['To evaluate the anticoagulant and antineoplastic activities of chemically modified low-molecular-weight heparin (LMWH).', 'LMWH obtained by splitting unfractionated heparin (UFH) with sodium periodate oxidation and sodium borohydride reduction was subjected to acetylation catalyzed by DCC and DMAP to produce acetylated LMWH (ALMWH). The anticoagulant activity of ALMWH was determined in mice, and its antiproliferative and anti-invasion activities was assessed in human breast cancer cells MDA-MB-231 and MFC-7.', 'The anticoagulant activity of LMWH was decreased significantly after acetylation. The concentrations of commercial LMWH* and ALMWH for doubling the coagulation time (CT) were 33.04 µmol/L and 223.56 µmol/L, respectively, and the IC(50) of ALMWH for doubling CT was 6 times of that of LMWH*. ALMWH and LMWH at 0.1, 0.3, 0.9, 2.7 and 8.1 mmol/L both significantly inhibited the proliferation of MDA-MB-231 and MCF-7 cells in a concentration-dependent manner, but ALMWH produced stronger inhibitory effects. The IC(50) of LMWH and ALMWH for inhibiting cell proliferation was 3168.4 µmol/L and 152.6 µmol/L in MCF-7 cells, and 12299.6 µmol/L and 22.2 µmol/L in MDA-MB-231 cells, respectively. ALMWH and LMWH all markedly suppressed the invasion of MDA-MB-231 cells with comparable effects.'] Does [ Chemical modification endow heparin with low anticoagulant and high antineoplastic activities ]?