1
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Hien TT, Ambite I, Wan MLY, Cavalera M, Esmaeili P, Chaudhuri A, Sabari S, Babjuk M, Svanborg C. Long-term prevention of bladder cancer progression by alpha1-oleate alone or in combination with chemotherapy. Int J Cancer 2023; 153:584-599. [PMID: 36891980 DOI: 10.1002/ijc.34500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 02/10/2023] [Accepted: 02/13/2023] [Indexed: 03/10/2023]
Abstract
Bladder cancer is common and one of the most costly cancer forms, due to a lack of curative therapies. Recently, clinical safety and efficacy of the alpha1-oleate complex was demonstrated in a placebo-controlled study of nonmuscle invasive bladder cancer. Our study investigated if long-term therapeutic efficacy is improved by repeated treatment cycles and by combining alpha1-oleate with low-dose chemotherapy. Rapidly growing bladder tumors were treated by intravesical instillation of alpha1-oleate, Epirubicin or Mitomycin C alone or in combination. One treatment cycle arrested tumor growth, with a protective effect lasting at least 4 weeks in mice receiving 8.5 mM of alpha1-oleate alone or 1.7 mM of alpha-oleate combined with Epirubicin or Mitomycin C. Repeated treatment cycles extended protection, defined by a lack of bladder pathology and a virtual absence of bladder cancer-specific gene expression. Synergy with Epirubicin was detected at the lower alpha1-oleate concentration and in vitro, alpha1-oleate was shown to enhance the uptake and nuclear translocation of Epirubicin, by tumor cells. Effects at the chromatin level affecting cell proliferation were further suggested by reduced BrdU incorporation. In addition, alpha1-oleate triggered DNA fragmentation, defined by the TUNEL assay. The results suggest that bladder cancer development may be prevented long-term in the murine model, by alpha1-oleate alone or in combination with low-dose Epirubicin. In addition, the combination of alpha1-oleate and Epirubicin reduced the size of established tumors. Exploring these potent preventive and therapeutic effects will be of immediate interest in patients with bladder cancer.
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Affiliation(s)
- Tran Thi Hien
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Ines Ambite
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Murphy Lam Yim Wan
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Michele Cavalera
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Parisa Esmaeili
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Arunima Chaudhuri
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Samudra Sabari
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Marek Babjuk
- Department of Urology, Motol Hospital and Second Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Catharina Svanborg
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
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2
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Ho JCS, Mir SA, Cavalera M, Esmaeili P, Tran TH, Yann ZC, Tran TH, Chaudhuri A, Bendt AK, Wenk MR, Svanborg C. Lipid bilayer composition as a determinant of cancer cell sensitivity to tumoricidal protein-lipid complexes. Biofactors 2022; 48:1145-1159. [PMID: 35388547 DOI: 10.1002/biof.1841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 03/24/2022] [Indexed: 11/10/2022]
Abstract
Complexes formed by the alpha1 N-terminal peptide of alpha-lactalbumin and oleic acid (alpha1-oleate) interact with lipid bilayers. Plasma membrane perturbations trigger tumor cell death but normal differentiated cells are more resistant, and their plasma membranes are less strongly affected. This study examined membrane lipid composition as a determinant of tumor cell reactivity. Bladder cancer tissue showed a higher abundance of unsaturated lipids enriched in phosphatidylcholine, PC (36:4) and PC (38:4), and sphingomyelin, SM (36:1) than healthy bladder tissue, where saturated lipids predominated and the lipid extracts from bladder cancer tissue inhibited the tumoricidal effect of the complex more effectively than healthy tissue extracts. Furthermore, unsaturated PC in solution inhibited tumor cell death, and the complex interacted with giant unilamellar vesicles formed by PC, confirming the affinity of alpha1-oleate for fluid membranes enriched in PC. Quartz Crystal Microbalance with dissipation monitoring (QCM-D) detected a preference of the complex for the liquid-disordered phase, suggesting that the insertion into PC-based membranes and the resulting membrane perturbations are influenced by membrane lipid saturation. The results suggest that the membrane lipid composition is functionally important and that specific unsaturated membrane lipids may serve as "recognition motifs" for broad-spectrum tumoricidal molecules such as alpha1-oleate.
