatory T cells and cause durable partial responses, particularly in chemo/immune-naïve patients. These agents are enabling the rational design of novel combination trials to simultaneously increase antigen presentation, deplete regulatory T cells and block immune check-points in order to activate melanoma antigen-specific immunity. Although melanoma metastases have been found to contain thousands of mutations, the V600E BRAF mutation is clearly a driver of the neoplastic phenotype and is present in 40-60% of melanomas. Two separate small molecule antagonists of B-Raf have been found to yield very high partial response rates in metastatic melanoma, and the B-Raf inhibitor, vemurafenib (PLX4032), was recently observed to increase median overall survival in an interim analysis. However, B-Raf inhibitor resistance through up-regulation or activating mutations of alternative oncogenic signalling receptors and enzymes is proving to be a major challenge. Inhibitors of c-Kit and mitogen-activated protein kinase (MEK) have also been found to have activity against melanomas and MEK inhibitors are now being examined as a strategy to overcome B-Raf inhibitor resistance. In summary, these studies reveal that, for the first time, several immunotherapeutic and targeted agents are yielding dramatic clinical responses and improvements in overall survival in patients with unresectable stage III and IV melanoma.
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Affiliation(s)
- Nagendra Natarajan
- Division of Medical Oncology/Hematology, University of Louisville School of Medicine, James Graham Brown Cancer Center, KY 40202, USA
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Abstract
Abnormal choline metabolism is emerging as a metabolic hallmark that is associated with oncogenesis and tumour progression. Following transformation, the modulation of enzymes that control anabolic and catabolic pathways causes increased levels of choline-containing precursors and breakdown products of membrane phospholipids. These increased levels are associated with proliferation, and recent studies emphasize the complex reciprocal interactions between oncogenic signalling and choline metabolism. Because choline-containing compounds are detected by non-invasive magnetic resonance spectroscopy (MRS), increased levels of these compounds provide a non-invasive biomarker of transformation, staging and response to therapy. Furthermore, enzymes of choline metabolism, such as choline kinase, present novel targets for image-guided cancer therapy.
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Affiliation(s)
- Kristine Glunde
- The Johns Hopkins University In Vivo Cellular and Molecular Imaging Center, The Russell H. Morgan Department of Radiology and Radiological Science, 720 Rutland Avenue, 212 Traylor Building, Baltimore, Maryland 21205, USA
- Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland 21231, USA
| | - Zaver M. Bhujwalla
- The Johns Hopkins University In Vivo Cellular and Molecular Imaging Center, The Russell H. Morgan Department of Radiology and Radiological Science, 720 Rutland Avenue, 212 Traylor Building, Baltimore, Maryland 21205, USA
- Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland 21231, USA
| | - Sabrina M. Ronen
- Department of Radiology, University of California San Francisco School of Medicine, UCSF Mission Bay Campus, Byers Hall, San Francisco, California CA94158-2330, USA
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Miyake T, Parsons SJ. Functional interactions between Choline kinase α, epidermal growth factor receptor and c-Src in breast cancer cell proliferation. Oncogene 2011; 31:1431-41. [PMID: 21822308 PMCID: PMC3213328 DOI: 10.1038/onc.2011.332] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Epidermal growth factor receptor (EGFR) family members and c-Src are co-overexpressed in many cancers. The synergistic effect of EGFR and c-Src has been shown in the tumorigenesis of breast and other cancers. Reported mechanisms of synergy include transcriptional regulation by STAT5b and the regulation of cellular ATP production by mitochondrial protein COX II. Here, we report a new mechanism of EGFR-c-Src synergy through choline kinase α (CHKA). The first enzyme of the phosphatidyl choline production pathway, CHKA, is overexpressed in many cancers, and the product of the enzyme, phosphocholine, is also increased in tumor cells. In this report, we find that CHKA forms a complex with EGFR in a c-Src-dependent manner. Endogenous CHKA and EGFR co-immunoprecipitated from a variety of breast cancer cell lines and immortalized mammary epithelial cells. CHKA interacted with the EGFR kinase domain upon c-Src co-overexpression and was phosphorylated in a c-Src-dependent manner on Y197 and Y333. Overexpression of EGFR and c-Src increased total cellular activity and protein levels of CHKA. Mutation of CHKA Y197 and Y333 reduced complex formation, EGFR-dependent activation of CHKA enzyme activity and epidermal growth factor (EGF)-dependent DNA synthesis. Furthermore, small interfering RNA-mediated knockdown of CHKA in MCF-7 and MCF-10A cells reduced EGF-dependent cell proliferation. Together, these results strongly implicate a new c-Src-dependent link between CHKA and EGFR, which contributes to the regulation of cell proliferation and tumorigenesis.
