In-vitro uptake of radioactive lipiodol I-131 and I-125 by hepatoblastoma: implications for targeted radiotherapy

Lipiodol, a stable iodine addition product of fatty ethyl esters derived from poppyseed oil, has been used as a vehicle for targeted cytotoxic or radiotherapeutic treatment in adults with unresectable hepatocellular carcinoma and in a few children with advanced hepatoblastoma (HB). Prolonged retention of lipiodol by the cancer cells might enable more effective targeted therapy to advanced, multifocal, or metastatic HB. To investigate the uptake and cytotoxic efficacy of beta and Auger electron-emitting radioconjugates on HB cells, monolayers of HB (C3a, Hep Tow1) and normal human hepatocyte cell lines were exposed to lipiodol131 (L131), lipiodol125 (L125), or a cocktail of both isotopes. Uptake of radioactivity was assessed autoradiographically using phosphoimages and the cytotoxicity assessed by trypan blue exclusion and clonogenic assay. The uptake of the different radioconjugates was identical in both HB cell lines. The "cocktail" of both radioactive lipiodols caused the greatest cytotoxicity to HB C3a, and HepTow1. L125 alone had a similar level of uptake and cytotoxicity as L131. Radioactive iodine alone did not show any cytotoxicity on any of the liver cell lines in culture for up to 72 h. These experimental results provide support for a clinical strategy of combinations ("cocktails") of radioconjugates in targeted radiotherapy in patients with HB.