Galectin-1-binding glycoforms of haptoglobin with altered intracellular trafficking, and increase in metastatic breast cancer patients

• Published in: PloS one 2011-10, Vol.6 (10), p.e26560
• Main Authors: Carlsson, Michael C, Cederfur, Cecilia, Schaar, Viveka, Balog, Crina I A, Lepur, Adriana, Touret, Franck, Salomonsson, Emma, Deelder, André M, Fernö, Mårten, Olsson, Håkan, Wuhrer, Manfred, Leffler, Hakon
• Format: Article
• Language: English
• Subjects: Affinity; Affinity chromatography; Aged; Analysis; Antigens; Basic Medicine; Binding Sites; Biology; Biomarkers; Breast cancer; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Cancer; Cancer metastasis; Cancer patients; Carbohydrates; Case-Control Studies; Cell Line, Tumor; Chromatography; Endocytosis; Female; Galectin 1 - chemistry; Galectin 1 - immunology; Galectin 1 - metabolism; Galectin-1; Glycoproteins; Haptoglobin; Haptoglobins - chemistry; Haptoglobins - metabolism; Hemoglobin; Humans; Hypotheses; Immobilized Proteins - chemistry; Immobilized Proteins - metabolism; Immunoglobulin M; Immunoglobulin M - immunology; Immunology; Intracellular; Intracellular Space - metabolism; Laboratories; LAMP-2 protein; Lectins; Lysosomes; Macrophages; Macrophages - cytology; Macrophages - metabolism; Mass spectrometry; Mass spectroscopy; Medical and Health Sciences; Medical diagnosis; Medicin och hälsovetenskap; Medicine; Medicinska och farmaceutiska grundvetenskaper; Metastases; Metastasis; Microbiology in the medical area; Middle Aged; Mikrobiologi inom det medicinska området; Models, Molecular; Mutants; N-Acetylneuraminic Acid; N-glycans; Neoplasm Metastasis; Parasitology; Patients; Physiology; Polysaccharides; Polysaccharides - metabolism; Prostate cancer; Protein Binding; Protein Multimerization; Protein Structure, Quaternary; Protein Transport; Proteins; Scientific imaging; Substrate Specificity; Tumors
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0026560

Sera from 25 metastatic breast cancer patients and 25 healthy controls were subjected to affinity chromatography using immobilized galectin-1. Serum from the healthy subjects contained on average 1.2 mg per ml (range 0.7-2.2) galectin-1 binding glycoproteins, whereas serum from the breast cancer patients contained on average 2.2 mg/ml (range 0.8-3.9), with a higher average for large primary tumours. The major bound glycoproteins were α-2-macroglobulin, IgM and haptoglobin. Both the IgM and haptoglobin concentrations were similar in cancer compared to control sera, but the percentage bound to galectin-1 was lower for IgM and higher for haptoglobin: about 50% (range 20-80) in cancer sera and about 30% (range 25-50) in healthy sera. Galectin-1 binding and non-binding fractions were separated by affinity chromatography from pooled haptoglobin from healthy sera. The N-glycans of each fraction were analyzed by mass spectrometry, and the structural differences and galectin-1 mutants were used to identify possible galectin-1 binding sites. Galectin-1 binding and non-binding fractions were also analyzed regarding their haptoglobin function. Both were similar in forming complex with haemoglobin and mediate its uptake into alternatively activated macrophages. However, after uptake there was a dramatic difference in intracellular targeting, with the galectin-1 non-binding fraction going to a LAMP-2 positive compartment (lysosomes), while the galectin-1 binding fraction went to larger galectin-1 positive granules. In conclusion, galectin-1 detects a new type of functional biomarker for cancer: a specific type of glycoform of haptoglobin, and possibly other serum glycoproteins, with a different function after uptake into tissue cells.