The detailed chromosome constitution of a benzpyrene-induced rat sarcoma. A tentative model for G-band analysis in solid tumors

The chromosomes of a 3,4-benzpyrene-induced subcutaneous rat sarcoma, BP19, were analyzed in 3 samples: (1) direct fixation of the solid tumor in vivo, (2) and (3) fixation of passage 2 of the tumor in vitro. Samples (1) and (2) were stained conventionally in orcein, whereas (3) was treated according to the G-banding technique. Except for a somewhat higher proportion of polyploid cells in (2) and (3), chromosome conditions were the same in the 3 samples, and the early in vitro passage with its excellent properties vis-à-vis G-banding could serve as a substitute for the solid tumor, which was refractory to G-banding, as is usual with solid tumors in direct fixation. The chromosome set of the tumor cells was shown by measurements to have gained an average amount of chromosome length corresponding to 1.6 times the longest rat chromosome. The typical tumor karyotype was monosomic for chromosomes A1, A3, B4, C12 and one D chromosome (D14 or D15) and had gained an average of 6 marker chromosomes. The detailed band analysis of the 32 different markers observed indicated that the losses of normal chromosomes were largely compensated and that large parts of A1 and A2 existed as trisomic. On the basis of the marker chromosomes certain pathways for the evolution of the tumor karyotype were established.