Polyamines are necessary for cell proliferation and are detected at higher concentrations in most tumor tissues. Bovine serum amine oxidase (BSAO) can generate in situ cytotoxic products such as H 2 O 2 and aldehydes from oxidation of polyamines, as a new approach in cancer therapy [1]. The present results show that multidrug-resistant human colon adenocarcinoma cells (LoVo) are significantly more sensitive than corresponding wild-type cells to the cytotoxic products. Pre-treatment of the cells with anandamide (AEA) (Figure 1), an endocannabinoid which effect can be either central, in the brain, mediated by CB 1 receptors, or peripheral in other organs and tissues where CB 2 receptors are expressed, sensitized both cell lines to the subsequent exposure to spermine metabolites amplifying the ability of these products to induce cell death [2]. The sensitizing effect was also greater on multidrug-resistant cells than wild-type ones, an aspect of particular importance since conventional cancer therapy suffers from the development of drug resistance. Cell viability was determined using MTT assay [3]. Concentrations 0-100 µM of AEA were tested, for incubation times up to 24 h; and concentrations 0-8 µM of spermine in presence of BSAO were used, for incubation times up to 1 h.