BMC Cancer. 2013 Jan 17;13:24.

Specific genes involved in synthesis and editing of heparan sulfate proteoglycans show altered expression patterns in breast cancer

Iván Fernández-Vega, Olivia García, Ainara Crespo, Sonia Castañón, Primitiva Menéndez, Aurora Astudillo and Luis M Quirós*

Author information:

Iván Fernández-Vega: Department of Pathology, Hospital Universitario Central de Asturias, Oviedo, 33006, Spain.
Olivia García: Department of Morphology and Cell Biology, University of Oviedo, Oviedo, 33006, Spain
Ainara Crespo: Department of Biotechnology, Neiker-Tecnalia Arkaute, Vitoria-Gasteiz, 01080, Spain
Sonia Castañón: Department of Biotechnology, Neiker-Tecnalia Arkaute, Vitoria-Gasteiz, 01080, Spain
Primitiva Menéndez: Department of Pathology, Hospital Universitario Central de Asturias, Oviedo, 33006, Spain.
Aurora Astudillo : Department of Pathology, Hospital Universitario Central de Asturias, Oviedo, 33006, Spain
Luis M Quirós: University Institute of Oncology of Asturias, and Department of Functional Biology, University of Oviedo, Oviedo, 33006, Spain



The expression of a specific set of genes controls the different structures of heparan sulfate proteoglycans (HSPGs), which are involved in the growth, invasion and metastatic properties of cancerous cells. The purpose of this study is to increase knowledge of HSPG alterations in breast cancer.

Twenty-three infiltrating ductal adenocarcinomas (IDCs), both metastatic and non-metastatic were studied. A transcriptomic approach to the structure of heparan sulfate (HS) chains was used, employing qPCR to analyze both the expression of the enzymes involved in their biosynthesis and editing, as well as the proteoglycan core proteins. Since some of these proteoglycans can also carry chondroitin sulfate chains, we extended the study to include the genes involved in the biosynthesis of these glycosaminoglycans. Histochemical techniques were also used to analyze tissular expression of particular genes showing significant expression differences, of potential interest.

No significant change in transcription was detected in approximately 70% of analyzed genes. However, 13 demonstrated changes in both tumor types (40% showing more intense deregulation in the metastatic), while 5 genes showed changes only in non-metastatic tumors. Changes were related to 3 core proteins: overexpression of syndecan-1 and underexpression of glypican-3 and perlecan. HS synthesis was affected by lower levels of some 3-O-sulfotransferase transcripts, the expression of NDST4 and, only in non metastatic tumors, higher levels of extracellular sulfatases. Furthermore, the expression of chondroitin sulfate also was considerably affected, involving both the synthesis of the saccharidic chains and sulfations at all locations. However, the pro-metastatic enzyme heparanase did not exhibit significant changes in mRNA expression, although in metastatic tumors it appeared related to increased levels of the most stable form of mRNA. Finally, the expression of heparanase 2, which displays anti-metastatic features, experienced a strong deregulation in all patients analyzed.

IDCs show alterations in the expression of HSPG genes; principally the expression and localization of proteoglycans and the sulfation patterns of glycosaminoglycan chains, depending on the metastatic nature of the tumor. In addition, the anti-proliferative molecule heparanase 2 experiences strong deregulation, thus highlighting it as a potentially interesting diagnostic factor.

PMID:  23327652



Proteoglycans are a family of glycoproteins which are characterized by containing one or more glycosaminoglycan chains covalently attached to their protein core. Glycosaminoglycans are linear, anionic polysaccharides consisting of repeating disaccharides. Heparan sulfate proteoglycans comprise a small, specific group of proteins covalently linked to heparan sulfate chains. Heparan sulfate is the most complex type of glycosaminoglycan, and its basic structure is a chain of alternating glucuronic acid and N-acetylglucosamine that is modified by a series of interdependent enzymatic reactions which includes N-sulfation, epimerization and various O-sulfations. After biosynthesis, the heparan sulfate chains can change their patterns of sulfation through the action of two specific sulfatases, and can also be fragmented by the effect of the enzyme heparanase.

Heparan sulfate proteoglycans are ubiquitous in tissues, mainly those associated with the cell surface and the extracellular matrix. They have been implicated in a variety of normal physiological functions that largely depend on the fine structure of the glycosaminoglycan chains. Cells exercise exquisite control over heparan sulfate proteoglycan composition and sequence, varying among cell types, development stage and as results of cell transformation in pathological processes.

Tumour heparan sulfate proteoglycans differ in composition from those in the corresponding normal tissue. As a result of these modifications, some processes appear to be affected, such as cancer cell signalling, growth and survival, cell adhesion, and differentiation, migration and angiogenesis. On this basis, the possibility of selective targeting of tumour cells and tumour microvasculature by agents that bind heparan sulfate or modify its synthesis has been proposed.

In this work, the differential expression of the majority of the genes responsible for the synthesis of heparan sulfate proteoglycans in breast tumours compared to to normal tissue is analyzed. The tumours were subdivided into two groups according to presence or absence of metastasis in lymph nodes since this element is a key predictor of progression. The study included genes coding for core protein and heparan sulfate chain synthesis and modification. It was also extended to include the genes involved in the biosynthesis of chondroitin sulfate, since chains of this glycosaminoglycan appear to be covalently bound to some heparan sulfate proteoglycans.

The analysis indicated that about 25% of the genes examined experienced significant changes in their transcript levels. Most of the changes occurred independently of the presence of metastasis, although some variations showed more intense changes in metastatic than non-metastatic tumours. In contrast, however, certain alterations were only detected in the group of non-metastatic tumours. This study increases our knowledge of the alterations of heparan sulfate proteoglycans in relation to cancer progression.


The University Institute of Oncology of Asturias is supported by Obra Social Cajastur, Asturias, Spain.
FIG1: Structure of heparan sulfate proteoglycans. Heparan sulfate proteoglycans are commonly arranged on the cell surface and in the extracellular matrix (ECM). Cell-associated proteoglycans include integral membrane syndecans and glycosyl-phosphatidylinositol-anchored glypicans. Some core proteins are composed of various domains that can harbour several protein modules. Breast cancer alterations include the overexpression of syndecan-1 and the underexpression of glypican-3 and perlecan. Heparan sulfate chains undergo a series of enzymatic reactions, including N-sulfation, epimerization and various O-sulfations, resulting in clusters of highly sulfated regions. Through their fine structure, heparan sulfate chains are able to interact selectively with many different types of soluble and insoluble ligands. Some heparan sulfate proteoglycans also include chondroitin sulfate chains in their structure. Certain enzymes responsible for the synthesis of glycosaminoglycan chains are altered in breast tumours, depending on the presence or absence of lymph node metastases

Luis M., Quirós

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