Glycosaminoglycans are natural heteropolysaccharides that are present in every mammalian tissue. They are composed of repeating disaccharide units that consist of either sulfated or non‐sulfated monosaccharides. Their molecular size and the sulfation type vary depending on the tissue, and their state either as part of proteoglycan or as free chains. In this regard, glycosami‐noglycans play important roles in physiological and pathological conditions. During recent years, cell biology studies have revealed that glycosaminoglycans are among the key macromolecules that affect cell properties and functions, acting directly on cell receptors or via interactions with growth factors. The accumulated knowledge regarding the altered structure of glycosaminoglycans in several diseases indicates their importance as biomarkers for disease diagnosis and progression, as well as pharmacological targets. This review summarizes how the fine structural characteristics of glycosaminoglycans, and enzymes involved in their biosynthesis and degradation, are involved in cell signaling, cell function and cancer progression. Prospects for glycosaminoglycan‐based therapeutic targeting in cancer are also discussed.

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Cell surface heparan sulfate proteoglycans (HSPGs), syndecans and glypicans, play crucial roles in the functional properties of cancer cells, such as proliferation, adhesion, migration and invasion. Platelet-derived growth factor (PDGF)/PDGF receptor (PDGF-R) mediated signaling, on the other hand, is highly associated with cancer progression. Specifically, PDGF-Ra and PDGF-Rb expressions documented in breast cancer tissue specimens as well as breast cancer cell lines are correlated with tumor aggressiveness and metastasis. Imatinib (Glivec Ò ) is a tyrosine kinase inhibitor specific for PDGF-Rs, c-ΚΙΤ and BCR-ABL. In this study we evaluated the effects of imatinib on the properties of breast cancer cells as well as on the expression of HSPGs in the presence and absence of PDGF-BB. These studies have been conducted in a panel of three breast cancer cell lines of low and high metastatic potential. Our results indicate that imatinib exerts a significant inhibitory effect on breast cancer cell proliferation, invasion and migration as well as on the cell surface expression of HSPGs even after exposure of PDGF. These effects depend on the aggressiveness of breast cancer cells and the type of HSPG. It is suggested that imatinib may be of potential therapeutic usefulness in breast cancer regimes.

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