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Affiliation(s)
- T Miyake
- Department of Microbiology and Cancer Center, University of Virginia Health System, Charlottesville, VA, USA
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70
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Glunde K, Jiang L, Moestue SA, Gribbestad IS. MRS and MRSI guidance in molecular medicine: targeting and monitoring of choline and glucose metabolism in cancer. NMR IN BIOMEDICINE 2011; 24:673-90. [PMID: 21793073 PMCID: PMC3146026 DOI: 10.1002/nbm.1751] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
MRS and MRSI are valuable tools for the detection of metabolic changes in tumors. The currently emerging era of molecular medicine, which is shaped by molecularly targeted anticancer therapies combined with molecular imaging of the effects of such therapies, requires powerful imaging technologies that are able to detect molecular information. MRS and MRSI are such technologies that are able to detect metabolites arising from glucose and choline metabolism in noninvasive in vivo settings and at higher resolution in tissue samples. The roles played by MRS and MRSI in the diagnosis of different types of cancer, as well as in the early monitoring of the tumor response to traditional chemotherapies, are reviewed. The emerging roles of MRS and MRSI in the development and detection of novel targeted anticancer therapies that target oncogenic signaling pathways or markers in choline or glucose metabolism are discussed.
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Affiliation(s)
- Kristine Glunde
- Johns Hopkins University In Vivo Cellular and Molecular Imaging Center, Russell H. Morgan, Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Lu Jiang
- Johns Hopkins University In Vivo Cellular and Molecular Imaging Center, Russell H. Morgan, Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Siver A. Moestue
- Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway
| | - Ingrid S. Gribbestad
- Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway
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71
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Podo F, Canevari S, Canese R, Pisanu ME, Ricci A, Iorio E. MR evaluation of response to targeted treatment in cancer cells. NMR IN BIOMEDICINE 2011; 24:648-672. [PMID: 21387442 DOI: 10.1002/nbm.1658] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 11/22/2010] [Accepted: 11/29/2010] [Indexed: 05/30/2023]
Abstract
The development of molecular technologies, together with progressive sophistication of molecular imaging methods, has allowed the further elucidation of the multiple mutations and dysregulatory effects of pathways leading to oncogenesis. Acting against these pathways by specifically targeted agents represents a major challenge for current research efforts in oncology. As conventional anatomically based pharmacological endpoints may be inadequate to monitor the tumor response to these targeted treatments, the identification and use of more appropriate, noninvasive pharmacodynamic biomarkers appear to be crucial to optimize the design, dosage and schedule of these novel therapeutic approaches. An aberrant choline phospholipid metabolism and enhanced flux of glucose derivatives through glycolysis, which sustain the redirection of mitochondrial ATP to glucose phosphorylation, are two major hallmarks of cancer cells. This review focuses on the changes detected in these pathways by MRS in response to targeted treatments. The progress and limitations of our present understanding of the mechanisms underlying MRS-detected phosphocholine accumulation in cancer cells are discussed in the light of gene and protein expression and the activation of different enzymes involved in phosphatidylcholine biosynthesis and catabolism. Examples of alterations induced in the MRS choline profile of cells exposed to different agents or to tumor environmental factors are presented. Current studies aimed at the identification in cancer cells of MRS-detected pharmacodynamic markers of therapies targeted against specific conditional or constitutive cell receptor stimulation are then reviewed. Finally, the perspectives of present efforts addressed to identify enzymes of the phosphatidylcholine cycle as possible novel targets for anticancer therapy are summarized.