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Affiliation(s)
- James C S Ho
- School of Materials Science & Engineering, Nanyang Technological University, Singapore, Singapore
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Sartaj Ahmad Mir
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, YLL School of Medicine, National University of Singapore, Singapore, Singapore
| | - Michele Cavalera
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Parisa Esmaeili
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Tuan Hiep Tran
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Zandra Chew Yann
- School of Materials Science & Engineering, Nanyang Technological University, Singapore, Singapore
| | - Thi Hien Tran
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Arunima Chaudhuri
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Anne K Bendt
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, Singapore, Singapore
| | - Markus R Wenk
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, YLL School of Medicine, National University of Singapore, Singapore, Singapore
| | - Catharina Svanborg
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
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3
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Bladder cancer therapy using a conformationally fluid tumoricidal peptide complex. Nat Commun 2021; 12:3427. [PMID: 34103518 PMCID: PMC8187399 DOI: 10.1038/s41467-021-23748-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 04/15/2021] [Indexed: 02/05/2023] Open
Abstract
Partially unfolded alpha-lactalbumin forms the oleic acid complex HAMLET, with potent tumoricidal activity. Here we define a peptide-based molecular approach for targeting and killing tumor cells, and evidence of its clinical potential (ClinicalTrials.gov NCT03560479). A 39-residue alpha-helical peptide from alpha-lactalbumin is shown to gain lethality for tumor cells by forming oleic acid complexes (alpha1-oleate). Nuclear magnetic resonance measurements and computational simulations reveal a lipid core surrounded by conformationally fluid, alpha-helical peptide motifs. In a single center, placebo controlled, double blinded Phase I/II interventional clinical trial of non-muscle invasive bladder cancer, all primary end points of safety and efficacy of alpha1-oleate treatment are reached, as evaluated in an interim analysis. Intra-vesical instillations of alpha1-oleate triggers massive shedding of tumor cells and the tumor size is reduced but no drug-related side effects are detected (primary endpoints). Shed cells contain alpha1-oleate, treated tumors show evidence of apoptosis and the expression of cancer-related genes is inhibited (secondary endpoints). The results are especially encouraging for bladder cancer, where therapeutic failures and high recurrence rates create a great, unmet medical need.
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4
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Vansarla G, Håkansson AP, Bergenfelz C. HAMLET a human milk protein-lipid complex induces a pro-inflammatory phenotype of myeloid cells. Eur J Immunol 2021; 51:965-977. [PMID: 33348422 PMCID: PMC8248127 DOI: 10.1002/eji.202048813] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 11/06/2020] [Accepted: 12/18/2020] [Indexed: 12/15/2022]
Abstract
HAMLET is a protein‐lipid complex with a specific and broad bactericidal and tumoricidal activity, that lacks cytotoxic activity against healthy cells. In this study, we show that HAMLET also has general immune‐stimulatory effects on primary human monocyte‐derived dendritic cells and macrophages (Mo‐DC and Mo‐M) and murine RAW264.7 macrophages. HAMLET, but not its components alpha‐lactalbumin or oleic acid, induces mature CD14low/–CD83+ Mo‐DC and M1‐like CD14+CD86++ Mo‐M surface phenotypes. Concomitantly, inflammatory mediators, including IL‐2, IL‐6, IL‐10, IL‐12 and MIP‐1α, were released in the supernatant of HAMLET‐stimulated cells, indicating a mainly pro‐inflammatory phenotype. The HAMLET‐induced phenotype was mediated by calcium, NFκB and p38 MAPK signaling in Mo‐DCs and calcium, NFκB and ERK signaling in Mo‐M as inhibitors of these pathways almost completely blocked the induction of mature Mo‐DCs and M1‐like Mo‐M. Compared to unstimulated Mo‐DCs, HAMLET‐stimulated Mo‐DCs were more potent in inducing T cell proliferation and HAMLET‐stimulated macrophages were more efficient in phagocytosis of Streptococcus pneumoniae in vitro. This indicates a functionally activated phenotype of HAMLET‐stimulated DCs and macrophages. Combined, we propose that HAMLET has a two‐fold anti‐bacterial activity; one inducing direct cytotoxic activity, the other indirectly mediating elimination of bacteria by activation of immune cells of the myeloid lineage.
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Affiliation(s)
- Goutham Vansarla
- Division of Experimental Infection Medicine, Department of Translational Medicine, Lund University, Malmö, SE-214 28, Sweden
| | - Anders P Håkansson
- Division of Experimental Infection Medicine, Department of Translational Medicine, Lund University, Malmö, SE-214 28, Sweden
| | - Caroline Bergenfelz
- Division of Experimental Infection Medicine, Department of Translational Medicine, Lund University, Malmö, SE-214 28, Sweden
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5
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α-Lactalbumin, Amazing Calcium-Binding Protein. Biomolecules 2020; 10:biom10091210. [PMID: 32825311 PMCID: PMC7565966 DOI: 10.3390/biom10091210] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/14/2020] [Accepted: 08/17/2020] [Indexed: 02/06/2023] Open
Abstract
α-Lactalbumin (α-LA) is a small (Mr 14,200), acidic (pI 4–5), Ca2+-binding protein. α-LA is a regulatory component of lactose synthase enzyme system functioning in the lactating mammary gland. The protein possesses a single strong Ca2+-binding site, which can also bind Mg2+, Mn2+, Na+, K+, and some other metal cations. It contains several distinct Zn2+-binding sites. Physical properties of α-LA strongly depend on the occupation of its metal binding sites by metal ions. In the absence of bound metal ions, α-LA is in the molten globule-like state. The binding of metal ions, and especially of Ca2+, increases stability of α-LA against the action of heat, various denaturing agents and proteases, while the binding of Zn2+ to the Ca2+-loaded protein decreases its stability and causes its aggregation. At pH 2, the protein is in the classical molten globule state. α-LA can associate with membranes at neutral or slightly acidic pH at physiological temperatures. Depending on external conditions, α-LA can form amyloid fibrils, amorphous aggregates, nanoparticles, and nanotubes. Some of these aggregated states of α-LA can be used in practical applications such as drug delivery to tissues and organs. α-LA and some of its fragments possess bactericidal and antiviral activities. Complexes of partially unfolded α-LA with oleic acid are cytotoxic to various tumor and bacterial cells. α-LA in the cytotoxic complexes plays a role of a delivery carrier of cytotoxic fatty acid molecules into tumor and bacterial cells across the cell membrane. Perhaps in the future the complexes of α-LA with oleic acid will be used for development of new anti-cancer drugs.
