Chromosomal alterations in the course of viral leukemogenesis in the rat

Appearance of altered cell-surface fucosyl glycopeptides in concomitance with chromosomal alterations in the gross virus-infected pre-leukemic thymus of the rat

The appearance of a class of fast-eluting cell-surface glycopeptides that are encountered almost exclusively in malignant and certain pre-malignant cells was monitored in the course of leukemogenesis in the thymus of rats injected at birth with Gross leukemia virus. The altered glycopeptides appeared as early as 15 days after virus injection, when the animals were still clinically healthy and no histological signs of the disease were present in the thymus. Their amount was further increased at 30 days, and reached a maximum in the fully developed lymphoma. The development of this early phenotypic marker of malignancy appeared to be concomitant with that of chromosomal anomalies in the thymus. Since these anomalies are non-random, the existence of a causal relationship between the glycopeptide change and the loss of specific chromosomes might be hypothesized.

Chromosome and cell surface marker studies in 1-propyl-1-nitrosourea-induced thymic lymphomas of the rat

Immunological cell surface markers were studied in seven transplantable 1-propyl-1-nitrosourea-induced thymic lymphoma lines in F344 rats by reactivity to anti-Thy-1.1, anti-rat Ig (anti-Ig), and anti-rat T-cell (anti-T) sera, and by the capacity to form rosettes with guinea pig red blood cells. All the tumor lines were estimated to be sensitive to anti-Thy-1.1 but insensitive to anti-Ig serum in the presence of complement. The differences in reactivity to anti-T serum and rosette-forming capacity (RFC) allowed classification of the lines into three types. In type I, three lines were highly sensitive to anti-T serum but low in RFC, indicating that these lymphomas probably originated from relatively mature intrathymic T cells. In type II, two lines were moderately sensitive to anti-T serum and relatively high in RFC, indicating that these lymphomas derived from intrathymic T cells. In type III lymphomas, the remaining two lines were not only insensitive to anti-T serum but also low in RFC, suggesting that these lymphomas might have arisen from immature precursors of T and/or B cells. The chromosome study revealed that type I lymphomas were diploid, with slight numerical and structural variations. Type II lymphomas were pseudodiploid or hypotetraploid, with considerable variation in the number and morphology of chromosomes. Type III lymphomas had a diploid or hyperdiploid constitution, with a moderate degree of karyotypic variation. Neither consistent nor common karyotypic alterations among the seven lines were found, although the karyotypic instability seemed to be related to the immunological types of the lymphoma lines, possibly reflecting the differentiation process of the target cells involved in the malignant transformation.