AgNOR content and PCNA expression in transplanted malignant neurinoma in rats

Malignant neurinomas can be induced in BD IX rats by transplacental application of ethylnitroso-urea during pregnancy. Tumors develop in the offspring in trigeminal and spinal nerves and can be easily transplanted upon rats of the same strain. During the first passages a considerable shortening of subsequent induction periods takes place. Concurrently, silver stained Nucleolar Organizer Regions (AgNORs) increase in number and other measured AgNOR parameters change in a similar way. The number of cells that express the proliferation marker PCNA equally becomes more frequent during the first subcutaneously transplanted generations. There is high correlation between AgNOR parameters, number of PCNA expressing cells, induction times and passage. It is concluded that the first generations of the transplantation model of these tumors can be used to test the validity of proliferation indicators. Our results show further that AgNORs in fact belong to the group of markers of proliferation.