Uncovering the role of modified citrus pectin in cancer

Abstract

Background: Modified citrus pectin (MCP) is a polysaccharide consisting of galacturonic acid with anti-cancer activity that can act synergistically with other treatments to reduce tumor growth, stimulate programmed cell death and reduce the number of metastases. In addition, MCP prevents acute and severe renal syndromes caused by radiation/chemotherapy. All of these effects were reported to be due to MCP ability to specifically inhibit Galectin-3 protein functions. Aims: The aim of this work was to evaluate the anticancer effect of MCP in a Balb/c nude mice xenograft model of ovarian cancer. Methods: The human ovary cancer cell line, SKOV-3, was subcutaneously injected in Balb/c nude mice and tumor growth was monitored daily with a caliper. When tumors reached 250-300 mm3, 20 mg/kl of MCP was administered intravenously (I.V.) in a daily based for 21 days. Tumor growth and mice weight were monitored daily. Additionally, MCP was radiolabeled with 99m-technetium (99m-Tc) with the incubation of MCP (2.5 mg) in saline with SnCl2 (4 mg/ ml), HCl (0.01 M), NaOH (0.01 M) and 99mTc (129,5 MBq) at pH=7 for 30 min. The radiochemical purity was determined by iTLC-SG with acetone and ethanol/NH3/H2O (1:2:5). 99mTc-MCP (37 MBq) was administrated I.V. in Balb/C nude mice bearing SKOV-3 tumors and after 1, 2 and 4 hours, SPECT/CT image was acquired (Albira SI Buker). Ex-vivo biodistribution studies were performed after the I.V. injection of 10 MBq of 99mTc-MCP for 1-hour. The % of injected dose per gram (%ID/g) of tissues of interest was calculated. The tumors were removed, fixed, cut and used for autoradiography studies and stained with hematoxylin and eosin (H&E) to verify hypoxic regions. Results: The I.V. administration of MCP was able to significantly reduce SKOV-3 tumor growth (52% tumor volume reduction) in comparison with the non-treated group, after 21 of treatment. Our biodistribution studies showed that 99mTc-MCP was mainly found in kidneys, bladder and liver of mice (%ID/g = 12.25, 38.57 and 5.71, respectively), and was able to reach the tumor (%ID/g = 0.765 ± 0.045) 1-hour after I.V. administration. 99mTc-MCP accumulation in the tumor site was visualized by μSPECT/CT imaging 1 hour after I.V. administration. The autoradiography and stained (H&E) study demonstrated a correlation between MCP and regions of tumor necrosis. Because of MCP high accumulation in kidneys, renal toxicity was also evaluated. We were able to find that MCP doesn’t induce renal toxicity when administered in a daily base at a concentration of 20 mg/Kg. Conclusion: In this work we demonstrated that a daily treatment of MCP was able to reduce tumor growth of ovarian tumor xenografts (SKOV-3 cells) without showing renal toxicity. We found too that MCP can reach the tumor site, binding mainly in regions of necrosis. However, other studies are needed to unravel the mechanisms of action that act on the antitumor effect of MCP.