Preclinical evidence has suggested that anticoagulants, including the unfractionated heparin (UFH), exert an anti-tumor effect, whereas the role of anticoagulants in tumor development and metastatic processes has not been fully elucidated yet. Heparin is the major inhibitor of heparanase, which cleaves heparan sulfate and hence participates in degradation of the extracellular matrix. This enzyme also releases a lot of biologically active substance including some growth factors, cytokines, adhesion molecules, and angiogenic factors. Thus, heparin can affect proliferation, migration, and invasion of cancer cells. Moreover, heparin can interfere with adherence of cancer cells to vascular endothelium. This study was designed to evaluate the effects of UFH in the inhibition of liver metastasis of pancreatic cancer. We made a clinical liver metastasis-simulating mouse model, in which cancer cells were intra-portal injected via small laparotomy. Moreover, synergistic effect of combination therapy with UFH and gemcitabine was investigated.

Male BALB/c nude mice were xenografted with intra-portal vein injection of AsPC-1, a human pancreatic adenocarcinoma cell line. Mice were divided randomly into four groups; 1) positive control (PC) without any treatment, 2) gemcitabine treated group (GEM), 3) UFH treated group, and 4) combined treatment group (GEM+UFH). All mice were sacrificed on 28th day after transplantation of cells. The liver weight, the number of liver metastases, induction angiogenesis in metastasis foci were investigated. Heparan degrading enzyme, heparanase, were activated in liver metastasis, in which activity were measured by using the Heparan Degrading Enzyme Assay Kit. Gemcitabine inhibited tumor proliferation, whereas UFH little inhibited in vitro (WST assay). The number of liver metastases decreased significantly in the GEM (17.2±11.5) group, UFH (18.3±3.8) group and GEM+UFH (9.3±2.5) group when compared with the PC group (23.3±7.0). Liver/body weight ratio was lower in the GEM (7.44±1.36 %) group, UFH (7.56±1.47 %) group and GEM+UFH (6.98±0.63 %) group when compared with the PC group (7.99±0.94 %). Tumor vessels were identified by immunohistochemical staining of tumor metastasis sections with antibody against CD31. There was a large reduction in the number of CD31-positive vessels in the tumor of UFH or/and GEM-treated mice as compared with control group.

UFH exhibited anti-tumor effect by inhibiting angiogenesis, and invasiveness of tumor cells. Furthermore, when UFH and gemcitabine were administered simultaneously, our results suggested the possibility of a synergistic effect. Thus UFH might be a potent drug for the treatment of pancreatic cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4175.