Relationship of doxorubicin- and radiation-induced apoptosis with Ki-67 labeling index in human tumors in vivo

In the use of doxorubicin and radiation for treatment of human malignant tumors in vivo, the relationship between treatment-induced apoptosis and Ki-67 labeling index was investigated. Four human tumor xenografts (ependymoblastoma, NNE; primitive neuroectodermal tumor, YKP; small cell lung carcinoma, GLS; glioblastoma, KYG) were transplanted under the skin of thigh of the nude mice (BALB/cA JcL-nu). The mice were given a single radiation dose of 1 Gy, or doxorubicin alone intraperitoneally at a dose of 8 mg/kg. After treatment, sections of tumor specimens were prepared from paraffin-embedded tissues. Hematoxylin and eosin staining, TUNEL staining, and immunohistochemical analysis of Ki-67 were performed. In NNE, apoptotic cells appeared most frequently after treatment compared with all other tumors, and the incidence of apoptosis in the radiation-treated group was much higher than in the doxorubicintreated group. As the incidence of apoptosis in NNE increased, the Ki-67 labeling index tended to decrease. In GLS and KYG, there was a low incidence of treatment-induced apoptosis, although the Ki-67 labeling index decreased transiently after treatment. In YKP, few apoptotic cells appeared and Ki-67 the labeling index was unchanged throughout the time course after treatment. Ki-67 labeling index in malignant tumors after treatment may be affected by various kinds of cell deaths and treatment methods. (author)