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6
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Pedersen JN, Frislev HKS, Pedersen JS, Otzen D. Structures and mechanisms of formation of liprotides. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2020; 1868:140505. [PMID: 32721568 DOI: 10.1016/j.bbapap.2020.140505] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 07/16/2020] [Indexed: 12/11/2022]
Abstract
Many proteins form complexes called liprotides with oleic acid and other cis-fatty acids under conditions where the protein is partially unfolded. The complexes vary in structure depending on the ratio of protein and lipid, but the most common structural organization is the core-shell structure, in which a layer of dynamic, partially unfolded and extended proteins surrounds a micelle-like fatty acid core. This structure, first reported for α-lactalbumin together with OA, resembles complexes formed between proteins and anionic surfactants like SDS. Liprotides first rose to fame through their anti-carcinogenic properties which still remains promising for topical applications though not yet implemented in the clinic. In addition, liprotides show potential in drug delivery thanks to the ability of the micelle core to solubilize and stabilize hydrophobic compounds, though applications are challenged by their sensitivity to acidic pH and dynamic exchange of lipids which makes them easy prey for serum "hoovers" such as albumin. However, liprotides are also of fundamental interest as a generic "protein complex structure", demonstrating the many and varied structural consequences of protein-lipid interactions. Here we provide an overview of the different types of liprotide complexes, ranging from quasi-native complexes via core-shell structures to multi-layer structures, and discuss the many conditions under which they form. Given the many variable types of complexes that can form, rigorous biophysical analysis (stoichiometry, shape and structure of the complexes) remains crucial for a complete understanding of the mechanisms of action of this fascinating group of protein-lipid complexes both in vitro and in vivo.
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Affiliation(s)
- Jannik Nedergaard Pedersen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Henriette Kristina Søster Frislev
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark; Novo Nordisk, Hallas Alle 1, DK-4400 Kalundborg, Denmark
| | - Jan Skov Pedersen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark; Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Daniel Otzen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark; Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark.
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7
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Hien TT, Ambite I, Butler D, Wan MLY, Tran TH, Höglund U, Babjuk M, Svanborg C. Bladder cancer therapy without toxicity-A dose-escalation study of alpha1-oleate. Int J Cancer 2020; 147:2479-2492. [PMID: 32319672 DOI: 10.1002/ijc.33019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 03/20/2020] [Accepted: 04/06/2020] [Indexed: 12/22/2022]
Abstract
Potent chemotherapeutic agents are required to counteract the aggressive behavior of cancer cells and patients often experience severe side effects, due to tissue toxicity. Our study addresses if a better balance between efficacy and toxicity can be attained using the tumoricidal complex alpha1-oleate, formed by a synthetic, alpha-helical peptide comprising the N-terminal 39 amino acids of alpha-lactalbumin and the fatty acid oleic acid. Bladder cancer was established, by intravesical instillation of MB49 cells on day 0 and the treatment group received five instillations of alpha1-oleate (1.7-17 mM) on days 3 to 11. A dose-dependent reduction in tumor size, bladder size and bladder weight was recorded in the alpha1-oleate treated group, compared to sham-treated mice. Tumor markers Ki-67, Cyclin D1 and VEGF were inhibited in a dose-dependent manner, as was the expression of cancer-related genes. Remarkably, toxicity for healthy tissue was not detected in alpha1-oleate-treated, tumor-bearing mice or healthy mice or rabbits, challenged with increasing doses of the active complex. The results define a dose-dependent therapeutic effect of alpha1-oleate in a murine bladder cancer model.
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Affiliation(s)
- Tran Thi Hien
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Ines Ambite
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Daniel Butler
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Murphy Lam Yim Wan
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - Tuan Hiep Tran
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | | | - Marek Babjuk
- Department of Urology, Hospital Motol and Second Faculty of Medicine, Charles University, Prague 5, Czech Republic
| | - Catharina Svanborg
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
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8
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El-Fakharany EM, Redwan EM. Protein-lipid complexes: molecular structure, current scenarios and mechanisms of cytotoxicity. RSC Adv 2019; 9:36890-36906. [PMID: 35539089 PMCID: PMC9075609 DOI: 10.1039/c9ra07127j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 10/21/2019] [Indexed: 02/04/2023] Open
Abstract
Some natural proteins can be complexed with oleic acid (OA) to form an active protein-lipid formulation that can induce tumor-selective apoptosis. The first explored protein was human milk α-lactalbumin (α-LA), called HAMLET when composed with OA in antitumor form. Several groups have prepared active protein-lipid complexes using a variety of approaches, all of which depend on target protein destabilization or direct OA-protein incubation to alter pH to acid or alkaline condition. In addition to performing vital roles in inflammatory processes and immune responses, fatty acids can disturb different metabolic pathways and cellular signals. Therefore, the tumoricidal action of these complexes is related to OA rather than the protein that keeps OA in solution and acts as a vehicle for transferring OA molecules to tumor cells. However, other studies have suggested that the antitumor efficacy of these complexes was exerted by both protein and OA together. The potential is not limited to the anti-tumor activity of protein-lipid complexes but extends to other functions such as bactericidal activity. The protein shell enhances the solubility and stability of the bound fatty acid. These protein-lipid complexes are promising candidates for fighting various cancer types and managing bacterial and viral infections.
