RAT-TUMOR CYTOGENETICS - A CRITICAL-EVALUATION OF THE LITERATURE

Cancer cytogenetics is a valuable tool for the analysis of cellular an d molecular aberrations during malignant transformation and tumor prog ression. The rat has served as an important experimental model to inve stigate various steps in oncogenesis. An attempt was made to compile d ata on rat tumor cytogenetics from previously published data in order to provide a basis for further research, especially when combining cla ssic and molecular cytogenetics, a yet underdeveloped area of research in rat tumorigenesis. The wealth of data presented here provides a co ntrast to its impact on biological specificity. Because of the differe nt experimental procedures involved with tumor induction and the appli cation of carcinogens at relatively high dosages, as well as occasiona l less than careful histological documentation, a delineation of unamb iguous chromosome alterations, critical in the process of carcinogenes is, is rare in the rat. Future studies should be performed with sponta neously arising rat tumors and/or tumors after low, single-dose carcin ogen 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, especi ally for solid tumors, to avoid erroneous karyotype analyses because o f contaminating normal cells. The combined karyological and molecular genetic approach to an analysis of tumor-specific changes, still hinde red by an almost complete lack of cell type-, chromosome-, or gene-spe cific molecular probes for the rat, should become a focus of research in order to continue having the advantages this species offers for sta ge-specific analysis of tumorigenesis.