In vivo treatment of rats with unfractionated heparin (UFH) or low molecular weight heparin (LMWH) does not affect experimentally induced colon carcinoma metastasis

Recent randomized trials have suggested that treatment with low molecular w eight heparin (LMWH) improves survival of cancer patients with venous throm boembolism, as compared to treatment with unfractionated heparin (UFH). Exp erimental studies have shown that UFH has activities besides its anticoagul ant function which may affect progression of malignancy, including stimulat ion of new blood vessel formation. In contrast, LMWH has been suggested to inhibit angiogenesis. In the present study, we compared quantitatively the effects of treatment with UFH, LMWH or placebo on the development of experi mentally induced colon carcinoma metastases in rat liver and on tumor-assoc iated angiogenesis. It is shown that UFH and LMWH in therapeutic dosages ne ither affect development of metastases nor tumor blood vessel formation in this animal model. These results indicate that heparins do not affect colon cancer metastasis in liver. Further studies in other animal models are req uired to establish the mechanisms by which heparins potentially affect canc er.