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Affiliation(s)
- Esmail M El-Fakharany
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City for Scientific Research and Technology Applications (SRTA-City) New Borg EL-Arab 21934 Alexandria Egypt
| | - Elrashdy M Redwan
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City for Scientific Research and Technology Applications (SRTA-City) New Borg EL-Arab 21934 Alexandria Egypt
- Department of Biological Sciences, Faculty of Sciences, King Abdulaziz University P. O. Box 80203 Jeddah Saudi Arabia
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9
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Abstract
Oleic acid (OA) is a monounsaturated fatty acid that upon binding to milk proteins, such as α-lactalbumin and lactoferrin, forms potent complexes, which exert selective anti-tumor activity against malignant cells but are nontoxic for healthy normal cells. We showed that the interaction of OA with albumins isolated from human, bovine, and camel milk results in the formation of complexes with high antitumor activity against Caco-2, HepG-2, PC-3, and MCF-7 tumor cells. The antitumor effect of the complexes is mostly due to the action of oleic acid, similar to the case of OA complexes with other proteins. Viability of tumor cells is inhibited by the albumin-OA complexes in a dose dependent manner, as evaluated by the MTT assay. Strong induction of apoptosis in tumor cells after their treatment with the complexes was monitored by flow cytometry, cell cycle analysis, nuclear staining, and DNA fragmentation methods. The complex of camel albumin with OA displayed the most pronounced anti-tumor effects in comparison with the complexes of OA with human and bovine albumins. Therefore, these results suggest that albumins have the potential to be used as efficient and low cost means of tumor treatment.
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10
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Rath EM, Cheng YY, Pinese M, Sarun KH, Hudson AL, Weir C, Wang YD, Håkansson AP, Howell VM, Liu GJ, Reid G, Knott RB, Duff AP, Church WB. BAMLET kills chemotherapy-resistant mesothelioma cells, holding oleic acid in an activated cytotoxic state. PLoS One 2018; 13:e0203003. [PMID: 30157247 PMCID: PMC6114908 DOI: 10.1371/journal.pone.0203003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 08/13/2018] [Indexed: 12/29/2022] Open
Abstract
Malignant pleural mesothelioma is an aggressive cancer with poor prognosis. Here we have investigated in vitro efficacy of BAMLET and BLAGLET complexes (anti-cancer complexes consisting of oleic acid and bovine α-lactalbumin or β-lactoglobulin respectively) in killing mesothelioma cells, determined BAMLET and BLAGLET structures, and investigated possible biological mechanisms. We performed cell viability assays on 16 mesothelioma cell lines. BAMLET and BLAGLET having increasing oleic acid content inhibited human and rat mesothelioma cell line proliferation at decreasing doses. Most of the non-cancer primary human fibroblasts were more resistant to BAMLET than were human mesothelioma cells. BAMLET showed similar cytotoxicity to cisplatin-resistant, pemetrexed-resistant, vinorelbine-resistant, and parental rat mesothelioma cells, indicating the BAMLET anti-cancer mechanism may be different to drugs currently used to treat mesothelioma. Cisplatin, pemetrexed, gemcitabine, vinorelbine, and BAMLET, did not demonstrate a therapeutic window for mesothelioma compared with immortalised non-cancer mesothelial cells. We demonstrated by quantitative PCR that ATP synthase is downregulated in mesothelioma cells in response to regular dosing with BAMLET. We sought structural insight for BAMLET and BLAGLET activity by performing small angle X-ray scattering, circular dichroism, and scanning electron microscopy. Our results indicate the structural mechanism by which BAMLET and BLAGLET achieve increased cytotoxicity by holding increasing amounts of oleic acid in an active cytotoxic state encapsulated in increasingly unfolded protein. Our structural studies revealed similarity in the molecular structure of the protein components of these two complexes and in their encapsulation of the fatty acid, and differences in the microscopic structure and structural stability. BAMLET forms rounded aggregates and BLAGLET forms long fibre-like aggregates whose aggregation is more stable than that of BAMLET due to intermolecular disulphide bonds. The results reported here indicate that BAMLET and BLAGLET may be effective second-line treatment options for mesothelioma.
