Chromosome numbers and DNA-content in intracerebrally transplanted experimental gliomas

Flow cytometric DNA analysis and chromosomal aberrations in malignant glioblastomas

In this study we combined flow cytometry with fluorescence in situ hybridization to detect numerical aberrations in chromosomes. Fifty-nine human malignant gliomas were examined by flow cytometry for DNA-content and cell cycle analysis and for numerical aberrations of chromosome 1 by in situ hybridization using a chromosome specific centromere probe. Of the gliomas analysed, 42% were diploid and 58% showed aneuploid tumour cell populations. The DNA index was heterogeneous ranging from 1.0 to 2.3. The S-phase analysis showed proliferation activity from a very low range of 0.7% up to 17.0%. In general, diploid gliomas exhibited a lower S-phase activity than aneuploid gliomas. Of the aneuploid gliomas, 15% showed a peridiploid pattern with a DNA index mean of 1.1. In these peridiploid tumours a trisomy of chromosome 1 could be detected by fluorescence in situ hybridization (FISH). The frequency of trisomic chromosome 1 in malignant gliomas reflects a very slight increase in DNA index from diploid to peridiploid (DNA index 1.1). Comparison of chromosome numbers and DNA content gave good correlation. Also important, the results reflects the cell cycle, specifically the extent of S-phase activity. In general, cell proliferation of diploid and peridiploid gliomas is much less than in higher aneuploid gliomas. The analysis of DNA content may thus yield results with respect to the biological behaviour of tumours in general.

Comparative genomic in situ hybridization discloses chromosomal copy number changes in a transplanted brain tumor line of the rat (Rattus norvegicus)

We investigated chromosomal copy number changes in ethylnitrosourea-induced and serially transplanted gliomas of the rat by flow cytometry and Comparative Genomic in situ Hybridization (CGH). CGH analysis of a primary and four transplanted tumors revealed several genomic aberrations, including whole chromosome and subchromosomal gains and losses. Gains involved rat Chromosomes (RNO) 2, 3, 4, 5, 7, 9, 11, 12, 13, and Y, whereas losses affected RNO5, 13, 20, and Y. The primary tumor exhibited gain of RNO2q31qter and gain of RNO4. While gain of RNO2 was seen in nearly all investigated passages, gain of RNO4 was apparent in the primary tumor and in passage 2 and 5 tumors. Chromosomal alterations detected as single events were restricted to the transplanted tumors and included gain of RNO3q11, 3q41qter, 5q36, 7q34qter, 9q37, 11q, and Y, and loss of RNO5, 13, and 20q. Flow cytometry disclosed different aneuploid cell clones in the tumors investigated. The results are discussed in analogy to findings in human glial tumors.

Quantitative DNA analysis of an intracerebrally transplanted brain tumour model after experimental chemotherapy with BCNU and CCNU

In the present study we investigated the susceptibility of high passages of the rat glial transplantation tumour G-XIII to chemotherapy using nitrosourea compounds. We observed a significant increase in lifespan (ILS) of animals treated with BCNU (37%, p < 0.01) and CCNU (27%, p < 0.01). There were no difference in the efficiency between these two substances. Using a semi-quantitative score system no histopathological changes were observed which were associated with the response to therapy. The only predicative parameter in the present study was the quantitative DNA distribution pattern. There was a close correlation between treatment and the occurrence of unimodal DNA distribution patterns indicating clonal regrowth of recurrent tumours. Moreover, we also observed a correlation of the DNA distribution pattern of recurrent tumours with the result of experimental chemotherapy. Survival times of animals suffering from tumours containing unimodal DNA histogram was significantly longer than survival times of rats with multimodal DNA distribution, i.e. bimodal or broad DNA histograms. A unimodal, near-diploid stem line was only present in treated animals suggesting that these clones are more resistant against therapy using nitrosourea compounds. Our data indicate DNA cytophotometry as comprehensive tool for the monitoring of therapy response and the design of experimental chemotherapy using rat glial tumours.

Chemical carcinogenesis in the nervous system: past and future

The model of experimental tumors of the nervous system has greatly contributed to our understanding of growth and management of intracranial tumors, but has been somewhat neglected in the last years, because a wealth of new data concerning oncogenic action came from viral oncogenesis. These new issues led to a much better insight into human tumor induction and promotion. Yet one example of the impact of oncogenic transformation stems from the "neurooncogenic" model: the discovery of the neu oncogene and its product as a putative differentiation receptor in the cell membrane of experimental Schwann cell derived tumors. In the light of this unique finding the history of the "neurooncogenic" model and the morphological and "clinical" result of tumors produced within the model are reviewed. There is a large open field for future investigation both in basic and applied science.