In vitro assessment of Lipiodol-targeted radiotherapy for liver and colorectal cancer cell lines.

Intra-arterial Lipiodol has been used to deliver targeted therapies to primary, and some metastatic, liver cancers. Targeted radiotherapy has been used by substituting the iodine in Lipiodol with 131Iodine (131I). Early clinical results are encouraging, but the variable response may partly depend on local pharmacokinetics. This study evaluated the in vitro cytotoxic effects of 131I-Lipiodol on human hepatocellular carcinoma (Hep-G2), human colorectal metastatic cancer (SW620), human colorectal hepatic cancer (LoVo) and human umbilical vein endothelial cells (HUVEC) cell lines. The cell cultures were exposed to 131I-Lipiodol for 48 h, following which cell counts and viability were assessed by haemocytometer, S-Rhodamine uptake and radioactivity assay. The effect of exposure to control Lipiodol, 131I-Lipiodol and 131I alone was evaluated. 131I-Lipiodol was cytotoxic against all the cancer cell lines but not against the non-malignant (HUVEC) cell line. The cytotoxicity effects were very similar in all the cancer cell lines. There were no cytotoxic effects following exposure to plain 131I in any of the cell lines (malignant and non-malignant). A similar trend was seen with radioactivity counts using a gamma counter. The cytotoxic effect of 131I-Lipiodol had a graded effect with an increase in cytotoxicity following the increase in the radioactive dose. This study showed that there was a marked cytotoxic effect by 131I-Lipiodol on all the cancer cell lines. There was no difference between the controls and the 131Iodine. This suggests that effective 131I-Lipiodol targeted therapy is dependent on the uptake and retention of Lipiodol by malignant cells.