T-cell leukemia induced by 1-propyl-1-nitrosourea in Fischer rats

Genetic regulation of development of thymic lymphomas induced by N-propyl-N-nitrosourea in the rat

To clarify the linkage between Hbb and Tls-1 (thymic lymphoma susceptible-1) loci and to investigate other loci concerned in thymic lymphomagenesis, the BUF/Mna rat, which is highly sensitive to the lymphomagenic activity of N-propyl-N-nitrosourea (PNU), the WKY/NCrj rat, reported to be resistant, and their cross offspring were subjected to genetic analysis. F1 hybrid and backcross generations were raised from the 2 strains, and 6 genetic markers including Hbb were analyzed in individuals of the backcross generation. However, no linkage between Hbb and Tls-1 loci could be demonstrated since WKY rats also developed a high incidence of thymic lymphomas in response to PNU. Nevertheless, thymic lymphomas developed more rapidly and reached a larger size in the BUF rats. F1 rats expressed a rather rapid and large tumor growth phenotype, while the [(WKY X BUF) X WKY] backcross generation consisted of rats with either rapidly growing or slowly growing tumors. It was thus concluded that rapid development of thymic lymphomas is determined by a gene, provisionally designated Tls-3. Analysis of the relationship between 6 genetic markers and development of thymic lymphoma in the backcross generation demonstrated that the Tls-3 locus is loosely linked to the Gc locus, suggesting a possible location on rat chromosome 14. Tls-3 may not be identical with Tls-1 and other genes known to be relevant to thymic tumors, but its relationship with Tls-2 remains obscure.

Survival of T- and B-Phenotype Diffuse Aggressive Non-Hodgkin's Lymphomas

Survival of immunophenotyped non-Hodgkin's lymphomas (NHLs) diagnosed as diffuse mixed, diffuse large and large cell immunoblastic by the working formulation was evaluated based on phenotypic categories. These subtypes were grouped as diffuse aggressive NHLs due to their similarities, and categorized into T- and B-phenotype NHLs. There were 45 (57.7%) cases of T-NHL and 33 (42.3%) B-NHL. Major clinical factors such as sex, age, stage, B-symptoms and site of disease, as well as performance status (PS), LDH, primary site and number of extra-nodal sites involved showed equal distributions between T- and B-NHLs. Combination chemotherapeutic regimens based on doxorubicin were used in 84% of these cases. Complete remission was achieved in 73.6% of T-NHL and 74.1% of B-NHL. Median survival for the T- and B-NHL was the same over 30 months. Projected survival at 5 years was also similar, T-NHL (35%) and B-NHL (38%). Unilaterally, survival was adversely affected in stage III/IV of T-NHL and for age over 65 years for B-NHL. Survival was unfavorable for the B-NHL without B-symptoms when compared to T-NHLs. Multivariately, only sex, B-symptoms and PS significantly (P < 0.05) affected the survival of T-NHL. Although the overall results indicate that the response and survival of T- and B-NHL are similar, the differences observed on the effect of sex, age, stage, B-symptoms and PS on survival of T- and B-NHLs imply that, their influence on T-NHLs was different from that for B-NHLs. Therefore we suggest that separate prognostic models are needed for the T- and B-phenotype NHLs.

Sequential observations of thymic lymphoma development induced in 10-week-old F344 rats by N-propyl-N-nitrosourea

N-Propyl-N-nitrosourea (PNU) is a strong carcinogen which induces thymic lymphoma and other tumors in F344 rats. In the present experiment, sequential changes of the thymus, spleen, bone marrow, and other organs were examined histologically in F344 rats which were continuously given PNU in the drinking water. Hematopoietic organs, such as the bone marrow, spleen, and thymus rapidly became hypoplastic. Atrophy of the thymus was followed by repopulation and hyperplasia. The latter was characterized by lymphoblast-like cells and was followed by development of early stage lymphoma, which arose from the 10th experimental week onwards. At first, thymic lymphoma was observed to involve thymic lobes unilaterally, later spreading to bilateral lobes, and at the 16th experimental week, metastatic foci were evident in the bone marrow of one rat. In contrast, hypoplasia of the bone marrow continued until the end of the experiment, while hypoplasia of the red splenic pulp continued until the 12th experimental week. These results indicate that PNU-induced lymphomas arise from within the thymus, although it is not possible to rule out a role for the bone marrow as including target cells of PNU. This PNU-thymic lymphoma system in F344 rats should serve as a good model for the study of experimentally induced thymic lymphoma.

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.