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To follow the biodistribution of exogenous hyaluronan in tumor-bearing animals, a total of seventeen inbred rats with hepatic metastases from a colonic adenocarcinoma received 125I-labelled hyaluronan by intravenous injections. Group I received only labeled hyaluronan (25 microg), whereas group II received 2.5 mg chondroitin sulphate prior to labeled hyaluronan, to block receptor uptake in normal liver endothelial cells. Animals in group III received intravenous, as well as intraperitoneal chondroitin sulphate (2.5 mg), to see if a better and prolonged blocking could be achieved. Radioactivity was visualized by whole body autoradiography, using phosphorimaging and the average radioactivity determined as phosphoimaging density units of the total area of hepatic metastases, normal liver, and skeletal muscle by computer-based image analysis. At 5 h, tumors in groups II and III showed higher uptake (4.8+/-1.8, P = .01 and 3.6+/-1.1, P = .01, respectively), in comparison to group I (1.8+/-0.6), and the mean normal liver/tumor concentration ratio was reduced from 21.4+/-10.1 in group I to 5.7+/-2.7 in group II and 3.5+/-1.1 in group III (P = .008 and P = .01, respectively). Our study shows that hyaluronan targets liver metastases of a colon adenocarcinoma. Furthermore, chondroitin sulphate pretreatment increases tumor uptake, while uptake at normal receptor sites is significantly reduced. The results also suggest that after blocking of normal hyaluronan/chondroitin sulphate receptors in healthy tissue, hyaluronan may be used to deliver drugs to specific hyaluronan receptor-positive sites of pathology. |
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