1
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Guo Z, Bergeron KF, Lingrand M, Mounier C. Unveiling the MUFA-Cancer Connection: Insights from Endogenous and Exogenous Perspectives. Int J Mol Sci 2023; 24:9921. [PMID: 37373069 DOI: 10.3390/ijms24129921] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 06/01/2023] [Accepted: 06/07/2023] [Indexed: 06/29/2023] Open
Abstract
Monounsaturated fatty acids (MUFAs) have been the subject of extensive research in the field of cancer due to their potential role in its prevention and treatment. MUFAs can be consumed through the diet or endogenously biosynthesized. Stearoyl-CoA desaturases (SCDs) are key enzymes involved in the endogenous synthesis of MUFAs, and their expression and activity have been found to be increased in various types of cancer. In addition, diets rich in MUFAs have been associated with cancer risk in epidemiological studies for certain types of carcinomas. This review provides an overview of the state-of-the-art literature on the associations between MUFA metabolism and cancer development and progression from human, animal, and cellular studies. We discuss the impact of MUFAs on cancer development, including their effects on cancer cell growth, migration, survival, and cell signaling pathways, to provide new insights on the role of MUFAs in cancer biology.
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Affiliation(s)
- Zhiqiang Guo
- Biological Sciences Department, Université du Québec à Montréal (UQAM), Montréal, QC H3P 3P8, Canada
| | - Karl-Frédérik Bergeron
- Biological Sciences Department, Université du Québec à Montréal (UQAM), Montréal, QC H3P 3P8, Canada
| | - Marine Lingrand
- Department of Biochemistry, McGill University, Montréal, QC H3A 1A3, Canada
| | - Catherine Mounier
- Biological Sciences Department, Université du Québec à Montréal (UQAM), Montréal, QC H3P 3P8, Canada
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2
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Hansen JS, Tran TH, Cavalera M, Paul S, Chaudhuri A, Lindkvist-Petersson K, Ho JCS, Svanborg C. Peptide-Oleate Complexes Create Novel Membrane-Bound Compartments. Mol Biol Evol 2020; 37:3083-3093. [PMID: 32521018 DOI: 10.1093/molbev/msaa138] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
A challenging question in evolutionary theory is the origin of cell division and plausible molecular mechanisms involved. Here, we made the surprising observation that complexes formed by short alpha-helical peptides and oleic acid can create multiple membrane-enclosed spaces from a single lipid vesicle. The findings suggest that such complexes may contain the molecular information necessary to initiate and sustain this process. Based on these observations, we propose a new molecular model to understand protocell division.
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Affiliation(s)
- Jesper S Hansen
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden.,Experimental Medical Science, Medical Structural Biology, Lund University, Lund, Sweden
| | - Tuan Hiep Tran
- 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
| | - Sanchari Paul
- 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
| | | | - James C S Ho
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden.,Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore
| | - Catharina Svanborg
- Department of Microbiology, Immunology and Glycobiology, Institute of Laboratory Medicine, Lund University, Lund, Sweden
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3
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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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4
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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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5
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Yang J, Wang T, Zhao L, Rajasekhar VK, Joshi S, Andreou C, Pal S, Hsu HT, Zhang H, Cohen IJ, Huang R, Hendrickson RC, Miele MM, Pei W, Brendel MB, Healey JH, Chiosis G, Kircher MF. Gold/alpha-lactalbumin nanoprobes for the imaging and treatment of breast cancer. Nat Biomed Eng 2020; 4:686-703. [PMID: 32661307 PMCID: PMC8255032 DOI: 10.1038/s41551-020-0584-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 06/11/2020] [Indexed: 02/03/2023]
Abstract
Theranostic agents should ideally be renally cleared and biodegradable. Here, we report the synthesis, characterization and theranostic applications of fluorescent ultrasmall gold quantum clusters that are stabilized by the milk metalloprotein alpha-lactalbumin. We synthesized three types of these nanoprobes that together display fluorescence across the visible and near-infrared spectra when excited at a single wavelength through optical colour coding. In live tumour-bearing mice, the near-infrared nanoprobe generates contrast for fluorescence, X-ray computed tomography and magnetic resonance imaging, and exhibits long circulation times, low accumulation in the reticuloendothelial system, sustained tumour retention, insignificant toxicity and renal clearance. An intravenously administrated near-infrared nanoprobe with a large Stokes shift facilitated the detection and image-guided resection of breast tumours in vivo using a smartphone with modified optics. Moreover, the partially unfolded structure of alpha-lactalbumin in the nanoprobe helps with the formation of an anti-cancer lipoprotein complex with oleic acid that triggers the inhibition of the MAPK and PI3K-AKT pathways, immunogenic cell death and the recruitment of infiltrating macrophages. The biodegradability and safety profile of the nanoprobes make them suitable for the systemic detection and localized treatment of cancer.