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Affiliation(s)
- Emma M. Rath
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Yuen Yee Cheng
- Asbestos Diseases Research Institute (ADRI), Concord, NSW, Australia
- University of Sydney, Sydney, NSW, Australia
| | - Mark Pinese
- Kinghorn Cancer Centre and Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Kadir H. Sarun
- Asbestos Diseases Research Institute (ADRI), Concord, NSW, Australia
| | - Amanda L. Hudson
- Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, University of Sydney, Sydney, NSW, Australia
| | - Christopher Weir
- Northern Blood Research Centre, Kolling Institute, University of Sydney, Sydney, NSW, Australia
| | - Yiwei D. Wang
- Burns Research, ANZAC Research Institute, Concord Hospital, University of Sydney, Concord, NSW, Australia
| | | | - Viive M. Howell
- Bill Walsh Translational Cancer Research Laboratory, Kolling Institute, University of Sydney, Sydney, NSW, Australia
| | - Guo Jun Liu
- Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Rd, Lucas Heights, NSW, Australia
- Brain and Mind Centre and Faculty of Health Sciences, University of Sydney, Sydney, NSW, Australia
| | - Glen Reid
- Asbestos Diseases Research Institute (ADRI), Concord, NSW, Australia
- University of Sydney, Sydney, NSW, Australia
| | - Robert B. Knott
- Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Rd, Lucas Heights, NSW, Australia
| | - Anthony P. Duff
- Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Rd, Lucas Heights, NSW, Australia
| | - W. Bret Church
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
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11
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Fang B, Zhang M, Wu H, Fan X, Ren F. Internalization properties of the anti-tumor α-lactalbumin-oleic acid complex. Int J Biol Macromol 2017; 96:44-51. [DOI: 10.1016/j.ijbiomac.2016.12.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 11/30/2016] [Accepted: 12/12/2016] [Indexed: 10/20/2022]
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12
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Ho JC, Nadeem A, Svanborg C. HAMLET – A protein-lipid complex with broad tumoricidal activity. Biochem Biophys Res Commun 2017; 482:454-458. [DOI: 10.1016/j.bbrc.2016.10.092] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 10/24/2016] [Indexed: 12/22/2022]
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13
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A Characeae Cells Plasma Membrane as a Model for Selection of Bioactive Compounds and Drugs: Interaction of HAMLET-Like Complexes with Ion Channels of Chara corallina Cells Plasmalemma. J Membr Biol 2016; 249:801-811. [DOI: 10.1007/s00232-016-9930-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 09/07/2016] [Indexed: 01/10/2023]
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14
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15
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Hoque M, Gupta J, Rabbani G, Khan RH, Saleemuddin M. Behaviour of oleic acid-depleted bovine alpha-lactalbumin made LEthal to tumor cells (BAMLET). MOLECULAR BIOSYSTEMS 2016; 12:1871-80. [DOI: 10.1039/c5mb00905g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Oleic acid (OA) complexes of human alpha-lactalbumin (α-LA) and several other proteins are effective in the killing of a variety of tumor cells.
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Affiliation(s)
- Mehboob Hoque
- Interdisciplinary Biotechnology Unit
- Aligarh Muslim University
- Aligarh 202002
- India
| | - Jyoti Gupta
- Interdisciplinary Biotechnology Unit
- Aligarh Muslim University
- Aligarh 202002
- India
| | - Gulam Rabbani
- Interdisciplinary Biotechnology Unit
- Aligarh Muslim University
- Aligarh 202002
- India
| | - Rizwan Hasan Khan
- Interdisciplinary Biotechnology Unit
- Aligarh Muslim University
- Aligarh 202002
- India
| | - M. Saleemuddin
- Interdisciplinary Biotechnology Unit
- Aligarh Muslim University
- Aligarh 202002
- India
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16
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Protein receptor-independent plasma membrane remodeling by HAMLET: a tumoricidal protein-lipid complex. Sci Rep 2015; 5:16432. [PMID: 26561036 PMCID: PMC4642337 DOI: 10.1038/srep16432] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 10/06/2015] [Indexed: 01/07/2023] Open
Abstract
A central tenet of signal transduction in eukaryotic cells is that extra-cellular ligands activate specific cell surface receptors, which orchestrate downstream responses. This ‘’protein-centric” view is increasingly challenged by evidence for the involvement of specialized membrane domains in signal transduction. Here, we propose that membrane perturbation may serve as an alternative mechanism to activate a conserved cell-death program in cancer cells. This view emerges from the extraordinary manner in which HAMLET (Human Alpha-lactalbumin Made LEthal to Tumor cells) kills a wide range of tumor cells in vitro and demonstrates therapeutic efficacy and selectivity in cancer models and clinical studies. We identify a ‘’receptor independent” transformation of vesicular motifs in model membranes, which is paralleled by gross remodeling of tumor cell membranes. Furthermore, we find that HAMLET accumulates within these de novo membrane conformations and define membrane blebs as cellular compartments for direct interactions of HAMLET with essential target proteins such as the Ras family of GTPases. Finally, we demonstrate lower sensitivity of healthy cell membranes to HAMLET challenge. These features suggest that HAMLET-induced curvature-dependent membrane conformations serve as surrogate receptors for initiating signal transduction cascades, ultimately leading to cell death.
