Effect Of Herceptin Combined With Doxorubicin On Rat Cardiotoxicity

Herceptin is a humanized monoclonal antibody for treating the patients with metastatic breast cancers overexpresing human epidermal growth factor receptor(HER-2).Herceptin combined with doxorubicin markedly increased the incidence of cardiacdysfunction in clinical trials.Based on the stable and reliable rat heart's model, The current study was designed to investigate the cardiotoxicity aggravated by Herceptin combined with doxorubicin. The main methods and results are described as follows:1. Establishment of rat heart's model and study on myocardial pathological and ultrastructural alterationsThirty-six female rats were randomized into four groups(n=9):Control group: rats were treated only normal saline by intraperioneal injection at six tines every other dayHerceptin group: rats were treated doxorubicin by intraperioneal injection (1.0mg.kg-1 body weight at five tines every other day)Doxorubicin group: rats were treated doxorubicin by intraperioneal injection (2.0mg.kg-1 body weight at five tines every other day)Herceptin combined with doxorubicin group.the rats of doxorubicin treated (2.0mg.kg-1 body weight at five times every other day)were combined with Herceptin (1.0mg.kg-1 body weight at six tines every other day)The denaturation changes of myocardium were evaluated by the modified pathologic staining .Diffuse positive staining were observed in myocardium of doxorubicin group and Herceptin combined with doxorubicin group.The ultrastructural changes of myocyte were observed under electron microscope. In doxorubicin group, the most significant ultrastructural changes were mitochondrial swelling and damage of capillary endothelium, which were more severe in Herceptin combined withdoxorubicin group. There were significant differences between doxorubicin group and Herceptin combined with doxorubicin group in positive density (/><0.05). 2. Detection of myocyte snperoxiaized indexesThe value of malon dialdehyde (MDA) was measured by thiobarbituric acid(TBA) method and the activity of glutathione peroxidase(GSH-Px) was measured by 5,5'-dithiobis-2-nitrobenzoic acid (DTNB)method. The value of MDA in Control group and Herceptin group were(0.70±0.03)and(0.73±0.05)nmol/mg respectively, the activity of GSH-Px in Control group and Herceptin group were (81.31 ±0.13 ) and (78.43±0.15 ) U/mg respectively. Herceptin group is similar to Control group. The value of MDA in Doxorubicin group and Herceptin combined with doxorubicin group were (0.88±0.10) and (0.94±0.13) nmol/mg respectively, the activity of GSH-Px in Doxorubicin group and Herceptin combined with doxorubicin group were (67.88±0.24) and (63.37±0.28) U/mg respectively,, Herceptin markedly increased the ratio of apoptosis of myocardial cells from (5.35±0.27) % in Doxorubicin group to (8.27±0.38) % in Herceptin combined with doxorubicin group measured by flow cytometry (PO.05).Oxygen free radicals were observed by electron microscope combined with cytochemical technique. Oxygen free radicals could be only observed which were precipitated on the luminal face of endothelia in doxorubicin group and Herceptin combined with doxorubicin group.3. cardiomyocyte apoptosis induced by Herceptin and doxorubicin The damage and apoptosis of myocardium were observed by electron microscope and tdt-mediated dUTP nick end labeling(TUNEL). The ratio of myocardial apoptosis cells was quantified with flow cytometry.The expression of Bcl-2 and Bax were analyzed by immunohistochemistry with SABC method. Bcl-2 expression was downregulated and Bax expression upregulated in Herceptin combined with doxorubicin group than that in doxorubicin group (P<0.05). The results of this study indicate that:1. It had small influence on rat's cardiomocytes used by Herceptin alone, but it can aggravate rats' cariotoxicity combined with doxorubcin.