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Affiliation(s)
- Jiang Yang
- Center for Molecular Imaging and Nanotechnology (CMINT), Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Tai Wang
- Chemical Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Lina Zhao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
| | | | - Suhasini Joshi
- Chemical Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Chrysafis Andreou
- Center for Molecular Imaging and Nanotechnology (CMINT), Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Suchetan Pal
- Center for Molecular Imaging and Nanotechnology (CMINT), Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Hsiao-Ting Hsu
- Center for Molecular Imaging and Nanotechnology (CMINT), Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Hanwen Zhang
- Center for Molecular Imaging and Nanotechnology (CMINT), Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Ivan J Cohen
- Center for Molecular Imaging and Nanotechnology (CMINT), Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Louis V. Gerstner Jr Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Ruimin Huang
- Center for Molecular Imaging and Nanotechnology (CMINT), Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Ronald C Hendrickson
- Proteomics and Microchemistry Core Laboratory, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Matthew M Miele
- Proteomics and Microchemistry Core Laboratory, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Wenbo Pei
- Chemical Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Matthew B Brendel
- Molecular Cytology Core Laboratory, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - John H Healey
- Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Gabriela Chiosis
- Chemical Biology Program, Sloan Kettering Institute, New York, NY, USA
- Breast Cancer Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Moritz F Kircher
- Center for Molecular Imaging and Nanotechnology (CMINT), Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY, USA.
- Department of Radiology, Weill Cornell Medical College, New York, NY, USA.
- Department of Imaging, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA, USA.
- Department of Radiology, Brigham & Women's Hospital and Harvard Medical School, Boston, MA, USA.
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6
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Muller MP, Jiang T, Sun C, Lihan M, Pant S, Mahinthichaichan P, Trifan A, Tajkhorshid E. Characterization of Lipid-Protein Interactions and Lipid-Mediated Modulation of Membrane Protein Function through Molecular Simulation. Chem Rev 2019; 119:6086-6161. [PMID: 30978005 PMCID: PMC6506392 DOI: 10.1021/acs.chemrev.8b00608] [Citation(s) in RCA: 133] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The cellular membrane constitutes one of the most fundamental compartments of a living cell, where key processes such as selective transport of material and exchange of information between the cell and its environment are mediated by proteins that are closely associated with the membrane. The heterogeneity of lipid composition of biological membranes and the effect of lipid molecules on the structure, dynamics, and function of membrane proteins are now widely recognized. Characterization of these functionally important lipid-protein interactions with experimental techniques is however still prohibitively challenging. Molecular dynamics (MD) simulations offer a powerful complementary approach with sufficient temporal and spatial resolutions to gain atomic-level structural information and energetics on lipid-protein interactions. In this review, we aim to provide a broad survey of MD simulations focusing on exploring lipid-protein interactions and characterizing lipid-modulated protein structure and dynamics that have been successful in providing novel insight into the mechanism of membrane protein function.
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Affiliation(s)
- Melanie P. Muller
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology
- Department of Biochemistry
- Center for Biophysics and Quantitative Biology
- College of Medicine
- University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Tao Jiang
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology
- Department of Biochemistry
- Center for Biophysics and Quantitative Biology
- University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Chang Sun
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology
- Department of Biochemistry
- University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Muyun Lihan
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology
- Department of Biochemistry
- Center for Biophysics and Quantitative Biology
- University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Shashank Pant
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology
- Department of Biochemistry
- Center for Biophysics and Quantitative Biology
- University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Paween Mahinthichaichan
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology
- Department of Biochemistry
- University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Anda Trifan
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology
- Department of Biochemistry
- Center for Biophysics and Quantitative Biology
- University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology
- Department of Biochemistry
- Center for Biophysics and Quantitative Biology
- College of Medicine
- University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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7
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Rao E, Foderà V, Leone M, Vetri V. Direct observation of alpha-lactalbumin, adsorption and incorporation into lipid membrane and formation of lipid/protein hybrid structures. Biochim Biophys Acta Gen Subj 2019; 1863:784-794. [PMID: 30742952 DOI: 10.1016/j.bbagen.2019.02.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 02/06/2019] [Accepted: 02/07/2019] [Indexed: 02/02/2023]
Abstract
The interaction between proteins and membranes is of great interest in biomedical and biotechnological research for its implication in many functional and dysfunctional processes. We present an experimental study on the interaction between model membranes and alpha-lactalbumin (α-La). α-La is widely studied for both its biological function and its anti-tumoral properties. We use advanced fluorescence microscopy and spectroscopy techniques to characterize α-La-membrane mechanisms of interaction and α-La-induced modifications of membranes when insertion of partially disordered regions of protein chains in the lipid bilayer is favored. Moreover, using fluorescence lifetime imaging, we are able to distinguish between protein adsorption and insertion in the membranes. Our results indicate that, upon addition of α-La to giant vesicles samples, protein is inserted into the lipid bilayer with rates that are concentration-dependent. The formation of heterogeneous hybrid protein-lipid co-aggregates, paralleled with protein conformational and structural changes, alters the membrane structure and morphology, leading to an increase in membrane fluidity.