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Wen H, Strømland Ø, Halskau Ø. α-Lactalbumin:Oleic Acid Complex Spontaneously Delivers Oleic Acid to Artificial and Erythrocyte Membranes. J Mol Biol 2015; 427:3177-87. [PMID: 26297199 DOI: 10.1016/j.jmb.2015.08.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 08/08/2015] [Indexed: 10/23/2022]
Abstract
Human α-lactalbumin made lethal to tumor cells (HAMLET) is a tumoricidal complex consisting of human α-lactalbumin and multiple oleic acids (OAs). OA has been shown to play a key role in the activity of HAMLET and its related complexes, generally known as protein-fatty acid (PFA) complexes. In contrast to what is known about the fate of the protein component of such complexes, information about what happens to OA during their action is still lacking. We monitored the membrane, OA and protein components of bovine α-lactalbumin complexed with OA (BLAOA; a HAMLET-like substance) and how they associate with each other. Using ultracentrifugation, we found that the OA and lipid components follow each other closely. We then firmly identify a transfer of OA from BLAOA to both artificial and erythrocyte membranes, indicating that natural cells respond similarly to BLAOA treatment as artificial membranes. Uncomplexed OA is unable to similarly affect membranes at the conditions tested, even at elevated concentrations. Thus, BLAOA can spontaneously transfer OA to a lipid membrane. After the interaction with the membrane, the protein is likely to have lost most or all of its OA. We suggest a mechanism for passive import of mainly uncomplexed protein into cells, using existing models for OA's effect on membranes. Our results are consistent with a membrane destabilization mediated predominantly by OA insertion being a significant contribution to PFA cytotoxicity.
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Affiliation(s)
- Hanzhen Wen
- Department of Molecular Biology, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway
| | - Øyvind Strømland
- Department of Molecular Biology, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway
| | - Øyvind Halskau
- Department of Molecular Biology, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway.
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Zhou J, Xu B. Enzyme-instructed self-assembly: a multistep process for potential cancer therapy. Bioconjug Chem 2015; 26:987-99. [PMID: 25933032 PMCID: PMC4533114 DOI: 10.1021/acs.bioconjchem.5b00196] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2015] [Revised: 04/30/2015] [Indexed: 01/01/2023]
Abstract
The central dogma of the action of current anticancer drugs is that the drug tightly binds to its molecular target for inhibition. The reliance on tight ligand-receptor binding, however, is also the major root of drug resistance in cancer therapy. In this article, we highlight enzyme-instructed self-assembly (EISA)-the integration of enzymatic transformation and molecular self-assembly-as a multistep process for the development of cancer therapy. Using apoptosis as an example, we illustrate that the combination of enzymatic transformation and self-assembly, in fact, is an inherent feature of apoptosis. After the introduction of EISA of small molecules in the context of supramolecular hydrogelation, we describe several key studies to underscore the promises of EISA for developing cancer therapy. Particularly, we will highlight that EISA allows one to develop approaches to target "undruggable" targets or "untargetable" features of cancer cells and provides the opportunity for simultaneously interacting with multiple targets. We envision that EISA, used separately or in combination with current anticancer therapeutics, will ultimately lead to a paradigm shift for developing anticancer medicine that inhibit multiple hallmark capabilities of cancer.
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Affiliation(s)
- Jie Zhou
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States
| | - Bing Xu
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States
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Ho JCS, Nadeem A, Rydström A, Puthia M, Svanborg C. Targeting of nucleotide-binding proteins by HAMLET--a conserved tumor cell death mechanism. Oncogene 2015; 35:897-907. [PMID: 26028028 DOI: 10.1038/onc.2015.144] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/24/2015] [Accepted: 03/29/2015] [Indexed: 12/20/2022]
Abstract
HAMLET (Human Alpha-lactalbumin Made LEthal to Tumor cells) kills tumor cells broadly suggesting that conserved survival pathways are perturbed. We now identify nucleotide-binding proteins as HAMLET binding partners, accounting for about 35% of all HAMLET targets in a protein microarray comprising 8000 human proteins. Target kinases were present in all branches of the Kinome tree, including 26 tyrosine kinases, 10 tyrosine kinase-like kinases, 13 homologs of yeast sterile kinases, 4 casein kinase 1 kinases, 15 containing PKA, PKG, PKC family kinases, 15 calcium/calmodulin-dependent protein kinase kinases and 13 kinases from CDK, MAPK, GSK3, CLK families. HAMLET acted as a broad kinase inhibitor in vitro, as defined in a screen of 347 wild-type, 93 mutant, 19 atypical and 17 lipid kinases. Inhibition of phosphorylation was also detected in extracts from HAMLET-treated lung carcinoma cells. In addition, HAMLET recognized 24 Ras family proteins and bound to Ras, RasL11B and Rap1B on the cytoplasmic face of the plasma membrane. Direct cellular interactions between HAMLET and activated Ras family members including Braf were confirmed by co-immunoprecipitation. As a consequence, oncogenic Ras and Braf activity was inhibited and HAMLET and Braf inhibitors synergistically increased tumor cell death in response to HAMLET. Unlike most small molecule kinase inhibitors, HAMLET showed selectivity for tumor cells in vitro and in vivo. The results identify nucleotide-binding proteins as HAMLET targets and suggest that dysregulation of the ATPase/kinase/GTPase machinery contributes to cell death, following the initial, selective recognition of HAMLET by tumor cells. The findings thus provide a molecular basis for the conserved tumoricidal effect of HAMLET, through dysregulation of kinases and oncogenic GTPases, to which tumor cells are addicted.