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Affiliation(s)
- Franca Podo
- Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy.
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Moestue SA, Engebraaten O, Gribbestad IS. Metabolic effects of signal transduction inhibition in cancer assessed by magnetic resonance spectroscopy. Mol Oncol 2011; 5:224-41. [PMID: 21536506 DOI: 10.1016/j.molonc.2011.04.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 04/13/2011] [Accepted: 04/14/2011] [Indexed: 12/31/2022] Open
Abstract
Despite huge efforts in development of drugs targeting oncogenic signalling, the number of such drugs entering clinical practice to date remains limited. Rational use of biomarkers for drug candidate selection and early monitoring of response to therapy may accelerate this process. Magnetic resonance spectroscopy (MRS) can be used to assess metabolic effects of drug treatment both in vivo and in vitro, and technological advances are continuously increasing the utility of this non-invasive method. In this review, we summarise the use of MRS for monitoring the effect of targeted anticancer drugs, and discuss the potential role of MRS in the context of personalised cancer treatment.
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Affiliation(s)
- Siver Andreas Moestue
- Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
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A novel small molecule antagonist of choline kinase-α that simultaneously suppresses MAPK and PI3K/AKT signaling. Oncogene 2011; 30:3370-80. [PMID: 21423211 PMCID: PMC3136659 DOI: 10.1038/onc.2011.51] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Choline kinase-α expression and activity are increased in multiple human neoplasms as a result of growth factor stimulation and activation of cancer-related signaling pathways. The product of choline kinase-α, phosphocholine, serves as an essential metabolic reservoir for the production of phosphatidylcholine, the major phospholipid constituent of membranes and substrate for the production of lipid second messengers. Using in silico screening for small molecules that may interact with the choline kinase-α substrate binding domain, we identified a novel competitive inhibitor, N-(3,5-dimethylphenyl)-2-[[5-(4-ethylphenyl)-1H-1,2,4-triazol-3-yl]sulfanyl] acetamide (termed CK37) that inhibited purified recombinant human choline kinase-α activity, reduced the steady-state concentration of phosphocholine in transformed cells, and selectively suppressed the growth of neoplastic cells relative to normal epithelial cells. Choline kinase-α activity is required for the downstream production of phosphatidic acid, a promoter of several Ras signaling pathways. CK37 suppressed MAPK and PI3K/AKT signaling, disrupted actin cytoskeletal organization, and reduced plasma membrane ruffling. Finally, administration of CK37 significantly decreased tumor growth in a lung tumor xenograft mouse model, suppressed tumor phosphocholine, and diminished activating phosphorylations of ERK and AKT in vivo. Together, these results further validate choline kinase-α as a molecular target for the development of agents that interrupt Ras signaling pathways, and indicate that receptor-based computational screening should facilitate the identification of new classes of choline kinase-α inhibitors.
