The chromosomes of fifty primary Rous rat sarcomas

Chromosome counts of 90Sr-induced osteosarcomas in mice. II. Variation of the chromosome counts of slow and fast growing tumours in hyper- and nonhyperimmunized hosts

Highly inbred CBA mice were used. The registration of chromosome abnormalities was limited to numerical deviations and the occurrence of metacentric chromosomes. By separate serial transplantation from a 90Sr-induced osteosarcoma two parallel transfer series (B and b) were established. From these series transplantation was also performed to hyperimmunized hosts B (Hi) and b (Hi). Besides differences in mean outgrowth period between B-and b-generations, a variation in chromosome pattern was observed. However, this variation should not be evaluated as a typical chromosomal progression of fast and slow growing tumour series.

Chromosome counts of 90Sr-induced osteosarcomas in mice. IV. Variation of chromosome counts when using tumours of predetermined age for transplantation

Transplanted tumours from a 90Sr-induced primary tumour were used as an experimental model to eliminate any connection between the chromosome distribution and outgrowth period of radiation-induced transplanted tumours. For this reason repeated transplantations were performed from different tumours of predetermined age from a transfer generation, to receive separate but parallel transfer generations. From each one of these generations a tumour of the same age as used to establish a particular generation was used for continued transplantation. It was then observed that the percentage of 40-chromosome cells in general decreased with the age of the tumour used for transplantation. Furthermore, early established transfer generations were often characterized by more slow growing tumours. However, it should be realized that even if a true relationship between chromosome pattern and outgrowth period cannot be eliminated, the differences found may be due to accidental variations.

An approach to the problem of heterogeneity of human tumour-cell populations

1. Successive sampling of ovarian cancers during cytostatic treatment showed several cases of notable changes in their ploidy distribution and one change in model chromosome number, indicating selection of a resistant tumour-cell population. 2. Studies of cell suspensions from human tumour specimens incubated with [3H]-TdR after exposure in vitro to various cytostatic agents have shown variation in labelling between different parts of the same tumour, as well as between the primary tumour and its metastases or ascitic tumour-cell population, which may be accounted for by variation in sensitivity of the tumour-cell population. 3. Studies of nuclear morphology in 20 endometrial cancers before and after progesterone therapy demonstrate considerable variation in the proportion of cells undergoing secretory conversion within the same tumour, indicating primary heterogeneity of the tumour-cell population in response to progesterone.

Chromosomes in solid tumors

Systematic chromosomal studies in solid tumors have been scanty (excepting meningiomas), because of the fact that it is difficult to obtain tumor material at desired times and only in about 10--15% of the cases adequate chromosome preparations are suitable with a direct technique or short term culture. A few facts that emerge from the study of various solid tumors are as follows: 1. modal number of chromosomes in parimary tumors tends to be lower that of metastatic; 2. certain chromosomes and chromosome regions are more susceptible for breakage to oncogenic conditions, hence, there is non-random involvement of certain chromosomes in human neoplasia and 3. certain chromosome changes are more often associated with metastatic spread than others.

Analysis of karyotype variation following carcinogen treatment of Chinese hamster primary cell lines

Chinese hamster primary fibroblasts derived from several embryos were treated with the carcinogens benzo(a)pyrene, 7,12-dimethylbenz(a)anthracene or N-methyl-N'-nitro-N-nitrosoguanidine. Karyotype analysis, sister chromatid exchange frequency, evidence of transformation by growth in agar, cell morphology and reaction to cytocholasin B were tested at regular intervals over many culture passages. Carcinogen treatment was found to shorten the time period before onset of permanent karyotypically changed stem and side lines and in vitro transformation. Chromosomes X, 6 and 10 were more frequently involved in all cultures in these karyotype changes which were usually preceded by a period of chromosome variation. Spontaneous chromatid aberrations and aneuploidy increased in frequency with time in culture and generally appeared prior to the expression of transformation. No specific chromosomes were involved with the different carcinogens. There was no correlation between in vitro transformation and karyotype evolution and the criteria for transformation were present independently of one another. It is suggested that the lack of correlation between the parameters tested indicates that the expression of in vitro transformation is a result of selection for growth advantage from a cell population expressing an increasing degree of genetic instability and variation with time in culture.

Non-random karyotypic evolution in chronic myeloid leukemia

The chromosome banding pattern was analyzed in bone-marrow cells and/or spleen cells of 10 patients in the blastic phase of chronic myeloid leukemia (CML). It was obvious from the karyotype analysis that the chromosome aberrations occurring addition to the Philadelphia chromosome (Ph1) were strictly non-random. An extra Ph1, trisomy 8 and/or trisomy for the long arm of chromosome 17 were observed in all cases. This consistent pattern of chromosome involvement in CML was confirmed in 57 cases from the literature studied with banding techniques. In 88% of the total number of cases with further changes at least one of the three main chromosomal aberrations was found ("major route" of karyotypic evolution).

Trisomy of chromosome 15 in spontaneous leukemia of AKR mice

Karyotypes of spontaneous thymomas of AKR mice were determined by trypsin-Giemsa banding methods. Trisomy of chromosome 15 occurred in 10 of 11 leukemic mice. Seven of the thymomas were predominantly trisomic for chromosome 15, one was trisomic for chromosome 12, and one exhibited multiple trisomies of chromosomes 3, 12, 15, and 17. Trisomy was not found in the norm-l AKR tissues examined.