Non-natural heparin mimetic sulfated trimaltose C-C-linked dimers (STMCαα, STMCαβ and STMCββ, Fig. 1) are promising antimetastatic drugs which inhibit heparanase and selectins (1). Heparanases accelerate tumour growth and selectins can mediate tumour cell interactions. Heparin is an inhibitor of heparanase and selectins.
The central hydrolase-resistant C-C bond confers unusual configurations and conformations determining different biological activity. The adhesion of LS-180 colon carcinoma cells to immobilized P-selectin was used to evaluate the P-selectin inhibitory activity of STMCs. Inhibition of heparanase enzymatic activity was tested by a method based on HPLC-ESI quantitative analysis of a competitor substrate and by in vitro tests using a naturally produced sulfate-labeled ECM substrate. P-selectin and heparanase were inhibited by STMCαβ, while STMCαα inhibits only heparanase. STMCββ was found not to be effective in either case.
STMCαβ attenuated metastasis of B16-BL6 melanoma cells and MC-38GFP colon carcinoma cells in wild-type mice by 82%. STMCαα reduced only B16-BL6 metastasis by 65%. The three STMCs at concentrations ≤2 mg/mL yielded little or no cytotoxicity in MG63 and HeLa cancer cell lines.
The most promising compound STMCαβ was subjected to structural and conformational analysis based on NMR techniques (homonuclear COSY, TOCSY and NOESY and heteronuclear HSQC, HMBC). To better represent the basic structure and conformational properties of these oligosaccharides including this singular C-C bond, the average conformation is drawn and refined using molecular mechanics.
(1) Borsig, L. et al. Neoplasia, 2011, 13, 445–452; Vismara, E.et al. Molecules, 2012, 17, 9912-9930