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Human prostate cell lines from normal and tumourigenic epithelia differ in the pattern and control of choline lipid headgroups released into the medium on stimulation of protein kinase C. Br J Cancer 2011; 104:673-84. [PMID: 21266973 PMCID: PMC3049586 DOI: 10.1038/sj.bjc.6606077] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Background: Expression of protein kinase C alpha (PKCα) is elevated in prostate cancer (PCa); thus, we have studied whether the development of tumourigenesis in prostate epithelial cell lines modifies the normal pattern of choline (Cho) metabolite release on PKC activation. Methods: Normal and tumourigenic human prostate epithelial cell lines were incubated with [3H]-Cho to label choline phospholipids. Protein kinase C was activated with phorbol ester and blocked with inhibitors. Choline metabolites were resolved by ion-exchange chromatography. Phospholipase D (PLD) activity was measured by transphosphatidylation. Protein expression was detected by western blotting and/or RT–PCR. Choline uptake was measured on cells in monolayers over 60 min. Results: Normal prostate epithelial cell lines principally released phosphocholine (PCho) in contrast to tumourigenic lines, which released Cho. In addition, only with normal cell lines did PKC activation stimulate Cho metabolite release. Protein kinase C alpha expression varied between normal and tumourigenic cell lines but all showed a PKCα link to myristoylated alanine-rich C kinase substrate (MARCKS) protein. The five cell lines differed in Cho uptake levels, with normal PNT2C2 line cells showing highest uptake over 60 min incubation. Normal and tumourigenic cell lines expressed mRNA for PLD1 and PLD2, and showed similar levels of basal and PKC-activated PLD activity. Conclusions: The transition to tumourigenesis in prostate epithelial cell lines results in major changes to Cho metabolite release into the medium and PKC signalling to phosphatidylcholine turnover. The changes, which reflect the metabolic and proliferative needs of tumourigenic cells compared with untransformed cells, could be significant for both diagnosis and treatment.
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75
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Gallego-Ortega D, Gómez del Pulgar T, Valdés-Mora F, Cebrián A, Lacal JC. Involvement of human choline kinase alpha and beta in carcinogenesis: a different role in lipid metabolism and biological functions. ACTA ACUST UNITED AC 2010; 51:183-94. [PMID: 21035492 DOI: 10.1016/j.advenzreg.2010.09.010] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 09/05/2010] [Indexed: 10/18/2022]
Abstract
We have summarized here the importance of ChoKα1 in human carcinogenesis. ChoKα1 displays its oncogenic activity through activation of specific signaling pathways that influence on cell proliferation and survival. It is overexpressed in a large number of human tumors with an incidence of 40-60% of all tumors investigated. Currently, there is an active effort in the development of strategies to knockdown the activity of ChoKα through specific siRNA or small molecules inhibitors. Results from genetic silencing or from treatment with MN58b, a well characterized ChoKα inhibitor showing antiproliferative and antitumoral effect in mice xenografts, provide strong support to this concept, indicating that the design of new antitumoral drugs must be selective against this isoform. However, affecting the other two known isoforms of ChoK may have also therapeutic consequences since the physiologically active form of ChoK may be constituted by homo or heterodimers. Furthermore, alteration of the ChoKβ activity might lead to a change in the lipid content of the cells of particular tissues such as skeletal muscle as described in the ChoKβ null mice (Sher et al., 2006). Finally, the identification of the ChoKα1 isoform as an excellent novel tool for the diagnosis and prognosis of cancer patients may have clinical consequences of immediate usefulness. On one hand, the use of specific monoclonal antibodies against ChoKα1 as a tool for diagnosis in paraffin embedded samples from patient biopsies, through standard immunohistochemistry techniques, can now be achieved (Gallego-Ortega et al., 2006). On the other hand, it has been recently described the prognostic value of determination of ChoKα1 expression levels in non-small cell lung cancer using real time quantitative PCR technology (Ramírez de Molina et al., 2007). Therefore, further research should be supported on the utility of ChoK isoforms as a promising area to improve cancer diagnosis and treatment.
