[Mechanism of cardiotoxicity associated with Herceptin using (131)I-Herceptin radioimmunoimaging].

Objective To study the mechanism of cardiotoxicity associated with Herceptin. Methods Herceptin was labeled with iodine-131 using the Iodogen method. Radioimmunoimaging was performed in 5 rabbits at 3 h to 5 days following 131I-Herceptin injection to investigate the biodistribution of Herceptin. 131I-Herceptin uptake in each organ or tissue relative to that in the muscular tissue (O/M ratio) was calculated and compared. On the fifth day following the injection, the organs including the heart, lung, liver and muscles were taken for measurement of the weight and radiocounts. HER2 expression was measured by immunohistochemistry in these organs and tissues. Results The O/M ratio of the heart was significantly higher than that of the lung (P=0.032) and liver (P=0.019) at 3 h after Herceptin injection, but educed significantly at 24 h (P=0.001). The uptake of 131I-Herceptin in the myocardium was slightly higher that that in the muscle and intestine, but lower than that in the lung and spleen. HER2 expression showed no significant difference between the myocardium and the other tissues such as the liver, lung, and kidney (H=3.236, P=0.172). Conclusion Myocardium expresses low levels of HER2 and accumulates Herceptin no more than the other tissues.