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Affiliation(s)
- Estella Rao
- Dipartimento di Fisica e Chimica, Università di Palermo, 90128 Palermo, Italy
| | - Vito Foderà
- Department of Pharmacy, Universitetsparken 2, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Maurizio Leone
- Dipartimento di Fisica e Chimica, Università di Palermo, 90128 Palermo, Italy
| | - Valeria Vetri
- Dipartimento di Fisica e Chimica, Università di Palermo, 90128 Palermo, Italy.
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8
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Nedergaard Pedersen J, Frederix PWJM, Skov Pedersen J, Marrink SJ, Otzen DE. Role of Charge and Hydrophobicity in Liprotide Formation: A Molecular Dynamics Study with Experimental Constraints. Chembiochem 2018; 19:263-271. [PMID: 29156084 DOI: 10.1002/cbic.201700496] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Indexed: 12/15/2022]
Abstract
Bovine α-lactalbumin (aLA) and oleate (OA) form a complex that has been intensively studied for its tumoricidal activity. Small-angle X-ray scattering (SAXS) has revealed that this complex consists of a lipid core surrounded by partially unfolded protein. We call this type of complex a liprotide. Little is known of the molecular interactions between OA and aLA, and no technique has so far provided any high-resolution structure of a liprotide. Here we have used coarse-grained (CG) molecular dynamics (MD) simulations, isothermal titration calorimetry (ITC) and SAXS to investigate the interactions between aLA and OA during the process of liprotide formation. With ITC we found that the strongest enthalpic interactions occurred at a molar ratio of 12.0±1.4:1 OA/aLA. Liprotides formed between OA and aLA at several OA/aLA ratios in silico were stable both in CG and in all-atom simulations. From the simulated structures we calculated SAXS spectra that show good agreement with experimentally measured patterns of matching liprotides. The simulations showed that aLA assumes a molten globular (MG) state, exposing several hydrophobic patches involved in interactions with OA. Initial binding of aLA to OA occurs in an area of aLA in which a high amount of positive charge is located, and only later do hydrophobic interactions become important. The results reveal how unfolding of aLA to expose hydrophobic residues is important for complex formation between aLA and OA. Our findings suggest a general mechanism for liprotide formation and might explain the ability of a large number of proteins to form liprotides with OA.
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Affiliation(s)
- Jannik Nedergaard Pedersen
- Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
| | - Pim Wilhelmus Johannes Maria Frederix
- Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
| | - Jan Skov Pedersen
- Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
| | - Siewert Jan Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands
| | - Daniel E Otzen
- Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 14, 8000, Aarhus C, Denmark
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9
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Augmenting the cytotoxicity of oleic acid-protein complexes: Potential of target-specific antibodies. Biochimie 2017; 137:139-146. [PMID: 28341551 DOI: 10.1016/j.biochi.2017.03.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 03/18/2017] [Indexed: 01/16/2023]
Abstract
HAMLET (Human Alpha-Lactalbumin Made LEthal to Tumor cells), a complex of oleic acid (OA) with partially unfolded human α-lactalbumin, shows remarkable toxicity towards a spectrum of tumor cells as well as few differentiated cells including mammalian erythrocytes. Human erythrocytes, for this reason, have been used as convenient model cells to study toxic properties of the OA complexes. The toxicity of HAMLET-like complexes, prepared using immunoglobulin gamma (IgG) isolated from the sera of rabbits immunized with human erythrocytes as well as those unimmunized, towards the red cells was investigated. The OA complex of the IgG prepared by the heat-treatment procedure comprised of protein monomers and oligomers with bound OA. The IgG in the complexes retained most secondary but only partial tertiary structure and complex formation with OA did not abolish the ability of anti-erythrocyte IgG to bind to the erythrocytes. Anti-erythrocyte IgG-OA complexes were remarkably more hemolytic than those prepared using non-specific IgG, while complexes prepared using affinity purified anti-erythrocyte IgG were most effective in hemolyzing the cells. The work suggests that antibodies that exhibit affinity towards target cells may be useful in the preparation of selective and highly toxic OA complexes for the cells.
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