Rat tumor cytogenetics: a critical evaluation of the literature

Cancer cytogenetics is a valuable tool for the analysis of cellular and molecular aberrations during malignant transformation and tumor progression. The rat has served as an important experimental model to investigate various steps in oncogenesis. An attempt was made to compile data on rat tumor cytogenetics from previously published data in order to provide a basis for further research, especially when combining classic and molecular cytogenetics, a yet underdeveloped area of research in rat tumorigenesis. The wealth of data presented here provides a contrast to its impact on biological specificity. Because of the different experimental procedures involved with tumor induction and the application of carcinogens at relatively high dosages, as well as occasional less than careful histological documentation, a delineation of unambiguous chromosome alterations, critical in the process of carcinogenesis, is rare in the rat. Future studies should be performed with spontaneously arising rat tumors and/or tumors after low, single-dose carcinogen exposure in order to reduce unspecific karyotype alterations not intrinsically related to tumor initiation and progression. Short-term culture or early passages in vitro should be methods of choice, especially for solid tumors, to avoid erroneous karyotype analyses because of contaminating normal cells. The combined karyological and molecular genetic approach to an analysis of tumor-specific changes, still hindered by an almost complete lack of cell type-, chromosome-, or gene-specific molecular probes for the rat, should become a focus of research in order to continue having the advantages this species offers for stage-specific analysis of tumorigenesis.