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Affiliation(s)
- J C S Ho
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - A Nadeem
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - A Rydström
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - M Puthia
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - C Svanborg
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
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Hoque M, Nanduri R, Gupta J, Mahajan S, Gupta P, Saleemuddin M. Oleic acid complex of bovine α-lactalbumin induces eryptosis in human and other erythrocytes by a Ca(2+)-independent mechanism. Biochim Biophys Acta Gen Subj 2015; 1850:1729-39. [PMID: 25913522 DOI: 10.1016/j.bbagen.2015.04.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 04/08/2015] [Accepted: 04/16/2015] [Indexed: 12/20/2022]
Abstract
BACKGROUND Complexes of oleic acid (OA) with milk α-lactalbumin, received remarkable attention in view of their selective toxicity towards a spectrum of tumors during the last two decades. OA complexes of some structurally related/unrelated proteins are also tumoricidal. Erythrocytes are among the few differentiated cells that are sensitive and undergo hemolysis when exposed to the complexes. METHODS The effects of OA complex of bovine α-lactalbumin (Bovine Alpha-lactalbumin Made LEthal to Tumor cells, BAMLET) on human, goat and chicken erythrocytes on calcein leakage, phosphatidylserine exposure, morphological changes and hemolysis were studied by confocal microscopy, FACS analysis, scanning electron microscopy and measuring hemoglobin release. RESULTS Erythrocytes exposed to BAMLET undergo eryptosis-like alterations as revealed by calcein leakage, surface phosphatidylserine exposure and transformation to echinocytes at low concentrations and hemolysis when the concentration of the complex was raised. Ca(2+) was not essential and restricted the alterations when included in the medium. The BAMLET-induced alterations in human erythrocytes were prevented by the cation channel inhibitors, amiloride and BaCl2 but not by inhibitors of thiol proteases, sphingomyelinase and by the antioxidant N-acetyl cysteine. CONCLUSIONS The work shows for the first time that low concentrations of BAMLET induces eryptosis in erythrocytes by a novel mechanism not requiring Ca(2+) and hemolysis by detergent-like action by the released OA at higher concentrations. GENERAL SIGNIFICANCE The study points out to the need for a comprehensive evaluation of the toxicity of OA complexes of α-lactalbumin and other proteins towards erythrocytes and other differentiated cells before being considered for therapy.
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Affiliation(s)
- Mehboob Hoque
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India
| | | | - Jyoti Gupta
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India
| | - Sahil Mahajan
- CSIR-Institute of Microbial Technology, Chandigarh 160036, India
| | - Pawan Gupta
- CSIR-Institute of Microbial Technology, Chandigarh 160036, India
| | - M Saleemuddin
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India.
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21
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Ho J, Sielaff H, Nadeem A, Svanborg C, Grüber G. The molecular motor F-ATP synthase is targeted by the tumoricidal protein HAMLET. J Mol Biol 2015; 427:1866-74. [PMID: 25681694 DOI: 10.1016/j.jmb.2015.01.024] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 01/17/2015] [Accepted: 01/20/2015] [Indexed: 10/24/2022]
Abstract
HAMLET (human alpha-lactalbumin made lethal to tumor cells) interacts with multiple tumor cell compartments, affecting cell morphology, metabolism, proteasome function, chromatin structure and viability. This study investigated if these diverse effects of HAMLET might be caused, in part, by a direct effect on the ATP synthase and a resulting reduction in cellular ATP levels. A dose-dependent reduction in cellular ATP levels was detected in A549 lung carcinoma cells, and by confocal microscopy, co-localization of HAMLET with the nucleotide-binding subunits α (non-catalytic) and β (catalytic) of the energy converting F1F0 ATP synthase was detected. As shown by fluorescence correlation spectroscopy, HAMLET binds to the F1 domain of the F1F0 ATP synthase with a dissociation constant (KD) of 20.5μM. Increasing concentrations of the tumoricidal protein HAMLET added to the enzymatically active α3β3γ complex of the F-ATP synthase lowered its ATPase activity, demonstrating that HAMLET binding to the F-ATP synthase effects the catalysis of this molecular motor. Single-molecule analysis was applied to study HAMLET-α3β3γ complex interaction. Whereas the α3β3γ complex of the F-ATP synthase rotated in a counterclockwise direction with a mean rotational rate of 3.8±0.7s(-1), no rotation could be observed in the presence of bound HAMLET. Our findings suggest that direct effects of HAMLET on the F-ATP synthase may inhibit ATP-dependent cellular processes.
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Affiliation(s)
- James Ho
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Sölvegatan 23, S-223 62 Lund, Sweden
| | - Hendrik Sielaff
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
| | - Aftab Nadeem
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Sölvegatan 23, S-223 62 Lund, Sweden
| | - Catharina Svanborg
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Sölvegatan 23, S-223 62 Lund, Sweden.
| | - Gerhard Grüber
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore.