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Chaves Neto AH, Queiroz KC, Milani R, Paredes-Gamero EJ, Justo GZ, Peppelenbosch MP, Ferreira CV. Profiling the changes in signaling pathways in ascorbic acid/β-glycerophosphate-induced osteoblastic differentiation. J Cell Biochem 2010; 112:71-7. [DOI: 10.1002/jcb.22763] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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77
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Marcucci H, Paoletti L, Jackowski S, Banchio C. Phosphatidylcholine biosynthesis during neuronal differentiation and its role in cell fate determination. J Biol Chem 2010; 285:25382-93. [PMID: 20525991 DOI: 10.1074/jbc.m110.139477] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Neuronal differentiation is characterized by neuritogenesis and neurite outgrowth, processes that are dependent on membrane biosynthesis. Thus, the production of phosphatidylcholine (PtdCho), the major membrane phospholipid, should be stimulated during neuronal differentiation. We demonstrate that during retinoic acid (RA)-induced differentiation of Neuro-2a cells, PtdCho synthesis was promoted by an ordered and sequential activation of choline kinase alpha (CK(alpha)) and choline cytidylyltransferase alpha (CCT(alpha)). Early after RA stimulation, the increase in PtdCho synthesis is mainly governed by the biochemical activation of CCT(alpha). Later, the transcription of CK(alpha)- and CCT(alpha)-encoding genes was induced. Both PtdCho biosynthesis and neuronal differentiation are dependent on ERK activation. A novel mechanism is proposed by which PtdCho biosynthesis is coordinated during neuronal differentiation. Enforced expression of either CK(alpha) or CCTalpha increased the rate of synthesis and the amount of PtdCho, and these cells initiated differentiation without RA stimulation, as evidenced by cell morphology and the expression of genes associated with neuritogenesis. The differentiation resulting from enforced expression of CCT(alpha) or CK(alpha) was dependent on persistent ERK activation. These results indicate that elevated PtdCho synthesis could mimic the RA signals and thus determine neuronal cell fate. Moreover, they could explain the key role that PtdCho plays during neuronal regeneration.
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Affiliation(s)
- Hebe Marcucci
- Departamento de Ciencias Biológicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario, Suipacha 531, Rosario, Argentina
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78
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Agarwal AK, Garg A. Enzymatic activity of the human 1-acylglycerol-3-phosphate-O-acyltransferase isoform 11: upregulated in breast and cervical cancers. J Lipid Res 2010; 51:2143-52. [PMID: 20363836 DOI: 10.1194/jlr.m004762] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The conversion of lysophosphatidic acid (LPA) to phosphatidic acid is carried out by the microsomal enzymes 1-acylglycerol-3-phosphate-O-acyltransferases (AGPATs). These enzymes are specific for acylating LPA at the sn-2 (carbon 2) position on the glycerol backbone and are important, because they provide substrates for the synthesis of phospholipids and triglycerides. At least, mutations in one isoform, AGPAT2, cause near complete loss of adipose tissue in humans. We cloned a cDNA predicted to be an AGPAT isoform, AGPAT11. This cDNA has been recently identified also as lysophosphatidylcholine acyltransferase 2 (LPCAT2) and lyso platelet-activating factor acetyltransferase. When AGPAT11/LPCAT2/lyso platelet-activating factor acetyltransferase cDNA was expressed in CHO and HeLa cells, the protein product localized to the endoplasmic reticulum. In vitro enzymatic activity using lysates of Human Embryonic Kidney-293 cells infected with recombinant AGPAT11/LPCAT2/lyso platelet-activating factor-acetyltransferase cDNA adenovirus show that the protein has an AGPAT activity but lacks glycerol-3-phosphate acyltransferase enzymatic activity. The AGPAT11 efficiently uses C18:1 LPA as acyl acceptor and C18:1 fatty acid as an acyl donor. Thus, it has similar substrate specificities for LPA and acyl-CoA as shown for AGPAT9 and 10. Expression of AGPAT11 mRNA was significantly upregulated in human breast, cervical, and colorectal cancer tissues, indicating its adjuvant role in the progression of these cancers. Our enzymatic assays strongly suggest that the cDNA previously identified as LPCAT2/lyso platelet-activating factor-acetyltransferase cDNA has AGPAT activity and thus we prefer to identify this clone as AGPAT11 as well.
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Affiliation(s)
- Anil K Agarwal
- Division of Nutrition and Metabolic Diseases, Department of Internal Medicine and Center for Human Nutrition, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
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