Identification of pro- and anti-proliferative oligosaccharides of heparins

Heparins, unfractionated heparin (UFH) and low molecular weight heparins (LMWHs), are heterogeneous mixtures of anticoagulant and non-anticoagulant oligosaccharides. In addition to their well-known anticoagulant effect, heparins have shown to mediate a wide range of non-anticoagulant effects, including the modulation of cellular growth. However, contradictory results have been reported with regard to their effects on cellular proliferation, with some studies suggesting anti-proliferative while others indicating pro-proliferative effects. This study investigated the proliferation of human colonic epithelial cancer cells in the presence of UFH and LMWHs (enoxaparin and dalteparin). In our experimental setting, all heparins caused a dose-dependent reduction in cellular growth, which correlated well with the induction of cell cycle arrest in the G(1) phase and which was not associated with significant changes in cell viability. The effects on cellular proliferation of 14 different oligosaccharides of enoxaparin obtained through ion-exchange chromatography were also assessed. Surprisingly, only two oligosaccharides showed distinctive anti-proliferative effects while the majority of oligosaccharides actually stimulated proliferation. Interestingly, the smallest oligosaccharide devoid of any anticoagulant activity showed the strongest anti-proliferative effect. Notably, heparins are currently standardised only according to their anticoagulant activity but not based on other non-anticoagulant properties. Our results indicate that slight differences in the composition of heparins' non-anticoagulant oligosaccharides, due to different origins of material and preparation methods, have the potential to cause diverse effects and highlight the need for additional characterisation of non-anticoagulant activities.