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Abstract
Serotonin (5-hydroxytryptamine, 5-HT) is a very simple molecule that plays key roles in complex communication mechanisms within the animal body. In the mammary glands, serotonin biosynthesis and secretion are induced in response to dilation of the alveolar spaces. Since its discovery several years ago, mammary 5-HT has been demonstrated to perform two homeostatic functions. First, serotonin regulates lactation and initiates the transition into the earliest phases of involution. Second, serotonin is a local signal that induces parathyroid hormone-related peptide (PTHrP), which allows the mammary gland to drive the mobilization of calcium from the skeleton. These processes use different receptor types, 5-HT7 and 5-HT2, respectively. In this review, we provide synthetic perspectives on the fundamental processes of lactation homeostasis and the adaptation of calcium homeostasis for lactation. We analyze the role of the intrinsic serotonin system in the physiological regulation of the mammary glands. We also consider the importance of the mammary serotonin system in pathologies and therapies associated with lactation and breast cancer.
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Affiliation(s)
- Nelson D Horseman
- Department of Molecular and Cellular Physiology, Systems Biology and Physiology Program, University of Cincinnati, Cincinnati, Ohio 45208;
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Hoque M, Dave S, Gupta P, Saleemuddin M. Oleic acid may be the key contributor in the BAMLET-induced erythrocyte hemolysis and tumoricidal action. PLoS One 2013; 8:e68390. [PMID: 24039698 PMCID: PMC3770648 DOI: 10.1371/journal.pone.0068390] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 06/03/2013] [Indexed: 12/19/2022] Open
Abstract
A chance discovery of the tumoricidal action of a human milk fraction led to the characterization of the active component as oleic acid complex of the α-lactalbumin, which was given the acronym HAMLET. We report in this study that the oleic acid complex of bovine α-lactalbumin (BAMLET) is hemolytic to human erythrocytes as well as to those derived from some other mammals. Indirect immunofluorescence analysis suggested binding of BAMLET to erythrocytes prior to induction of hemolysis. Free OA was hemolytic albeit at higher concentrations, while sodium oleate caused hemolysis at far lower concentrations. Amiloride and BaCl2 offered protection against BAMLET-induced hemolysis suggesting the involvement of a cation leak channel in the process. BAMLET coupled to CNBr-activated Sepharose was not only hemolytic but also tumoricidal to Jurkat and MCF-7 cells in culture. The Sepharose-linked preparation was however not toxic to non-cancerous peritoneal macrophages and primary adipocytes. The tumoricidal action was studied using the MTT-assay while apoptosis induction measured by the annexin V-propidium iodide assay. Repeated incubation of the immobilized BAMLET with erythrocytes depleted oleic acid and decreased the hemolytic activity of the complex. Incubation of MCF-7 and Jurkat cells with OA, soluble or immobilized BAMLET resulted in increase in the uptake of Lyso Tracker Red and Nile red by the cells. The data presented support the contention that oleic acid plays the key role, both in BAMLET-induced hemolysis and tumoricidal action.
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Affiliation(s)
- Mehboob Hoque
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Sandeep Dave
- Institute of Microbial Technology (CSIR), Chandigarh, India
| | - Pawan Gupta
- Institute of Microbial Technology (CSIR), Chandigarh, India
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Ho JCS, Storm P, Rydström A, Bowen B, Alsin F, Sullivan L, Ambite I, Mok KH, Northen T, Svanborg C. Lipids as tumoricidal components of human α-lactalbumin made lethal to tumor cells (HAMLET): unique and shared effects on signaling and death. J Biol Chem 2013; 288:17460-71. [PMID: 23629662 DOI: 10.1074/jbc.m113.468405] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Long-chain fatty acids are internalized by receptor-mediated mechanisms or receptor-independent diffusion across cytoplasmic membranes and are utilized as nutrients, building blocks, and signaling intermediates. Here we describe how the association of long-chain fatty acids to a partially unfolded, extracellular protein can alter the presentation to target cells and cellular effects. HAMLET (human α-lactalbumin made lethal to tumor cells) is a tumoricidal complex of partially unfolded α-lactalbumin and oleic acid (OA). As OA lacks independent tumoricidal activity at concentrations equimolar to HAMLET, the contribution of the lipid has been debated. We show by natural abundance (13)C NMR that the lipid in HAMLET is deprotonated and by chromatography that oleate rather than oleic acid is the relevant HAMLET constituent. Compared with HAMLET, oleate (175 μm) showed weak effects on ion fluxes and gene expression. Unlike HAMLET, which causes metabolic paralysis, fatty acid metabolites were less strongly altered. The functional overlap increased with higher oleate concentrations (500 μm). Cellular responses to OA were weak or absent, suggesting that deprotonation favors cellular interactions of fatty acids. Fatty acids may thus exert some of their essential effects on host cells when in the deprotonated state and when presented in the context of a partially unfolded protein.
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Affiliation(s)
- James C S Ho
- Department of Microbiology, Immunology, and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Sölvegatan 23, S-223 62 Lund, Sweden
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